TECHNICAL SPECIFICATION
SPÉCIFICATION TECHNIQUE
TECHNISCHE SPEZIFIKATION
ICS 91.010.30
CEN/TS 19101
November 2022
English Version
Design of fibre-polymer composite structures
Calcul des structures en matériaux composites
Bemessung von Tragwerken aus FaserverbundKunststoffen
This Technical Specification (CEN/TS) was approved by CEN on 22 August 2022 for provisional application.
The period of validity of this CEN/TS is limited initially to three years. After two years the members of CEN will be requested to
submit their comments, particularly on the question whether the CEN/TS can be converted into a European Standard.
CEN members are required to announce the existence of this CEN/TS in the same way as for an EN and to make the CEN/TS
available promptly at national level in an appropriate form. It is permissible to keep conflicting national standards in force (in
parallel to the CEN/TS) until the final decision about the possible conversion of the CEN/TS into an EN is reached.
CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,
Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Türkiye and
United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2022 CEN
All rights of exploitation in any form and by any means reserved
worldwide for CEN national Members.
Ref. No. CEN/TS 19101:2022 E
CEN/TS 19101:2022 (E)
Contents
Page
European foreword ............................................................................................................................................ 5
0 Introduction...................................................................................................................................................... 6
1
Scope.......................................................................................................................................................... 7
2
Normative references.......................................................................................................................... 9
3
3.1
3.2
3.3
Terms, definitions, symbols and abbreviations ...................................................................... 10
Terms and definitions ....................................................................................................................... 10
Symbols and abbreviations ............................................................................................................. 21
Symbols for member axes ................................................................................................................ 46
4
4.1
4.2
4.3
4.4
4.5
Basis of design ...................................................................................................................................... 50
General rules ........................................................................................................................................ 50
Principles of limit state design....................................................................................................... 50
Basic variables ..................................................................................................................................... 50
Verification by the partial factor method .................................................................................. 52
Design assisted by testing ................................................................................................................ 61
5
5.1
5.2
5.3
5.4
Materials ................................................................................................................................................ 62
Glass transition temperature ......................................................................................................... 62
Composite materials .......................................................................................................................... 62
Core materials ...................................................................................................................................... 64
Adhesives ............................................................................................................................................... 66
6
6.1
6.2
6.3
6.4
6.5
Durability ............................................................................................................................................... 67
General.................................................................................................................................................... 67
Environmental conditions ............................................................................................................... 68
Effects and measures for specific environmental conditions ............................................. 69
Effects of combined environmental conditions ....................................................................... 72
Measures for connections and joints ........................................................................................... 72
7
7.1
7.2
7.3
7.4
Structural analysis.............................................................................................................................. 73
Structural modelling for analysis ................................................................................................. 73
Global analysis ..................................................................................................................................... 80
Imperfections ....................................................................................................................................... 82
Methods of analysis ............................................................................................................................ 86
8
8.1
8.2
8.3
8.4
8.5
Ultimate limit states........................................................................................................................... 88
General.................................................................................................................................................... 88
Ultimate limit states of laminates ................................................................................................. 88
Ultimate limit states of profiles ..................................................................................................... 96
Ultimate limit states of sandwich panels ................................................................................ 107
Creep rupture .................................................................................................................................... 128
9
9.1
9.2
9.3
9.4
Serviceability limit states ............................................................................................................. 131
General................................................................................................................................................. 131
Deflections.......................................................................................................................................... 131
Vibrations ........................................................................................................................................... 133
Matrix cracking ................................................................................................................................. 134
10
10.1
Fatigue ................................................................................................................................................. 134
General................................................................................................................................................. 134
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10.2
10.3
10.4
Fatigue actions .................................................................................................................................. 135
Fatigue verification ......................................................................................................................... 135
Fatigue testing .................................................................................................................................. 136
11
11.1
11.2
11.3
11.4
11.5
Detailing .............................................................................................................................................. 138
General ................................................................................................................................................ 138
Profiles ................................................................................................................................................ 138
Sandwich panels and member laminates ............................................................................... 138
Bolted connections.......................................................................................................................... 140
Adhesive connections .................................................................................................................... 143
12
12.1
12.2
12.3
12.4
12.5
Connections and joints .................................................................................................................. 143
General rules ..................................................................................................................................... 143
Bolted connections.......................................................................................................................... 144
Bolted joints....................................................................................................................................... 163
Adhesive joints and connections................................................................................................ 165
Hybrid joints and connections .................................................................................................... 170
Annex A (informative) Creep coefficients ............................................................................................ 171
A.1
Use of this annex .............................................................................................................................. 171
A.2
Scope and field of application ..................................................................................................... 171
A.3
Pultruded composite profiles ..................................................................................................... 171
A.4
Composite laminates ...................................................................................................................... 172
A.5
Core materials................................................................................................................................... 172
Annex B (informative) Indicative values of material properties for preliminary design .. 174
B.1
Use of this annex .............................................................................................................................. 174
B.2
Scope and field of application ..................................................................................................... 174
B.3
General ................................................................................................................................................ 174
B.4
Fibres ................................................................................................................................................... 174
B.5
Resins ................................................................................................................................................... 175
B.6
Core materials................................................................................................................................... 176
B.7
Ply properties ................................................................................................................................... 178
B.8
Laminate properties ....................................................................................................................... 188
Annex C (normative) Buckling of orthotropic laminates and profiles ...................................... 191
C.1
Use of this annex .............................................................................................................................. 191
C.2
Scope and field of application ..................................................................................................... 191
C.3
General ................................................................................................................................................ 191
C.4
Elastic buckling of orthotropic laminates............................................................................... 192
C.5
Elastic buckling of profiles ........................................................................................................... 196
Annex D (normative) Structural fire design........................................................................................ 215
D.1
Use of this annex .............................................................................................................................. 215
D.2
Scope and field of application ..................................................................................................... 215
D.3
Assumptions ...................................................................................................................................... 215
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CEN/TS 19101:2022 (E)
D.4
Basis of design ................................................................................................................................... 215
D.5
Material properties ......................................................................................................................... 220
D.6
Tabulated design data .................................................................................................................... 229
D.7
Simplified design methods ........................................................................................................... 230
D.8
Advanced design methods ............................................................................................................ 230
Annex E (informative) Bridge details .................................................................................................... 232
E.1
Use of this annex .............................................................................................................................. 232
E.2
Scope and field of application ..................................................................................................... 232
E.3
General................................................................................................................................................. 232
E.4
Bridge bearings ................................................................................................................................ 232
E.5
Expansion joints ............................................................................................................................... 232
E.6
Parapets .............................................................................................................................................. 234
E.7
Adhesive deck-girder connections ............................................................................................ 234
E.8
Crash barrier fixations ................................................................................................................... 234
Bibliography .................................................................................................................................................... 236
4
CEN/TS 19101:2022 (E)
European foreword
This document (CEN/TS 19101:2022) has been prepared by Technical Committee CEN/TC 250
“Structural Eurocodes”, the secretariat of which is held by BSI. CEN/TC 250 is responsible for all
Structural Eurocodes and has been assigned responsibility for structural and geotechnical design matters
by CEN.
Attention is drawn to the possibility that some of the elements of this document may be the subject
of patent rights. CEN shall not be held responsible for identifying any or all such patent rights.
This document has been prepared under Mandate M/515 issued to CEN by the European Commission
and the European Free Trade Association.
This document has been drafted to be used in conjunction with relevant execution, material, product and
test standards, and to identify requirements for execution, materials, products and testing that are relied
upon by this document.
According to the CEN-CENELEC Internal Regulations, the national standards organizations of the
following countries are bound to announce this Technical Specification: Austria, Belgium, Bulgaria,
Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary,
Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal,
Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland,
Türkiye and the United Kingdom.
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CEN/TS 19101:2022 (E)
0 Introduction
0.1 Introduction to CEN/TS 19101
This document for the design of fibre-polymer composite structures, which was prepared in line with the
Eurocodes, is intended for use by designers, clients, manufacturers, constructors, relevant authorities (in
exercising their duties in accordance with national or international regulations), educators, software
developers, and committees drafting standards for related product, testing and execution standards.
NOTE 1 Some aspects of design are most appropriately specified by relevant authorities or, where not specified,
can be agreed on a project-specific basis between relevant parties such as designers and clients. The Eurocodes
identify such aspects making explicit reference to relevant authorities and relevant parties.
NOTE 2 Fibre-polymer composites are also commonly referred to as fibre-reinforced polymers (FRP) or as composites.
0.2 Verbal forms used in this Technical Specification
The verb “shall" expresses a requirement strictly to be followed and from which no deviation is permitted
in order to comply with the Eurocodes.
The verb “should” expresses a highly recommended choice or course of action. Subject to national
regulation and/or any relevant contractual provisions, alternative approaches could be used/adopted
where technically justified.
The verb “may" expresses a course of action permissible within the limits of the Eurocodes.
The verb “can" expresses possibility and capability; it is used for statements of fact and clarification of concepts.
0.3 National Annex to CEN/TS 19101
This Technical Specification gives values within notes indicating where national choices can be made.
Therefore, a national document implementing CEN/TS 19101 can have a National Annex containing all
Nationally Determined Parameters to be used for the assessment of buildings and civil engineering works
in the relevant country.
When not given in the National Annex, the national choice will be the default choice specified in the
relevant Technical Specification.
The national choice can be specified by a relevant authority.
When no choice is given in the Technical Specification, in the National Annex, or by a relevant authority,
the national choice can be agreed for a specific project by appropriate parties.
National choice is allowed in CEN/TS 19101 through the following clauses:
4.3.1.2(4), NOTE 2
4.4.7.1(2), NOTE
12.4.5.1(1), NOTE 1
4.4.6(1), NOTE
4.4.7.1(3), NOTE
D4.5(1), NOTE
4.4.6(2), NOTE
8.5(2), NOTE 4
4.4.6(3), NOTE
10.3(1), NOTE 1
National choice is allowed in CEN/TS 19101 on the application of the following informative annexes:
Annex A
Annex B
Annex E
The National Annex can contain, directly or by reference, non-contradictory complementary information
for ease of implementation, provided it does not alter any provisions of the Eurocodes.
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CEN/TS 19101:2022 (E)
1 Scope
1.1 Scope of CEN/TS 19101
(1) This document applies to the design of buildings, bridges and other civil engineering structures in
fibre-polymer composite materials, including permanent and temporary structures. It complies with the
principles and requirements for the safety, serviceability and durability of structures, the basis of their
design and verification that are given in EN 1990.
NOTE
In this document, fibre-polymer composite materials are referred to as composite materials or as
composites.
(2) This document is only concerned with the requirements for resistance, serviceability, durability and
fire resistance of composite structures.
NOTE 1
NOTE 2
Specific requirements concerning seismic design are not considered.
Other requirements, e.g. concerning thermal or acoustic insulation, are not considered.
(3) This document gives a general basis for the design of composite structures composed of (i) composite
members, or (ii) combinations of composite members and members of other materials (hybridcomposite structures), and (iii) the joints between these members.
(4) This document applies to composite structures in which the values of material temperature in
members, joints and components in service conditions are (i) higher than -40 °C and (ii) lower than
Tg - 20 °C, where Tg is the glass transition temperature of composite, core and adhesive materials, defined
according to 5.1(1).
NOTE 1
Composite structures have a temperature-dependent behaviour. The temperature-dependence of the
properties of composite, core and adhesive materials is considered through a conversion factor for temperature,
ηc , as defined in 4.4.7.2, which depends on the Tg and the maximum material temperature in service conditions
( Ts ).
NOTE 2
5.1(1) defines requirements for the Tg of composite, core and adhesive materials as a function of the Ts .
(5) This document applies to:
(i) composite members, i.e. profiles and sandwich panels, and
(ii) bolted, bonded and hybrid joints and their connections.
NOTE 1
Profiles and sandwich panels can be applied in structural systems such as beams, columns, frames,
trusses, slabs, plates and shells.
NOTE 2
Sandwich panels include homogenous core and web-core panels. In web-core panels, the cells between
webs can be filled (e.g. with foam) or remain empty (e.g. panels from pultruded profiles).
NOTE 3
NOTE 4
bonding.
This document does not apply to sandwich panels made of metallic face sheets.
Built-up members can result from the assembly of two or more profiles, through bolting and/or adhesive
NOTE 5
The main manufacturing processes of composite members include pultrusion, filament winding, hand
layup, resin transfer moulding (RTM), resin infusion moulding (RIM), vacuum-assisted resin transfer moulding
(VARTM).
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NOTE 6
This document does not apply to composite cables or special types of civil engineering works (e.g.
pressure vessels, tanks or chemical storage containers).
(6) This document applies to:
(i) the composite components of composite members, i.e. composite plies, composite laminates, sandwich
cores and plates or profiles, and
(ii) the components of joints or their connections, i.e. connection plates or profiles (e.g. cleats), bolts, and
adhesive layers.
NOTE 1
Composite components are composed of composite materials (i.e. fibres and matrix resins) and core
materials. Components of joints and their connections are also composed of composite, steel or adhesive materials.
NOTE 2
The fibre architecture of composite components can comprise a single type of fibres or a hybrid of two
or more types of fibres.
NOTE 3
This document does not apply to composite components used for internal reinforcement of concrete
structures (composite rebars) or strengthening of existing structures (composite rebars, strips or sheets).
(7) This document applies to composite materials, comprising:
(i) glass, carbon, basalt or aramid fibres, and
(ii) a matrix based on unsaturated polyester, vinylester, epoxy or phenolic thermoset resins.
NOTE
resins.
This document does not apply to composite materials comprising a matrix based on thermoplastic
NOTE 1
The core of sandwich panels can be reinforced by composite webs and inserts.
(8) This document applies to the core materials (i) polymeric foams, and (ii) balsa wood.
NOTE 2
This document does not apply to honeycomb cores.
(9) This document applies to thermoset adhesives, including epoxy, polyurethane, and acrylic resins.
NOTE
This document does not apply to thermoplastic adhesives.
(10) This document applies to other types of fibres, thermoset resins, homogeneous cores and thermoset
adhesives than those specified in 1.1(6)-(9), provided that their mechanical and physical properties are
obtained from appropriate testing according to Clause 5, and that they are in line with the other relevant
clauses of this document.
1.2 Assumptions
(1) The assumptions of EN 1990 apply to this document.
(2) This document is intended to be used in conjunction with EN 1990, EN 1991 (all parts), EN 1997 (all
parts), EN 1998 (all parts), ENs, EADs and ETAs for construction products relevant to composite
structures.
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CEN/TS 19101:2022 (E)
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments) applies.
NOTE See the Bibliography for a list of other documents cited that are not normative references, including those
referenced as recommendations (i.e. in ‘should’ clauses), permissions (‘may’ clauses), possibilities ('can' clauses),
and in notes.
EN 1990:— 1, Basis of structural and geotechnical design
EN 1991 (all parts), Eurocode 1: Actions on structures
EN 1991-1-2:— 2, Eurocode 1: Actions on structures — Part 1-2: General actions — Actions on structures
exposed to fire
EN 1993-1-4, Eurocode 3: Design of steel structures — Part 1-4: General rules — Supplementary rules for
stainless steels
EN 1993-1-8:— 3, Eurocode 3: Design of steel structures — Part 1-8: Design of joints
EN 1997 (all parts), Eurocode 7: Geotechnical design
EN 1998 (all parts), Eurocode 8: Design of structures for earthquake resistance
EN 13706-1, Reinforced plastics composites — Specifications for pultruded profiles — Part 1: Designation
EN 13706-2:2002, Reinforced plastics composites — Specifications for pultruded profiles — Part 2:
Methods of test and general requirements
EN 13706-3, Reinforced plastics composites — Specifications for pultruded profiles — Part 3: Specific
requirements
EN 16245 (all parts), Fibre-reinforced plastic composites — Declaration of raw material characteristics
ISO 6721-11, Plastics — Determination of dynamic mechanical properties — Part 11: Glass transition
temperature
Under preparation. Stage at the time of publication: prEN 1990:2021.
Under preparation. Stage at the time of publication: prEN 1991-1-2:2021.
3 Under preparation. Stage at the time of publication: prEN 1993-1-8:2021.
1
2
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CEN/TS 19101:2022 (E)
3 Terms, definitions, symbols and abbreviations
For the purposes of this document, the terms and definitions given in EN 1990 and the following terms,
definitions, symbols and abbreviations apply.
3.1 Terms and definitions
3.1.1 Terms relating to constituent materials
3.1.1.1
accelerator
substance used in small proportions that accelerates the chemical reaction between the polymer resin
system and the curing agent
3.1.1.2
additive
specialist chemical substance that is added to the polymer resin to impart specific matrix properties, such
as removal from processing mould, flame retardancy and UV protection; known also as modifier
3.1.1.3
bi-directional ply
ply with all the continuous fibres aligned in two orientations
3.1.1.4
chopped strand mat
CSM
non-woven mat with short strands cut (approximately 50 mm long) from continuous fibre (or filament)
strands and fairly evenly distributed and randomly oriented in a swirled pattern within the plane of the
mat; the mat is held together by a binder
3.1.1.5
composite material
material composed of layers of rovings, fabrics, and mats, embedded in a polymer matrix
3.1.1.6
continuous fibre mat
CFM
non-woven mat with yarns or strands (of continuous fibres) fairly evenly distributed and randomly
oriented in a swirled pattern within the plane of the mat; the mat is held together by a binder
3.1.1.7
core
central part of a sandwich panel to which top and bottom composite face sheets are attached
3.1.1.8
fibre
general term for a material in a filamentary form
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CEN/TS 19101:2022 (E)
3.1.1.9
filler
relatively inert substance added to the polymer resin to alter its physical, mechanical, thermal, electrical
or other properties (e.g. shrinkage or flammability), or to lower cost
3.1.1.10
gel coat
thin layer of unreinforced quick-setting resin, sometimes containing a colorant, applied on the outer
surface of a composite component to improve the surface properties
3.1.1.11
mat ply
ply comprising randomly oriented chopped or swirled continuous fibres loosely held together with a binder
3.1.1.12
non-woven fabric
textile structure produced by bonding or interlocking of continuous fibres, or both, accomplished by
mechanical, chemical, thermal or solvent means, and combinations thereof
3.1.1.13
ply
single layer (or lamina) in a laminate with a number of individual layers of fibres
3.1.1.14
resin
solid, semisolid or pseudosolid organic material that has an indefinite and often high relative molecular
mass, exhibits a tendency to flow when subjected to stress, and usually has a softening or melting range
3.1.1.15
roving
collection of parallel strands (assembled roving) or parallel continuous filaments (direct roving)
assembled without intentional twist
3.1.1.16
sizing
coating applied to fibres during their manufacture to improve handling and fibre-matrix
adhesion/compatibility, protect from water absorption and abrasion, lubricate the fibres and reduce
static electricity
3.1.1.17
surface veil
very thin mat, usually 0,18 mm to 0,51 mm thick, of highly filamentized non-reinforcing fibres
Note 1 to entry: Usually present in pultruded composite materials to enhance the quality of the surface finish, to
block out the fibre pattern of the underlying fibre layers and to add ultraviolet protection and a moisture diffusion
barrier.
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3.1.1.18
tape
prepreg of finite width consisting of resin impregnated unidirectional fibres
3.1.1.19
thermoset
class of polymers that, when cured using heat, chemical, or other means, changes into a substantially
infusible and insoluble material, through the formation of cross-links (primary bonds) between the
molecular chains
3.1.1.20
tow
large number of filaments collected into a loose strand or assemblage substantially without twist;
commonly used in referring to carbon fibres; typically designated by a number followed by K, meaning
multiplication by 1 000 (e.g. a 12K tow has 12 000 filaments)
3.1.1.21
unidirectional ply
ply with all the continuous fibres aligned in a single orientation
3.1.1.22
woven fabric
generic architecture consisting of interlaced yarns or fibres, usually a planar structure; the warp direction
of the woven fabric is taken to be the longitudinal direction, which is the direction of the principal load
action
3.1.1.23
woven roving
woven fabric formed by the weaving of rovings
3.1.2 Terms relating to manufacturing
3.1.2.1
cure
process of hardening of a thermosetting polymer resin (by cross-linking of the molecular structure); may
be accomplished by addition of curing agents, with or without catalyst, and with or without heat energy
3.1.2.2
cure temperature
temperature profile to which the composite material or adhesive is subjected to during the curing process
3.1.2.3
fibre content
quantity of fibres in the composite material; usually expressed as the percentage of volume or weight
fraction in the composite material
3.1.2.4
filament winding
automated composite manufacturing process in which continuous filaments (or tapes) are covered with
resin and wound onto a rotating mandrel in a predetermined pattern design under controlled tension
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CEN/TS 19101:2022 (E)
3.1.2.5
gel time
period of time from a pre-determined starting point to the onset of gelation time (gel point) as defined
by a specific test method
3.1.2.6
hand layup
composite manufacturing process in which a polymer resin and the fibre layers are applied manually
either to an open mould or to a working surface in a number of successive layers
3.1.2.7
layup
fabrication process involving the stacking of successive plies (also referred to as laminae or layers)
3.1.2.8
post-cure
additional elevated temperature cure of the matrix usually without pressure
Note 1 to entry: For certain resins, complete cure is attained only by exposure of the polymer matrix to higher
temperatures.
3.1.2.9
pultrusion
automated, continuous closed mould manufacturing process for thin-walled open and closed composite
shapes (or profiles or sections), having constant cross-sectional area in the direction of pultrusion
3.1.2.10
resin infusion moulding
RIM
composite manufacturing process in which a catalysed polymer resin is infused into a closed mould
already containing the preform for the component, with application of vacuum
3.1.2.11
resin transfer moulding
RTM
composite manufacturing process in which a catalysed polymer resin is injected into a closed mould
already containing the preform for the component
3.1.2.12
vacuum-assisted resin transfer moulding
VARTM
composite manufacturing process in which a catalysed polymer resin is introduced into a closed mould
already containing the preform for the component, with simultaneous application of vacuum to assist in
resin flow
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CEN/TS 19101:2022 (E)
3.1.3 Terms relating to composite components and members
3.1.3.1
balanced laminate
laminate in which the individual layers (or plies) are stacked so that there is a balance maintained of + θ
oriented layers and - θ oriented layers at the same height from the laminate’s mid-plane
3.1.3.2
component
constituent of a composite member (e.g. ply, laminate, core) or a connection between composite members
(e.g. cleat, bolt, adhesive)
3.1.3.3
hybrid-composite structure
structure composed of a combination of composite members and members of other materials (e.g. steel,
concrete)
3.1.3.4
hybrid laminate
laminate with a fibre architecture made from two or more different fibre types (e.g. glass and carbon)
3.1.3.5
interface
surface between two materials (e.g. where there is contact between fibre, sizing and matrix)
3.1.3.6
interphase
region of nanometre thickness where the sizing and matrix combine and the matrix has different physical
and chemical properties from the bulk matrix
3.1.3.7
laminate
relatively thin flat or curved composite component of members (such as profiles and sandwich panels)
or structural systems (such as plates and shells), with two dimensions considerably larger than the third
(thickness) direction, formed from curing and consolidating one or more plies of one or more composite
materials
3.1.3.8
member
physically distinguishable part of a structure (e.g. profile, sandwich panel, cable), possibly made up of
components (e.g. plies, laminates, cores)
Note 1 to entry: Members are connected by joints or connections, which are composed of further components
(connection plates, bolts, adhesive layers), to form structural systems (e.g. beams, columns, trusses, slabs, plates,
shells).
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CEN/TS 19101:2022 (E)
3.1.3.9
profile
prismatic composite member manufactured by pultrusion or other composite manufacturing processes
used in structural systems, such as beams, columns, frames and trusses
Note 1 to entry: For pultruded profiles, rovings are aligned along the member axis and fibres with other
orientations can also be (and often are) used.
3.1.3.10
sandwich panel
two-dimensional composite member used in structural systems such as slabs, plates and shells
comprising, in its simplest form, a relatively thick and lightweight core bonded to two relatively thin,
parallel and high strength composite face sheets
3.1.3.11
sublaminate
thinner representative laminate of a full-thickness laminate, in terms of constituent materials, fibre
architecture and processing method
3.1.3.12
symmetric laminate
laminate in which each lamina (or ply) type, angles and composition is exactly mirrored about the midplane of the composite material
3.1.3.13
web-core sandwich panel
sandwich panel comprising composite webs, with or without core infills between the webs
3.1.4 Terms relating to design
3.1.4.1
conversion factor
factor accounting for changes of material properties due to effects of environmental conditions (e.g.
moisture, temperature) and effects of ageing (long-term effects of exposure to environmental conditions)
3.1.4.2
conversion factor for moisture
factor accounting for changes of material properties due to moisture absorption over time (including
ageing effects resulting from long-term exposure)
3.1.4.3
conversion factor for temperature
factor accounting for changes of material properties due to material temperatures deviating from 20 °C
in service conditions (excluding effects of long-term exposure)
3.1.4.4
creep
time-dependent deformation resulting from sustained stress
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CEN/TS 19101:2022 (E)
3.1.4.5
creep coefficient
coefficient accounting for the creep effects on the deformations of composite structures, by reducing the
initial mean values of the relevant elastic moduli of materials
3.1.4.6
creep rupture
failure (by rupture) of a composite material at a sustained stress level that can be considerably lower
than the corresponding short-term strength
3.1.4.7
fail-safe structural member or joint
member or joint in which local failure of the member or joint does not result in failure of the structure or
critical parts thereof
3.1.4.8
fibre-dominated property of composite material
property of composite material mainly governed by the fibres; at elevated temperature, such property
has low sensitivity to polymer matrix softening; fibre-dominated properties include tensile strength and
modulus and compressive modulus in direction(s) with high ratio of fibres
3.1.4.9
flexible core
core of a sandwich panel with relatively low ratio between the flexural stiffness of the core and the
flexural stiffness of the face sheets
3.1.4.10
glass transition temperature
representative temperature of the glass transition process experienced by a composite material, a
polymeric core material or an adhesive at elevated temperature, in which the material changes from a
glassy state to a rubbery state; taken as the onset value of the storage modulus decay obtained from
dynamic mechanical analysis
3.1.4.11
linear viscoelasticity
mechanical behaviour of materials in which (i) the stress is proportional to the strain at a given time (creep
compliance is independent of the stress level) and (ii) the linear (Boltzmann) superposition principle holds
3.1.4.12
matrix-dominated property of composite material
property of composite material governed by the polymer matrix; at elevated temperature, such property
has high sensitivity to polymer matrix softening; matrix-dominated properties include compressive
strength, interlaminar shear strength, in-plane shear strength and modulus, and tensile strength and
modulus and compressive modulus in direction(s) with low ratio of fibres
3.1.4.13
non-fail-safe structural member or joint
member or joint in which local failure of the member or joint could lead to failure of the structure or
critical parts thereof
16
CEN/TS 19101:2022 (E)
3.1.4.14
pseudo-ductility
ability of a composite component or member to sustain irreversible inelastic deformation without
significant loss of resistance, during progressive composite material failure and associated dissipation of
inelastic energy
3.1.4.15
relaxation
time-dependent decrease in stress in a solid under given constraint conditions
3.1.4.16
rigid core
core of a sandwich panel with relatively high ratio between the flexural stiffness of the core and the
flexural stiffness of the face sheet
3.1.4.17
service temperature
temperature range (minimum and maximum temperatures) to which composite structures are exposed
to throughout their design service life
3.1.4.18
thick face sheet
face sheet of a sandwich panel with relatively low ratio of the distance between the centroid axes of the
face sheets to the face sheet thickness
3.1.4.19
thin face sheet
face sheet of a sandwich panel with relatively high ratio of the distance between the centroid axes of the
face sheets to the face sheet thickness
3.1.5 Terms relating to failure modes
3.1.5.1
crippling
failure of a composite component (e.g. a web of a profile) under transverse loads, in a phenomenon that
may involve crushing, buckling or a combination thereof
3.1.5.2
delamination
separation of the layers of material in a laminate, which can occur locally or cover a significant area of the
laminate, at any time in the cure or subsequent design service life of the laminate
Note 1 to entry: This failure mode can arise from a wide variety of causes, being linked to a relatively low out-ofplane (through thickness) tensile strength.
3.1.5.3
dimpling
buckling of the face sheet of a sandwich panel into or out of the individual cells of a discontinuous core
(e.g. honeycomb) due to localized compressive or shear stresses
Note 1 to entry: This is also referred to as intracell buckling.
17
CEN/TS 19101:2022 (E)
3.1.5.4
indentation
crushing of the core material of a sandwich panel caused by a transverse (out-of-plane) concentrated load
3.1.5.5
punching
shear failure of the core of a sandwich panel caused by a transverse (out-of-plane) concentrated load
3.1.5.6
shear crimping
core-dominated buckling of a sandwich panel under in-plane compression governed by the transverse
shear stiffness of the core
3.1.5.7
wrinkling
short wave buckling of the face sheet or web of a sandwich panel due to in-plane compression, which may
occur either towards the core or outwards, depending on the stiffness of the core in compression
3.1.6 Terms relating to joints and connections
3.1.6.1
joint
composition of several connections (e.g. double-lap joint)
3.1.6.2
connection
single location at which two members or laminates are connected (e.g. single-lap connection)
3.1.6.3
hybrid connection or joint
connection or joint where the members are interconnected by a combination of bolting and adhesive
bonding
3.1.6.4
lap-shear connection
connection made by overlapping two (thin-walled) components and forming a load carrying connection
between them
3.1.6.5
cleat
angle profile (made of composite or other material, e.g. steel or stainless steel) used to join composite
members
EXAMPLE
Double angle web cleats used to join an I-beam and an H-column, with one leg-side having a bolted
connection to the web of the beam and the other leg-side having a bolted connection to the outstand flanges of the
column).
3.1.6.6
adherend
component or member in an adhesively bonded connection or joint
18
CEN/TS 19101:2022 (E)
3.1.6.7
adhesive
substance (polymer or non-polymer-based, in liquid, film or paste form) capable of holding materials
together by surface attachment
3.1.6.8
adhesive failure
failure of an adhesively bonded connection such that the separation occurs at the adhesive-adherend interface
3.1.6.9
cohesive failure
failure of an adhesively bonded connection such that the separation is within the adhesive or within the
adherend
3.1.6.10
fibre-tear failure
failure of an adhesively bonded connection occurring exclusively within the composite matrix, characterized
by the appearance of reinforcing fibres on both ruptured surfaces (a specific type of cohesive failure)
3.1.6.11
fillet
portion of an adhesive which fills the corner or angle formed where two adherends are joined
3.1.6.12
tapering
gradual reduction of the thickness of the adherends along the overlap of an adhesively bonded connection
to reduce stress concentrations
3.1.7 Terms relating to defects
3.1.7.1
blistering
surface bump that grows because a pocket of gas or liquid develops within the composite material
3.1.7.2
chalking
surface defect resulting from the breakdown of the polymer matrix of the composite material or of the
protective gel coat for a release of a powdery, chalk-like appearance or deposit, as a consequence of poor
application, UV or weather degradation
3.1.7.3
crazing
network of fine cracks at or under the surface of the matrix material in the finished composite component
3.1.7.4
fibre blooming
progressive exposure of the topmost fibre layers of the composite material due to UV-induced
degradation of the polymer resin system
19
CEN/TS 19101:2022 (E)
3.1.7.5
flaking
detachment of surface material resulting from a chemical degradation mechanism at the level of the
topmost layer (for example, chemical reactions induced by UV radiation)
3.1.7.6
hydrolysis
chemical degradation mechanism resulting from a chemical reaction in which water molecules break
down the chemical bonds of a particular substance
Note 1 to entry: This reaction occurs in polymeric materials in the presence of water or moisture (particularly at
higher temperatures). The susceptibility of each material to hydrolysis depends on the presence and position of
water-sensitive groups in the polymer backbone, as well as on morphology aspects.
3.1.7.7
pitting
chemical degradation mechanism resulting from the attack of the surface of fibres of composite materials
induced by exposure to chemical solutions
Note 1 to entry: The susceptibility of each material to pitting depends on the composition of its fibre architecture,
and also on the nature of the chemical, temperature and duration of exposure.
3.1.7.8
plasticization
physical degradation mechanism of composite materials or polymeric adhesives caused by the
absorption of small molecules (low molecular weight) into the macromolecular chains of polymers
Note 1 to entry: Water molecules, in particular, act as plasticizing agent for polymeric materials and can modify
their thermal and mechanical properties.
3.1.7.9
saponification
chemical degradation mechanism of polymers resulting from the alkaline hydrolyses of ester groups
Note 1 to entry: In an alkali environment, the ester link of unsaturated polyesters can undergo hydrolysis; the
susceptibility of each material depends on its chemical structure and its crosslinking geometry.
3.1.7.10
swelling
volumetric changes due to absorption of moisture, independent of thermal expansion
20
CEN/TS 19101:2022 (E)
3.2 Symbols and abbreviations
3.2.1 Symbols
Latin upper case letters
A
Aeff
Am
Anet
Ans
Ant
Av
D
Dc
Df
Dk
D0
D11
D12
D22
D66
D*
E
gross area of a cross-section
area over which the concentrated load is uniformly distributed
area defined by the middle line of a closed cross-section
net area of a cross-section
net area of a laminate subjected to shear
net area of a laminate subjected to tension
shear area of a cross-section
flexural stiffness per unit width of a symmetric sandwich section of constant thickness
with homogeneous core
flexural stiffness per unit width of the core of a sandwich section (about its own neutral axis)
flexural stiffness per unit width of each face sheet of a sandwich section (about its own
neutral axis)
characteristic value of the flexural stiffness per unit width of a sandwich beam
flexural stiffness per unit width of the face sheets of sandwich sections (about the neutral
axis of the sandwich section)
longitudinal flexural stiffness
coupling flexural stiffness
transverse flexural stiffness
shear flexural stiffness
flexural stiffness per unit width of a symmetrical web-core sandwich section of constant
thickness with homogeneous core infill
elastic modulus
21
CEN/TS 19101:2022 (E)
Ec
elastic modulus of the core or core infill (web-core sandwich) of sandwich sections;
compressive modulus of adhesive
elastic modulus of the equivalent homogeneous core of web-core sandwich sections
Ec*
Ed
E d ( γ Ff ⋅ Qfat )
E d,fi
E d,min
Ed,max
Ef
E f,1
E f,2
(E )
i ,c,k f
(E )
i ,c,k w
(E )
⊥ ,k c
Er
Et
Ew
Ex
E x,c
22
design value of effect of actions
design value of an action effect in a structural member or joint (an internal force and/or
moment), caused by the fatigue action model
design value of effect of actions for the fire situation (including effects of thermal
expansions and deformations)
minimum design value of an action effect in a member or joint (obtained from the
permanent and fatigue loads)
maximum design value of an action effect in a member or joint (obtained from the
permanent and fatigue loads)
constant elastic modulus of each face sheet of sandwich sections
elastic modulus in the longitudinal direction of fibres
elastic modulus in the transverse direction of fibres
characteristic value of the compressive modulus in the i direction of the face sheet
characteristic value of the compressive modulus in the i direction of the web
characteristic value of the elastic modulus of the core in the direction perpendicular to
the plane of the web in web-core sandwiches (based on the value of the tensile or
compressive modulus, whichever is lower)
elastic modulus of resins
tensile modulus of adhesives
elastic modulus of the web
in-plane elastic modulus in x direction of balanced symmetrical bi-directional laminates
in-plane compressive modulus in x direction of composite pultruded profiles, composite
laminates/plies or core materials
CEN/TS 19101:2022 (E)
E x,c,k
E x,t
E xfull
Ey
E y,c
E y,c,k
(E )
y,c,k w
E y,t
E z,c
(E )
z,k c
E z,t
E1
E1UD
E2
E2UD
Fcr,sw
FEd
characteristic value of the in-plane compressive modulus in the x direction
in-plane tensile modulus in x direction of composite pultruded profiles, composite
laminates/plies or core materials
effective full section flexural modulus of composite profiles
in-plane elastic modulus in y direction of balanced symmetrical bi-directional laminates
in-plane compressive modulus in y direction of composite or core materials
characteristic value of the in-plane compressive modulus in the y direction
characteristic value of the in-plane compressive modulus in the transverse (y) direction
of the web
in-plane tensile modulus in y direction of composite materials or core materials
out-of-plane compressive modulus of core materials
characteristic value of the out-of-plane elastic modulus of the core
out-of-plane tensile modulus of core materials
in-plane elastic modulus in the 1 direction of UD plies
longitudinal elastic modulus of a fictitious UD ply
in-plane elastic modulus in the 2 direction of UD plies
transverse elastic modulus of a fictitious UD ply
elastic critical in-plane flexural buckling load for global (sway) buckling mode
design value of actions used in assessment of Ed
F1 , F2 , F12 , strength coefficients of Tsai-Wu failure criterion to predict failure of orthotropic plies
F6 , F11 , F22 ,
F66
G
shear modulus of the core of sandwich sections, adhesive materials, or mat plies
23
CEN/TS 19101:2022 (E)
Gc
shear modulus of the homogeneous core or core infill (web-core sandwich) of sandwich
sections
Gf
(G )
iz,k c
GI,Ed
GII,Ed
GIc ,Rd
GIIc ,Rd
(G )
⊥ ,k c
(Gk )c
Gk,ic
Gr
Gxy
Gxy,k
Gxyfull
Gxy
Gxz
Gyx
Gyz
Gzx
Gzy
24
shear modulus of fibres
characteristic value of the out-of-plane shear modulus ( iz plane) of the core
design value of the strain energy release rate for crack initiation in Mode I
design value of the strain energy release rate for crack initiation in Mode II
design value of the critical strain energy release rate for crack initiation in Mode I
design value of the critical strain energy release rate for crack initiation in Mode II
characteristic value of the shear modulus of the core in the plane perpendicular to the
web that includes the i direction
characteristic value of the out-of-plane shear modulus of the core
characteristic values of the critical strain energy release rate for crack initiation
shear modulus of resins
in-plane shear modulus of composite laminates/plies, or balanced symmetrical bidirectional laminates
characteristic value of the in-plane shear modulus (xy plane)
effective full section shear modulus of composite profiles
in-plane shear modulus (xy plane) of core materials
out-of-plane shear modulus (xz plane) of core materials
in-plane shear modulus (xy plane) of core materials
out-of-plane shear modulus (yz plane) of core materials
out-of-plane shear modulus (xz plane) of core materials
out-of-plane shear modulus (yz plane) of core materials
CEN/TS 19101:2022 (E)
G12
It
Iw
Iz
HEd
Hi
K
L
M
Mcr,Rd
MEd
Mf
MLT,Rd
MRd
MRd1
MRd2
N
Nbs,Rd
Nc,Ed
in-plane shear modulus of UD plies
torsional constant of a profile cross-section
warping constant of a profile cross-section
minor-axis second moment of area of a profile cross-section
total design horizontal load, including equivalent forces, transmitted from the floor
(storey shear) of a frame
horizontal forces applying to the supporting system (associated to sway imperfections)
slip modulus
span (Clause 9), or
distances between holes (Clause 11), or
unbraced profile length (Annex C)
bending moment
design value of the bending moment resistance to local buckling of a profile
design value of the bending moment about a principal axis at each cross-section of a profile
mass volume fraction (or content) of a composite material
design value of the bending moment resistance to lateral-torsional buckling of a profile
design value of the bending moment resistance about a principal axis of a profile
design value of the bending moment resistance of a cross-section to material failure
(about a principal axis)
design value of the bending moment resistance to global buckling of a profile (about a
principal axis) or local buckling of the cross-section (including the interaction thereof)
axial force (in general), or
number of cycles of the fatigue action (Clause 10)
design value of the block-shear resistance for a multi-bolted connection, with laminate
of constant thickness
design value of the compressive force at each cross-section of a profile
25
CEN/TS 19101:2022 (E)
Nc,Rd
Nc,Rd1
Nc,Rd2
Ncr,Rd
NE,Rd
NEd
NEd,i
NFT,Rd
Ni ,Ed
(N )
i ,Ed f
Npo,Rd
NT,Rd
Nt,Ed
Nt,Rd
Nty,Ed
Nty,Rd
Nx,nt,Rd
Ny,nt,Rd
Nz,Ed
26
design value of the compressive resistance in the longitudinal (x) direction of a profile
design value of the compressive resistance to crushing of a cross-section
design value of the compressive resistance to global buckling of a profile or local buckling
of a cross-section (including the interaction thereof)
design value of the compressive resistance to local buckling of a profile
design value of the flexural buckling resistance of a profile (with or without considering
the effects of shear deformation)
design value of the axial force for the connection force
design value of the connection force transferred at the i th -bolt row’s section
design value of the compressive resistance to flexural-torsional buckling of a profile
design value of the axial force applied to a sandwich panel
design value of the axial force per unit width in the face sheets, in the i direction
design value of the pull-out resistance per bolt
design value of the compressive resistance to torsional buckling of a profile
design value of the tensile force at each cross-section of a profile
design value of the tensile resistance of a cross-section in the longitudinal (x) direction
design value of the tensile force or prying action for tying force failure
design value of the tying force resistance of a web cleated beam-to-column joint of two
leg-angles having constant thickness outstands
design value of the net-tension resistance in the x direction
design value of the net-tension resistance in the y direction
design value of the out-of-plane (z direction) tensile force transferred at the bolt
CEN/TS 19101:2022 (E)
Nz,Rd
N1,Ed
N2,Ed
Pc,d
Pcb,d
Pcs,d
PEd
Pi ,c,d
Qfat
R
R {...}
Rac,k
Rac,Rd
Rd
Rf,k
Rd,t,fi
S
T
design value of the bolt tension resistance (12.2.4.2), or
design value for the resistance for the out-of-plane tension force (12.2.4.3)
contribution of NEd at the first row of bolts ( i = 1)
contribution of NEd at the second row of bolts ( i = 2)
design value of the buckling load per unit width (of a sandwich panel)
design value of the buckling load component corresponding to pure bending (Euler
buckling load)
design value of the buckling load component corresponding to transverse shear forces
design value of the transverse concentrated load; design value of the applied transverse
concentrated load or support reaction borne by the web
design value of the buckling load in the i direction (of a sandwich panel)
constant amplitude fatigue action
radius of a profile with circular section (Clause 8), or
ratio between minimum or maximum design value of an action effect in a member or
member-joint (Clause 10), or
coefficient to identify which section wall of a profile subjected to compression or bending
first triggers local buckling (Annex C)
output of the resistance model
characteristic value of the adhesive connection resistance
design value of the adhesive connection resistance
design value of resistance
characteristic value of the fatigue resistance of a member or member-joint (at constant
amplitude)
design resistance in the fire situation
shear stiffness per unit width of a symmetric sandwich section with homogeneous core
and thin face sheets
maximum tightening torque
27
CEN/TS 19101:2022 (E)
TEd
TEd(SV)
TEd(W)
Tg
TRd
Ts
design value of the uniform torsional moment of a cross-section associated to the SaintVenant's torsion
design value of the non-uniform torsional moment of a cross-section for constrained warping
glass transition temperature of composite, core or adhesive materials
design value of the torsional resistance of a cross-section
maximum material temperature of composite, core or adhesive materials in service conditions
V
Vb,i ,Ed
V br,Rd
Vbr,i ,Ed
VEd
(VEd )w
Vf
Vi ,Ed
(V )
i ,Ed c
VRd
VRd1
VRd2
Vso,i ,Ed
28
design value of the torsional moment at each cross-section of a profile
shear force
design value of the connection force per bolt at the i th -row of bolts
design value of the pin-bearing resistance per bolt
design value of the bearing force transferred per bolt at the i th -bolt row for pin-bearing
failure
design value of shear force (in general), or
total design vertical load, transmitted from the floor (storey thrust) of a frame (Clause 7)
design value of the shear force in the web component (of a sandwich panel)
fibre volume fraction (or content) of a ply or composite material
design value of the acting transverse shear force per unit width in the examined i direction
design value of the shear force in the core component of web-core sandwiches with core infill
design value of the shear resistance of a cross-section
design value of the shear resistance to material failure of a cross-section
design value of the shear resistance to local buckling of a cross-section
design value of bearing force transferred by a column line of bolts for shear-out failure
CEN/TS 19101:2022 (E)
Vso,1,Ed
Vso,2,Ed
Vso,i ,Rd
Vso,1,Rd
Vso,2,Rd
Vx
Vx,br,Rd
Vx,exp
Vy,br,Rd
Vwc,Ed
Vwc,Rd
W
Wnet
Wy
X d,fi
Xk
X k ,i
X k,θ
Xn
design value of the bearing force transferred by a bolt at the first row of bolts for shearout failure
design value of the bearing force transferred by a column line of two bolts for shear-out
failure
design value of the shear-out resistance per line of bolts, Vso,3,Rd or Vso,4,Rd , in a laminate
of constant thickness
design value of the shear-out failure resistance
design value of the shear-out resistance per line of bolts
coefficient of variation of a material or product property
design value of the pin-bearing resistance per bolt in the x direction
coefficient of variation of the tested sample
design value of the pin-bearing resistance per bolt in the y direction
design value of the shear force acting over the area of a laminate at the fillet radius
junction between two legs of leg-angles of composite material
design value of the shear resistance at the fillet radius junction between two legs of legangles of composite material
elastic flexural modulus of a cross-section
elastic flexural modulus of a net cross-section
major-axis elastic modulus of a cross-section
design value of mechanical (strength and stiffness) material properties for the fire situation
characteristic value of material properties (strength or stiffness, generally f k or E k )
characteristic value of a material or product property i
characteristic value of a property at temperature θ
nominal value of a material property
29
CEN/TS 19101:2022 (E)
X m (0)
X m (t )
initial mean value of elastic or shear modulus X (at time t = 0 )
mean value of elastic or shear modulus X at time t to take into account creep effects
Latin lower case letters
ad
b
bc
bf
bi
bw
cE
cLT
cp,θ
cr,i
c1
c2
d
di
dw
d0
30
design value of geometrical parameters
web spacing of a web-core sandwich section (Clause 7 and 8.4), or
width of the flange of a profile section (8.3)
core infill width between webs of a web-core sandwich section
flange width of a profile section
width of the section wall i of a profile section
web width of a profile section
empirical constant (for flexural buckling)
empirical constant (for lateral-torsional buckling)
design value of the ratio between the effective specific heat as a function of temperature
θ and the corresponding value at 20 °C
bolt row load distribution coefficient for the i th -bolt row
equivalent uniform moment coefficient that depends on the shape of the bending moment
diagram
coefficient associated with load level and dependent on the shape of the bending moment
diagram and out-of-plane restraint conditions
distance between the centroid axes of the face sheets of a sandwich section (Clauses 7 and
8), or
nominal bolt diameter (Clauses 11 and 12)
diameter of i th hole
diameter of the washer
nominal bolt hole diameter (Clauses 11 and 12), or
CEN/TS 19101:2022 (E)
distance from the centroid to the shear centre of cross-section (Annex C)
d1
d2
e
e0,d
e1
hole clearance (inner diameter) of washer
outside diameter of washer
lever arm distance from the centre of the nearest line of bolt holes to the centre of the
beam’s web
initial bow imperfection
end edge distance from the first row of bolts
fc
compressive strength of adhesive materials
fcy
fE,cr,k
fFT,cr,k
fi ,b,cr,d
fi ,b,cr,k
fi ,b,d
fi ,c,d
(f )
i ,c,d c
(f )
i ,c,d f
fi ,c,k
(f )
i ,c,k c
(f )
i ,c,k f
fi ,cr,d
compressive stress at yield of adhesive materials
characteristic value of the critical flexural buckling stress (without considering the effects
of shear deformation)
characteristic value of the critical flexural-torsional buckling stress of a profile
design value of the critical buckling bending stress in the i direction of a laminate
characteristic value of the critical buckling bending stress in the i direction of a laminate
design value of the in-plane bending strength in the i direction of a laminate
design value of the compressive strength in the i direction of a laminate
design value of the in-plane compressive strength in the i direction of the core
design value of the in-plane compressive strength in the i direction of the face sheet
characteristic value of the compressive strength in the i direction of a laminate
characteristic value of the in-plane compressive strength in the i direction of the core
characteristic value of the in-plane compressive strength in the i direction of the face sheet
design value of the critical buckling compressive stress in the i direction of a laminate
31
CEN/TS 19101:2022 (E)
(f )
i ,cr,d f
fi ,cr,k
(f )
i ,cr,k f
fi ,f,d
design value of the tensile strength in the i direction of a laminate
(f )
i ,t,d c
(f )
i ,t,d f
fi , t ,k
i ,t,k c
(f )
i ,t,k f
(f )
i ,v,d c
(f )
i ,v,k c
)
i ,wr,d f
)
i ,wr,k f
fiz,ILS,d
(f )
iz,v,k c
ft
32
design value of the in-plane tensile strength in the i direction of the core
design value of the in-plane tensile strength in the i direction of the face sheet
characteristic value of the tensile strength in the i direction of a laminate
(f )
fLT,cr,k
characteristic value of the critical buckling compressive stress in the i direction of the
face sheet
characteristic value of the flexural strength in the i direction of a laminate
fi ,t,d
(f
characteristic value of the critical buckling compressive stress in the i direction of a laminate
design value of the flexural strength in the i direction of a laminate
fi ,f,k
(f
design value of the critical buckling compressive stress in the i direction of the face sheet
characteristic value of the in-plane tensile strength in the i direction of the core
characteristic value of the in-plane tensile strength in the i direction of the face sheet
design value of the shear strength in the i direction of the core
characteristic value of the shear strength in the i direction of the core
design value of the wrinkling stress in the i direction of the face sheet
characteristic value of the wrinkling stress in the i direction of the face sheet
design value of the interlaminar shear strength ( iz plane) of a laminate
characteristic value of the out-of-plane shear strength ( iz plane) of the core,
perpendicular to the face sheets
characteristic value of the critical lateral-torsional buckling stress of a profile
tensile strength of adhesive materials
CEN/TS 19101:2022 (E)
f T,cr,k
characteristic value of the critical torsional buckling stress of a profile
f ty
tensile stress at yield of adhesive materials
(f )
design value of the out-of-plane shear strength of the core
v,d c
f Vx
factor that accounts for statistical uncertainty
f x,b,cr,k
(f
(f
(f
(f
(f
)
x,b,cr,k f
x,b,cr,k
)
SS
f
)
x,b,cr,d w
)
x,b,cr,k w
x,b,cr,k
)
f x,br,d
f x,br,k
f x,c
(f )
x,c,d w
f x,c,k
(f )
x,c,k w
f x,cr,k
SS
w
characteristic value of the critical stress associated to local buckling of a profile in bending
characteristic value of the critical stress of a compressed flange (of a profile in bending)
for a uniform stress distribution over the flange width
characteristic value of the critical stress of a compressed flange (of a profile in bending)
for a uniform stress distribution over the flange width, corresponding to a simply
supported (SS) boundary condition along the web-flange junction
design value of the in-plane critical buckling bending stress in the longitudinal (x)
direction of the web
characteristic value of the in-plane critical buckling bending stress in the longitudinal (x)
direction of the web
characteristic value of the in-plane critical buckling bending stress in the longitudinal (x)
direction of the web (of a profile in bending) for a linear stress distribution along the web
height, corresponding to a simply supported (SS) boundary condition along the webflange junction
design value of the pin-bearing strength in the x direction of a laminate
characteristic value of the pin-bearing strength in the x direction of a laminate
in-plane compressive strength in x direction of composite laminates, core materials, or
balanced symmetrical bi-directional laminates
design value of the compressive strength in the longitudinal (x) direction of the web
characteristic value of the compressive strength in the longitudinal (x) direction
characteristic value of the compressive strength in the longitudinal (x) direction of the web
characteristic value of the critical stress associated to local buckling of a profile in
compression
33
CEN/TS 19101:2022 (E)
(f )
x,cr,k f
(f )
SS
x,cr,k f
(f )
x,cr,k w
(f )
x,cr,k
SS
w
f x,f
x,t,d w
f x,t,k
x,t,k w
)
x,wr,d w
)
x,wr,k w
f xy,cr,d
)
xy,cr,d w
f xy,cr,k
f xy,v,d
34
)
xy,cr,k w
f xy,v
design value of the tensile strength in the longitudinal (x) direction of the web
characteristic value of the tensile strength in the x direction of a laminate
(f )
(f
characteristic value of the critical stress of a compressed web for a uniform stress
distribution over the web width, corresponding to a simply supported (SS) boundary
condition along the web-flange junction
design value of the tensile strength in the x direction of a laminate
(f )
(f
characteristic value of the critical stress of a compressed web for a uniform stress
distribution over the web width
in-plane tensile strength in x direction of composite laminates, core materials, or
balanced symmetrical bi-directional laminates
f x,t,d
(f
characteristic value of the critical stress of a compressed flange for a uniform stress
distribution over the flange width, corresponding to a simply supported (SS) boundary
condition along the web-flange junction
flexural strength in x direction of a laminate
f x,t
(f
characteristic value of the critical stress of a compressed flange for a uniform stress
distribution over the flange width
characteristic value of the tensile strength in the longitudinal (x) direction of the web
design value of the wrinkling stress in the longitudinal (x) direction of the web
characteristic value of the wrinkling stress in the longitudinal (x) direction of the web
design value of the critical buckling shear stress of a laminate
design value of the critical buckling shear stress of the web
characteristic value of the critical buckling shear stress of a laminate
characteristic value of the critical buckling shear stress of the web
in-plane shear strength of laminates, or balanced symmetrical bi-directional laminates
design value of the in-plane shear strength of a laminate
CEN/TS 19101:2022 (E)
(f
)
xy,v,d w
f xy,v,k
(f
)
xy,v,k w
f xz,ILS
out-of-plane shear strength (xz plane) of core materials, perpendicular to face sheets
f xz,v,d
design value of the out-of-plane shear strength (xz plane) of a laminate
f xz,v,k
)
xz,v,k c
f y,br,d
f y,br,k
f y,c
(f )
y,c,d w
(f )
y,c,k w
(f )
y,cr,d w
(f )
y,cr,k w
f y,f,d
f y,f,k
characteristic value of the in-plane shear strength of the web
characteristic value of the interlaminar shear strength (xz plane) of a laminate
f xz,v
f y,f
characteristic value of the in-plane shear strength of a laminate
interlaminar shear strength (xz plane) of laminates, or of balanced symmetrical bidirectional laminates
f xz,ILS,k
(f
design value of the in-plane shear strength of the web
characteristic value of the out-of-plane shear strength (xz plane) of a laminate
characteristic value of the out-of-plane shear strength (zx plane) of the core,
perpendicular to the face sheets
design value of the pin-bearing strength in the y direction of a laminate
characteristic value of the pin-bearing strength in the y direction of a laminate
in-plane compressive strength in y direction of laminates, core materials, or balanced
symmetrical bi-directional laminates
design value of the compressive strength in the transverse (y) direction of the web
characteristic value of the compressive strength in the transverse (y) direction of the web
design value of the critical buckling compressive stress in the transverse (y) direction of
the web
characteristic value of the critical buckling compressive stress in the transverse (y)
direction of the web
flexural strength in y direction of a laminate
design value of the flexural strength in the y direction of a laminate
characteristic value of the flexural strength in the y direction of a laminate
35
CEN/TS 19101:2022 (E)
f y,t
in-plane tensile strength in y direction of laminates, core materials, or balanced
symmetrical bi-directional laminates
f y,t,d
design value of the tensile strength in the y direction of a laminate
f y,t,k
(f
(f
)
y,wr,d w
)
y,wr,k w
f yz,ILS
(f )
yz,v,k c
)
wr,v,d w
)
wr,v,k w
fz,c
(f )
z,c,d c
fz,c,lim
(f )
(f
z,c,k c
)
zi ,v,k c
fz,t
fz,t,d
(f )
z,t,d c
36
characteristic value of the wrinkling stress in the transverse (y) direction of the web
characteristic value of the interlaminar shear strength (yz plane) of a laminate
f yz,v
(f
design value of the wrinkling stress in the transverse (y) direction of the web
interlaminar shear strength (yz plane) of a laminate
f yz,ILS,k
(f
characteristic value of the tensile strength in the y direction of a laminate
out-of-plane shear strength (yz plane) of core materials, perpendicular to face sheets
characteristic value of the out-of-plane shear strength (yz plane) of core materials,
perpendicular to the face sheets
design value of the shear wrinkling stress of the web
characteristic value of the shear wrinkling stress of the web
out-of-plane compressive strength of core materials
design value of the out-of-plane compressive strength of core materials
limiting out-of-plane compressive strength of a laminate
characteristic value of the out-of-plane compressive strength of core materials
characteristic value of the out-of-plane shear strength ( zi plane) of the core, parallel to
the face sheets
out-of-plane tensile strength of a laminate or core materials
design value of the out-of-plane tensile strength of a laminate
design value of the out-of-plane tensile strength of core materials
CEN/TS 19101:2022 (E)
fz,t,k
(f )
z,t,k c
fzx,v
(f
)
zx,v,k c
fzy,v
(f )
zy,v,k c
f1,c
f1,t
f12,v
f13,v
f2,c
f2,t
f23,v
h
hw
hr
i
i0
leff
characteristic value of the out-of-plane tensile strength of a laminate
characteristic value of the out-of-plane tensile strength of core materials
out-of-plane shear strength (xz plane) of core materials, parallel to face sheets
characteristic value of the out-of-plane shear strength (xz plane) of core materials,
parallel to the face sheets
out-of-plane shear strength (yz plane) of core materials, parallel to face sheets
characteristic value of the out-of-plane shear strength (yz plane) of core materials,
parallel to the face sheets
longitudinal compressive strength of UD plies, balanced bi-directional plies, or mat plies
longitudinal tensile strength of UD plies, balanced bi-directional plies, or mat plies
in-plane shear strength of UD plies, balanced bi-directional plies, or mat plies
intralaminar shear strength of UD plies, balanced bi-directional plies, or mat plies
transverse compressive strength of UD plies, balanced bi-directional plies, or mat plies
transverse tensile strength of UD plies, balanced bi-directional plies, or mat plies
intralaminar shear strength of UD plies, balanced bi-directional plies, or mat plies
height of a structure (Clause 7), or
height of the web of a profile section (Clause 8), or
depth of the leg-angle (Clause 12)
web depth (equal to the distance between the face sheets’ centroids)
depth of the shear plane at the fillet radius of the leg-angle (Clause 12)
radius of gyration about the relevant axis of a profile cross-section
polar radius of gyration about the shear centre of a profile cross-section
effective width for the verifications of transverse compression in the web (of sandwich
panels)
37
CEN/TS 19101:2022 (E)
l0
k
kcc
kc,creep
ksw
ktc
kt,creep
kw
kz
k
kθ
m
n
nb,i
nb,1
nb,2
nw
p1
p2
38
buckling length
effective length parameter to take into account the restraining effects of end supports to
flexural buckling of a profile about the relevant axis of bending
reduction factor accounting for the bearing compressive stress concentration in front of
the bolt from having a clearance hole with limit on dimension
strength reduction factor for compressive creep rupture for continuous unidirectional
fibres
second-order sway effects due to vertical loads
stress concentration factor for specific bolted connection configurations (net tension failure)
strength reduction factor for tensile creep rupture for continuous unidirectional fibres
warping end restraint parameter for torsional buckling of a profile cross-section
effective length parameter allowing for the effect of minor-axis rotation at supports
rotational spring
temperature-dependent reduction factor ( X k,θ / X k ) for a strength or stiffness property
number of columns in a row of a frame (Clause 7), or
exponent that depends on the actual connection configuration (12.4.5.4)
number of test results (4.4.5), or
exponent that depend on the actual connection configuration (12.4.5.4)
number of bolts at the i th bolt row
number of bolts at the first row of bolts ( i = 1)
number of bolts at the second row of bolts ( i = 2)
d2 -to- d1 ratio
spacing between centres of bolts in a line in the load transfer direction
spacing measured perpendicular to the load transfer direction between adjacent lines of bolts
CEN/TS 19101:2022 (E)
ri
s
sn
ss
t
ta
tc
tf
ti
t l-a
tk
t max
t min
tw
u
w
w1
w2
w3
radius of curvature of the face sheet, with regard to its centroid, in the iz plane (positive
for concave, negative for convex)
staggered pitch, the spacing of the centres of two consecutive holes in the chain
measured parallel to the member axis
width obtained by a dispersion of the load or support reaction at 45 ° through a z depth
width along the web on which the load is applied or the support reaction acts
laminate thickness (in general), or
time (Clauses 4, 8.5, 9, Annex A, Annex D)
thickness of the adhesive layer
thickness of the core of a sandwich section
constant thickness of each face sheet of a sandwich section (Clause 7 and 8.4), or
flange thickness of a profile section (8.3 and Annex C)
thickness of the ply i of a laminate (Annex B), or
thickness of the section wall i of a profile section (Annex C)
thickness of a leg-angle cleat
thickness of the wall k where a hole is located
thickness of the thickest wall of a cross-section
thickness of the thinnest wall of a cross-section (Clause 8), or
total minimum thickness from the pair of web cleats subjected to Vwc,Ed (Clause 12)
web thickness of a sandwich or a profile section
control perimeter
width of the component
initial part of the deflection under permanent loads of the relevant combination of actions
long-term part of the deflection under permanent loads including quasi-permanent loads
instantaneous deflection due to variable actions excluding the quasi-permanent loads
39
CEN/TS 19101:2022 (E)
wc
wmax
w tot
wGk
wQk,1
wQk,j
zg
precamber in the unloaded structural member (if applied)
remaining total deflection taking into account the precamber
total deflection as the sum of w1 , w2 , w3
initial part of the deflection under permanent loads
instantaneous deflection due to the leading variable action
instantaneous deflection due to accompanying variable actions
distance between the point of load application and the shear centre of a profile
Greek upper case letters
ΦE
auxiliary coefficient for flexural buckling of a profile
ΦLT
auxiliary coefficient for lateral-torsional buckling of a profile
α
coefficient of linear thermal expansion of sandwich core materials
Greek lower case letters
α cr,sw
α f,1
α f,2
αh
αi , j
αm
αq
αr
40
factor by which the design load would have to be increased to cause elastic instability
of a structure in a global in-plane (sway) mode
coefficient of linear thermal expansion in 1 direction of fibres
coefficient of linear thermal expansion in 2 direction of fibres
reduction factor for length or height of a frame
coefficient of linear thermal expansion of the j th ply along the assigned direction i (x
or y)
reduction factor for the number of columns in a row of a frame
coefficient of linear thermal expansion of mat plies with randomly oriented fibres
coefficient of linear thermal expansion of resins
CEN/TS 19101:2022 (E)
αx , αy
α1 , α2
α1UD , α 2UD
β1
coefficient of linear thermal expansion in x and y direction of laminates
coefficient of linear thermal expansion in the longitudinal and transverse direction of
UD plies, balanced bi-directional plies, or mat plies
coefficient of linear thermal expansion of a fictitious UD ply with the same fibre volume
fraction as the mat ply
coefficient of moisture expansion in the longitudinal direction for swelling of plies
β 2 , β3
coefficients of moisture expansion in the transverse direction for swelling of plies
γM
single partial material factor accounting for the uncertainty in a resistance model
γ Ff
γ M,ac
γ M,creep
γ Mf
γ M,fi
γm
γ m,i
γ Rd
ε f,1
ε t,kcrack
crack
ε t,d
ε t,SLS
εr
ηc
partial factor for the fatigue action
partial factor for the adhesive connection resistance
partial factor for creep rupture
partial factor for the fatigue resistance
partial factor for the relevant mechanical material property for the fire situation
partial factor for a material or product property
partial factor for a material or product property accounting for unfavourable deviation
of the properties of a material or product i from their characteristic values, and
geometrical deviations (if these are not modelled explicitly)
partial factor associated with the uncertainty in a resistance model
tensile strain at failure in longitudinal direction of fibres
characteristic value of the tensile strain causing matrix cracking
design value of the tensile strain causing matrix cracking
tensile strain due to the frequent combination of actions
maximum tensile elongation of a thermoset resin type
conversion factor
41
CEN/TS 19101:2022 (E)
ηc,i
ηcm
ηct
ηfi
θ
λ
λf,1
λE
λLT
λr
λθ
λ1
λ2
ν
νf
νr
ν xy
ν xy,k
ν yx
ν yx,k
42
conversion factor, accounting for effects of temperature and moisture, effects of ageing
of materials, including the uncertainty of those effects
conversion factor for moisture effects
conversion factor for temperature effects
reduction factor applied to Ed in order to obtain E fi,d
temperature
thermal conductivity
thermal conductivity in longitudinal direction of fibres
profile slenderness for interaction between local and flexural buckling
profile slenderness for interaction between local and lateral-torsional buckling
thermal conductivity of resins
design value of the ratio between the effective thermal conductivity as a function of
temperature θ and the corresponding value at 20 °C
thermal conductivity in 1 direction of UD plies, or balanced bi-directional plies
thermal conductivity in 2 direction of UD plies, or balanced bi-directional plies
Poisson’s ratio of mat plies
Poisson's ratio of fibres
Poisson's ratio of resins
in-plane major Poisson’s ratio of laminates, or balanced symmetrical bi-directional
laminates
characteristic value of the in-plane major Poisson’s ratio of laminates, or balanced
symmetrical bi-directional laminates
in-plane minor Poisson’s ratio of laminates, or balanced symmetrical bi-directional
laminates
characteristic value of the minor Poisson’s ratio of laminates, or balanced symmetrical
bi-directional laminates
CEN/TS 19101:2022 (E)
ν 12
Poisson’s ratio of UD plies
ρ
density
ρf
density of fibres
ρr
density of resins
ρθ
σ c,creep,Ed
σ c,creep,Rd
σ f,1
design value of the in-plane axial compressive stress in the i direction at each section
of a laminate
design value of the out-plane bending stress in the i direction at each section of a laminate
σ i ,ob,Ed
(σ )
design value of the normal stress in the core
i ,Ed c
(σ )
i ,Ed f
(σ
(σ
design value of the compressive stress limit for creep rupture
design value of the in-plane bending stress in the i direction at each section of a laminate
σ i ,c ,Ed
(σ
design value of the maximum sustained compressive stress caused by the quasipermanent combinations of actions
tensile strength in longitudinal direction of fibres
σ i ,b,Ed
(σ
design value of the ratio between density as a function of temperature θ and the
corresponding value at 20 °C
)
i ,M,Ed c
)
i ,M,Ed f
)
i ,N,Ed c
)
i ,N,Ed f
σ i ,t ,Ed
σ r,c , σ r,t
design value of the in-plane stress (tensile or compressive) in the face sheets in the i
direction
design value of the bending stress in the core in the i direction
design value of the bending stress in the face sheets in the i direction
design value of the axial stress in the core in the i direction
design value of the axial stress in the face sheets in the i direction
design value of the in-plane axial tensile stress in the i direction at each section of a
laminate
compressive and tensile strength of resins
43
CEN/TS 19101:2022 (E)
σ t,creep,Ed
σ t,creep,Rd
(σ
(σ
)
x,M,Ed w
)
y,c,Ed w
(σ )
z,Ed c
σ z,t,Ed
design value of the maximum sustained tensile stress caused by the quasi-permanent
combinations of actions
design value of the tensile stress limit for creep rupture
design value of the in-plane bending stress in the web
design value of the compressive stress in the web, resulting from transverse
concentrated loads
design value of the out-of-plane stress in the core
design value of the out-of-plane tensile stress
σ 11 , σ 22
longitudinal and transverse stress in a ply resulting from the effect of the actions
(τ Ed )c
design value of the out-of-plane shear stress in the core
τ Ed
(τ )
Ed w
(SV)
τ Ed
(w)
τ Ed
(τ )
i ,Ed c
τ i z,Ed
τ max
τr
τ xy,Ed
τ 12
φ
φ (t )
44
design value of the shear stress due to torsion
design value of the out-of-plane shear stress in the web
design value of the shear stress due to uniform torsional moment
design value of the shear stress due to non-uniform torsional moment
design value of the shear stress in the core
design value of the interlaminar shear stresses in the iz plane of a laminate
maximum average shear stress of adhesive materials
shear strength of resins
design value of the in-plane shear stress at each section of a laminate
shear stress in a ply resulting from the effect of the actions
initial sway imperfection
creep coefficient at time t
CEN/TS 19101:2022 (E)
φ0
basic value for initial sway imperfection (equal to 1/200)
χE
reduction factor to take into account the interaction between local and flexural
buckling of a profile
χ E,shear
reduction factor to take into account the influence of shear deformation
buckling reduction factor for bending in the i direction to take into account
imperfections of a laminate
χ i ,b
buckling reduction factor for compression in the i direction to take into account
imperfections of a laminate
χ i ,c
χ LT
reduction factor to take into account the interaction between local and lateraltorsional buckling of a profile
χv
ψ 1,1 , ψ 2,1 , ψ 2,i
buckling reduction factor for in-plane shear to take into account imperfections of a
laminate
combination factors applied to variable actions
3.2.2 Abbreviations
CFM
continuous fibre mat
CLT
classical lamination theory
CZM
cohesive zone modelling
CSM
DCB
DMA
chopped strand mat
double cantilever beam
dynamic mechanical analysis
DSC
differential scanning calorimetry
ENF
end-notched flexure
FEM
finite element modelling
EAD
ETA
FRP
european assessment document
european technical approval
fibre-reinforced polymer
45
CEN/TS 19101:2022 (E)
HM
high modulus
HS
high strength
PET
polyethylene terephthalate
PUR
polyurethane
ILSS
PQM
interlaminar shear strength
production quality management
PVC
polyvinyl chloride
RTM
resin transfer moulding
RIM
resin infusion moulding
SLS
serviceability limit states
TMA
thermomechanical analysis
TG
TTSP
thermogravimetry
time-temperature superposition principle
UD
unidirectional
UV
ultraviolet
ULS
VARTM
VCCT
ultimate limit states
vacuum-assisted resin transfer moulding
virtual crack closure technique
3.3 Symbols for member axes
(1) Figure 3.1 shows the convention for the local axes (1, 2 and 3) of a unidirectional ply:
—
—
The axes 1 and 2 are for the in-plane directions of the ply, respectively in the direction of the fibres
and in the direction transverse to the fibres;
The axis 3 is for the out-of-plane direction of the ply.
NOTE
46
A unidirectional ply contains all reinforcing fibres aligned in one direction.
CEN/TS 19101:2022 (E)
Figure 3.1 — Reference axes (local) for a unidirectional ply
(2) Figure 3.2 shows the convention for the global axes (x, y and z) of a laminate, consisting of several
plies, each of them with a certain orientation:
—
—
—
The axes x and y are for the in-plane directions of the laminate, respectively in the longitudinal and
transverse directions;
The axis z is for the out-of-plane direction of the laminate;
The angle θ defining the orientation of each ply with respect to the laminate is measured counterclockwise from the local axis 1 of the ply to the global axis x of the laminate.
Figure 3.2 — Reference axes (global) for a laminate with several plies with different fibre
orientations, with reference to a ply (abcd, Figure 3.1)
(3) Figure 3.3 shows the convention for the global axes (x, y and z) of a profile, consisting of several
laminates:
—
—
The axis x is along the member longitudinal axis;
The axes y and z are for the cross-section axes.
47
CEN/TS 19101:2022 (E)
NOTE 1
In general, y and z are for the cross-section axes, respectively parallel and perpendicular to the flanges.
NOTE 2
For angle sections, y and z are for the cross-section axes parallel and perpendicular to the smaller leg (or
orthogonal leg for angle sections with equal legs).
NOTE 3
In I-section profiles, the principal material directions of orthotropy of the flanges are aligned with the
xyz coordinate system in Figure 3.3; on the other hand, in the web, x and y denote the in-plane longitudinal and
transverse directions, and z the out-of-plane direction of the web laminate.
Figure 3.3 — Reference axes (global) for a profile, with reference to a laminate (ABCD, Figure 3.2)
(4) Figure 3.4 shows the convention for the global axes (x, y and z) of homogeneous-core and web-core
sandwich panels:
—
—
The axes x and y are for the midplane of the core, respectively in the longitudinal and transverse
directions;
The axis z is the out-of-plane direction.
NOTE 1
The principal material directions of orthotropy of the face sheet laminates and the core are aligned with
the xyz coordinate system in Figure 3.4.
NOTE 2
In webs of web-core sandwiches, x and y denote the in-plane longitudinal and transverse directions, and
z the out-of-plane direction of the web laminate.
48
CEN/TS 19101:2022 (E)
a) Configuration of homogeneous-core sandwich
Key
1
face sheets
3
foam core
2
4
b) Configuration of web-core sandwich
core
web
Figure 3.4 — Configuration of sandwich panels
49
CEN/TS 19101:2022 (E)
4 Basis of design
4.1 General rules
4.1.1 Basic requirements
(1) The design of composite structures shall be in accordance with the general rules given in EN 1990
and the specific design provisions for composite structures given in this document.
(2) The fire design of composite structures shall be in accordance with the principles and application
rules given in Annex D.
4.1.2 Structural reliability and quality management
(1) The rules for structural reliability and quality management given in EN 1990 shall be satisfied, as well
as applicable European product and manufacturing process standards for fibre-polymer composite
materials.
4.1.3 Design service life
(1) For the specification of the intended design service life, the rules given in EN 1990 shall be followed.
4.1.4 Durability
(1) For the consideration of durability, the general rules given in EN 1990 and in Clause 6 shall be
followed.
NOTE Clause 6 applies to the durability of composite structures, providing guidance on the selection and
processing of constituent materials, describing the most relevant environmental conditions and their main effects
on materials over time, and recommending protective measures.
4.2 Principles of limit state design
(1) Composite structures shall be designed according to the rules for limit state design given in EN 1990.
4.3 Basic variables
4.3.1 Actions, temperature- and time-dependent effects
4.3.1.1
General
(1) The characteristic values of actions for the design of composite structures shall be obtained from the
relevant parts of EN 1991, EN 1997 and EN 1998.
NOTE 1
Permanent actions can include those that cause permanent strains or stresses, such as differential
settlements of supports and locked-in thermal stresses (when composite structures are constructed at high or low
temperature).
NOTE 2
NOTE 3
For fatigue actions, see Clause 10, which covers fatigue verifications.
For fire actions, see Annex D, which gives rules for the fire design of composite structures.
(2) In sandwich panels, the additional self-weight caused by absorption of resin by foam or balsa cores
during manufacturing may be quantified by weighing sandwich panels after production.
NOTE Absorption of resin by foam or balsa cores during manufacturing (in resin infusion in particular) can
significantly increase the self-weight of sandwich panels.
50
CEN/TS 19101:2022 (E)
(3) Composite structures, members and components should be designed in a way that impact actions do
not lead to a structural collapse, unacceptable loss of functionality or reduced durability.
(4) Where ground-structure interaction has a significant influence on the action effects in composite
structures, the properties of the ground and the effects of the interaction should be taken into account in
accordance with EN 1997-1 and EN 1998, as relevant.
(5) Actions not covered by EN 1991, EN 1997 and EN 1998 shall be derived in accordance with EN 1990
and as specified by the relevant authority or, where not specified, agreed for a specific project by the
relevant parties.
4.3.1.2
Temperature-dependent effects
(1) The values of thermal actions should be used to define both (i) thermal action effects in composite
members, joints and components, and (ii) temperature effects on material properties.
(2) To define thermal action effects, the values of the minimum and maximum material temperatures in
composite members, joints and components, in service conditions, should be determined based on the
minimum and maximum service temperatures, defined according to EN 1991-1-5, using an appropriate
thermal model.
NOTE 1
EN 1991-1-5 gives values of both annual minimum and maximum shade air temperature with an annual
probability of exceedance of 0,02. This is equivalent to a mean return period of 50 years.
NOTE 2
Values of annual minimum or maximum shade air temperature based on an annual probability of
exceedance other than 0,02 can be considered. For that purpose, the methodology given in EN 1991-1-5:2003, A.2,
can be used.
NOTE 3
Information on both annual minimum and maximum shade air temperature used to define thermal
action effects can be given in the National Annex to EN 1991-1-5.
(3) In the absence of specific information for composite structures in EN 1991-1-5, temperature
differences in composite bridges may be derived by an appropriate thermal model taking into account
the composition of the composite structure and the surfacing.
(4) To define temperature effects on material properties, the values of the minimum and maximum
material temperatures in composite members, joints and components, in service conditions, should be
determined based on the minimum and maximum service temperatures, defined according to
EN 1991-1-5, considering appropriate probabilities of non-exceedance and reference periods, and using
an appropriate thermal model.
NOTE 1
EN 1990:—, 6.1.2.3(3) provides probabilities of non-exceedance and reference periods that can be
considered for the definition of the frequent and quasi-permanent values of the minimum and maximum service
temperatures.
NOTE 2
Additional guidance on the definition of the minimum and maximum service temperatures to define
temperature effects on material properties can be given in the National Annex.
4.3.1.3
Time-dependent effects
(1) Time-dependent effects shall be taken into account, including creep, relaxation and wear.
(2) Time-dependent effects due to creep should be evaluated under the quasi-permanent combination of
actions, and applied in all relevant combinations of actions.
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CEN/TS 19101:2022 (E)
4.3.2 Material and product properties
(1) The characteristic values, X k , or the nominal values, X n , of material and product properties shall be
determined by testing in accordance with EN 1990 and Clause 5.
NOTE For a preliminary design, the ply or laminate material properties can be taken from literature or
determined using an analytical modelling method considering the constituent material properties. Annex B
provides indicative (mean) values for the physical and mechanical properties of fibres, resins, plies, laminates and
core materials that can be used for the preliminary design of composite structures.
(2) The mean values of the appropriate elastic moduli, modified by the relevant conversion factors (4.4.7),
should be used in structural analysis to determine deflections, vibrations and strains for the serviceability
limit states (SLS) design of composite structures or parts thereof (Clauses 7 and 9).
(3) The mean values of the appropriate elastic moduli, modified by the relevant conversion factors (4.4.7),
should be used in structural analysis to determine the distribution of internal forces and moments or
stresses for the ultimate limit states (ULS) design of composite structures or parts thereof (Clauses 7 and
8, and Annex C).
(4) The characteristic values (5% fractiles) of the appropriate elastic moduli, modified by the relevant
conversion factors (4.4.7), should be used in the stability analysis for the ultimate limit states (ULS)
design of composite structures or parts thereof (Clauses 7 and 8, and Annex C).
(5) The effects of environmental conditions on material and product properties shall be taken into
account in accordance with 4.4.7 and Clause 6.
4.3.3 Geometrical properties
(1) The geometrical properties for composite members and components to be used for design and
geometrical tolerances should comply with the relevant product standards, and with manufacturers and
execution specifications.
(2) Appropriate allowances shall be made in the design for geometrical tolerances.
NOTE
For pultruded profiles, geometrical tolerances are specified in EN 13706.
(3) For structural analysis and design, the nominal values of dimensions may be used.
4.4 Verification by the partial factor method
4.4.1 Design values of actions
(1) For the combination of actions and partial factors of actions relevant to the design of composite
structures, EN 1990:—, Annex A shall be used.
4.4.2 Design values of material properties
(1) The design value for a material property is obtained by dividing its characteristic value by the relevant
partial factor for materials, according to 4.4.5.
4.4.3 Design values of geometrical properties
(1) Design values of geometrical imperfections specified in this document are equivalent geometrical
imperfections that take into account the effects of:
— geometrical imperfections as defined in relevant product standards, and manufacturers and
execution specifications;
— imperfections due to fabrication and erection;
52
CEN/TS 19101:2022 (E)
— residual stresses.
4.4.4 Design resistances
(1) The design value of resistance, Rd , for a specific design situation should be calculated from Formula
(4.1), unless otherwise stated in this clause, see (2) and (3):
Rd =
where


X
R ηc,i ⋅ k,i ; ad ; ∑ FEd 
γ Rd 
γ m ,i

1
γ Rd
R {...}
ηc,i
X k,i
γ m,i
ad
FEd
i
(4.1)
is a partial factor accounting for the uncertainty in the resistance model, and for
geometrical deviations, if these are not modelled explicitly, according to 4.4.6;
denotes the output of the resistance model;
is the conversion factor accounting for effects of temperature and moisture, effects of
ageing of materials, including the uncertainty of those effects, according to 4.4.7;
represents the characteristic values of material or product properties (defined as 5%
fractiles);
is a partial factor for a material or product property accounting for unfavourable
deviations of the material or product properties from their characteristic values and the
random part of the conversion factor, according to 4.4.5;
denotes the design values of geometrical parameters;
denotes the design values of actions used in the assessment of the design value of the
effect of actions, Ed ;
is for the i th material or product property.
(2) For the ULS design of composite components and members (Clause 8) and bolted connections and
joints (12.2 and 12.3), the design value of resistance, Rd , should be calculated from Formula (4.2):
=
Rd
where
1
R {ηc,i ⋅ X k,i ; ad ; ∑ FEd }
γ Rd ⋅ γ m
γm
(4.2)
is a partial factor for a material or product property accounting for the unfavourable
deviations of the representative material or product property from its characteristic value
and the random part of the conversion factor.
NOTE In Clause 8, and in 12.2 and 12.3, for each ULS verification, the "representative" material or product
property to which γ m is to be applied is indicated. The "representative" material or product property is related to
the property with dominating uncertainty, i.e. the property with the largest influence on the resistance uncertainty.
(3) For the creep rupture design (8.5), fatigue design (Clause 10), adhesive connections design (12.4),
and fire design (Annex D), the design value of resistance, Rd , should be calculated from Formula (4.3):
53
CEN/TS 19101:2022 (E)
X


Rd =R ηc,i ⋅ k,i ; ad ; ∑ FEd 
γM


where
γM
(4.3)
is the single partial material factor accounting for the uncertainty in the resistance model,
unfavourable deviations of the relevant material or product properties from their
characteristic values and the random part of the conversion factor, and geometrical
deviations, if these are not modelled explicitly.
(4) The conversion factor ηc , accounting for the effects of specified environmental conditions on the
mechanical properties of materials, should be obtained as indicated in 4.4.7. Alternatively, when the
composite, core and adhesive materials or environmental conditions are different from those given in
4.4.7, material properties to be used in design should be determined by testing (see 4.5) to represent the
actual exposure conditions.
4.4.5 Partial factors for materials
(1) The partial factor for a material or product property, γ m , depends on the coefficient of variation of the
material or product property, Vx , and shall be determined from testing (see 4.5).
(2) If Vx or a realistic upper bound of its value is known from prior knowledge, the value of γ m shall be
taken from Table 4.1 as a function of Vx . A minimum value of Vx = 0,05 should be considered.
Table 4.1 — Material partial factor γ m as a function of Vx when Vx is known
Vx
γm
0,05
1,07
0,10
1,15
0,15
1,23
0,20
1,32
0,25
1,41
0,30
1,51
0,35
1,61
0,40
1,71
0,45
1,82
NOTE These values are based on the design value method (see EN 1990:—,
Annex C), a lognormal distribution of the material or product property, a
sensitivity factor of 0,8, and a 50-year reliability index of 3,8.
NOTE 1 Prior knowledge might come from the evaluation of previous test results in comparable test series
(including tests conducted within the quality control system of the manufacturer). Engineering judgement can be
used to determine what can be considered as comparable (EN 1990).
NOTE 2 For 0,05 ≤ Vx ≤ 0,45, the values of Table 4.1 can be linearly interpolated.
(3) If Vx is not known from prior knowledge, to estimate Vx , the coefficient of variation of the tested
sample, Vx,exp , shall be multiplied by the factor fVx that accounts for the statistical uncertainty,
=
Vx Vx,exp ⋅ fVx . The values of fVx given in Table 4.2 as a function of the number of specimens tested in a
single batch, n , shall be used. Based on such estimated value of Vx , the value of γ m shall then be taken
from Table 4.1.
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CEN/TS 19101:2022 (E)
Table 4.2 — Factor fVx to take into account the statistical uncertainty of Vx , as a function of the
number of test results, n
n
fVx
5
1,70
10
1,19
15
20
1,12
1,08
25
1,07
30
1,05
50
1,03
100
1,02
999
1,00
NOTE These values are based on the assumption that the material or product
property is lognormally distributed.
(4) When composite material properties are determined by testing at the sub-laminate or ply levels, as
indicated in 5.2.2(7), the material partial factors, γ m , given in 4.4.5(2) (corresponding to testing at those
levels), may be applied to the elastic properties of composite laminates.
(5) When composite material properties are determined by testing at the sub-laminate or ply levels, as
indicated in 5.2.2(7), the material partial factors, γ m , given in 4.4.5(2) (corresponding to testing at those
levels), may be applied to the strength properties of composite laminates provided they are multiplied
by a sub-laminate correction factor of 1,2.
NOTE 1 The sub-laminate correction factor of 1,2 accounts for the additional uncertainty when determining
composite laminate strength properties from sub-laminate of ply tests.
NOTE 2 Tensile testing can also be performed on full laminate specimens whose thickness exceeds the 10 mm limit
specified in ISO 527, if the testing machine capacity is sufficient and the resulting failure mode is appropriate.
(6) A different sub-laminate correction factor may be used if supported by test data.
NOTE
Guidance on design assisted by testing is provided in EN 1990:—, Annex D.
4.4.6 Partial factors for resistance models
(1) For profiles and laminates, the partial factor for the resistance model, γ Rd , as specified in 4.4.4(1),
should be used.
NOTE
The values of the partial factor for the resistance model, γ Rd , are given in Table 4.3(NDP) for profiles and
laminates, unless the National Annex gives different values.
Table 4.3(NDP) — Values of γ Rd for profiles and laminates
Material failure
1,40
Global buckling
Flexural
1,30
Lateral-torsional Flexural-torsional
1,30
1,55
Local buckling
1,30
(2) For sandwich panels, the partial factor for the resistance model, γ Rd , as specified in 4.4.4(1), should
be used.
NOTE
The values of the partial factor for the resistance model, γ Rd , are given in Table 4.4(NDP) for sandwich
panels, unless the National Annex gives different values.
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CEN/TS 19101:2022 (E)
Table 4.4(NDP) — Values of γ Rd for sandwich panels
Composite
material
failure
Core
material
failure
Global
buckling
Local
buckling
1,40
1,50
1,40
1,30
Face sheet/web
Core
indentation
wrinkling
1,50
Core
punching
failure
1,50
1,50
(3) For bolted connections, the partial factor for the resistance model, γ Rd , as specified in 4.4.4(1), should
be used.
The values of the partial factor for the resistance model, γ Rd , are given in Table 4.5(NDP) for bolted
NOTE
connections, unless the National Annex gives different values.
Table 4.5(NDP) — Values of γ Rd for bolted connections
Net-tension
failure
Pin-bearing
failure
Shear-out
failure
Block-shear
failure
Pull-out
failure
1,50
1,50
1,50
1,50
1,50
(4) When composite material properties are determined by testing at the sub-laminate or ply levels, as
indicated in 5.2.2(7), the partial factors for resistance models, γ Rd , given in 4.4.6(1) to 4.4.6(3) may be
applied.
(5) For creep rupture, fatigue, adhesive connections and fire design, the partial factor associated with the
uncertainty in the resistance models, γ M , as specified in 4.4.4(3), shall be taken from 8.5 (creep rupture),
10.3(1) (fatigue design), 12.4.5.1(1) (adhesive connections), and D.4.5(1) (fire design).
4.4.7 Nominal conversion factors
4.4.7.1
General
(1) The conversion factor, ηc , in Formulae (4.1) to (4.3) should be calculated from Formula (4.4):
η=
ηct ⋅ηcm
c
where
ηct
ηcm
(4.4)
is the conversion factor for temperature effects;
is the conversion factor for moisture effects.
NOTE 1 The conversion factor for temperature, ηct , accounts for changes of material properties due to material
temperatures in service conditions according to 1.1(4) (-40 °C < Ts < Tg - 20 °C) relative to the material properties
at 20 °C, excluding effects of long-term exposure. Effects of long-term exposure to temperature are negligible if the
temperature remains within the specified material temperatures in service conditions and the matrix is sufficiently
cured.
NOTE 2 Long-term exposure to elevated temperatures below Tg usually contributes to increase mechanical
properties of polymeric materials due to post-curing effects.
NOTE 3 The conversion factor for moisture, ηcm , accounts for changes of material properties due to moisture
absorption over time, including ageing effects resulting from long-term exposure.
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CEN/TS 19101:2022 (E)
(2) The values of the nominal conversion factors for temperature effects given in 4.4.7.2 for specific
composite, core and adhesive materials should be used.
NOTE
The National Annex can give different values of ηct .
NOTE
The National Annex can give different values of ηcm .
(3) The values of the nominal conversion factors for moisture effects given in 4.4.7.3 for specific
composite, core and adhesive materials, for specific environmental conditions and for a 50-year period
should be used.
(4) The 50-year period for the conversion factors for moisture effects referred in 4.4.7.1(3) may be
extended (e.g. to 100 years for bridges). In that case, appropriate maintenance and inspection procedures
and/or protective systems with guaranteed effectiveness over the design service life should be applied.
(5) As an alternative to the nominal conversion factors given in 4.4.7.2 and 4.4.7.3, the temperature- and
moisture-dependent material properties may be determined from testing, representative of the actual
exposure conditions. Where appropriate, standard test protocols and state-of-the-art methods for
durability evaluation (e.g. Arrhenius law, time-temperature superposition principle) may be used.
(6) The durability provisions given in Clause 6 should be followed, for environmental conditions acting
individually or in combination.
NOTE Clauses 6 and 11 and Annex E give provisions for good practice on material selection and design, protective
measures and detailing.
4.4.7.2
Temperature
(1) For composite materials with glass, carbon or basalt fibres and thermoset polymer matrix of either
unsaturated polyester, vinylester or epoxy, the conversion factor for temperature, ηct , should be
determined from:
— for fibre-dominated properties,


Ts − 20
; 1,0
Tg − 20

(4.5)
Ts − 20

; 1,0
Tg − 20

(4.6)
η=
min 1,0 − 0,25 ⋅
ct

— for matrix-dominated properties,

η=
min 1,0 − 0,80 ⋅
ct

where
Ts
Tg
is the maximum material temperature in service conditions (in °C), as defined in 1.1(4);
is the glass transition temperature (in °C), obtained as defined in 5.1(1).
NOTE 1 Fibre- and matrix-dominated properties have respectively low and high sensitivity to matrix softening.
NOTE 2 Fibre-dominated properties include tensile strength and modulus and compressive modulus in direction(s)
with high ratio of fibres (e.g. for pultruded profiles, the longitudinal direction, x-direction in Figure 3.3). Matrixdominated properties include compressive strength, interlaminar shear strength, in-plane shear strength and
modulus, and tensile strength and modulus and compressive modulus in direction(s) with low ratio of fibres.
NOTE 3 For adhesive connections between composite adherends, the resistance to fibre-tear failure is matrixdominated.
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CEN/TS 19101:2022 (E)
(2) For sandwich core materials, the conversion factor for temperature, ηct , should be determined from:
— for polymeric foam core materials, namely polyurethane (PUR), polyethylene terephthalate (PET)
and polyvinyl chloride (PVC) foams (densities from 40 to 300 kg/m3),

η=
min 1,0 − 0,46 ⋅
ct

— for balsa wood,

Ts − 20
; 1,0
Tg − 20

(4.7)


 0,2

ηct min 1,0 − 
=
+ 0,004  ⋅(Ts − 20); 1,0
 ρ



where
ρ
(4.8)
is the density of balsa wood in (kg/m3).
(3) For epoxy adhesives, the conversion factor for temperature, ηct , should be determined from Formula
(4.9):

η=
min 1,0 − 0,85 ⋅
ct

4.4.7.3
Moisture

Ts − 20
; 1,0
Tg − 20

(4.9)
(1) For unprotected composite materials with glass, carbon or basalt fibres and thermoset polymer
matrix of either unsaturated polyester, vinylester or epoxy, and for epoxy adhesives, the conversion
factor for moisture, ηcm , should be determined from Table 4.6 for three exposure classes.
Table 4.6 — Values of ηcm for unprotected composite materials (glass, carbon or basalt fibres;
thermoset polymer matrix of unsaturated polyester, vinylester or epoxy; fibre volume fraction
of at least 35%) and epoxy adhesives
Exposure
classes
Conversion
factor ηcm
I
1,00
Indoor exposure with service temperature according to 1.1(4)
II
0,85
III
0,60
Outdoors exposure with service temperature according to 1.1(4),
without (i) continuous exposure to water, (ii) permanent immersion in
water, (iii) permanent exposure to a relative humidity higher than
80%, (iv) combined UV-radiation and frequent freeze-thaw cycles
58
Influence of moisture
Continuous exposure to water (or seawater), or permanent immersion
in water (or seawater), or permanent exposure to a relative humidity
higher than 80% (material temperature up to 25 °C)
CEN/TS 19101:2022 (E)
(2) Composite structures should be prevented from continuous contact with moisture (exposure class
III) through a protective system (e.g. protective surface coating, edge and bolt hole protection), to prevent
extensive environmental degradation over the design service life. When a protective system is applied, a
different value of ηcm from that given in Table 4.6 may be used (to be determined by testing, see
4.4.7.1(5)), provided that the effectiveness of the protective system over the design service life is
guaranteed.
(3) For core materials and web cores used in sandwich panels, ηcm may be taken equal to 1,0, provided
that diffusion of moisture from the face sheets to the core or webs is prevented by adequate materials
selection and thickness of the face sheets, and construction detailing (6.3.2(6)).
4.4.8 Creep effects
(1) The creep effects on the strength and deformations of composite structures shall be considered in the
design.
(2) The creep effects on the strength of composite structures shall be considered according to 8.5, where
limits are imposed to the stress levels in composite members and components for the quasi-permanent
combinations of actions.
(3) The creep effects on the deformations of composite structures shall be considered according to 9.2
and 9.4, by imposing limits to such deformations for the relevant combinations of actions.
(4) The creep effects on the deformations of composite structures should be taken into account by
reducing the initial mean values of the relevant elastic moduli of materials, through a creep coefficient,
as indicated in Formula (4.10) (see also 4.4.8(8) for alternative approaches):
X m (t ) =
where
X m (0)
1 + φ(t )
t
(4.10)
is the time;
X m (t )
is the mean value of elastic or shear modulus X at time t to take into account creep
effects;
φ(t )
is the creep coefficient at time t .
X m (0)
is the initial mean value of elastic or shear modulus X (at time t = 0 );
NOTE 1
While Formula (4.10) considers an apparent reduction in the elastic moduli of materials to determine
long-term deformations in composite structures, the actual values of elastic moduli used to determine the
momentary response of composite structures or their dynamic behaviour remain unaffected.
NOTE 2 The creep coefficient for composite, core and adhesive materials depends on several factors, including the
environmental conditions (temperature and relative humidity), the type of loading and the stress level.
NOTE 3 For composite sandwich panels, creep deformations due to shear are generally more significant than those
due to bending, especially in homogeneous-core sandwich panels.
(5) The values for the creep coefficient φ(t ) given in Tables 4.7, 4.8 and 4.9, for t = 50 years, and for
different elastic moduli of pultruded composite profiles, composite laminates/plies and core materials
(defined in 5.2 and 5.3), respectively, should be used.
NOTE 1 The values given in Tables 4.7, 4.8 and 4.9 are valid for linear viscoelasticity and the materials and
environmental conditions indicated in the tables. Annex A provides creep coefficients for additional periods.
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CEN/TS 19101:2022 (E)
NOTE 2 Linear viscoelasticity means that the stress is proportional to the strain at a given time (creep compliance
is independent of the stress level) and the linear (Boltzmann) superposition principle holds.
NOTE 3 For composite materials and polymeric foam core materials, in general, linear viscoelasticity applies for
relatively low stresses (for composite materials with glass fibres, typically up to 25% to 30% of the short-term
strength).
NOTE 4 In general, the viscoelasticity of composite, core and adhesive materials increases with increasing
temperature and relative humidity.
NOTE 5 For composite materials, the creep coefficient decreases with increasing fibre content along the direction
of the applied stresses.
NOTE 6 For polymeric foam core materials, the creep coefficient generally decreases with increasing density, while
for end-grain balsa the creep coefficient is independent of density. In addition, the creep behaviour of polymeric
foam core materials is generally orthotropic.
NOTE 7 For woven (0/90°) laminates/plies, the creep coefficient for Gxy given in Table 4.8 and Annex A for UD
laminates/plies can be considered as a conservative assumption.
NOTE 8 For woven ( ± 45°) laminates/plies, the creep coefficient for Gxy can be considered to be similar to the
creep coefficient given in Table 4.8 and Annex A for woven (0/90°) laminates/plies for E x,t and E x,c .
NOTE 9 The creep coefficients given in Table 4.9 and Annex A can be used for core materials with densities higher
than 100 kg/m3, for which they are expected to provide conservative estimates of creep deformations.
Table 4.7 — Values for the creep coefficient φ (t ) , for t = 50 years, for different elastic and shear
moduli of pultruded composite profiles (glass, carbon or basalt fibres; fibre volume fraction of at
least 35%; material temperature up to 25 °C; relative humidity up to 65%)
Material
Pultruded composite profiles
Property
φ (t = 50 years)
E xfull
0,70
E x,t
0,26
Gxyfull
E x,c
2,09
0,41
Table 4.8 — Values for the creep coefficient φ (t ) , for t = 50 years, for different elastic and shear
moduli of composite laminates/plies (glass, carbon or basalt fibres; fibre volume fraction of at
least 35%; material temperature up to 25 °C; relative humidity up to 65%)
Type of fibres
Unidirectional (UD)
laminates/plies
Woven (0/90°) laminates/plies
Chopped strand mat (CSM)
laminates/plies
60
Property
φ (t = 50 years)
E x,t
0,14
Gxy
2,52
E x,c
E x,t , E x,c
E x,t , E x,c
0,41
0,68
2,67
CEN/TS 19101:2022 (E)
Table 4.9 — Values for the creep coefficient φ (t ) , for t = 50 years, for the out-of-plane shear
modulus, Gxz , of different core materials (material temperature up to 22 °C for polymeric foams
and up to 25 °C for end-grain balsa; relative humidity up to 65%)
Property
φ (t = 50 years)
PUR foam (up to 100 kg/m3)
Gxz
5,70
End-grain balsa (up to 100 kg/m3)
Gxz
3,75
Material
PET foam (up to 100 kg/m3)
Gxz
0,65
(6) As an alternative to 4.4.8(5) and Tables 4.7, 4.8 and 4.9, the creep coefficient for composite, core and
adhesive materials may be determined by testing, according to EN ISO 899 or ASTM D2990.
NOTE 1 For composite materials with higher fibre volume fraction than the minimum value defined in Tables 4.7
and 4.8, and for core materials with densities higher than the ones defined in Table 4.9, the actual creep coefficients
are expected to be lower than those given in those tables.
NOTE 2 Test data can be used for the long-term prediction of creep using, when applicable, Findley’s law and
accelerated characterisation methodologies of creep behaviour, such as: (i) time-temperature superposition
principle (TTSP), (ii) time-stress superposition principle (TSSP), and/or (iii) time-temperature-stress
superposition principle (TTSSP).
(7) For materials, properties and environmental conditions not covered by Tables 4.7 to 4.9, the creep
coefficients should be determined by testing, according to 4.4.8(6).
(8) Creep effects on the deformations of composite sandwich panels or hybrid members may be
determined by testing, in case of sandwich panels according to ASTM C480/C480M.
NOTE In this case, the sandwich panel or hybrid member is tested, instead of testing the individual components
separately.
4.5 Design assisted by testing
(1) The resistance-side parameters used in the analysis and design of structures or structural members
and joints may be determined by testing.
NOTE 1 Guidance on design assisted by testing is provided in EN 1990:—, Annex D.
NOTE 2 EN 1990 (D.7.3) addresses the direct assessment of the design values of resistance for ULS verifications.
Whenever relevant, the conversion factors provided in 4.4.7 can be used in combination with such design values of
resistance.
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CEN/TS 19101:2022 (E)
5 Materials
5.1 Glass transition temperature
(1) The glass transition temperature ( Tg ) of composite, polymeric core and adhesive materials shall be
the temperature at the onset value of the storage modulus decay of the unaged material, determined
based on ISO 6721-11 and as illustrated in Figure 5.1. It shall be at least 20 °C above the maximum
material temperature in service conditions ( Ts , see 1.1(4)), and it should be at least 60 °C.
Key
1
glassy state
3
tangent lines
2
inflection point in glass transition region
Figure 5.1 — Determination of glass transition temperature ( Tg )
NOTE The glass transition temperature is determined as the temperature at the intersection of two tangent lines
of the storage modulus curve, in a plot of the logarithm of the storage modulus vs. the linear temperature, obtained
from Dynamic Mechanical Analysis (DMA). The first tangent line approaches the curve in the glassy state, while the
second tangent line is constructed at the inflection point in the glass transition region. Further guidance can be
found in ASTM D7028, Appendix.
5.2 Composite materials
5.2.1 Raw materials: fibres, resins, additives and fillers
(1) The sizing of the fibres shall guarantee compatibility between the fibres and the resin of the composite
material.
(2) Additives and/or fillers may be added to the resin to provide the matrix with specific mechanical and
other engineering properties. The effect of additives and/or fillers on the short- and long-term
mechanical properties of a composite material shall be taken into account.
(3) Requirements for raw materials shall be specified in accordance with EN 16245 (all parts). Raw
materials that are not scoped by EN 16245 (e.g. epoxy resin, aramid fibre) shall be specified in a similar
way.
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CEN/TS 19101:2022 (E)
5.2.2 Material properties
(1) This subclause applies to balanced symmetric composite laminates.
(2) Composite material properties used for the analysis and design of composite structures should be
characterised as per standard test methods referred in Table 5.1.
(3) Material properties in addition to those listed in Table 5.1 should be as specified by a relevant
authority or, where not specified, as agreed for a specific project by the relevant parties.
(4) For a preliminary design, the material properties listed in Table 5.1 may be estimated using literature
values for the constituent material properties and/or the individual ply level properties, by using
micromechanical modelling, Classical Lamination Theory (CLT) and an appropriate failure criterion.
NOTE Indicative values are given in Annex B for mechanical properties of typical balanced and symmetric
laminates.
(5) Material properties should be determined by extracting coupon specimens from different regions of
a composite member and testing them according to the standard test methods referred in Table 5.1.
(6) To avoid damaging a composite member by extracting coupons as indicated in 5.2.2(5), composite
material properties may be determined by testing laminates manufactured using the same constituent
materials and composite processing method used to produce the corresponding laminate of the
composite member.
(7) As an alternative to 5.2.2(5), composite material properties may be determined by testing sublaminate or ply level specimens manufactured using the same constituent materials and composite
processing method used to produce the corresponding laminate. The material properties of the fullthickness laminate shall be established using the sub-laminate or ply level test results, CLT and an
appropriate failure criterion.
NOTE 1 A sub-laminate is a thinner representative laminate of a full-thickness laminate, in terms of constituent
materials, fibre architecture and processing method.
NOTE 2 Due to the thickness of the laminate, performing the standard tests listed in Table 5.1 can require a coupon
specimen having dimensions that are not practical and thus only testing at the sub-laminate or ply level can be
performed.
NOTE 3 Annex B describes analytical methods to determine the strength properties of laminates using the CLT
based on the ply properties (determined by testing) and appropriate failure criteria.
(8) When, owing to the geometry of the cross-section shape of a composite profile, extracting a coupon
specimen in accordance with a test standard in Table 5.1 is impractical, testing shall be performed using
representative laminates of the profile’s composite material manufactured in accordance with Clause 6
of EN 13706-2:2002 or in an equivalent way.
NOTE There are cross-section geometries of composite profiles where the width of a flange outstand and/or the
height of a web is less than that required for the coupon size according to the standard test methods in Table 5.1
(e.g. for tensile properties in the transverse direction).
(9) Mechanical properties for the section of a composite profile may be determined at section level in
accordance with EN 13706-2:2002, Annex G, namely the effective full section flexural modulus ( E xfull ) and
shear modulus ( Gxyfull ).
(10) For composite profiles manufactured by pultrusion, the properties indicated in EN 13706 should be
used as a minimum for the analysis and design.
NOTE
EN 13706 describes mandated property data for two grades of pultruded profiles, E17 and E23.
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Table 5.1 — Laminate material properties
Property
In-plane tensile modulus (in x and y direction)
In-plane tensile strength (in x and y direction)
Out-of-plane tensile strength (in z direction)
In-plane compressive modulus (in x and y direction)
In-plane compressive strength (in x and y direction)
In-plane shear modulus (xy plane)
In-plane shear strength (xy plane)
In-plane major and minor Poisson’s ratio (xy plane)
Flexural strength (in x and y direction)
Interlaminar shear strength (yz and xz planes)
Density
Glass transition temperature a
Coefficient of linear thermal expansion (in x and y direction)
Thermal conductivity b
NOTE 1: See Figure 3.2 for xyz axes.
Symbol
Standard test method
E x,t , E y,t
EN ISO 527
f x,t , f y,t
EN ISO 527
fz,t
ASTM D7291/D7291M
f x,c , f y,c
EN ISO 14126
E x,c , E y,c
Gxy
f xy,v
ν xy , ν yx
f x,f , f y,f
f yz,ILS ,
f xz,ILS
ρ
Tg
αx , αy
λ
EN ISO 14126
ASTM D7078/D7078M
ASTM D5379/D5379M
ASTM D7078/D7078M
ASTM D5379/D5379M
EN ISO 527
EN ISO 14125
EN ISO 14130
EN ISO 1183-1
ISO 6721-11
ISO 11359-2
EN ISO 22007-2
EN ISO 22007-4
NOTE 2: For shear, the 1st and 2nd indices are the in-plane directions normal and parallel to the stress direction.
The glass transition temperature is determined according to 5.1(1) and as illustrated in Figure 5.1.
Thermal conductivity is used to assess material thermal insulation capability, and for structural fire design
purposes.
a
b
5.3 Core materials
(1) Core material properties used for the analysis and design of composite sandwich panels should be
characterized as per standard test methods referred in Table 5.2.
(2) The density of core materials should be at least 40 kg/m3.
(3) Size-effect induced differences between coupon-based and full-scale properties shall be taken into
account in design calculations.
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Table 5.2 — Sandwich core material properties
Property
Symbol
Out-of-plane tensile modulus (in z direction)
E z,t
Out-of-plane tensile strength (in z direction)
fz,t
Out-of-plane compressive modulus (in z direction)
E z,c
Out-of-plane compressive strength (in z direction)
fz,c
Out-of-plane shear moduli (xz and yz planes)
Gxz , Gyz
Out-of-plane shear strengths (xz and yz planes),
perpendicular to face sheets
f xz,v , f yz,v
In-plane tensile modulus (in x and y direction)
E x,t , E y,t
In-plane tensile strength (in x and y direction)
f x,t , f y,t
In-plane compressive modulus (in x and y direction)
E x,c , E y,c
In-plane compressive strength (in x and y direction)
f x,c , f y,c
Out-of-plane shear strengths (xz and yz planes), parallel
to face sheets
In-plane shear moduli (xy plane)
Density
Glass transition temperature c
fzx,v , fzy,v
Gxy , Gyx
ρ
Tg
Standard test method
ASTM C297/C297M
ISO 13061-6 (balsa wood)
ISO 1926 (foam)
ASTM C297/C297M
ISO 13061-6 (balsa wood)
ISO 1926 (foam)
ASTM C365/C365M
ISO 13061-17 (balsa wood)
EN ISO 844 (foam)
ASTM C365/C365M
ISO 13061-17 (balsa wood)
EN ISO 844 (foam)
ASTM C273/C273M a
ASTM D5379/D5379M
(balsa wood) b
ISO 1922 (foam)
ASTM C393/C393M
ASTM C273/C273M
ISO 1922 (foam)
ISO 13061-7 (balsa wood)
ISO 1926 (foam)
ASTM D1623 (foam)
ISO 13061-7 (balsa wood)
ISO 1926 (foam)
ASTM D1623 (foam)
ASTM C365/C365M
ISO 13061-5 (balsa wood)
EN ISO 844 (foam)
ASTM C365/C365M
ISO 13061-5 (balsa wood)
EN ISO 844 (foam)
ASTM C273/C273M a
ASTM C271/C271M
ISO 13061-2 (balsa wood)
EN ISO 845 (foam)
ISO 6721-11
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Table 5.2 — Sandwich core material properties (continued)
Property
Coefficient of linear thermal expansion
Thermal conductivity d
Symbol
Standard test method
ASTM E228
EN 13471 (foam)
α
λ
EN 12667
NOTE 1 See Figure 3.4 for xyz axes.
NOTE 2 For shear, the 1st index is the direction normal to shear plane and the 2nd index is the stress direction.
NOTE 3 Core materials are generally anisotropic.
Test method to be adapted from ASTM C273/C273M, which applies to xz and yz shear.
Test method for composite laminates adapted to balsa wood.
c The glass transition temperature is determined according to 5.1(1) and as illustrated in Figure 5.1.
d Thermal conductivity is used to assess material thermal insulation capability, and for structural fire design
purposes.
a
b
5.4 Adhesives
(1) Bulk material properties of adhesives used in 12.4 should be determined in accordance with the test
standards in Table 5.3.
Table 5.3 — Adhesive material properties
Property
Symbol
Standard test method
Tensile modulus
Et
EN ISO 527-2
Tensile strength
ft
EN ISO 527-2
Tensile stress at yield
f ty
Compressive modulus
Ec
Compressive strength
fc
Compressive stress at yield
Shear modulus
Maximum average shear stress
Glass transition temperature a
a
fcy
G
τ max
Tg
EN ISO 527-2
EN ISO 604
EN ISO 604
EN ISO 604
ISO 11003-2
ISO 11003-2
ISO 6721-11
The glass transition temperature is determined according to 5.1(1) and as illustrated in Figure 5.1.
NOTE 1 The characterization of the adhesives does not allow any conclusions to be drawn about the stiffness and
resistance of a bonded connection.
NOTE 2 Guidance for a design assisted by testing of adhesive joints and connections is provided in 12.4.5.2.
(2) For adhesively bonded connections designed based on fracture mechanics, the fracture mechanics
properties may be determined in accordance with 12.4.5.4.
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6 Durability
6.1 General
(1) Composite structures and their members and joints shall meet the requirements of serviceability and
ultimate limit states throughout their design service life, without significant loss of utility, with
anticipated maintenance but without major repair being necessary, in line with the general requirements
of EN 1990.
(2) The durability and the required protective systems for composite structures shall be established by
considering their intended use, direct and indirect actions, environmental conditions, design service life,
maintenance programme and actions.
NOTE Composite structures can present good weathering performance with reduced maintenance costs over
their design service live, provided that constituent materials, construction details, manufacturing process and
protective measures are appropriate.
(3) The following factors affecting the durability of composite structures and of their composite members
and joints (6.1(1)) should be considered during design:
—
polymer matrix: type of resin, additives and fillers;
—
fibre-matrix interphase: compatibility between embedded fibres and surrounding resin matrix, fibre
sizing;
—
—
—
—
—
—
—
fibres: types of fibre(s), fibre content and layup, including surface veil;
composite processing method (including temperature, moisture and consolidation pressure in
curing procedure), namely with respect to the degree of cure of the resin matrix, including postcuring procedures;
production quality of composite material and resulting defects (e.g. void content, fibre misalignment
and geometrical imperfections);
construction details;
installation and quality control;
special measures (e.g. application of a protective system);
maintenance and type of use over the design service life of the composite structure.
NOTE 1 Post-curing of composite components can improve their durability performance, thereby contributing to a
longer design service life.
NOTE 2 Dynamic Mechanical Analysis (DMA) in accordance with ISO 6721-11 provides a measure of the degree of
cure, through the relative ratio of the glass transition temperature (see 5.1(1) and Figure 5.1), obtained from two
consecutive DMA scans.
NOTE 3 Interlaminar shear strength (ILSS) of a composite material, determined in accordance with EN ISO 14130
(5.2.2), provides a measure of the quality of the fibre-matrix bond.
(4) The suitability of the polymer resin-based matrix constituents should be assessed in consultation with
the supplier(s), namely for particularly aggressive environmental conditions.
NOTE Depending on their nature and concentration, additives and fillers used in the resin matrix of composite
materials can negatively affect their durability.
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(5) The following factors affecting the durability of bonded connections between composite components
or between a composite component and a conventional structural material component (e.g. concrete,
steel) should be considered during design: the physical and mechanical properties of the adherends and
the adhesive, and the adhesive-adherend interface conditions (which depend on the procedures of
surface preparation, adhesive application and bond curing).
6.2 Environmental conditions
(1) In addition to mechanical actions, the environmental conditions to which composite structures can
be exposed to over the design service life shall be identified.
NOTE Environmental conditions are physical and chemical conditions, which are generally considered in terms
of their effects over time on the degradation of physical and/or mechanical properties. Environmental conditions
can also, at any time, impose indirect actions on composite structures (e.g. by way of thermal induced stresses or
swelling stresses owing to moisture uptake).
(2) The following environmental conditions should be considered acting separately (6.3) or in
combination (6.4):
—
temperature;
—
chemicals;
—
—
moisture (humidity, water);
ultraviolet (UV) radiation.
NOTE The effects of combined environmental conditions (e.g. temperature and moisture, chemicals and
temperature, freeze-thaw cycles, with or without UV radiation) can be worse for composite material durability than
the effects of those conditions acting in isolation.
(3) When appropriate, other environmental conditions not listed in 6.2(2), such as wear and impact,
should be considered in the design of composite structures, by means of appropriate construction
detailing and/or a protective system (e.g. foam filling the cavities of cellular sections, surface protection).
NOTE When composite materials are subjected to wear and impact loads, a variety of degradation mechanisms
potentially affect their physical and/or mechanical properties, including superficial crazing, cracking and
delamination. These mechanisms also promote increased propensity for moisture ingress into the bulk of composite
materials.
(4) The effects of different environmental conditions on composite components should be taken into
account as follows:
—
—
For specified composite materials and environmental conditions, the set of conversion factors
provided in 4.4.7 that take into account the effects of temperature and moisture should be used;
For other composite materials and/or other environmental conditions, including combined
environmental conditions (6.4) not covered in 4.4.7, material and product properties to be used in
design should be determined by testing, representative of the actual exposure conditions. In these
cases, resin and/or fibre suppliers and/or composite material manufacturers should be consulted.
(5) The effects of different environmental conditions and actions on bonded connections should be
considered. For cases not covered in 4.4.7, the durability of bonded joints may be determined by testing,
representative of the actual exposure conditions.
(6) If a protective system is applied to a composite structure for enhanced durability, the conversion
factors to be used in design may be different from those provided in 4.4.7.
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(7) If a protective system is applied to a composite structure for enhanced durability, the effects of
environmental conditions and mechanical actions on the protective system itself and on its compatibility
with the composite structure over the design service life should be considered.
NOTE The durability of protective systems applied on composite structures depends on periodic inspection,
maintenance and rehabilitation (if necessary) over the design service life.
6.3 Effects and measures for specific environmental conditions
6.3.1 Thermal effects
(1) The potential degradation of composite structures when subjected to the following thermal effects
shall be considered:
—
—
—
service temperature conditions (material temperatures higher than –40 °C and below Tg – 20 °C,
1.1(4));
thermal cycles;
freeze-thaw cycles (6.4).
NOTE 1 The exposure to material temperatures below -40 °C and the exposure to elevated material temperatures
(above Tg – 20 °C), including the exposure to fire (Annex D), are considered as accidental design situations.
NOTE 2 Exposure of composite materials, or polymeric cores or adhesives to temperatures approaching or
exceeding their Tg (5.1(1)) can result in significant reductions of their stiffness- and strength-related properties.
Such exposure can also result in an increase in their viscoelasticity and an increased creep rate.
NOTE 3 The reduction in mechanical properties of composite materials from exposure to elevated temperature is
mainly caused by the softening of the polymer resin matrix, due to the glass transition process. Hence, for a given
exposure temperature, the magnitude of this reduction depends on the materials’ Tg , with matrix-dominated
mechanical properties presenting higher reductions than fibre-dominated properties.
NOTE 4 The elastic modulus and strength of the fibres in composite materials decrease with temperature: carbon
and aramid fibres present, respectively, the lowest and the highest property change to elevated temperatures;
basalt fibres present better performance at elevated temperatures compared to glass fibres. For temperatures
below the Tg of the polymer resin matrix, the change in mechanical properties of the fibres is generally very limited.
NOTE 5 Exposure of composite materials to higher temperature during their service life can result in an increase in
mechanical properties due to post-curing.
NOTE 6 Frequent exposure of composite materials to significantly low sub-zero temperatures can cause matrix
hardening, matrix microcracking and degradation of the fibre-matrix bond.
NOTE 7 Exposure of composite materials to thermal cycles can affect the fibre-matrix bond owing to the mismatch
in the coefficients of thermal expansion of the fibres and the polymer-based matrix. The mismatch in the coefficients
of thermal expansion of the fibres and the polymer matrix can be one order of magnitude; therefore, under thermal
changes, thermal stresses develop at the fibre-matrix interphase.
(2) For applications where composite surfaces are exposed to direct sunlight, the influence of the surface
colour of the composite material on the temperature rise of the composite structure should be
considered. Whenever relevant, tests should be performed in accordance with EN 16245-2.
NOTE A dark coloured surface has a higher solar energy absorptance than a lighter coloured surface and this can
significantly increase the temperature in the material.
(3) For composite sandwich panels, in addition to the aspects mentioned in 6.3.1(1) and (2) for the
composite face sheets, thermal effects should be considered for:
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—
changes in core material mechanical properties (with a Tg that may be lower than that of the
—
the stability of the composite face sheets under compression and shear deformations when the core
material has softened;
—
composite material);
the thermal stresses induced by the differences in thermal expansion coefficients between the core
material and the composite face sheet material, which may cause changes in interfacial bond between
the composite face sheet material and the core material.
(4) For composite sandwich panels having an insulating core exposed to a heat source (e.g. natural
sunlight), the following thermally induced effects shall be taken into account:
—
an undesired curvature of the composite sandwich panel or, if prevented, internal stresses;
—
fatigue-induced damage under thermal cycles.
—
damage within the composite face sheet material or core material and/or at the composite face sheet
material-core material interface;
NOTE When composite sandwich panels having an insulating core (e.g. foam or balsa wood) are exposed to a heat
source, significant and non-linear through-thickness temperature gradients can develop.
6.3.2 Moisture
(1) The potential degradation of composite structures when subjected to moisture (from humidity or
water) shall be considered, namely regarding the possible effects on physical and/or mechanical
properties of constituent materials.
NOTE 1 When composite materials, polymeric cores or adhesives are exposed to moisture over time, there are a
variety of degradation mechanisms that can affect their physical and/or stiffness- and strength- related properties,
including: plasticization; hydrolysis; saponification, and swelling. The complexity of the hygrothermal ageing
process increases when the different mechanisms superimpose with different rates and initiation times.
NOTE 2 The reduction of stiffness and strength of composite materials from moisture absorption is generally a slow
process that depends on the factors referred in 6.1(3), which can be partly reversible and partly irreversible.
NOTE 3 The resistance to moisture of composite materials is mainly governed by the polymeric resin and its degree
of cure. A proper embedment in the resin isolates and protects the fibres and reduces the level of moisture induced
degradation of the fibres and the interphase.
NOTE 4 Isophthalic polyester, vinylester and epoxy polymer resins generally show good resistance to moisture. Of
these three resin types, the best durability performance is usually achieved with an epoxy and the worse with an
isophthalic polyester. Orthophthalic polyester normally presents worse durability performance than isophthalic
polyester.
NOTE 5 The effect of salt-water on the mechanical properties of composite materials is generally less severe than
that of fresh water.
(2) The permeability of composite materials to moisture may be decreased by either having a surface
with a resin-rich layer or surface veil (as with pultruded profiles), of appropriate thickness, and by
increasing the degree of resin cure by post-curing. For additional protection against moisture absorption,
a protective system may be applied (e.g. a gel coat or other protective surface coating).
(3) Composite structures permanently submerged in water should be prevented from direct contact with
moisture by means of a protective system (e.g. barrier coat, gel coat, or other protective surface coating,
see 4.4.7.3(2)).
(4) To minimise surface degradation in marine or moist environments, an anti-fouling coating should be
applied.
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NOTE 1 Exposure of composite surfaces to moisture can lead to the growth of algae (marine fouling) or fungi, which
can over time damage any protective coating.
NOTE 2 Regular surface cleaning can minimize surface degradation in marine or moist environments.
(5) To prevent environmental degradation, the exposed adhesive edges of adhesive connections and bolt
holes of bolted connections should be prevented from continuous contact with moisture through a
protective system (e.g. protective surface coating, edge and bolt hole protection).
NOTE The protection of cut edges prevents the wicking effect along more porous interfaces, particularly along the
fibres.
(6) In composite sandwich panels, the possible debonding between the core material and a composite
face sheet caused by moisture absorption over time shall be considered. Diffusion of moisture to the
inside of the core material shall be prevented by means of adequate materials selection (e.g. for the
composite face sheet permeability) and construction detailing (e.g. protection/covering of open/free
edges, sealing of holes).
(7) When composite structures are protected against the degradation effects of moisture, the durability
and effectiveness of the protective system itself shall be considered (see Note to 6.2(7)).
6.3.3 Chemicals
(1) The potential degradation of composite structures when subjected to contact with one or more
chemical environments shall be considered. In the absence of test results giving the level of composite
material degradation and changes in physical and/or mechanical properties from chemical exposure,
resin and/or fibre suppliers and/or composite material manufacturers should be consulted.
NOTE 1 Exposure of composite materials to one or more chemical environments can have a qualitatively similar
degradation effect to exposure to moisture (6.3.2). Depending on their nature (type of compound(s) and
concentration), over time chemical environments can degrade the resin matrix, the fibre-matrix interphase and the
reinforcing fibres.
NOTE 2 Carbon fibres normally are reasonably resistant to most chemical environments likely to be found in civil
engineering applications, including both acidic and basic chemical environments. E-glass fibres are susceptible to
degradation in both acidic and basic environments (improved performance can be achieved with ECR- and AR-glass
fibre types, respectively). Basalt fibres are susceptible to acidic and basic environments, presenting better
performance than E-glass fibres in basic environments. Aramid fibres are also susceptible to degradation when
subjected to chemical environments, especially of alkaline type.
(2) Changes in physical and/or mechanical properties of composite materials accounting for the effects
of a chemical environment over time should be determined from testing, representative of the actual
exposure conditions.
(3) The permeability of composite materials to a chemical solution may be reduced by having at the
surface a resin-rich layer or surface veil (as with pultruded profiles), of appropriate thickness, and by
increasing the degree of polymer resin cure by post-curing. For additional protection against chemicals,
a surface protective system should be applied (e.g. a gel coat or other protective surface coating); in these
cases, material suppliers should be consulted.
(4) When composite structures are protected against the degradation effects of chemicals, the durability
of the protective system itself shall be considered (see Note to 6.2(7)).
(5) For composite sandwich panels, the provisions in 6.3.2(6) shall be considered to prevent core-face
sheet debonding and diffusion of a chemical solution into the core material.
6.3.4 UV radiation
(1) The potential degradation of physical and/or mechanical properties, and functionality of composite
structures when subjected to UV radiation shall be considered.
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NOTE 1 UV-induced degradation of composite materials can involve the following sequence of mechanisms (which
depend on the polymer resin type): gloss loss; chalking and discoloration (yellowing) of the surface; flaking of
surface resin; pitting; microcracking; blistering; severe loss of resin from outer surface, with progressive exposure
of the topmost fibre layers (known as "fibre blooming", potentially affecting the functionality of composite
structures); delamination of topmost ply of fibres.
NOTE 2 The degradation in the aesthetical, physical and/or mechanical properties of composite materials due to
UV radiation is generally limited to the surface, depending on the factors referred in 6.1(3).
NOTE 3 The UV resistance of unsaturated polyester, epoxy and vinylester polymer resins is typically ranked as
good, poor and variable, respectively.
NOTE 4 Glass, carbon and basalt fibres typically exhibit good resistance to UV radiation, while aramid fibres are
susceptible to degradation from UV radiation, and so need to be protected from direct sun exposure.
NOTE 5 Core materials used in composite sandwich panels (including their edges) are normally enclosed by the
composite face sheets and therefore are not exposed to direct UV radiation.
(2) Composite structures exposed to direct UV radiation should be protected through the composite
material(s) either having a surface veil or appropriate additives (UV blockers/UV absorbers), and/or by
means of an additional surface protection (e.g. a gel coat or an appropriate paint), namely when UV
radiation is significant.
(3) When composite structures are protected against the degradation effects of UV radiation, the
durability of the protective system itself shall be considered (see Note to 6.2(7)).
NOTE
A polymer resin based protective coating is itself susceptible to UV radiation.
6.4 Effects of combined environmental conditions
(1) Because the effects of combined environmental conditions can be worse than their individual effects,
the degradation of composite structures that are subjected to combined environmental conditions shall
be considered.
NOTE 1 When composite materials are exposed to freeze-thaw cycles (the combined exposure to moisture and
thermal cycles), owing to cyclic expansion and contraction of entrapped water (phase change), the level of
composite material degradation can be higher compared to the same composite material in a dry state and
temperature variation.
NOTE 2 Exposure of composite materials to outdoor weathering over time can involve the combined effects of
moisture, thermal effects and UV radiation (e.g. exposure to UV radiation, followed by moisture ingress and freezethaw). Here, the most deleterious effect of UV radiation is not due to direct photolytic effects (limited to the surface
layer region, 6.3.4), but to the increased propensity for moisture ingress into the composite laminate. Superficial
crazing and cracking from UV radiation degradation can serve as sites for quicker moisture absorption and for
fracture initiation. After prolonged exposure, the composite material degradation can progress into the bulk,
reaching the fibre-matrix interphase, and so both physical and mechanical properties can exhibit more significant
detrimental changes.
(2) For composite structures subjected to combined environmental conditions not covered in 4.4.7,
material or product properties required for design should be determined by testing, representative of the
service conditions that the composite structures are subjected to, and accounting for the worse relevant
combination of environmental conditions (see 4.4.7.1(5)).
6.5 Measures for connections and joints
(1) Bolted connections, metal fasteners and metallic components shall, where necessary, either be
inherently corrosion-resistant or be protected against corrosion.
(2) When using metal fasteners with composite materials comprising carbon fibres, insulation protection
should be applied to prevent galvanic corrosion.
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(3) For bolted connections, the exposed edges of bolt holes should be properly sealed to prevent
continuous contact with moisture (6.3.2(5)).
(4) For adhesive or hybrid adhesive-bolted connections, the exposed surfaces of the adhesive should be
properly sealed to prevent the direct sorption of moisture (6.3.2(5)) and direct exposure to UV radiation.
7 Structural analysis
7.1 Structural modelling for analysis
7.1.1 General
(1) The purpose of structural analysis is to establish the distribution of either internal forces, or stresses,
strains and displacements, over the whole or part of a structure.
(2) Structural analysis shall be based upon calculation model(s) of the structure or parts thereof that are
appropriate for the limit state under consideration. The method of analysis used shall be consistent with
the design assumptions.
(3) The calculation models shall be suitable for the structural analysis of composite structures taking into
account:
— the composition and layup of the composite material, and its associated orthotropic properties;
— the typical linear elastic behaviour of the composite material;
— the occurrence of shear deformation in composite members;
— the temperature-dependence of mechanical properties, (i) by applying the relevant conversion
factors (4.4.7.2) that take into account the changes of material properties due to material
temperatures in service conditions deviating from 20 °C (1.1(4)), or (ii) by using experimentallyobtained temperature-dependent material properties for elevated temperature exposure;
— the effects of moisture on the mechanical properties, by applying the relevant conversion factors
(4.4.7.3);
— the time-dependent effects of composite material viscoelasticity (creep and/or relaxation) by using
the relevant creep coefficients (4.4.8) and strength reduction factors for creep rupture (8.5), or from
experimentally obtained time-dependent mechanical properties;
— the effects of residual stresses, geometrical imperfections (7.3) and pre-existing defects, isolated or
in combination;
— the deformation characteristics at the supports of the structure or parts thereof;
— the support conditions during installation of the structure or parts thereof;
— the fatigue and/or dynamic behaviour of the structure or parts thereof.
(4) The possible non-linear material behaviour of composite and core materials and adhesives should be
considered in the calculation models where relevant.
NOTE The non-linear response of core materials can reduce the wrinkling stress of sandwich face sheets, see
8.4.1(7).
(5) The non-linear behaviour and energy dissipation capacity of joints may be considered in the
structural analysis.
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(6) For seismic design, the structural analysis should take into account the typical linear elastic behaviour
of composite members.
(7) The material stiffness properties and relevant conversion factors to be used in structural analysis
should be appropriate to the considered design problem and should be selected considering the least
favourable situation for design, for both SLS (4.3.2 and 9) and ULS (4.3.2, 8 and Annex C). In the case of
hybrid composite members and sandwich panels, the distribution of stresses among the member
components for the ULS verifications should be calculated using the mean values of the material
properties.
NOTE The consideration of conversion factors can result in lower internal forces and stresses in the structural
analysis of imposed deformations (e.g. differential settlement of supports), and is not necessarily conservative for
the structural analysis of vibrations (see 9.1(2)).
7.1.2 Laminates
(1) Out-of-plane and interlaminar stresses should be appropriately taken into account in the structural
analysis of laminates.
NOTE The influence of shear on the deformation of laminates increases with the decrease in both the aspect ratio
(ratio between shortest surface dimension and thickness) and the ratio between the elastic and the shear modulus.
(2) Occurrence of coupling between internal normal forces and moments shall be taken into account.
7.1.3 Profiles
(1) The following aspects should be appropriately taken into account in the structural analysis of profiles:
— possible differences in material properties of the various section walls (8.3.1(2) and (3));
— local effects originated by, for example, the introduction of concentrated loads.
(2) In the analysis of structures made of profiles, their equivalent full-section elastic moduli (5.2.2(9))
may be considered, assuming an equivalent homogeneous behaviour.
NOTE EN 13706-2:2002, Annex G describes a test method to obtain the effective full section elastic moduli of
composite profiles.
(3) In the analysis of structures made of built-up members (see Note 4 to 1.1(5)), the composite action at
the various interfaces should be appropriately taken into account.
7.1.4 Sandwich panels
7.1.4.1
General
(1) This subclause applies to plane or curved sandwich panels of constant or variable thickness and
symmetric cross section consisting of:
— identical, balanced and symmetric composite laminates for the two face sheets, which are considered
to be thin;
— either a rigid or flexible homogeneous core or a rigid and non-homogeneous web-core comprising
composite webs of balanced symmetric laminates, with or without core infill between the webs
(Figure 3.4).
NOTE 1 Sandwich panels which do not fulfil these conditions can be modelled and analysed according to 7.4.3.4.
NOTE 2 Definitions for thin and thick face sheets are given in 7.1.4.1(4).
NOTE 3 Definitions for flexible and rigid cores are given in 7.1.4.1(5).
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(2) The following aspects should be taken into account in the structural analysis of sandwich panels:
— anisotropy and non-linearity of the core;
— shear deformation in the core;
— for low-stiffness cores, change in core thickness due to out-of-plane compression;
— out-of-plane normal stresses for curved sandwich panels, especially for small radii of curvature;
— local effects on the sandwich panel or its components originated by, for example, the introduction of
concentrated loads, joints and connections between sandwich panels and components, and face sheet
or core discontinuities.
(3) The theoretical models of 7.1.4.1 may be applied for preliminary analyses using mean and average
(tension-compression) values of stiffness properties. If the models are applied for ULS and SLS
verifications, appropriate (mean, characteristic, design, tension or compression) values of flexural and
shear stiffness (including conversion factors) should be selected.
NOTE 1 The theoretical models of 7.1.4.1 assume pristine constituents, perfect face sheet/core adhesion and adopt
simplified elastic approaches. Non-linear behaviours due to material non-linearity or geometrical imperfections are
not taken into account in these models.
NOTE 2 Definitions for flexural stiffness of homogeneous core and web-core sandwich panels are given in 7.1.4.1(6)
and 7.1.4.1(7), respectively.
NOTE 3 Definitions for shear stiffness of homogeneous core and web-core sandwich panels are given in 7.1.4.1(8).
(4) The face sheets should be considered "thin" if 2Df D0 < 0,01, i.e.:
d
> 5,8
tf
If Formula (7.1) is not satisfied, the face sheets should be considered "thick".
(5) The core should be considered "flexible" if Dc D0 < 0,01, i.e.:
6 ⋅ (ηc )f ⋅ E f ⋅ t f ⋅ d 2
> 100
(ηc )c ⋅ E c ⋅ t c3
for a homogeneous core. If Formula (7.2) is not satisfied, the core should be considered "rigid".
NOTE
(7.1)
(7.2)
For a sandwich section with a web-core (ηc )c ⋅ Ec can be replaced by Ec* from 7.1.4.1(7), Formula (7.7).
(6) The flexural stiffness per unit width, D , of a symmetric sandwich of constant thickness with
homogeneous core (Figure 7.1a) should be determined from Formula (7.3):
D = 2Df + D0 + Dc
where
Df
(7.3)
is the flexural stiffness per unit width of each face sheet about its own neutral axis, given by
Formula (7.4),
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Df =
(ηc )f ⋅ E f ⋅ t f3
12
(7.4)
(ηc )f ⋅ E f ⋅ t f ⋅ d 2
2
(7.5)
(ηc )c ⋅ E c ⋅ t c3
12
(7.6)
D0
D0 =
Dc
Dc =
where
is the flexural stiffness per unit width of the face sheets about the neutral axis of the
sandwich section, given by Formula (7.5),
is the flexural stiffness per unit width of the core about its own neutral axis, which is
coincident with the neutral axis of the sandwich section, given by Formula (7.6),
Ef
is the elastic modulus of each face sheet;
(ηc )f
is defined in 4.4.7 (to be selected for E f );
Ec
(ηc )c
d
tf
is the elastic modulus of the core or core infill (web-core sandwich);
is defined in 4.4.7 (to be selected for E c );
is the distance between the centroid axes of the face sheets;
is the thickness of each face sheet;
tc
is the thickness of the core.
(7) The flexural stiffness per unit width, D* , of a symmetrical web-core sandwich of constant thickness with
homogeneous core infill (Figure 7.1b) should be calculated according to 7.1.4.1(6), replacing (ηc )c ⋅ E c by
the elastic modulus of the equivalent homogeneous core, Ec* (which includes the conversion factors), given
by Formula (7.7):
E c* =
where
t w ⋅ (ηc )w ⋅ E w + b c ⋅ (ηc )c ⋅ E c
b
Ew
(ηc )w
bc
b
tw
76
is the elastic modulus of the web;
is defined in 4.4.7 (to be selected for E w );
is the core infill width between the webs;
is the web spacing;
is the web thickness.
(7.7)
CEN/TS 19101:2022 (E)
a) Homogeneous-core sandwich
b) Web-core sandwich
Figure 7.1 — Cross-sectional geometry of sandwich panels
(8) The shear stiffness per unit width, S , of a symmetric sandwich section with homogeneous core and
thin face sheets should be determined from Formula (7.8):
S= G ⋅
where
G
d2
tc
(7.8)
is the shear modulus of the sandwich core, given by Formulae (7.9) and (7.10),
— for a flexible core:
=
G (ηc )c ⋅ Gc
— for a rigid core:
G=
where
(ηc )c ⋅ Gc
(ηc )c ⋅ E c ⋅ t c2
1+
6 ⋅ (ηc )f ⋅ E f ⋅ t f ⋅ d
Gc
(7.9)
(7.10)
is the shear modulus of the homogeneous core.
NOTE In the case of a web-core sandwich, the shear stiffness corresponds to the shear stiffness of the webs; their
shear area can be calculated according to Table 8.1.
(9) When face sheets are thin, the bending, shear and axial stress distributions in a homogeneous core
sandwich of constant thickness, subjected to a bending moment M , a shear force V and an axial force N , may
be approximated as having the profiles illustrated in Figures 7.2 (rigid core) and 7.3 (flexible core). Stresses
for the case of a single M (not biaxial case) may be calculated using the formulae in Table 7.1.
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a) Bending stress distribution
b) Shear stress distribution
c) Axial stress distribution
a) Bending stress distribution
b) Shear stress distribution
c) Axial stress distribution
Figure 7.2 — Stress distributions in homogeneous core sandwiches with thin face sheets and
rigid core
Figure 7.3 — Stress distributions in homogeneous core sandwiches with thin face sheets and
flexible core
Table 7.1 — Bending, shear and axial stresses in a homogeneous core sandwich section with thin
face sheets and a rigid or flexible core
Stress component
Bending stress b
Rigid core a
σ f(M) = ±
(σ )
(M)
c
max
Shear stress =
(τ c )max
Axial stress b
=±
M ⋅ t c ⋅ (ηc )c ⋅ E c
2D
V  (ηc )f ⋅ E f ⋅ t f ⋅ d (ηc )c ⋅ E c ⋅ t c2 
+


D
2
8

σ (f N ) =
σ c(N) =
N ⋅(ηc )f ⋅ E f
2t f ⋅(ηc )f ⋅ E f + t c ⋅(ηc )c ⋅ E c
N ⋅ (ηc )c ⋅ E c
2t f ⋅ (ηc )f ⋅ E f + t c ⋅ (ηc )c ⋅ E c
M , V and N values per unit width.
NOTE
M ⋅ d ⋅ (ηc )f ⋅ E f
2D
Flexible core a
σ f(M) = ±
M
tf ⋅ d
σ c(M) = 0
τc =
σ f(N) =
V
d
N
2t f
σ c(N) = 0
The formulae given in Table 7.1 are not applicable in the vicinity of openings or other discontinuities.
a If stresses, caused by the Poisson effect, exist in directions other than that of M or N stresses, they should
be taken into account.
b The sign of bending and axial stresses (positive for tension, negative for compression) shall be taken into account.
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(10) Bending and shear stress distributions in a web-core sandwich of constant thickness may be
obtained from 7.1.4.1(9) by replacing (ηc )c ⋅ E c with Ec* , from 7.1.4.1(7). This procedure yields stresses in
an equivalent homogeneous core, which should be transformed to obtain the actual stresses in the web
and core infill.
(11) Stresses in the out-of-plane (z) direction shall be taken into account when the sandwich panel has
curvature. The sandwich construction and the core material shall provide sufficient out-of-plane (also
referred to as flatwise) tensile and compressive resistances.
(12) When the face sheets are thick, the stress distribution within the sandwich section should be
determined using finite element analysis.
7.1.4.2
Face sheets
(1) A face sheet shall have sufficient strength and stiffness to resist the in-plane tension and compression
stresses and to resist the wrinkling failure mode.
(2) For a face sheet with a sharp change of direction, concentrated deviation stresses occur at the location
of the directional change; at these locations web components may be introduced into the core to resist
the deviation stresses.
7.1.4.3
Core
(1) The core shall be sufficiently stiff under shear and out-of-plane (z direction) forces to provide
sufficient composite action with the face sheets, to minimize the change in the sandwich thickness (and
thereby its flexural stiffness), and to avoid wrinkling of the face sheets.
(2) The stress state in the vicinity of inserts, i.e. associated stress concentrations, should be verified.
(3) To introduce concentrated loads, e.g. at supports, the core should be locally reinforced by inserting
either solid webs, or composite profiles, or a higher-strength core material to avoid failure by local
indentation.
(4) The orientation of an anisotropic core material in a composite sandwich panel should be selected to
account for the directions and magnitudes of the internal forces.
7.1.5 Joints
(1) Where the effects of the behaviour of the joints on the distribution of internal forces and moments
within a structure, and on the overall deformations of the structure, are significant, they should be taken
into account.
(2) To identify whether the effects of joint behaviour need to be taken into account in the structural
analysis, a distinction should be made between three joint models, as follows:
— simple joints, in which the joint does not transmit bending moments;
— continuous joints, in which the joint does not allow any relative rotation between connected
members, and hence the joint behaviour has no effect on the analysis;
— semi-continuous joints, in which the joint allows relative rotation and bending moment transfer
between connected members, and hence the behaviour of the joint should be taken into account in
the analysis.
NOTE
Provisions for the various types of joints are given in Clause 12.
(3) Bolted joints may be regarded as either simple or semi-continuous.
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NOTE Semi-continuous bolted joints can exhibit pseudo-ductile behaviour and cause an associated redistribution
of internal forces in the case of pin-bearing failure (12.2.3.2).
(4) For bolted joints, the force at every bolt in a group of bolts forming a bolted connection should be
established taking into account the elastic stiffnesses of the material(s).
(5) Bonded joints may be regarded as continuous or semi-continuous depending on the relative in-plane
stiffness of the adhesive layer.
NOTE Semi-continuous bonded joints can exhibit pseudo-ductile behaviour and cause an associated
redistribution of internal forces, depending on the non-linear constitutive behaviour of the adhesive and the
thickness of the adhesive layer.
7.1.6 Hybrid-composite structures
(1) In hybrid-composite structures, the composite action between composite members or components
and members or components of other materials should be appropriately taken into account.
NOTE 1 In hybrid-composite bridge superstructures, for instance, consisting of composite decks adhesively bonded
or mechanically fastened to steel or concrete girders, the composite decks can act as top chords of the girders. The
top chord contribution depends on the composite decks’ in-plane relative stiffness (with respect to that of the
girders), the through thickness shear stiffness of the deck cores, and the shear (slip) stiffness of the deck-to-girder
connections. Stress distributions in composite decks and steel or concrete girders and deflections of hybrid
structures can be obtained by applying the simplified analysis described in EN 1995-1-1, Annex B, using the slip
modulus, K . In the case of adhesively bonded joints, the ratio between the adhesive layer shear modulus and
thickness can be used for the slip modulus.
NOTE 2 The combination of composite members with members of ductile materials (e.g. steel) and/or ductile joints
in hybrid-composite structures can provide ductility to the hybrid-composite system and thus compensate for the
composite material brittleness.
7.2 Global analysis
7.2.1 General
(1) Analysis of structural response should be carried out taking into account linear elastic behaviour up
to failure, unless otherwise required due to geometrical and/or material non-linearities (7.4.1(3)).
(2) The internal forces and moments, and the stress distributions within a member, component, or joint
should be determined through a global analysis of the structure, considering, when relevant, the
deformability of the joints.
7.2.2 Consideration of second-order effects
(1) The internal forces and moments, and the stress distributions within a member, component, or joint
may generally be determined using either:
— first-order analysis, based on the initial geometry of the structure, or
— second-order analysis, taking into account the influence of the deformation of the structure, with
consideration of imperfections.
(2) The effects of the deformed geometry (second-order effects) should be taken into account in the
analysis if they increase the action effects significantly or modify significantly the structural behaviour.
(3) The second-order effects due to global (sway) buckling (Figure 7.4) may be neglected for the global
analysis if the condition in Formula (7.11) is satisfied:
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α cr,sw =
where
α cr,sw
FEd
Fcr,sw
Fcr,sw
FEd
≥ 10
(7.11)
is the factor by which the design load would have to be increased to cause elastic
instability of the structure in a global in-plane (sway) mode;
is the design load on the structure;
is the elastic critical in-plane flexural buckling load for global (sway) buckling mode
(determined from elastic buckling analysis).
NOTE For frames, buckling modes can be classified as sway or non-sway. Sway modes are characterized by
significant relative displacements of the vertical member ends, in the plane of a frame of members (Figure 7.4).
Figure 7.4 — Frame with a global buckling mode (sway)
7.2.3 Methods of analysis for ultimate limit states design
(1) The method of analysis (first- or second-order analysis combined with consideration of
imperfections) should be compatible with the cross-section and member verification requirements in
Clause 8.
(2) According to the type of composite structure and the extent of the global analysis, imperfections and
second-order effects should be considered using one of the following approaches:
—
—
entirely in the global analysis;
partially in the global analysis and partially by verification of the elastic buckling resistance of
individual members in accordance with 8.2 to 8.4.
(3) Second-order effects may be calculated by using an analysis appropriate to the structure (including
incremental and iterative procedures). For frames where the first sway buckling mode is predominant,
first-order linear elastic analysis may be carried out with subsequent amplification of relevant action
effects (e.g. bending moments) by appropriate factors.
(4) For single storey frames designed on the basis of linear elastic global analysis, second-order sway
effects due to vertical loads may be calculated approximately from a first-order theory, by increasing the
horizontal forces (e.g. horizontal action of wind) and equivalent forces due to imperfections and other
possible sway effects by the factor:
ksw =
α cr,sw
α cr,sw − 1
(7.12)
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provided that α cr,sw ≥ 3,0 , where α cr,sw may be calculated according to Formula (7.11). If α cr,sw < 3,0 , a
more accurate second-order analysis should be conducted.
(5) For multi-storey frames, second-order sway effects may be calculated by means of the method given
in 7.2.3(4) provided that all storeys have a similar distribution of (i) vertical loads, (ii) horizontal loads
and (iii) frame stiffness with respect to the applied storey shear forces.
7.3 Imperfections
7.3.1 Basis
(1) Appropriate allowances should be considered in the structural analysis to cover the effects of
imperfections.
NOTE Imperfections include geometrical imperfections, such as out-of-straightness, misalignment, unevenness,
inaccuracies of fit in the area of joints and connections and eccentricities, and effects such as residual stresses due
to curing.
(2) Equivalent geometrical imperfections should be used with values that reflect the possible effects of
all types of imperfections, unless these effects are included in the resistance formulae for member design
(7.3.3(4)).
(3) The following imperfections should be taken into account as relevant:
— global (sway) imperfections for analysis of frames;
— bow and other local imperfections for member analysis.
(4) In the case of sandwich panels, the following potential local imperfections should also be considered:
non-parallel face sheets, face sheet waviness and joint eccentricities.
(5) The effects of global and local imperfections shall be taken into account if their presence results in
geometrical non-linearities, out-of-plane stresses or, in the case of sandwich sections, if they increase face
sheet or core stresses.
(6) Both in-plane and out-of-plane elastic buckling, including torsional buckling, should be taken into
account in the most unfavourable mode.
(7) The assumed shape of sway and bow imperfections may be derived from the linear elastic buckling
modes of a structure or part thereof in the plane of instability considered.
(8) Imperfections may be neglected for SLS design.
7.3.2 Sway imperfections for global analysis of frames
(1) For frames that are susceptible to buckling in a sway mode, the effect of imperfections should be taken
into account in the frame analysis by means of an equivalent initial sway imperfection, φ (Figure 7.5).
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Figure 7.5 — Equivalent initial sway imperfection
(2) The equivalent initial sway imperfection, φ , may be determined from Formula (7.13):
φ =φ0 ⋅α h ⋅ α m
where
φ0
αh
h
αm
(7.13)
is the basic value, equal to 1/200;
is the reduction factor for length or height (in metres), where the following applies:
αh =
2
h
and
α h ≤ 1,0 ;
is the height of the structure (in metres);
is the reduction factor for the number of columns in a row,
αm
=
m
1

0,5  1 + 
m

is the number of columns in a row including only those columns which carry a vertical
load NEd not less than 50% of the average value of all the columns in the vertical plane
considered.
(3) The initial sway imperfection φ should apply in all relevant horizontal directions in one planar
direction at a time.
(4) For frames, sway imperfections may be disregarded if Formula (7.14) is satisfied:
HEd ≥ 0,15 ⋅ VEd
where
HEd
VEd
(7.14)
is the total design horizontal load, including equivalent forces (see 7.3.2(5) and (6)),
transmitted from the floor (storey shear);
is the total design vertical load, transmitted from the floor (storey thrust).
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(5) For the determination of horizontal forces applying to the supporting system (such as floor
diaphragms), Hi , the configuration of imperfections as illustrated in Figure 7.6 may be applied, where φ
is a sway imperfection determined from Formula (7.13), assuming a single storey height h .
Figure 7.6 — Configuration of sway imperfections for horizontal forces on floor diaphragms
(6) The effects of the initial sway imperfections may be taken into account by systems of equivalent
horizontal forces, in accordance with Figure 7.7.
Figure 7.7 — Replacement of the initial sway imperfections by equivalent horizontal forces
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7.3.3 Bow and local imperfections for member analysis
(1) The effects of bow and other local geometrical imperfections, including pre-existing defects, shall be
considered in a structural analysis of a member if they result in significant geometrical non-linear effects.
NOTE Such effects are considered significant if the internal forces and moments or stresses induced by the least
favourable imperfections are more than 10% of those resulting from the design loads on the member without
imperfections.
(2) The effects of pre-existing manufacturing defects in structural analysis may be assessed in the
modelling by introducing artificial defects placed in critical locations (e.g. in compressed sandwich face
sheets or joints).
(3) The maximum admissible size of the actual defect may be estimated by using finite element analysis
and taking into account material strength. If the size is smaller than the minimum size detectable using
an appropriate inspection method, a more refined numerical analysis using fracture mechanics should be
performed.
(4) Bow and other local geometrical imperfections shall be determined in accordance with the tolerances
stated by the manufacturer.
NOTE 1 For pultruded composite profiles, EN 13706-2 defines indicative values of geometrical tolerances.
NOTE 2 For laminates and profiles, the effects of bow and other local geometrical imperfections are included in the
formulae for buckling resistance given in 8.2 and 8.3, respectively, and C.5 (for profiles).
NOTE 3 The formulae for buckling resistance given in Annex C do not take into account potential creep effects on
imperfections.
(5) For sandwich panels, the effects of local geometrical imperfections are included in the formulae for
wrinkling resistance given in 8.4.
(6) For the analysis of a member subjected to compression, bow imperfections may be considered in the
form of an initial bow imperfection, e0,d , with the corresponding system of equivalent forces, in
accordance with Figure 7.8.
Figure 7.8 — Replacement of the initial bow imperfections by equivalent horizontal forces
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(7) When relevant, the effects of creep on the amplification of bow and other local imperfections should
be taken into account in the design, namely by considering the additional bending moments.
7.4 Methods of analysis
7.4.1 General
(1) Composite structures may be analysed by applying either analytical or finite element modelling
approaches.
(2) Structural analysis may be performed using linear elastic methods.
(3) Non-linear methods of analysis taking into account geometrical, contact and material non-linearities
may provide a more reliable modelling of the structural behaviour and should be used in the following
cases:
— the deformations of the structure significantly affect the distribution of internal forces and moments
(7.2.3);
— materials with non-linear behaviour are used and stressed beyond their proportional limit;
— non-linear or changing boundary conditions apply.
(4) When finite element analysis is performed, an appropriate failure criterion should be used.
(5) For the analysis of local effects, detailed local finite element modelling should be performed.
7.4.2 Analytical models
7.4.2.1
General
(1) When using analytical models, the assumptions and modelling approach shall be conservative, namely
regarding the definition of material properties, boundary conditions and actions.
7.4.2.2
Laminates
(1) The analysis of thick laminates (7.1.2(1)) should be made by applying the Mindlin plate theory to
include the effects of shear deformation.
(2) The analysis of thin laminates may be made applying the Love-Kirchhoff plate theory, neglecting the
effects of shear deformation.
7.4.2.3
Profiles
(1) The analysis of structures made of profiles should be made applying the Timoshenko beam theory to
include the effects of shear deformation.
7.4.2.4
Sandwich panels
(1) Structural analysis of symmetric sandwich beams with homogeneous, incompressible core and thin
face sheets may be conducted using first-order shear deformation beam theory (e.g. Timoshenko beam
theory). To take into account the out-of-plane compressibility of the core, relevant high-order shear
deformation theories should be applied.
(2) For sandwich members subjected to cylindrical bending, beam theory may be applied by using an
apparent elastic modulus of the sandwich section to take into account the Poisson effect.
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7.4.3 Finite element models
7.4.3.1
General
(1) Results obtained from finite element models should be verified and validated by comparing the
numerical results with relevant and reliable analytical results, and/or experimental data, and/or other
finite element results.
NOTE Verification and validation of finite element models can be done following equivalent procedures according
to prEN 1993-1-14:— 4, Clause 7, taking into account the specific material characteristics of composite materials.
(2) The finite element type shall be chosen according to the type of composite component and/or the
type of structure being modelled.
(3) Appropriately refined meshes should be used in areas with high stress or strain gradients.
(4) Modelling of boundary conditions at structural supports should be consistent with the construction
details and construction stages of the structure.
7.4.3.2
Laminates
(1) Laminates may be modelled by flat or curved 2D or 3D finite elements depending on their geometry.
(2) When modelling at laminate level with non-layered 2D or 3D finite elements, any differences in the
values of axial stiffness and bending stiffness should be accounted for in the structural analysis.
7.4.3.3
Profiles
(1) Profiles used as beams and columns may be modelled using one-dimensional (1D) finite elements.
(2) Shell (2D) and solid (3D) finite elements should be used to analyse local effects (e.g. effects of
concentrated loads, web crippling due to transverse loads).
(3) For buckling analysis of profiles, shell finite elements should be used.
7.4.3.4
Sandwich panels
(1) Sandwich panels should be modelled by using: (i) appropriate shell and/or solid finite elements to
separately model the face sheets and the core component; or (ii) specific layered sandwich finite
elements. 2D finite element analysis may be performed if either plane stress or plane strain conditions
apply, otherwise, a 3D finite element analysis should be performed.
(2) Face sheets comprising a symmetric and balanced laminate may be modelled as a single layer with
orthotropic elastic properties.
(3) The modelling methodology should allow the stresses in the core and in the face sheets to be evaluated
separately.
(4) For global structural analyses, the finite element modelling should take into account (i) the shear
strain distribution across the core thickness (uniform/non-uniform for flexible/rigid cores, respectively);
(ii) the out-of-plane compressibility of low-stiffness cores; and (iii) out-of-plane stresses in curved
sandwich panels.
(5) For structural analysis of local effects, the finite element modelling should take into account local
flexure of the face sheets, i.e. the non-uniform distribution of axial stresses through the face sheet
thickness.
4
Under preparation.
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8 Ultimate limit states
8.1 General
(1) Clause 8 includes the ultimate limit states (ULS) verifications for the following types of composite
components and members:
— laminates (8.2);
— profiles (8.3);
— sandwich panels (8.4).
NOTE Figures 3.2, 3.3 and 3.4 provide the conventions for the coordinate axes for laminates, profiles and
sandwich panels, respectively.
(2) Clause 8 includes also ULS verifications for creep rupture (8.5).
(3) The ULS verifications shall be made according to the provisions given in this clause and the additional
provisions given in Annex C for the elastic buckling resistances of orthotropic laminates and profiles.
(4) The ULS verifications in 8.2 to 8.4 shall be made using the design values of resistance as defined in
4.4.4(1) and (2), considering the partial factor γ m as defined in 4.4.5, the partial factor γ Rd as defined in
4.4.6, and the conversion factor ηc as defined in 4.4.7.
(5) The ULS verification in 8.5 shall be made using the design values of resistance as defined in 4.4.4(3),
considering the partial factor for creep rupture γ M,creep as defined in 8.5, and the conversion factor ηc as
defined in 4.4.7.
(6) Whenever relevant, the creep effects on the deformations of composite structures should be
considered in stability verifications (Clause 8), namely when they increase significantly the eccentricities
of quasi-permanent loads (second-order effects).
8.2 Ultimate limit states of laminates
8.2.1 General
(1) Balanced symmetrical laminates shall be verified following the rules given in this subclause, unless
specified otherwise.
(2) Unbalanced and/or non-symmetrical laminates shall be verified by testing, or by numerical modelling
(at ply or laminate levels) verified by testing.
NOTE
Guidance on design assisted by testing is provided in EN 1990:—,Annex D.
(3) Significant stiffness variations through the laminate thickness, caused by considerably varying ply
thicknesses, large fibre angles or different fibre materials, should be minimized in order to not reduce the
interlaminar shear strength.
(4) The effects of stress concentrations from holes, openings and other details shall be taken into account
when determining the laminate resistance.
(5) The effects of geometrical imperfections in the buckling resistance of laminates may be taken into
account by numerical modelling.
(6) The elastic critical buckling stresses of balanced symmetrical laminates may be estimated using the
formulae given in subclause C.4, which are applicable to geometrically perfect laminates, and refer to
specific boundary conditions and loading cases.
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CEN/TS 19101:2022 (E)
(7) For boundary conditions and loading cases not scoped in subclause C.4, the elastic critical buckling
stresses of balanced symmetrical laminates may be estimated by numerical modelling, which should be
verified by testing.
8.2.2 In-plane axial stresses
8.2.2.1
In-plane axial tensile stresses
(1) The design value of the in-plane axial tensile stress in the i direction, σ i ,t,Ed , at each section of the
laminate, shall satisfy the condition in Formula (8.1):
σ i ,t,Ed ≤ fi ,t,d
where
i
is either for the x or y direction of the laminate;
fi ,t,d
=
fi ,t,d
where
(8.1)
is the design value of the tensile strength in the i direction of the laminate, given by
Formula (8.2),
ηc
⋅f
γ m ⋅ γ Rd i ,t,k
γm
is defined in 4.4.5 (to be selected for f x,t,k or f y,t,k );
ηc
is defined in 4.4.7 (to be selected for f x,t,k or f y,t,k );
γ Rd
is defined in 4.4.6 (Table 4.3, Material failure);
fi ,t,k
8.2.2.2
(8.2)
is the characteristic value of the tensile strength in the i direction of the laminate.
In-plane axial compressive stresses
(1) The design value of the axial compressive stress in the i direction, σ i ,c,Ed , at each section of the
laminate, shall satisfy the condition in Formula (8.3):
σ i ,c,Ed ≤ min { fi ,c,d ; fi ,cr,d }
where
i
fi ,c,d
fi ,cr,d
(8.3)
is either for the x or y direction of the laminate;
is the design value of the compressive strength in the i direction of the laminate;
is the design value of the critical buckling compressive stress in the i direction of the
laminate under uniform compression.
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CEN/TS 19101:2022 (E)
(2) The design value of the compressive strength in the i direction of the laminate, fi ,c,d , should be
determined from Formula (8.4):
=
fi ,c,d
where
ηc
⋅f
γ m ⋅ γ Rd i ,c,k
γm
is defined in 4.4.5 (to be selected for f x,c,k or f y,c,k );
ηc
is defined in 4.4.7 (to be selected for f x,c,k or f y,c,k );
γ Rd
fi ,c,k
(8.4)
is defined in 4.4.6 (Table 4.3, Material failure);
is the characteristic value of the compressive strength in the i direction of the laminate.
(3) The design value of the critical buckling compressive stress in the i direction of the laminate under
uniform compression, fi ,cr,d , should be determined from Formula (8.5):
fi ,cr,d
=
where
γm
γ Rd
fi ,cr,k
1
⋅χ ⋅ f
γ m ⋅ γ Rd i ,c i ,cr,k
(8.5)
is defined in 4.4.5 (to be selected for E i ,c,k , the characteristic value of the in-plane
compressive modulus in the i direction, except for laminates with free-simply supported
edges, for which Gxy,k , the characteristic value of the in-plane shear modulus, should be
considered instead);
is defined in 4.4.6 (Table 4.3, Local buckling);
is the characteristic value of the critical buckling compressive stress in the i direction,
obtained as in C.4.2.1 for flat laminates, and considering the appropriate values of the
conversion factor, ηc , for the relevant material properties (defined in 4.4.7);
is the buckling reduction factor for compression in the i direction to take into account
the effect of imperfections in elastic post-buckling regime.
(4) For flat laminates (for which χ i ,c ≥ 1,0 ), χ i ,c may be conservatively taken as 1,0. For curved laminates
χ i ,c
(for which χ i ,c < 1,0 ), the values of fi ,cr,k and χ i ,c should be determined by testing, and/or by numerical
modelling, which should be verified by testing.
NOTE 1 The elastic local post-buckling behaviour of flat laminates is stable and imperfections do not reduce the
elastic resistance below the critical buckling compressive stress; thus, for flat laminates, χ i ,c ≥ 1,0 . The elastic local
post-buckling behaviour of curved laminates is unstable and imperfections reduce the elastic resistance below the
critical buckling compressive stress; curved laminates are imperfection sensitive and thus χ i ,c < 1,0 .
NOTE 2 Guidance on design assisted by testing is provided in EN 1990:—, Annex D.
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CEN/TS 19101:2022 (E)
8.2.3 In-plane shear stresses
(1) The design value of the in-plane shear stress, τ xy,Ed , at each section of the laminate, shall satisfy the
condition in Formula (8.6):
τ xy,Ed ≤ min { f xy,v,d ; f xy,cr,d }
where
f xy,v,d
f xy,cr,d
(8.6)
is the design value of the in-plane shear strength of the laminate;
is the design value of the critical buckling shear stress of the laminate under in-plane
shear loading.
(2) The design value of the in-plane shear strength of the laminate, f xy,v,d , should be determined from
Formula (8.7):
=
f xy,v,d
where
ηc
⋅f
γ m ⋅ γ Rd xy,v,k
γm
is defined in 4.4.5 (to be selected for f xy,v,k );
ηc
is defined in 4.4.7 (to be selected for f xy,v,k );
γ Rd
(8.7)
is defined in 4.4.6 (Table 4.3, Material failure);
f xy,v,k
is the characteristic value of the in-plane shear strength of the laminate, considering the
appropriate values of the conversion factor, ηc , for the relevant material properties
(defined in 4.4.7).
(3) The design value of the critical buckling shear stress of the laminate under in-plane shear loading,
f xy,cr,d , should be determined from Formula (8.8):
=
f xy,cr,d
where
1
⋅χ ⋅ f
γ m ⋅ γ Rd v xy,cr,k
γm
γ Rd
f xy,cr,k
χv
(8.8)
is defined in 4.4.5 (to be selected for E y,c,k , the characteristic value of the in-plane
compressive modulus in the y direction);
is defined in 4.4.6 (Table 4.3, Local buckling);
is the characteristic value of the critical buckling shear stress of the laminate under inplane shear loading, obtained as in C.4.2.2 for flat laminates, and considering the
appropriate values of the conversion factor, ηc , for the relevant material properties
(defined in 4.4.7);
is the buckling reduction factor for in-plane shear to take into account the effect of
imperfections in elastic post-buckling regime.
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CEN/TS 19101:2022 (E)
(4) For flat laminates (for which χ v ≥ 1,0 ), χ v may be conservatively taken as 1,0. For curved laminates
(for which χ v < 1,0 ), the values of f xy,cr,k and χ v should be determined by testing, and/or by numerical
modelling, which should be verified by testing.
NOTE 1 The rationale for the values of χ v to be used in Formula (8.8) are given in the Note 1 to 8.2.2.2(4).
NOTE 2 Guidance on design assisted by testing is provided in EN 1990: —, Annex D.
8.2.4 In-plane bending stresses
(1) The design value of the in-plane bending stress in the i direction, σ i ,b,Ed , at each section of the
laminate, shall satisfy the condition in Formula (8.9):
σ i ,b,Ed ≤ min { fi ,b,d ; fi ,b,cr,d }
where
i
fi ,b,d
(8.9)
is either for the x or y direction of the laminate;
fi ,b,cr,d
is the design value of the in-plane bending strength in the i direction of the laminate;
is the design value of the critical buckling bending stress in the i direction of the laminate
under in-plane bending.
(2) The design value of the in-plane bending strength in the i direction of the laminate, fi ,b,d , should be
determined from Formula (8.10):
 η

ηc
fi ,b,d = min  c ⋅ fi ,t,k ;
⋅ fi ,c,k 
γ m ⋅ γ Rd
 γ m ⋅ γ Rd

where
i
(8.10)
is either for the x or y direction of the laminate;
γm
is defined in 4.4.5 (to be selected for fi ,t,k or fi ,c,k );
ηc
is defined in 4.4.7 (to be selected for fi ,t,k or fi ,c,k );
fi ,c,k
is the characteristic value of the compressive strength in the i direction of the laminate.
γ Rd
fi ,t,k
is defined in 4.4.6 (Table 4.3, Material failure);
is the characteristic value of the tensile strength in the i direction of the laminate;
(3) The design value of the critical buckling bending stress in the i direction of the laminate under inplane bending, fi ,b,cr,d , should be determined from Formula (8.11):
fi ,b,cr,d
=
where
92
1
⋅χ ⋅ f
γ m ⋅ γ Rd i ,b i ,b,cr,k
(8.11)
CEN/TS 19101:2022 (E)
γm
is defined in 4.4.5 (to be selected for E i ,c,k , the characteristic value of the in-plane
compressive modulus in the i direction);
γ Rd
fi ,b,cr,k
is defined in 4.4.6 (Table 4.3, Local buckling);
is the characteristic value of the critical buckling bending stress in the i direction,
obtained as in C.4.2.3, and considering the appropriate values of the conversion factor,
ηc , for the relevant material properties (defined in 4.4.7);
is the buckling reduction factor for bending in the i direction to take into account the
effect of imperfections in elastic post-buckling regime.
χ i ,b
(4) For flat laminates (for which χ i ,b ≥ 1,0 ), χ i ,b may be conservatively taken as 1,0. For curved laminates
(for which χ i ,b < 1,0 ), the values of fi ,b,cr,k and χ i ,b should be determined by testing, and/or by numerical
modelling, which should be verified by testing.
NOTE 1 The rationale for the values of χ i ,b to be used in Formula (8.11) are given in the Note 1 to 8.2.2.2(4).
NOTE 2 Guidance on design assisted by testing is provided in EN 1990:—, Annex D.
8.2.5 Out-of-plane bending stresses
(1) The design value of the out-plane bending stress in the i direction, σ i ,ob,Ed , at each section of the
laminate, shall satisfy the condition in Formula (8.12):
σ i ,ob,Ed ≤ fi ,f,d
where
i
fi ,f,d
(8.12)
is either for the x or y direction of the laminate;
is the design value of the flexural strength of the laminate in the i direction.
(2) The design value of the flexural strength in the i direction of the laminate, fi ,f,d , should be determined
from Formula (8.13):
=
fi ,f,d
where
i
ηc
⋅f
γ m ⋅ γ Rd i ,f,k
is either for the x or y direction of the laminate;
γm
is defined in 4.4.5 (to be selected for fi ,f,k );
ηc
is defined in 4.4.7 (to be selected for fi ,f,k );
γ Rd
fi ,f,k
(8.13)
is defined in 4.4.6 (Table 4.3, Material failure);
is the characteristic value of the flexural strength in the i direction of the laminate.
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CEN/TS 19101:2022 (E)
8.2.6 Interlaminar shear stresses
(1) The resistance to interlaminar shear stresses should be verified at each section where:
— load is introduced;
— transitions in laminate stiffness exist;
— laminates have significant out-of-plane curvature;
— laminates are relatively thick and have low width-to-thickness ratio
b
<10.
t
NOTE Stiffness transitions in a laminate can occur by either ply drops or transitions between web and flange
outstands. In hybrid laminates, stiffness transitions can also occur by way of the distribution of the separate plies
having, for example, carbon fibre or glass fibre layers.
(2) The design values of the interlaminar shear stresses in the iz plane, τ iz,Ed , at each section of the
laminate, shall satisfy the condition in Formula (8.14):
τ iz,Ed ≤ fiz,ILS,d
where
i
fiz,ILS,d
=
fiz,ILS,d
where
(8.14)
is either for the x or y direction of the laminate;
is the design value of the interlaminar shear strength in the iz plane of the laminate,
given by Formula (8.15),
ηc
⋅f
γ m ⋅ γ Rd iz,ILS,k
γm
is defined in 4.4.5 (to be selected for f xz,ILS,k or f yz,ILS,k );
ηc
is defined in 4.4.7 (to be selected for f xz,ILS,k or f yz,ILS,k );
γ Rd
(8.15)
is defined in 4.4.6 (Table 4.3, Material failure);
f xz,ILS,k , f yz,ILS,k
are the characteristic values of the interlaminar shear strength in the xz and yz
plane of the laminate, respectively.
8.2.7 Out-of-plane tensile stresses
(1) For laminates having out-of-plane (through-thickness) tensile forces, the design value of the out-ofplane tensile stress acting perpendicular to the xy plane, σ z,t,Ed , shall satisfy the condition in Formula (8.16):
σ z,t,Ed ≤ fz,t,d
where
94
fz,t,d
(8.16)
is the design value of the out-of-plane tensile strength of the laminate, given by Formula
(8.17),
CEN/TS 19101:2022 (E)
=
fz,t,d
where
ηc
⋅f
γ m ⋅ γ Rd z,t,k
γm
is defined in 4.4.5 (to be selected for fz,t,k );
ηc
is defined in 4.4.7 (to be selected for fz,t,k );
γ Rd
fz,t,k
(8.17)
is defined in 4.4.6 (Table 4.3, Material failure);
is the characteristic value of the out-of-plane tensile strength of the laminate.
8.2.8 Stress concentrations due to localized forces
(1) Local verification of the resistance of a laminate should be made wherever there is a concentrated
force (or reaction) acting in the plane of the laminate (xy plane).
(2) In the absence of a general formula, the resistance to crippling of the laminate due to localized forces
may be determined by either testing, and/or numerical modelling, which should be verified by testing.
NOTE
Guidance on design assisted by testing is provided in EN 1990:—, Annex D.
(3) In order to avoid premature failure due to localized forces, appropriate stiffening systems may be
employed.
8.2.9 Combined stresses
(1) The resistance of laminates subjected to combined stresses may satisfy a linear interaction failure
criterion (which represents a conservative approximation for in-plane stresses). For laminates subjected
to in-plane stresses the linear interaction failure criterion should be defined as in Formula (8.18):
 σ

 σ x,t,Ed

τ xy,Ed
σ y,c,Ed
σ x,c,Ed
or
+  y,t,Ed or

+
 ≤ 1,0
f
f
min
f
;
f
min
f
;
f
min
f
;
f
{
}
{
}
{
}
x,t,d
y,t,d
x,c,d
x,cr,d

xy,v,d
xy,cr,d
y,c,d
y,cr,d 



where
(8.18)
σ x,t ,Ed
is the design value of the axial tensile stress in the x direction of the laminate;
σ x,c ,Ed
is the design value of the axial compressive stress in the x direction of the laminate;
f x,cr,d
is the design value of the critical buckling compressive stress in the x direction of the
laminate under uniform compression (8.2.2.2(3));
f x,t,d
f x,c,d
τ xy,Ed
f xy,v,d
is the design value of the tensile strength in the x direction of the laminate (8.2.2.1);
is the design value of the compressive strength in the x direction of the laminate
(8.2.2.2(2));
is the design value of the in-plane shear stress of the laminate;
is the design value of the in-plane shear strength of the laminate (8.2.3(2));
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CEN/TS 19101:2022 (E)
f xy,cr,d
is the design value of the critical buckling shear stress of the laminate under in-plane
shear loading (8.2.3(3));
σ y,t,Ed
is the design value of the axial tensile stress in the y direction of the laminate;
σ y,c ,Ed
is the design value of the axial compressive stress in the y direction of the laminate;
f y,cr,d
is the design value of the critical buckling compressive stress in the y direction of the
laminate under uniform compression (8.2.2.2(3)).
f y,t,d
f y,c,d
is the design value of the tensile strength in the y direction of the laminate (8.2.2.1);
is the design value of the compressive strength in the y direction of the laminate
(8.2.2.2(2));
(2) As an alternative to 8.2.9(1), the resistance of laminates subjected to combined stresses (including inplane and out-of-plane directions) may be determined by testing, and/or by analytical formulae using the
approach given in Annex B, or numerical modelling, both appropriately verified.
NOTE
Guidance on design assisted by testing is provided in EN 1990:—, Annex D.
8.3 Ultimate limit states of profiles
8.3.1 General
(1) The following common cases of internal forces and moments in profiles should be considered:
— axial force (8.3.2): axial tension (8.3.2.1) and axial compression (8.3.2.2);
— bending (8.3.3);
— shear (8.3.4);
— transverse compression (concentrated loads, 8.3.5);
— torsion (8.3.6);
— combination of axial force and bending (8.3.7): combination of axial tension and bending (8.3.7.1)
and combination of axial compression and bending (8.3.7.2);
— combination of bending and shear (8.3.8).
(2) If the differences between the mechanical properties in the web(s) and flange(s) of a profile are
significant, the resistance calculations shall be based on the actual mechanical properties of the section
walls and not on a set of mechanical properties that are for the whole profile.
NOTE 1 Profiles can have different mechanical properties in the web(s) and flange(s).
NOTE 2 Mechanical properties for both types of walls can be provided by the manufacturer.
(3) When the web-flange junction(s) in a profile has a relatively higher matrix volume fraction than in the
walls, the differences in mechanical properties at the junction(s) with respect to the mechanical
properties of the walls should be considered to prevent premature failure.
NOTE Information can be provided by manufacturers about the layup (e.g. continuity of transverse fibres between
section walls) and fibre volume fraction of web-flange junctions.
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CEN/TS 19101:2022 (E)
(4) When local effects are relevant, namely due to load introduction, the resistance to interlaminar shear
stresses of profiles should be verified. This verification may be performed for the relevant cross-section
wall(s) (laminate(s)), according to 8.2.6.
(5) When determining the resistance of built-up members (see Note 4 to 1.1(5)), the stiffness and
strength of the connection method between the various profiles shall be appropriately taken into account.
8.3.2 Axial force
8.3.2.1
Axial tension
(1) The design value of the tensile force, Nt,Ed , at each cross-section, shall satisfy the condition in Formula
(8.19):
Nt,Ed ≤ Nt,Rd
where
(8.19)
Nt,Rd
is the design value of the tensile resistance of the cross-section in the longitudinal (x)
direction, which should be determined from Formulae (8.20) and (8.21):
— for sections without openings:
=
N
t,Rd
ηc
⋅ A ⋅ f x,t,k
γ m ⋅ γ Rd
(8.20)
ηc
⋅ 0,7 ⋅ Anet ⋅ f x,t,k
γ m ⋅ γ Rd
(8.21)
— for sections with circular openings with Anet > 0,6 ⋅ A :
Nt,Rd
=
where
γm
is defined in 4.4.5 (to be selected for f x,t,k );
ηc
is defined in 4.4.7 (to be selected for f x,t,k );
A
is the gross area of the cross-section;
γ Rd
f x,t,k
Anet
is defined in 4.4.6 (Table 4.3, Material failure);
is the characteristic value of the tensile strength in the longitudinal (x) direction of the
material;
is the net area of the cross-section.
NOTE For bolted connections subjected to in-plane actions, subclause 12.2 gives formulae for net tension failure
of composite laminates.
(2) For holes as openings, Anet should be determined from Formula (8.22):
Anet =
A−
where
n
∑t
i =1
k
⋅ di
(8.22)
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CEN/TS 19101:2022 (E)
n
is the number of holes across the cross-section area A ;
di
is the diameter of i th hole;
is the thickness of the wall k where the hole is located.
tk
8.3.2.2
Axial compression
(1) The design value of the compressive force, Nc,Ed , at each cross-section, shall satisfy the condition in
Formula (8.23):
Nc,Ed ≤ Nc,Rd
where
Nc,Rd
(8.23)
is the design value of the compressive resistance in the longitudinal (x) direction of the
profile, which should be determined from Formula (8.24),
Nc,Rd = min {Nc,Rd1 ; Nc,Rd2 }
and where
Nc,Rd1
Nc,Rd2
(8.24)
is the design value of the compressive resistance to crushing of the cross-section;
is the design value of the compressive resistance to global buckling of the profile or local
buckling of the cross-section (including the interaction thereof).
(2) The design value of the compressive resistance to crushing of the cross-section, Nc,Rd1 , should be
determined from Formulae (8.25) and (8.26):
— for sections without openings:
N=
c,Rd1
ηc
⋅ A ⋅ f x,c,k
γ m ⋅ γ Rd
(8.25)
ηc
⋅ 0,7 ⋅ Anet ⋅ f x,c,k
γ m ⋅ γ Rd
(8.26)
— for sections with circular openings with Anet > 0,6 ⋅ A :
Nc,Rd1
=
where
γm
is defined in 4.4.5 (to be selected for f x,c,k );
ηc
is defined in 4.4.7 (to be selected for f x,c,k );
A
is the gross area of the cross-section;
γ Rd
f x,c,k
Anet
98
is defined in 4.4.6 (Table 4.3, Material failure);
is the characteristic value of the compressive strength in the longitudinal (x) direction of
the material;
is the net area of the cross-section, obtained as in 8.3.2.1(2).
CEN/TS 19101:2022 (E)
(3) The design value of the compressive resistance to global buckling of the profile or local buckling of
the cross-section (including the interaction thereof), Nc,Rd2 , may be determined through either testing
(4.5(1)) or numerical modelling, which should be verified by testing. For profiles with double symmetric
cross-section or profiles with all section walls sharing a common junction, Nc,Rd2 may be obtained from
analytical formulae (see 8.3.2.2(7) and (8)).
(4) For numerical modelling, the characteristic value of the compressive resistance to buckling of the
profile (used to obtain the value of Nc,Rd2 ) may be determined from an elastic buckling analysis.
(5) When numerical modelling is used to determine Nc,Rd2 , the influence of imperfections and interaction
of local and global buckling modes shall be taken into account.
(6) Influence of imperfections and interaction of local and global buckling modes may be determined by
numerical analysis validated by testing, where equivalent imperfections, geometrical non-linearity and
material failure (if relevant) are considered.
(7) For profiles with double symmetric cross-section, the design value of the compressive resistance to
buckling of the profile, Nc,Rd2 , should be determined from Formula (8.27):
Nc,Rd2
= χ E ⋅ Ncr,Rd
where
Ncr,Rd
χE
(8.27)
is the design value of the compressive resistance to local buckling of the profile (C.5.2(1)
in Annex C);
is the reduction factor to take into account the interaction between local and flexural
buckling of the profile (C.5.2(8), Annex C).
(8) For profiles with all section walls sharing a common junction (the shear centre, such as for angle,
cruciform or tee sections), the design value of the compressive resistance to buckling of the profile, Nc,Rd2 ,
should be determined from Formula (8.28):
Nc,Rd2 = min {NE,Rd ; NT,Rd ; NFT,Rd }
where
(8.28)
NE,Rd
is the design value of the flexural buckling resistance of the profile (C.5.2(9), Annex C);
NFT,Rd
is the design value of the compressive resistance to flexural-torsional buckling of the
profile (C.5.3(6), Annex C).
NT,Rd
is the design value of the compressive resistance to torsional buckling of the profile
(C.5.3(2), Annex C);
8.3.3 Bending
(1) The design value of the bending moment about a principal axis, MEd , at each cross-section, shall satisfy
the condition in Formula (8.29):
MEd ≤ MRd
where
MRd
(8.29)
is the design value of the bending moment resistance of the profile about a principal axis,
which should be determined from Formula (8.30),
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CEN/TS 19101:2022 (E)
MRd = min {MRd1 ; MRd2 }
where
MRd1
MRd2
(8.30)
is the design value of the bending moment resistance of the cross-section to material
failure (about a principal axis);
is the design value of the bending moment resistance to global buckling of the profile
(about a principal axis) or local buckling of the cross-section (including the interaction
thereof).
(2) The design value of the bending moment resistance of the cross-section to material failure (about a
principal axis), MRd1 , should be determined from Formulae (8.31) and (8.32):
— for sections without openings:
 ηc

ηc
⋅ f x,t,k ;
⋅ f x,c,k 
MRd1= W ⋅ min 
γ m ⋅ γ Rd
 γ m ⋅ γ Rd

(8.31)
 η

ηc
⋅ f x,c,k 
MRd1 =0,7 ⋅ Wnet ⋅ min  c ⋅ f x,t,k ;
γ m ⋅ γ Rd
 γ m ⋅ γ Rd

(8.32)
— for sections with circular openings with Anet > 0,6 ⋅ A :
where
γm
is defined in 4.4.5 (to be selected for either f x,t,k or f x,c,k );
ηc
is defined in 4.4.7 (to be selected for either f x,t,k or f x,c,k );
Wnet
is the elastic flexural modulus of the net cross-section (about that axis), determined
disregarding the material corresponding to the holes;
γ Rd
W
f x,t,k
f x,c,k
is defined in 4.4.6 (Table 4.3, Material failure);
is the elastic flexural modulus of the gross cross-section (about that axis);
is the characteristic value of the tensile strength in the longitudinal (x) direction of the
material;
is the characteristic value of the compressive strength in the longitudinal (x) direction of
the material.
(3) In general, the design value of the bending moment resistance to global buckling of the profile or local
buckling of the cross-section (including the interaction thereof), MRd2 , may be determined from either
testing (4.5(1)) or numerical modelling, which should be verified by testing. For profiles with double
symmetric cross-section, MRd2 may be obtained from analytical formulae (8.3.3(7)).
(4) For numerical modelling, the characteristic value of the bending moment resistance to global buckling
of the profile or local buckling of the cross-section (used to obtain the value of MRd2 ) may be determined
from an elastic buckling analysis.
(5) When numerical modelling is used to determine MRd2 , the influence of imperfections and interaction
of local and global buckling modes shall be taken into account.
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CEN/TS 19101:2022 (E)
(6) Influence of imperfections and interaction of local and global buckling modes may be determined by
numerical modelling validated by testing, where equivalent imperfections, geometrical non-linearity and
material failure (if relevant) are considered.
(7) For profiles with double symmetric cross-section subjected to bending about the major principal axis
of the cross-section (y-axis, Figure 3.3), MRd2 should be calculated from Formula (8.33):
MRd2
= χ LT ⋅ Mcr,Rd
where
Mcr,Rd
(8.33)
is the design value of the bending moment resistance to local buckling of the cross-section
(C.5.4(1), Annex C);
χ LT
is the reduction factor to take into account the interaction between local and lateraltorsional buckling of the profile (C.5.4(8), Annex C).
(8) For profiles subjected to bending about the minor principal axis of the cross-section (z-axis, Figure
3.3), the design value of the bending moment resistance to local buckling of the cross-section, Mcr,Rd , may
be determined by either testing (4.5(1)), numerical modelling or analytical modelling, which should be
verified by testing. Mcr,Rd may be conservatively estimated using the formulae given in Annex C assuming
that the flange is simply supported by the web and subjected to a linear distribution of axial stresses over
the flange width. As an alternative, a numerical model may be used by assuming the same distribution of
normal stresses, but considering the flange constrained at the connection with the web, with the stiffness
of such rotational spring, k , being determined from Formula (8.34):
k =
(E ) ⋅t
12 ⋅ b ⋅ (1 −ν ⋅ν )
w
where
y,c,k
bw and t w
(E )
y,c,k w
ν xy,k and ν yx,k
w
3
w
xy,k
yx,k
(8.34)
are the width and thickness of the web, respectively;
is the characteristic value of the in-plane compressive modulus in the transverse
(y) direction of the web;
are the characteristic values of the major and minor Poisson’s ratios,
respectively.
NOTE Subscripts x and y are for longitudinal and transverse direction, respectively, and the subscript c is for
compression force.
(9) For profiles subjected to bending about the minor principal axis of the cross-section, the reduction
factor χ LT may be taken equal to 1,0.
NOTE For profiles subjected to bending about the minor principal axis of the cross-section, lateral-torsional
buckling does not occur.
8.3.4 Shear
(1) The design value of the shear force, VEd , at each cross-section, shall satisfy the condition in Formula
(8.35):
VEd ≤ VRd
where
(8.35)
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CEN/TS 19101:2022 (E)
VRd
is the design value of the shear resistance of the cross-section, which should be
determined from Formula (8.36),
VRd = min {VRd1 ;VRd2 }
where
VRd1
(8.36)
is the design value of the shear resistance to material failure of the cross-section;
VRd2
is the design value of the shear resistance to local buckling of the cross-section.
(2) The design value of the shear resistance to material failure of the cross-section, VRd1 , should be
determined from Formula (8.37):
ηc
⋅A ⋅ f
γ m ⋅ γ Rd v xy,v,k
V=
Rd1
where
(8.37)
γm
is defined in 4.4.5 (to be selected for f xy,v,k );
ηc
is defined in 4.4.7 (to be selected for f xy,v,k );
f xy,v,k
is the characteristic value of the in-plane shear strength (in the plane of the cross-section).
γ Rd
is defined in 4.4.6 (Table 4.3, Material failure);
AV
is the shear area of the cross-section, as given in Table 8.1 for commonly used thin-walled
cross-sections;
(3) The design value of the shear resistance to local buckling of the cross-section, VRd2 , should be
determined from Formula (8.38):
(
1
⋅A ⋅ f
γ m ⋅ γ Rd v xy,cr,k
V=
Rd2
where
γm
xy,cr,k
102
w
(8.38)
is defined in 4.4.5 (to be selected for E y,c,k , the characteristic value of the in-plane
compressive modulus in the transverse (y) direction);
γ Rd
(f )
)
is defined in 4.4.6 (Table 4.3, Local buckling);
w
is the characteristic value of the critical local buckling shear stress of the web
(C.4.2.2(1), Annex C), where the subscript w refers to the web, and considering the
appropriate values of the conversion factor, ηc , for the relevant material properties
(defined in 4.4.7).
CEN/TS 19101:2022 (E)
Table 8.1 — Shear area AV for common cross-sections
h⋅tw
(2 ⋅ b ⋅ t f )
1,2
2⋅ h⋅tw
h⋅tw
(2 ⋅ b ⋅ t f )
1,2
π ⋅ R ⋅t
h and b are respectively the height and width of the web(s) and flange, t w and t f are respectively
the thickness of the web(s) and flange, and R is the radius of the circular section mid-surface with
wall thickness t .
(4) For non-conventional cross-sections (including multicellular deck panels), AV may be obtained
through computational tools (in this case, the cross-section walls should be modelled using shear
deformable shell finite elements, e.g. via Mindlin shell theory).
8.3.5 Transverse compression
(1) Local verification of a web’s resistance under transverse compression should be made at each crosssection where there is a concentrated force (or reaction) acting in the plane of the web (z-axis, Figure
3.3).
(2) In the absence of a general formula, the resistance to web crippling may be determined from either
testing (4.5(1)) or numerical modelling, which should be verified by testing. In order to avoid premature
failure at these cross-sections, an appropriate stiffening system should be employed.
8.3.6 Torsion
(1) The design value of the torsional moment, TEd , at each cross-section, shall satisfy the condition in
Formula (8.39):
TEd ≤ TRd
where
TRd
(8.39)
is the design value of the torsional resistance of the cross-section.
(2) The design value of the torsional moment of the cross-section, TEd , should be determined from
Formula (8.40):
=
TEd TEd(SV) + TEd(W)
where
TEd(SV)
(8.40)
is the design value of the uniform torsional moment of the cross-section associated to the
Saint-Venant's torsion;
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CEN/TS 19101:2022 (E)
is the design value of the non-uniform torsional moment of the cross-section for
constrained warping.
TEd(W)
(3) The values for TEd(SV) and TEd(W) may be determined from elastic analysis taking into account the
boundary conditions of restraint at the profile’s supports, the distribution of the actions along the profile,
the elastic mechanical properties, and the torsional constant ( I t ) for uniform torsion and the warping
constant ( I w ) for non-uniform torsion.
NOTE For profiles with open cross-section, the effects of non-uniform torsion are typically much more relevant
than those caused by uniform torsion.
(4) Owing to the co-existence of both uniform and non-uniform torsional moments, the torsional
resistance may be estimated based on determining elastic shear stresses. For design, Formulae (8.39)
and (8.40) are equivalent to the stress-based criterion given in Formula (8.41):
(SV)
(W)
τ Ed = τ Ed
+ τ Ed
≤ f xy,v,d
where
τ Ed
is the design value of the shear stress due to torsion;
(W)
τ Ed
is the design value of the shear stress due to non-uniform torsional moment;
is the design value of the shear stress due to uniform torsional moment;
(SV)
τ Ed
f xy,v,d
=
f xy,v,d
where
(8.41)
is the design value of the in-plane shear strength (in the plane of the cross-section) of the
material, which is given by Formula (8.42),
ηc
⋅f
γ m ⋅ γ Rd xy,v,k
γm
is defined in 4.4.5 (to be selected for f xy,v,k );
ηc
is defined in 4.4.7 (to be selected for f xy,v,k );
γ Rd
(8.42)
is defined in 4.4.6 (Table 4.3, Material failure);
f xy,v,k
is the characteristic value of the in-plane shear strength of the material.
(5) For profiles with open cross-section (such as I, H, U or angle), the design value of the shear stress due
(SV)
to uniform torsion, τ Ed
, should be calculated from Formula (8.43):
(SV )
τ=
Ed
where
t max
It
104
TEd( )
⋅ t max
It
SV
is the thickness of the thickest wall in the cross-section;
is the torsional constant of the cross-section.
(8.43)
CEN/TS 19101:2022 (E)
(6) For profiles with closed cross-section (such as hollow, tubular, pipe or multi-cellular), the design value
(SV)
of the shear stress due to uniform torsion, τ Ed
, should be calculated from Formula (8.44):
TEd( )
2 ⋅ Am ⋅ t min
SV
(SV )
τ Ed
=
where
t min
(8.44)
is the thickness of the thinnest wall in the cross-section;
Am
is the area defined by the middle line in the closed cross-section.
(7) For profiles with two-flange cross-section (I or H, with equal flanges), the design value of the
(W)
maximum shear stress due to non-uniform torsion, τ Ed
, should be calculated from Formula (8.45):
( )
τ Ed
=
W
where
3
W
⋅ TEd( )
2 ⋅ bf ⋅ t f ⋅ bw
bf and t f
bw
(8.45)
are the width and the thickness of the two flanges, respectively;
is the width of the web.
(8) For profiles with channel cross-section (with equal sized flange outstands), the design value of the
(W)
maximum shear stress due to non-uniform torsion, τ Ed
, should be calculated from Formula (8.46):
(W)
τ Ed
where
3 ( bw + 3 ⋅ bf )
2
bf ⋅ t f ⋅ bw ⋅ ( bw + 6 ⋅ bf ) ⋅ ( 2 ⋅ bw + 3 ⋅ bf )
bf and t f
bw
⋅ TEd(
W)
(8.46)
are the width and the thickness of the flange, respectively;
is the width of the web.
(9) For profiles with angle, cruciform or tee sections, the design value of the shear stress due to non(W )
uniform torsion may be considered equal to zero, τ Ed
=0.
(10) For profiles with closed cross-section (tubes, pipes or multi-cellular), the shear stresses generated
by the non-uniform torsion may be assumed negligible in comparison with the shear stresses generated
(W)
by Saint-Venant's torsion, and so τ Ed
=0.
8.3.7 Combination of axial force and bending
8.3.7.1
Combination of axial tension and bending
(1) Cross-sections subjected to both axial tension and bending about the major principal axis (y-axis),
shall satisfy the condition in Formula (8.47):
Nt,Ed
Nt,Rd
+
MEd
≤ 1,0
MRd1
(8.47)
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CEN/TS 19101:2022 (E)
where
Nt,Ed
is the design value of the axial tensile force;
MEd
is the design value of the bending moment about the major principal axis (y-axis);
MRd1
is the design value of the bending moment resistance of the cross-section about the major
principal axis (y-axis, 8.3.3(2)).
Nt,Rd
is the design value of the tensile resistance of the cross-section (8.3.2.1(1));
(2) In addition to the verification of resistance of the cross-sections as given in 8.3.7.1(1), the stability of
the profile shall also be verified. The axial tensile force may be neglected when determining the design
value of the bending moment resistance to buckling of the profile.
NOTE In the absence of a more reliable evaluation for the interaction between axial tensile force and bending
moment, it is conservative to neglect the axial tensile force.
(3) For profiles subjected to axial tension and bi-axial bending, the design value of the resistance may be
determined by either testing (4.5(1)) or numerical modelling, which should be verified by testing.
8.3.7.2
Combination of axial compression and bending
(1) Cross-sections subjected to both axial compression and bending about the major principal axis (yaxis), shall satisfy the condition in Formula (8.48):
Nc,Ed
Nc,Rd1
where
+
Nc,Ed
MEd
Nc,Rd1
MRd1
MEd
≤ 1,0
MRd1
(8.48)
is the design value of the axial compressive force;
is the design value of the bending moment about the major principal axis (y-axis);
is the design value of the compressive resistance to crushing of the cross-section
(8.3.2.2(2));
is the design value of the bending moment resistance of the cross-section about the major
principal axis (y-axis, 8.3.3(2)).
(2) In addition to the verification of resistance of the cross-section as given in 8.3.7.2(1), the stability of
the profile shall also be verified. In the absence of a more reliable evaluation for the interaction between
axial compressive force and bending moment about a principal axis, the condition in Formula (8.49) shall
be satisfied:
Nc,Ed
Nc,Rd2
where
106

N
MEd  1 − c,Ed
NE,Rd

+
MRd2
Nc,Rd2


 ≤ 1,0
(8.49)
is the design value of the compressive resistance to global buckling of the profile or local
buckling of the cross-section (including the interaction thereof) (8.3.2.2(3) to (8));
CEN/TS 19101:2022 (E)
MRd2
is the design value of the bending moment resistance to global buckling of the profile
about a principal axis or local buckling of the cross-section (including the interaction
thereof) (8.3.3(3) to (9));
NE,Rd
is design value of the flexural buckling resistance of the profile (C.5.2(9), Annex C).
(3) For profiles subjected to axial compression and bi-axial bending, the design value of the resistance
may be obtained from either testing (4.5(1)) or numerical modelling, which should be verified by testing.
8.3.8 Combination of bending and shear
(1) Cross-sections subjected to both bending about a principal axis (y- or z-axis) and shear, shall satisfy the
condition in Formula (8.50):
2
2
 MEd   VEd 

 +
 ≤ 1,0
 MRd1   VRd 
where
MEd
(8.50)
is the design value of the bending moment (about that axis);
VEd
is the design value of the shear force (associated with MEd );
MRd1
is the design value of the bending moment resistance of the cross-section (about that axis)
(8.3.3(2)).
VRd
is the design value of the shear resistance of the cross-section (8.3.4(1));
(2) For profiles under non-uniform bending, as an alternative to Formula (8.50), a stress-based
interaction failure criterion may be used.
NOTE For profiles under non-uniform bending, the maximum flexural stresses and maximum shear stresses do
not exist at the same point in the cross-section.
(3) In addition to the verification of resistance of the cross-section as given in 8.3.8(1), the stability of the
profile shall be verified. In the absence of a general interaction formula for composite profiles, the resistance
may be determined by either testing (4.5(1)) or numerical modelling, which should be verified by testing.
8.4 Ultimate limit states of sandwich panels
8.4.1 General
(1) The verifications covered in this subclause are limited to uniaxial stresses. Interactions under
combined stresses should also be taken into account for ULS verifications.
NOTE
For face sheets and web laminates under combined stresses, design guidance is presented in 8.2.9.
(2) The principal failure modes of homogeneous-core and web-core sandwich panels listed in Table 8.2
should be considered as a minimum for the ULS verifications.
(3) Failure of sandwich panels by failure modes other than those listed in Table 8.2 should be identified
and verified.
NOTE Failure modes not considered in this subclause are: face sheet dimpling (intracell buckling), face sheet inplane shear failure or buckling, flexural core crushing, shear crimping, horizontal shear in web-face sheet
connections of web-core sandwiches.
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CEN/TS 19101:2022 (E)
Table 8.2 — Failure modes in homogenous-core and web-core sandwich panels
Homogeneouscore
Sandwich
component
Face sheet
Core
Failure mode
Face sheet tensile failure
Face sheet crushing
Face sheet wrinkling
Face sheet local buckling
Rigid
core
Flexible
core
With
core
infill
Without
core
infill
x
x
x
x
x
x
x
x
x
x
Core out-of-plane tensile or compressive failure
x
x
x
Core in-plane tensile or compressive failure
Core indentation
x
x
x
x
x
Web bending failure
x
x
Web local buckling due to in-plane bending
Web crushing due to transverse compression
x
Web wrinkling due to transverse compression
Web local buckling due to transverse compression
Face sheet/core delamination
Global buckling
x
x
x
x
x
x
x
Web wrinkling due to shear
Web wrinkling due to in-plane bending
x
x
x
Web local buckling due to shear
Sandwich
x
x
Web shear failure
Interface
x
Core shear failure
Core punching failure
Web
Web-core
x
x
x
x
x
x
x
x
x
(4) Local and global buckling verifications taking into account the effects of imperfections may be
conducted using analytical models, finite element analysis or testing.
NOTE 1 Local and global buckling verifications in this subclause are based on critical buckling stresses or loads and
do not include the effects of geometrical imperfections.
NOTE 2 Wrinkling verifications are based on wrinkling stresses, which take common imperfections into account.
(5) If the eccentricities or local bending moments induced by the most unfavourable geometrical
imperfections comprise more than 10% of the relevant eccentricities or local bending moments resulting
from the design loads, geometrical imperfections should be taken into account, as specified in 7.3.3(4)
and 8.4.1(6).
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CEN/TS 19101:2022 (E)
(6) Local and global stability verifications may be conducted as strength verifications, by taking into
account in the analysis initial geometrical imperfections and second-order effects. The most unfavourable
geometrical imperfections possible within the specified manufacturing tolerances should be considered
in this case.
NOTE
Tolerances can be taken into account according to 4.3.3.
NOTE
Polymeric foams can exhibit non-linear behaviour.
(7) If materials exhibiting non-linear behaviour are used beyond their proportional limit, material nonlinearities should be duly taken into account in the verifications, on both the action and resistance sides
(e.g. by using the appropriate secant or reduced modulus to estimate the design stresses and critical
stresses for local buckling or wrinkling, etc.).
8.4.2 Face sheet
8.4.2.1
Face sheet tensile failure
(1) The design value of the in-plane tensile stress in the face sheets, (σ i ,Ed )f ≥ 0 , shall satisfy the condition
in Formula (8.51):
(σ ) ≤ ( f )
where
i ,Ed f
i
refers to the x and y directions;
(f )
is the design value of the in-plane tensile strength in the examined i direction of the
face sheet, given by Formula (8.52),
i ,t,d f
f )
(=
i ,t,d f
where
(8.51)
i ,t,d f
ηc
⋅( f )
γ m ⋅ γ Rd i ,t,k f
(8.52)
is defined in 4.4.5 (to be selected for ( fi ,t,k )f );
γm
γ Rd
is defined in 4.4.6 (Table 4.4, Composite material failure);
is defined in 4.4.7 (to be selected for ( fi ,t,k )f );
ηc
(f )
is the characteristic value of the in-plane tensile strength in the examined i direction of
the face sheet.
i ,t,k f
(2) The value of (σ i ,Ed )f may be calculated from Formula (8.53):
(
) (
=
(σ i ,Ed )f σ i ,N,Ed ± σ i ,M,Ed
where
(σ
)
i ,N,Ed f
f
)
f
(8.53)
is the design value of the axial stress in the examined i direction in the face sheets,
determined using the design value of the applied in-plane axial force ( Ni ,Ed ) per unit
width and the relevant material stiffness properties (7.1.1(7));
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CEN/TS 19101:2022 (E)
(σ
)
i ,M,Ed f
(
(3) σ i ,N,Ed
8.4.2.2
)
f
(
is the design value of the bending stress in the examined i direction in the face sheets,
determined using the design value of the applied bending moment ( Mi ,Ed ) per unit
width and the relevant material stiffness properties (7.1.1(7)).
and σ i ,M,Ed
)
f
may be calculated as per Table 7.1 or by finite element analysis.
Face sheet crushing
(1) The design value of the normal compressive stress in the face sheets, (σ i ,Ed )f < 0 , shall satisfy the
condition in Formula (8.54):
(σ ) ≤ ( f )
where
i ,Ed f
i ,c,d f
i
(f )
i ,c,d f
where
refers to the x and y directions;
is the design value of the in-plane compressive strength in the examined i direction
of the face sheet, given by Formula (8.55),
ηc
⋅( f )
γ m ⋅ γ Rd i ,c,k f
f )
(=
i ,c,d f
(8.54)
(8.55)
is defined in 4.4.5 (to be selected for ( fi ,c,k )f );
γm
γ Rd
is defined in 4.4.6 (Table 4.4, Composite material failure);
ηc
(f )
i ,c,k f
is defined in 4.4.7 (to be selected for ( fi ,c,k )f );
is the characteristic value of the in-plane compressive strength in the examined i
direction of the face sheet.
(2) The value of (σ i ,Ed )f may be calculated as per 8.4.2.1(2) and (3).
8.4.2.3
Face sheet wrinkling
(1) The design value of the compressive stress in the face sheets, (σ i ,Ed )f < 0 , shall satisfy the condition
in Formula (8.56):
(σ ) ≤ ( f
where
i ,Ed f
i
(f
110
)
i ,wr,d f
)
i ,wr,d f
refers to the x and y directions;
(8.56)
is the design value of the wrinkling stress in the examined i direction of the face sheet,
given by Formula (8.57),
CEN/TS 19101:2022 (E)
1
⋅( f
)
γ m ⋅ γ Rd i ,wr,k f
( f=
)
i ,wr,d f
where
( ) , as defined in 8.4.2.3(3));
γm
is defined in 4.4.5 (to be selected for E z,k
γ Rd
(f
(8.57)
c
is defined in 4.4.6 (Table 4.4, Face sheet/web wrinkling);
)
is the characteristic value of the wrinkling stress in the examined i direction of the
face sheet (8.4.2.3(3) to (5)).
i ,wr,k f
(2) The value of (σ i ,Ed )f may be calculated as per 8.4.2.1(2) and (3).
(3) The value of
(f
)
i ,wr,k f
should be estimated using the semi-empirical Formula (8.58), which takes
common imperfections into account:
(f
where
)
i ,wr,k f
=0,65 ⋅ 3 (ηc )f ⋅ ( E i ,c,k )f  ⋅ (ηc )c ⋅ ( E z,k )c  ⋅ (ηc )c ⋅ ( Giz ,k )c 
(E )
i ,c,k f
(E )
z,k c
(G )
iz,k c
(ηc )f
(ηc )c
(8.58)
is the characteristic value of the compressive modulus in the examined i direction of
the face sheet;
is the characteristic value of the out-of-plane elastic modulus of the core (based on the
value of the tensile or compressive modulus, whichever is lower);
is the characteristic value of the out-of-plane shear modulus ( iz plane) of the core;
is defined in 4.4.7 (to be selected for ( E i ,c,k )f );
is defined in 4.4.7 (to be selected for the core material).
(4) If the core material is stressed beyond its proportional limit, the appropriate secant or reduced moduli
should be used in Formula (8.58) to estimate the wrinkling stress.
(5) As an alternative to Formula (8.58), finite element analysis may be used to conduct the wrinkling
verification as per 8.4.1(6). A sufficiently refined mesh should be used in the laminates to accurately
represent the wrinkling shape. In the absence of detailed information concerning geometrical
imperfections, the critical wrinkling stress may be computed and imperfections taken into account by
reducing the critical wrinkling stress by 40%.
8.4.2.4
Face sheet local buckling
(1) The design value of the compressive stress in the face sheets, (σ i ,Ed )f < 0 , shall satisfy the condition
in Formula (8.59):
(σ ) ≤ ( f
where
i ,Ed f
)
i ,cr,d f
(8.59)
111
CEN/TS 19101:2022 (E)
i
(f )
i ,cr,d f
(f
where
refers to the x and y directions;
is the design value of the critical buckling compressive stress in the examined i
direction of the face sheet, given by Formula (8.60),
1
⋅ χ ⋅( f
)
γ m ⋅ γ Rd i ,c i ,cr,k f
=
)
i ,cr,d f
γm
(8.60)
is defined in 4.4.5 (to be selected for E i ,c,k , the characteristic value of the in-plane
compressive modulus in the i direction of the face sheet, except for laminates with
free/simply supported edges, for which Gxy,k , the characteristic value of the in-plane
shear modulus of the face sheet, should be considered instead);
γ Rd
(f )
i ,cr,k f
is defined in 4.4.6 (Table 4.4, Local buckling);
is the characteristic value of the critical buckling compressive stress in the examined i
direction of the face sheet, as indicated in C.4.2.1, provided that the face sheet
laminate’s minimum length/width ratio complies with C.4.1(1), and considering the
appropriate values of the conversion factor, ηc , for the relevant material properties
(defined in 4.4.7). It may be conservatively assumed that the face sheet is simply
supported at the connections with the webs;
is the buckling reduction factor for compression in the i direction to take into account
imperfections, which can be taken as 1,0 for flat laminates (see Note 1 to 8.2.2.2(4)).
χ i ,c
(2) The value of (σ i ,Ed )f may be calculated as per 8.4.2.1(2) and (3).
8.4.3 Core
8.4.3.1
Core shear failure
(1) The design value of the shear stress in the core, (τ i ,Ed )c , shall satisfy the condition in Formula (8.61):
(τ ) ≤ ( f )
where
i ,Ed c
i ,v,d c
i
(f )
i ,v,d c
f )
(=
where
i ,v,d c
γm
γ Rd
112
(8.61)
refers to the x and y directions;
is the design value of the shear strength in the examined i direction of the core, given
by Formula (8.62),
ηc
⋅( f )
γ m ⋅ γ Rd i ,v,k c
is defined in 4.4.5 (to be selected for ( fi ,v,k )c );
is defined in 4.4.6 (Table 4.4, Core material failure);
(8.62)
CEN/TS 19101:2022 (E)
ηc
(f )
i ,v,k c
is defined in 4.4.7 (to be selected for ( fi ,v,k )c );
is the characteristic value of the shear strength in the examined i direction of the core.
NOTE Core shear failure occurs when the core, mainly subjected to shear, fails by fracture or yielding, i.e. the shear
stress in the core exceeds the material’s shear strength.
(2) The value of (τ i ,Ed )c may be calculated as per Table 7.1 or by finite element analysis, using the design
value of the acting transverse shear force per unit width Vi ,Ed and the material stiffness properties in the
examined i direction (7.1.1(7)).
(3) In web-core sandwiches with core infill, the design value of the shear force in the core component,
(Vi ,Ed )c , should be used. (Vi ,Ed )c may be estimated by distributing the acting transverse shear force among
the web and core infill components according to their shear stiffnesses (7.1.1(7)).
(4) The value of ( fi ,v,k )c shall be obtained from Formula (8.63):
(f )
where
i ,v,k c
= min
(f )
iz,v,k c
(f
)
zi ,v,k c
{( f ) , ( f ) }
iz,v,k c
zi ,v,k c
(8.63)
is the characteristic value of the out-of-plane shear strength (in the examined iz plane)
of the core, perpendicular to the face sheets;
is the characteristic value of the out-of-plane shear strength (in the examined zi plane)
of the core, parallel to the face sheets.
(5) The value of ( fi ,v,k )c should be taken as the core material’s yield, 2% offset or ultimate shear strength
in the relevant plane and direction, as defined in the standard test methods referred to in Table 5.2. The
selection should be based on the material’s shear behaviour and failure mode.
8.4.3.2
Core in-plane tensile or compressive failure
(1) The design value of the normal stress in the core, (σ i ,Ed )c , shall satisfy the condition in Formulae (8.64)
and (8.65):
(σ ) ≤ ( f )
i ,Ed c
i ,t,d c
(σ ) ≤ ( f )
where
i ,Ed c
i
(f )
i ,t,d c
(f )
i ,c,d c
i ,c,d c
if
if
(σ )
i ,Ed c
(σ )
i ,Ed c
≥0
<0
(8.64)
(8.65)
refers to the x and y directions;
is the design value of the in-plane tensile strength in the examined i direction of the
core;
is the design value of the in-plane compressive strength in the examined i direction of
the core, given by Formulae (8.66) and (8.67),
113
CEN/TS 19101:2022 (E)
f )
(=
i ,t,d c
f )
(=
i ,c,d c
where
ηc
⋅( f )
γ m ⋅ γ Rd i ,t,k c
ηc
⋅( f )
γ m ⋅ γ Rd i ,c,k c
if
if
(σ )
i ,Ed c
(σ )
i ,Ed c
≥0
(8.66)
<0
(8.67)
is defined in 4.4.5 (to be selected for ( fi ,t,k )c for tension and ( fi ,c,k )c for compression);
γm
γ Rd
is defined in 4.4.6 (Table 4.4, Core material failure);
(f )
is the characteristic value of the in-plane tensile strength in the examined i direction
of the core;
is defined in 4.4.7 (to be selected for ( fi ,t,k )c for tension and ( fi ,c,k )c for compression);
ηc
i ,t,k c
(f )
is the characteristic value of the in-plane compressive strength in the examined i
direction of the core.
i ,c,k c
NOTE Core failure due to in-plane tensile or compressive stresses occurs when the core, subjected to in-plane
stresses, fails by fracture (tension) or crushing (compression), i.e. the in-plane stresses in the core exceed the
relevant material’s in-plane strengths.
(2) The value of (σ i ,Ed )c may be calculated from Formula (8.68):
(
) (
=
(σ i ,Ed )c σ i ,N,Ed ± σ i ,M,Ed
where
(σ
(σ
c
)
)
c
(8.68)
is the design value of the axial stress in the examined i direction in the core,
determined using the design value of the applied in-plane axial force ( Ni ,Ed ) per unit
width and the relevant material stiffness properties (7.1.1(7));
i ,N,Ed c
)
is the design value of the bending stress in the examined i direction in the core,
determined using the design value of the applied bending moment ( Mi ,Ed ) per unit
width and the relevant material stiffness properties (7.1.1(7)).
i ,M,Ed c
(
(3) The values of σ i ,N,Ed
(4) The value of
)
(f )
i ,c,k c
c
(
and σ i ,M,Ed
)
c
may be calculated as per Table 7.1 or by finite element analysis.
should be taken as the core material’s 2% offset or ultimate compressive
strength, in the examined i direction, obtained as per standard test methods referred to in Table 5.2. The
selection should be based on the material’s compressive behaviour and failure mode.
8.4.3.3
Core out-of-plane tensile or compressive failure
(1) The design value of the out-of-plane stress in the core, (σ z,Ed )c , shall satisfy the condition in Formulae
(8.69) and (8.70):
(σ ) ≤ ( f )
z,Ed c
114
z,t,d c
if
(σ )
z,Ed c
≥0
(8.69)
CEN/TS 19101:2022 (E)
(σ ) ≤ ( f )
where
(σ )
z,Ed c
<0
(8.70)
z,c,d c
(f )
is the design value of the out-of-plane tensile strength of the core;
z,t,d c
(f )
z,c,d c
is the design value of the out-of-plane compressive strength of the core, given by
Formulae (8.71) and (8.72),
ηc
⋅( f )
γ m ⋅ γ Rd z,t,k c
f )
(=
z,t,d c
ηc
⋅( f )
γ m ⋅ γ Rd z,c,k c
f )
(=
z,c,d c
where
if
z,Ed c
if
if
(σ )
z,Ed c
(σ )
≥0
z,Ed c
<0
(8.71)
(8.72)
is defined in 4.4.5 (to be selected for ( fz,t,k )c for tension and ( fz,c,k )c for compression);
γm
γ Rd
is defined in 4.4.6 (Table 4.4, Core material failure);
(f )
is the characteristic value of the out-of-plane tensile strength of the core;
ηc
z,t,k c
(f )
z,c,k c
is defined in 4.4.7 (to be selected for ( fz,t,k )c for tension and ( fz,c,k )c for compression);
is the characteristic value of the out-of-plane compressive strength of the core.
NOTE 1 Out-of-plane tensile or compressive core failure occurs when the core, subjected to out-of-plane stresses,
in the z direction, fails by fracture (tension) or crushing (compression), i.e. the out-of-plane stresses in the core
exceed the material’s out-of-plane strengths.
NOTE 2 This failure mode can occur in homogeneous-core and web-core sandwiches with curved face sheets
(7.1.4.1(11)).
(2) The out-of-plane stress, (σ z,Ed )c , originating in a sandwich panel stressed in the z direction and with
curved face sheets in the iz plane may be calculated from Formula (8.73):
(σ )
z,Ed c
where
=
(N )
i ,Ed f
ri
(N )
i ,Ed f
ri
(8.73)
is the design value of the normal force per unit width in the examined i direction in the
face sheets, originating from both the applied internal bending moment and axial force
(positive for tension, negative for compression);
is the radius of curvature of the face sheet, with regard to its centroid, in the iz plane
(positive for concave, negative for convex).
115
CEN/TS 19101:2022 (E)
(3) The value of ( fz,c,k )c should be taken as the core material’s 2% offset or ultimate compressive strength
in the out-of-plane direction, obtained as per standard test methods referred to in Table 5.2. The selection
should be based on the material’s compressive behaviour and failure mode.
(4) In the presence of double-curved face sheets, out-of-plane stresses in the core originating from
curvatures in two orthogonal planes should also be taken into account.
8.4.3.4
Core indentation
(1) The design value of the out-of-plane compressive stress in the core, (σ z,Ed )c , resulting from out-of-
plane concentrated loads, shall satisfy the condition in Formula (8.74):
(σ ) ≤ ( f )
z,Ed c
where
z,c,d c
(f )
is the design value of the out-of-plane compressive strength of the core, given by
Formula (8.75),
z,c,d c
ηc
⋅( f )
γ m ⋅ γ Rd z,c,k c
f )
(=
z,c,d c
where
(8.74)
(8.75)
is defined in 4.4.5 (to be selected for ( fz,c,k )c );
γm
γ Rd
is defined in 4.4.6 (Table 4.4, Core indentation);
(f )
is the characteristic value of the out-of-plane compressive strength of the core
(8.4.3.3(1) and (3)).
is defined in 4.4.7 (to be selected for ( fz,c,k )c );
ηc
z,c,k c
NOTE 1 Core indentation occurs when the core, subjected to transverse (out-of-plane) concentrated loads, fails by
crushing, i.e. the out-of-plane compressive stress in the core exceeds the material’s out-of-plane compressive
strength.
NOTE 2 This failure mode can occur in homogeneous-core and web-core sandwiches with core infill, subjected to
transverse concentrated loads or support reactions.
(2) The value of (σ z,Ed )c resulting from transverse concentrated loads may be estimated from Formula
(8.76):
(σ )
where
z,Ed c
PEd
Aeff
116
=
PEd
Aeff
(8.76)
is the design value of the transverse concentrated load;
is the area over which the concentrated load is uniformly distributed.
CEN/TS 19101:2022 (E)
8.4.3.5
Core punching failure
(1) The design value of the out-of-plane shear stress in the core, (τ Ed )c , resulting from transverse
concentrated loads, shall satisfy the condition in Formula (8.77):
(τ Ed )c ≤ ( fv,d )c
where
(f )
v,d c
(f =
)
v,d c
where
is the design value of the out-of-plane shear strength of the core, given by Formula
(8.78),
ηc
⋅ min
γ Rd
γ Rd
)
xz,v,k c
/ γ m , ( f yz,v,k ) / γ m , ( fzx,v,k )c / γ m , ( fzy,v,k ) / γ m
c
c
is defined in 4.4.6 (Table 4.4, Core punching failure);
ηc
)
xz,v,k c
(f )
yz,v,k c
(f
{( f
}
)
zx,v,k c
(f )
zy,v,k c
(8.78)
(
)
(
)
is defined in 4.4.5 (to be selected for either ( f xz,v,k )c , or f yz,v,k
γm
(f
(8.77)
is defined in 4.4.7 (to be selected for either ( f xz,v,k )c , or f yz,v,k
c
, or fzx,v,k
(
) , or ( f ) );
c
, or fzx,v,k
(
) , or ( f ) );
c
c
zy,v,k c
zy,v,k c
is the characteristic value of the out-of-plane shear strength (xz plane) of the core,
perpendicular to the face sheets;
is the characteristic value of the out-of-plane shear strength (yz plane) of the core,
perpendicular to the face sheets;
is the characteristic value of the out-of-plane shear strength (xz plane) of the core,
parallel to the face sheets;
is the characteristic value of the out-of-plane shear strength (yz plane) of the core,
parallel to the face sheets.
NOTE 1 Core punching failure occurs when the core, subjected to transverse (out-of-plane) concentrated loads, fails
in shear, i.e. the out-of-plane shear stress in the core along a defined control perimeter exceeds the material’s outof-plane shear strength.
NOTE 2 This failure mode can occur in homogeneous-core sandwiches with rigid core subjected to transverse
concentrated loads or support reactions.
(2) The value of (τ Ed )c may be estimated from Formula (8.79):
(τ Ed )c =
where
PEd
d ⋅u
PEd
is the design value of the transverse concentrated load;
u
is the control perimeter (see 8.4.3.5(3)).
d
(8.79)
is the distance between the face sheets’ centroids (Figure 7.1);
117
CEN/TS 19101:2022 (E)
(3) The control perimeter u is selected as being at a distance d /2 from the loaded area and should be
constructed so as to minimize its length (Figure 8.1).
Figure 8.1 — Typical control perimeters around loaded areas
(4) In cases where the loaded area is situated near an edge or a corner or where the shear force
originating from the applied concentrated load or support reaction is not uniformly distributed along the
control perimeter u (e.g. openings near the loaded area), the control perimeter u should be reduced.
(
(5) The values of ( f xz,v,k )c , f yz,v,k
) , (f
c
) , (f )
zx,v,k c
zy,v,k c
should be taken as the core material’s yield, 2 %
offset or ultimate shear strength in the relevant plane and direction, as defined in the relevant standard
test methods referred to in Table 5.2. The selection should be based on the material’s shear behaviour
and failure mode.
8.4.4 Web
8.4.4.1
Web shear failure
( )
(1) The design value of the in-plane shear stress in the web, τ Ed
(8.80):
w
(τ ) ≤ ( f )
where
Ed w
(f
)
xy,v,d w
is defined in 4.4.5 (to be selected for f xy,v,k
γ Rd
118
(8.81)
(
γm
(f
is the design value of the in-plane shear strength of the web, given by Formula (8.81),
ηc
⋅( f
)
γ m ⋅ γ Rd xy,v,k w
xy,v,d w
ηc
(8.80)
xy,v,d w
( f=
)
where
, shall satisfy the condition in Formula
)
w
);
w
);
is defined in 4.4.6 (Table 4.4, Composite material failure);
(
)
xy,v,k w
is defined in 4.4.7 (to be selected for f xy,v,k
)
is the characteristic value of the in-plane shear strength of the web.
CEN/TS 19101:2022 (E)
( )
(2) In web-core sandwiches without core infill, τ Ed
(τ )
Ed w
where
=
VEd ⋅ b
tw ⋅ h
may be calculated from Formula (8.82):
VEd
is the design value of the acting transverse shear force per unit width;
tw
is the web thickness (Figure 7.1);
b
is the height of the sandwich panel (Figure 7.1).
( )
(3) In web-core sandwiches with core infill, τ Ed
(τ )
Ed w
=
(VEd )w
w
may be calculated from Formula (8.83):
tw ⋅ h
(VEd )w
8.4.4.2
Web wrinkling due to shear
( )
(8.84):
(τ ) ≤ ( f
Ed w
(f
)
)
wr,v,d w
(f
, shall satisfy the condition in Formula
(8.84)
is the design value of the shear wrinkling stress of the web, given by Formula (8.85),
1
γ m ⋅ γ Rd
⋅ ( f wr,v,k )w
(8.85)
(
γm
γ Rd
w
wr,v,d w
wr,v,d w
( f=
)
where
(8.83)
is the design value of the shear force in the web component and may be estimated by
distributing the acting transverse shear force among the web and core infill
components according to their shear stiffnesses (7.1.1(7)).
(1) The design value of the in-plane shear stress in the web, τ Ed
where
(8.82)
is the web spacing (Figure 7.1);
h
where
w
)
is defined in 4.4.5 (to be selected for E ⊥ ,k , as defined in 8.4.4.2(3));
)
wr,v,k w
c
is defined in 4.4.6 (Table 4.4, Face sheet/web wrinkling);
is the characteristic value of the shear wrinkling stress of the web, which should be
estimated as per 8.4.4.2(3) to (5).
( )
(2) The value of τ Ed
w
may be calculated as per 8.4.4.1(3), Formula (8.83).
119
CEN/TS 19101:2022 (E)
(3) For balanced symmetric laminates subjected to pure in-plane shear,
(f
)
wr,v,k w
may be selected as
being equal to the compression wrinkling stress in the principal stress direction (±45°). The value of
( fwr,v,k )w should be estimated using the semi-empirical Formula (8.86), which takes common
imperfections into account:
(f
where
)
i ,wr,k f
(
)
(
)
=0,65 ⋅ 3 (ηc )w ⋅ ( E i ,c,k )w  ⋅ (ηc )c ⋅ E ⊥ ,k  ⋅ (ηc )c ⋅ G⊥ ,k 
c 
c

i
(8.86)
refers to the principal compressive stress direction;
(E )
is the characteristic value of the compressive modulus in the i direction of the web;
i ,c,k w
(E )
is the characteristic value of the elastic modulus of the core in the direction
perpendicular to the plane of the web (based on the value of the tensile or
compressive modulus, whichever is lower);
⊥ ,k c
(G )
is the characteristic value of the shear modulus of the core in the plane perpendicular
to the web that includes the i direction;
⊥,k c
is defined in 4.4.7 (to be selected for ( E i ,c,k )w );
(ηc )w
(ηc )c
is defined in 4.4.7 (to be selected for the core material).
(4) If the core material is stressed beyond its proportional limit, the appropriate secant or reduced moduli
should be used in Formula (8.86) to estimate the wrinkling stress.
(5) As an alternative to Formula (8.86), finite element analysis may be used to conduct the wrinkling
verification (8.4.1(6)).
8.4.4.3
Web local buckling due to shear
( )
(1) The design value of the in-plane shear stress in the web, τ Ed
(8.87):
(τ ) ≤ ( f
where
Ed w
(f
where
(f
=
)
xy,cr,d w
γm
, shall satisfy the condition in Formula
xy,cr,d w
xy,cr,d w
γ Rd
120
)
)
w
(8.87)
is the design value of the critical buckling shear stress of the web, given by
Formula (8.88),
1
⋅ χ ⋅( f
)
γ m ⋅ γ Rd v xy,cr,k w
(8.88)
is defined in 4.4.5 (to be selected for E y,c,k , the characteristic value of the in-plane
compressive modulus in the y direction of the web);
is defined in 4.4.6 (Table 4.4, Local buckling);
CEN/TS 19101:2022 (E)
(f
)
xy,cr,k w
χv
is the characteristic value of the critical buckling shear stress of the web, as indicated
in C.4.2.2, provided that the web laminate’s minimum length/width ratio complies
with C.4.1(1), and considering the appropriate values of the conversion factor, ηc , for
the relevant material properties (defined in 4.4.7). It may be conservatively assumed
that the web is simply supported at the connections with the face sheets;
is the buckling reduction factor for in-plane shear to take into account imperfections,
which can be taken as 1,0 for flat laminates (see Note 1 to 8.2.2.2(4)).
( )
(2) The value of τ Ed
8.4.4.4
w
may be calculated as per 8.4.4.1, Formula (8.83).
Web in-plane bending failure
(
(1) The design value of the in-plane bending stress in the web, σ x,M,Ed
Formulae (8.89) and (8.90):
(σ
) ≤( f )
x,M,Ed w
(σ
where
x,t,d w
)
≤ ( f x,c,d )w
x,M,Ed w
(f )
x,t,d w
(f )
x,c,d w
f )
(=
x,t,d w
if
x,c,d w
)
≥0
x,M,Ed w
(σ
)
, shall satisfy the condition in
x,M,Ed w
(8.89)
<0
(8.90)
is the design value of the compressive strength in the longitudinal (x) direction of the
web, given by Formulae (8.91) and (8.92),
ηc
⋅( f )
γ m ⋅ γ Rd x,c,k w
γm
(σ
w
is the design value of the tensile strength in the longitudinal (x) direction of the web;
ηc
⋅( f )
γ m ⋅ γ Rd x,t,k w
( f=
)
where
if
)
if
if
(σ
)
x,M,Ed w
(σ
)
≥0
x,M,Ed w
<0
(8.91)
(8.92)
is defined in 4.4.5 (to be selected for ( f x,t,k )w for tension or ( f x,c,k )w for compression);
γ Rd
is defined in 4.4.6 (Table 4.4, Composite material failure);
(f )
is the characteristic value of the tensile strength in the longitudinal (x) direction of
the web;
ηc
x,t,k w
(f )
x,c,k w
is defined in 4.4.7 (to be selected for ( f x,t,k )w for tension or ( f x,c,k )w for compression);
is the characteristic value of the compressive strength in the longitudinal (x) direction
of the web.
NOTE Web in-plane bending failure occurs when the web, subjected to in-plane bending, fails by fracture or
crushing in its tensioned or compressed side respectively, i.e. the web in-plane stresses due to bending exceed the
relevant material’s in-plane strengths.
121
CEN/TS 19101:2022 (E)
(
(2) The value of σ x,M,Ed
(σ
)
w
may be calculated from the bending stress in the equivalent homogeneous core,
) , as per 7.1.4.1(9) and 7.1.4.1(10).
i ,M,Ed c
8.4.4.5
Web wrinkling due to in-plane bending
(
(1) The design value of the compressive stress in the web due to in-plane bending, σ x,M,Ed
satisfy the condition in Formula (8.93):
(σ
where
)
x,M,Ed w
(f
≤ ( f x,wr,d )w
)
x,wr,d w
( f=
)
where
x,wr,d w
(8.93)
1
⋅( f
)
γ m ⋅ γ Rd x,wr,k w
(8.94)
(
)
)
x,wr,k w
c
is defined in 4.4.6 (Table 4.4, Face sheet/web wrinkling);
(
is the characteristic value of the wrinkling stress in the longitudinal (x) direction of
the web (8.4.4.5(3) to (5)).
(2) The value of σ x,M,Ed
)
w
may be calculated from the bending stress in the equivalent homogeneous core,
) , as per 7.1.4.1(9) and 7.1.4.1(10).
i ,M,Ed c
(3) The value of
(f
)
x,wr,k w
should be estimated using the semi-empirical Formula (8.95), which takes
common imperfections into account:
(f
where
)
i ,wr,k w
i
i ,c,k w
(E )
⊥,k c
(G )
⊥,k c
(ηc )w
(ηc )c
(
)
(
)
=0,65 ⋅ 3 (ηc )w ⋅ ( E i ,c,k )w  ⋅ (ηc )c ⋅ E ⊥ ,k  ⋅ (ηc )c ⋅ G⊥ ,k 
c 
c

(E )
122
< 0 , shall
is defined in 4.4.5 (to be selected for E ⊥ ,k , as defined in 8.4.4.5(3));
γ Rd
(σ
w
is the design value of the wrinkling stress in the longitudinal (x) direction of the web,
given by Formula (8.94),
γm
(f
)
(8.95)
refers to the web’s longitudinal (x) direction;
is the characteristic value of the compressive modulus in the i direction of the web;
is the characteristic value of the elastic modulus of the core in the direction
perpendicular to the plane of the web (based on the value of the tensile or
compressive modulus, whichever is lower);
is the characteristic value of the shear modulus of the core in the plane perpendicular
to the web that includes the web’s transverse direction;
is defined in 4.4.7 (to be selected for ( E i ,c,k )w );
is defined in 4.4.7 (to be selected for the core material).
CEN/TS 19101:2022 (E)
(4) If the core material is stressed beyond its proportional limit, the appropriate secant or reduced moduli
should be used in Formula (8.95) to estimate the wrinkling stress.
(5) As an alternative to Formula (8.95), finite element analysis may be used to conduct the wrinkling
verification (8.4.2.3(5)).
8.4.4.6
Web local buckling due to in-plane bending
(
(1) The design value of the in-plane bending stress in the web in its longitudinal (x) direction, σ x,M,Ed
shall satisfy the condition in Formula (8.96):
(σ
where
(f
where
) ≤( f
x,M,Ed w
(f
)
)=
1
γ m ⋅ γ Rd
⋅ χ x,b ⋅ ( f x,b,cr,k )w
(8.97)
is defined in 4.4.5 (to be selected for E x,c,k , the characteristic value of the in-plane
compressive modulus in the longitudinal (x) direction of the web);
γ Rd
is defined in 4.4.6 (Table 4.4, Local buckling);
ηc
is defined in 4.4.7;
)
is the characteristic value of the in-plane critical buckling bending stress in the
longitudinal (x) direction of the web, as indicated in C.4.2.3, provided that the web
laminate’s minimum length/width ratio complies with C.4.1(1), and considering the
appropriate values of the conversion factor, ηc , for the relevant material properties
(defined in 4.4.7). It may be conservatively assumed that the web is simply supported
at the connections with the face sheets;
x,b,cr,k w
χ x,b
(
is the buckling reduction factor for bending in the longitudinal (x) direction to take
into account imperfections, which can be taken as 1,0 for flat laminates (see Note 1
to 8.2.2.2(4)).
(2) The value of σ x,M,Ed
(
,
is the design value of the in-plane critical buckling bending stress in the longitudinal
(x) direction of the web, given by Formula (8.97),
γm
(f
w
(8.96)
x,b,cr,d w
x,b,cr,d w
x,b,cr,d w
)
)
)
)
w
may be calculated from the bending stress in the equivalent homogeneous
core, σ i ,M,Ed , as per 7.1.4.1(9) and 7.1.4.1(10).
8.4.4.7
c
Web crushing due to transverse compression
(1) The design value of the compressive stress in the web,
concentrated loads shall satisfy the condition in Formula (8.98):
(σ
)
y,c,Ed w
, resulting from transverse
123
CEN/TS 19101:2022 (E)
(σ
where
) ≤( f )
y,c,Ed w
(f )
is the design value of the compressive strength in the transverse (y) direction of the
web, given by Formula (8.99),
y,c,d w
( f=
)
y,c,d w
where
(8.98)
y,c,d w
ηc
⋅( f )
γ m ⋅ γ Rd y,c,k w
(8.99)
(
γm
is defined in 4.4.5 (to be selected for f y,c,k
γ Rd
)
w
);
w
);
is defined in 4.4.6 (Table 4.4, Composite material failure);
(
ηc
is defined in 4.4.7 (to be selected for f y,c,k
(f )
)
is the characteristic value of the compressive strength in the transverse (y) direction
of the web.
y,c,k w
NOTE 1 Web crushing failure occurs when the web, subjected to transverse concentrated loads, fails by crushing,
i.e. the web in-plane transverse compressive stress exceeds the material’s in-plane transverse compressive
strength.
NOTE 2 This failure mode can occur in web-core sandwiches subjected to transverse concentrated loads or support
reactions.
(2) The design value of the compressive stress in the web,
(σ
)
y,c,Ed w
concentrated loads or reactions may be calculated from Formula (8.100):
(σ
where
)
y,c,Ed w
=
PEd
leff ⋅ t w
PEd
tw
leff
leff= ss + sn
where
ss
sn
124
, resulting from transverse
(8.100)
is the design value of the applied transverse concentrated load or support reaction
borne by the web;
is the web thickness (Figure 7.1b);
is the effective width for the verification of transverse compression in the web, given
by Formula (8.101),
(8.101)
is the width along the web on which the load or the support reaction is applied
(Figure 8.2);
is the width obtained by a dispersion of the load or support reaction at 45 ° at z depth
(Figure 8.2).
CEN/TS 19101:2022 (E)
z = t f , for verification of web crushing (8.4.4.7) and web wrinkling (8.4.4.8) due to transverse compression;
NOTE
z = h / 2 for verification of web local buckling due to transverse compression (8.4.4.9).
Figure 8.2 — Effective width for verification of transverse compression in web
8.4.4.8
Web wrinkling due to transverse compression
(1) The design value of the compressive stress in the web,
concentrated loads shall satisfy the condition in Formula (8.102):
(σ
where
) ≤( f
y,c,Ed w
(f
)
y,wr,d w
( f=
)
y,wr,d w
where
)
)
y,c,Ed w
, resulting from transverse
y,wr,d w
(8.102)
is the design value of the wrinkling stress in the transverse (y) direction of the web,
given by Formula (8.103),
1
⋅( f
)
γ m ⋅ γ Rd y,wr,k w
(8.103)
(
γm
(σ
)
is defined in 4.4.5 (to be selected for E ⊥ ,k , as defined in 8.4.4.5(3));
γ Rd
(f )
y,c,k w
c
is defined in 4.4.6 (Table 4.4, Face sheet/web wrinkling);
is the characteristic value of the wrinkling stress in the transverse (y) direction of the
web, and should be estimated as per 8.4.4.5(3) to (5), by selecting i as being equal to
the web’s transverse direction, y, and considering the appropriate values of the
conversion factors, ηc , for the relevant material properties (defined in 4.4.7).
NOTE 1 Compression wrinkling occurs in the web when the in-plane transverse compressive stress attains the
web’s wrinkling stress.
NOTE 2 This failure mode can occur in web-core sandwiches (with core infill) subjected to transverse concentrated
loads or support reactions.
(
(2) σ y,c,Ed
)
w
may be calculated as per 8.4.4.7(2).
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CEN/TS 19101:2022 (E)
8.4.4.9
Web local buckling due to transverse compression
(1) The design value of the compressive stress in the web,
concentrated loads shall satisfy the condition in Formula (8.104):
(σ
where
(f
where
) ≤( f )
y,c,Ed w
, resulting from transverse
(8.104)
is the design value of the critical local buckling compressive stress in the transverse
(y) direction of the web, given by Formula (8.105),
y,cr,d w
)=
)
y,c,Ed w
y,cr,d w
(f )
y,cr,d w
(σ
1
⋅ χ ⋅( f
)
γ m ⋅ γ Rd y,c y,cr,k w
(8.105)
γm
is defined in 4.4.5 (to be selected for E y,c,k , the characteristic value of the in-plane
γ Rd
is defined in 4.4.6 (Table 4.4, Local buckling);
compressive modulus in the transverse (y) direction of the web);
(f )
is the characteristic value of the critical local buckling compressive stress in the
transverse (y) direction of the web, and can be calculated as indicated in C.4.2.1,
considering the appropriate values of the conversion factor, ηc , for the relevant
y,cr,k w
material properties (defined in 4.4.7). The effective width of the web, leff (8.4.4.7(2)),
should be used in the calculations instead of the web depth, bw ;
χ y,c
is the buckling reduction factor for compression in the transverse (y) direction to
take into account imperfections, which may be taken as 1,0 for flat laminates (see
Note 1 to 8.2.2.2(4)).
NOTE 1 Web local buckling due to transverse compression occurs when the compressive stress in the web attains
the web’s critical buckling compressive stress.
NOTE 2 This failure mode can occur in web-core sandwiches without core infill, subjected to transverse
concentrated loads or support reactions.
(
(2) The value of σ y,c,Ed
8.4.5 Interface
8.4.5.1
)
w
may be calculated as per 8.4.4.7(2).
Face sheet/core delamination
(1) The out-of-plane tensile strength of the face sheet/core interface shall exceed the individual out-ofplane (z direction) tensile strengths of the face sheet and core materials, and thus interface failure shall
not occur. The out-of-plane (flatwise) tensile strength of the sandwich construction may be determined
according to ASTM C297/C297M.
(2) The shear strength of the face sheet/core interface shall exceed the minimum out-of-plane shear
strength of the face sheet and core materials, and thus interface failure shall not occur. Accordingly, only
core shear failure should be considered as an acceptable shear failure mode in sandwich flexure
experiments conducted according to ASTM C393/C393M.
126
CEN/TS 19101:2022 (E)
8.4.6 Sandwich panel
8.4.6.1
Global buckling
(1) Global stability verifications may be conducted as per 8.4.1(4) to (6).
(2) The effect of transverse shear should be taken into account for the verification of the global stability
of the sandwich panel.
(3) Boundary conditions should be taken into account in the global buckling analysis.
(4) Interactions under axial loads, axial and in-plane shear loads or in-plane and out-of-plane loads
should be taken into account for global stability verifications.
(5) The design value of the axial load applied to the sandwich panel, Ni ,Ed , shall satisfy the condition in
Formula (8.106):
Ni ,Ed ≤ Pi ,c,d
where
i
Pi ,c,d
(8.106)
refers to the x and y directions;
is the design value of the buckling load in the examined i direction, obtained by applying
the relevant partial and conversion factors to the bending and transverse shear
components of the critical buckling load.
(6) In the case of sandwich columns or wide sandwich panels with thin face sheets, subjected to uniaxial
loads and supported only at the edges perpendicular to the load direction (free edges parallel to the load
direction), the design value of the buckling load per unit width may be calculated from Formula (8.107):
Pc,d =
where
Pcb,d ⋅ Pcs,d
(8.107)
Pcb,d + Pcs,d
Pcb,d
Pcs,d
is the design value of the buckling load component corresponding to pure bending (Euler
buckling load);
is the design value of the buckling load component corresponding to transverse shear
forces.
(7) The value of Pcb,d in Formula (8.107) may be calculated from Formula (8.108):
Pcb,d
=
where
γm
γ Rd
π 2 ⋅ Dk
1
⋅
γ m ⋅ γ Rd ( l0 )2
(8.108)
is defined in 4.4.5 (to be selected for the in-plane compressive modulus of the face
sheets, E i ,c,k , as defined in 7.1.4.1(6) ( E f ));
(
)
f
is defined in 4.4.6 (Table 4.4, Global buckling);
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CEN/TS 19101:2022 (E)
Dk
is the characteristic value of the flexural stiffness per unit width of the sandwich
beam (7.1.4.1(6)), considering the appropriate values of the conversion factor, ηc ,
for the relevant material properties (defined in 4.4.7);
l0
is the buckling length, dependent on the boundary conditions.
(8) For sandwich beams with thin face sheets (7.1.4.1(4)) and flexible core (7.1.4.1(5)), Pcs,d in Formula
(8.107) may be calculated from Formula (8.109):
=
Pcs,d
where
ηc
(G ) ⋅ d 2
⋅ k c
γ m ⋅ γ Rd
tc
γm
is defined in 4.4.5 (to be selected for (Gk )c );
ηc
is defined in 4.4.7 (to be selected for (Gk )c );
γ Rd
(Gk )c
d
tc
(8.109)
is defined in 4.4.6 (Table 4.4, Global buckling);
is the characteristic value of the out-of-plane shear modulus of the core;
is the distance between the face sheets’ centroids (Figure 7.1);
is the core thickness (Figure 7.1).
(9) If the face sheet or core stresses corresponding to the buckling load obtained as per Formula (8.107)
exceed the proportional limit of the core material, the appropriate reduced moduli should be used in
Formula (8.107) to estimate the buckling load.
8.5 Creep rupture
(1) Creep rupture of composite members and components shall be prevented by limiting sustained
stresses. All relevant quasi-permanent combinations of actions according to EN 1990 shall be used to
verify creep rupture of composite members and components.
NOTE 1 Composite materials subjected to sustained stresses can fail suddenly after a time period, referred to as the
endurance time, due to a phenomenon known as creep rupture (tertiary creep). The endurance time depends on
the fibre type and architecture, the level of sustained stresses, the type of loading and environmental conditions.
NOTE 2 Creep rupture can occur under sustained tensile, compressive, bending and shear stresses.
NOTE 3 Creep rupture can be fibre- or matrix-dominated, depending on the direction of the sustained stresses and
fibre architecture.
(2) The design value of the maximum sustained tensile stress caused by the quasi-permanent
combinations of actions, σ t,creep,Ed , shall satisfy the condition in Formula (8.110), in the case of fibredominated creep rupture:
σ t,creep,Ed ≤ σ t,creep,Rd
where
128
σ t,creep,Rd
(8.110)
is the design value of the tensile stress limit for creep rupture, which should be
determined from Formula (8.111),
CEN/TS 19101:2022 (E)
σ t,creep,Rd =
where
ηc
γ M,creep
ηc
⋅ kt,creep ⋅ fi ,t,k
(8.111)
is defined in 4.4.7 (to be selected for fi ,t,k );
γ M,creep
is the partial factor for creep rupture;
is the strength reduction factor for tensile creep rupture for continuous
unidirectional fibres, taken from Table 8.3;
kt,creep
is the characteristic value of the tensile strength of the composite laminate in the fibre
( i ) direction.
fi ,t,k
Table 8.3 — Strength reduction factor for tensile creep rupture for continuous unidirectional
fibres, kt,creep , different types of fibres and a period of 50 years
Type of fibre
Glass
Aramid
Basalt
Carbon
kt,creep
0,4
0,5
0,6
0,9
NOTE 1 The values of kt,creep given in Table 8.3 are for tensile creep rupture of unidirectional laminates after 50
years.
NOTE 2 For laminates with fibre architecture other than purely unidirectional, the kt,creep values apply in the
continuous fibre directions.
NOTE 3 For aramid, basalt and carbon fibres, the fibre-type value of kt,creep given in Table 8.3 can be taken for both
50 and 100 years of sustained constant tensile stress, and for time durations between 50 and 100 years.
NOTE 4 The partial factor for creep rupture is γ M,creep = 1,5 , unless the National Annex gives different values.
(3) For periods different than 50 years, the extrapolation Formula (8.112), limited to 100 years, may be
used for composite laminates with glass fibres:
kt,creep (t ) =
0,9 − 0,088 ⋅ lg(t )
where t is time in hours.
(8.112)
(4) The value of σ t,creep,Ed should be taken as the mean tensile stress over the cross-sectional area for
members in tension, or the maximum tensile stress for members in bending.
(5) The design value of the maximum sustained compressive stress caused by the quasi-permanent
combinations of actions, σ c,creep,Ed , shall satisfy the condition in Formula (8.113), in the case of fibredominated creep rupture:
σ c,creep,Ed ≤ σ c,creep,Rd
where
σ c,creep,Rd
(8.113)
is the design value of the compressive stress limit for creep rupture, which should be
determined from Formula (8.114),
129
CEN/TS 19101:2022 (E)
σ c,creep,Rd =
where
ηc
γ M,creep
kc,creep
fi ,c,k
ηc
γ M,creep
⋅ kc,creep ⋅ fi ,c,k
(8.114)
is defined in 4.4.7 (to be selected for fi ,c,k );
is the partial factor for creep rupture (see Note 4 to 8.5(2));
is the strength reduction factor for compressive creep rupture for continuous
unidirectional fibres, which may be taken as 0,75 ⋅ kt,creep , for the corresponding fibre
type ( kt,creep as in Table 8.3);
is the characteristic value of the compressive strength of the composite laminate in
the fibre ( i ) direction.
NOTE In general, the resistance to creep rupture under compressive stresses in the fibre direction of the member
is lower than the corresponding resistance under tensile stresses, because in compression the viscoelastic effects
of the matrix can reduce fibre support.
(6) The value of σ c,creep,Ed should be taken as the mean compressive stress over the cross-sectional area
for members in compression, or the maximum compressive stress for members in bending.
(7) For members in bending and fibre-dominated creep rupture, the design value of the compressive
stress limit for creep rupture according to 8.5(5) should be selected.
NOTE Sustained shear stresses associated to sustained bending can lead to matrix-dominated creep rupture,
depending on the fibre-architecture.
(8) When establishing a design value of the maximum sustained stress caused by the quasi-permanent
combinations of actions in a member (8.5(4) and (6)), the presence of stress concentrations may be
neglected.
NOTE Stress concentrations exist in relatively small volumes of material and these regions are less likely to having
the critical defects for creep rupture at the stress limit.
(9) The quasi-permanent value of the maximum material temperature in service conditions ( Ts ), defined
considering the probabilities of non-exceedance and reference periods according to 4.3.1.2(4), may be
used to determine the conversion factor for temperature in 8.5(2) and 8.5(5).
(10) As an alternative to 8.5(2), design by testing for tensile creep rupture of composite laminates may
be performed in accordance with the test method for plastics in ISO 899-1.
(11) As an alternative to 8.5(5), design by testing for compressive creep rupture of composite laminates
may be performed in accordance with the test method for plastics in ASTM D2990.
(12) For a design situation not scoped by 8.5(2) to (7), design for creep rupture failure should be based
on testing (see 4.5(1)).
130
CEN/TS 19101:2022 (E)
9 Serviceability limit states
9.1 General
(1) Composite structures shall be designed and constructed such that all relevant serviceability criteria
are satisfied, namely those given in EN 1990:—, 5.4, including:
— deflections, which affect the appearance of the structure, the comfort of users and the functionality
of the structure, or cause damage to the finishing and non-structural elements (9.2);
— vibrations, which cause discomfort to users or affect the functionality of the structure (9.3);
— matrix cracking in case it has an adverse effect on the durability or functionality of the structure (9.4).
(2) For the calculation of deflections, vibrations and stresses that can cause matrix cracking, the effects
of environmental conditions on the stiffness of the material should be considered through the application
of conversion factors (4.4.7).
(3) For the calculation of deflections, the effects of creep should be considered through the application of
creep coefficients (4.4.8).
(4) The least favourable situation for the design should be assumed and conversion factors and creep
coefficients should be applied accordingly.
(5) Serviceability limit states (SLS) shall be verified using appropriate structural and action models.
(6) Any SLS and the associated loading and analysis models should be as specified by the relevant
authority or, where not specified, agreed for a specific project by the relevant parties.
(7) For SLS verifications, the quasi-permanent, frequent and characteristic values of the maximum
material temperature in service conditions ( Ts ), defined considering the probabilities of non-exceedance
and reference periods according to 1.1(4), may be used to determine the conversion factor for
temperature ( ηc ).
9.2 Deflections
(1) The deformation of a member or structure should not adversely affect its proper functionality,
integrity, appearance and the comfort of users. Appropriate limiting values of deflection taking into
account the nature of the structure, of the finishes, partitions and fixings and upon the function of the
structure should be established. As an alternative, it may be assumed that an acceptable function can be
achieved if the requirements of 9.2(2) are met.
(2) Maximum values of vertical deflections may be specified by the relevant authorities or, where not
specified, agreed for a specific project by relevant parties.
NOTE Suggested values of maximum permitted vertical and horizontal deflections for buildings are given in
EN 1990:—, Tables A.1.10 and A.1.11, unless the National Annex to EN 1990 gives different values.
(3) The maximum deflections of a member or structure should be determined for the relevant actions
and combinations of actions defined in EN 1990 using mean values of elastic moduli, accounting for the
environmental conditions through the appropriate conversion factors (4.4.7) and considering the creep
effects (4.4.8).
NOTE 1 The characteristic combination of actions is normally used in cases where excessive deformations can lead
to irreversible effects or permanent damage, namely in non-structural members.
NOTE 2 The frequent combination of actions and the frequent value of variable actions are normally used to assess
effects that are reversible, i.e. effects that occur with a certain frequency but that are reduced or fully recovered
when the action decreases or is removed.
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CEN/TS 19101:2022 (E)
NOTE 3 The quasi-permanent combination of actions is normally used to assess long-term (creep) effects and the
appearance of the member or structure.
(4) Vertical deflections should be calculated using the following parameters, shown in Figure 9.1,
wc
w1
w2
w3
w tot
wmax
L
is the precamber in the unloaded structural member (if applied);
is the initial part of the deflection under permanent loads of the relevant combination of
actions;
is the long-term part of the deflection under permanent loads including quasi-permanent
loads;
is the instantaneous deflection due to variable actions excluding the quasi-permanent
loads;
is the total deflection as the sum of w1 , w2 , w3 ;
is the remaining total deflection taking into account the precamber;
is the span.
Figure 9.1 — Components of deflection
(5) For composite structures consisting of members or components with the same creep behaviour for
the relevant stress states and under the assumption of a linear relationship between the actions and the
corresponding deformations, for the following combinations of actions, the values of deflections w1 , w2
, w3 , may be calculated from Formulae (9.1), (9.2) and (9.3),
— characteristic combination of actions:

w2 = wGk +

∑ψ
w3 =wQk,1 +
∑ψ
j
j >1
2,j
0,j

⋅ wQk,j  ⋅ φ(t )

⋅ wQk,j
— frequent combination of actions:

w2 = wGk +

∑ψ
j
w
=
ψ 1,1 ⋅ wQk,1
3
132
2,j

⋅ wQk,j  ⋅ φ(t )

(9.1a)
(9.1b)
(9.2a)
(9.2b)
CEN/TS 19101:2022 (E)
— quasi-permanent combination of actions:
w1 = wGk

w2 = wGk +

where
∑ψ
j
wGk
2,j

⋅ wQk,j  ⋅ φ(t )

(9.3b)
is the initial part of the deflection under permanent loads;
wQk,1
is the instantaneous deflection due to the leading variable action;
φ(t )
is the creep coefficient at time t ;
wQk,j
ψ 2,1 ,
ψ 2,i
(9.3a)
is the instantaneous deflection due to accompanying variable actions;
ψ 1,1 , are the combination factors applied to variable actions to determine their
combination value, as per EN 1990.
NOTE 1 Composite materials have different creep behaviour under axial stresses and shear stresses. For axial
stresses, in general, the creep behaviour in tension and compression is also different (4.4.8).
NOTE 2 In composite sandwich panels, in general, the creep behaviour of the face sheets and the core are different.
NOTE 3 In web-core sandwich panels, in general, the creep behaviour of the face sheets, the webs and the core are
different.
(6) For composite structures consisting of members or components with different creep behaviour, for
the relevant stress states, such differences should be considered when determining the final deflections.
(7) In bridges, the quasi-permanent component of Formulae (9.1a), (9.2a) and (9.3b) due to traffic loads
may be neglected.
NOTE
Creep deformations due to traffic loads in bridges normally recover during unloaded periods.
9.3 Vibrations
(1) Measures should be taken to prevent vibrations that cause discomfort to people or limit the functional
effectiveness of the structure.
NOTE An increase in self-weight due to resin absorption by the core of sandwich panels can affect the vibration
behaviour, see 4.3.1.1(2).
(2) Vibrations should be considered according to EN 1990:—, Annex A.
(3) When determining the dynamic response, a conservative value of damping ratio of 0,4 % may be used
for the structural analysis of footbridges of consequence classes CC3 and CC4, as per EN 1990:—,
Table 4.1, and a value of 1,0 % may be considered for other footbridges. Higher damping values may be
used if confirmed by representative experimental data.
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CEN/TS 19101:2022 (E)
9.4 Matrix cracking
(1) Matrix cracking of composite laminates may be prevented by imposing a limit to the tensile strain due
to the frequent combination of actions, ε t,SLS , considering the effects of creep in permanent and quasipermanent loads:
crack
ε t,SLS ≤ ε t,d
where
crack
ε t,d
crack
ε t,d
=
where
(9.4)
is the design value of the tensile strain causing matrix cracking, which should be taken as
ε t,kcrack
γm
γm
ε t,kcrack
(9.5)
is defined in 4.4.5 (to be selected for the tensile strength of the composite laminate);
is the characteristic value of the tensile strain causing matrix cracking.
NOTE Matrix cracking can be relevant for the in-service performance of composite structures under exposure
classes II and III (see Table 4.6).
crack
(2) For composite laminates consisting of polyester or epoxy resins, values of respectively ε t,k
= 0,3%
crack
and ε t,k
= 0,6% may be considered. Other values may be considered based on results of tests on
composite laminates.
NOTE
Matrix cracking can be identified from tensile tests (Table 5.1) based on the change of elastic stiffness.
(3) In bridges, creep deformations due to quasi-permanent loads may be neglected (see Note to 9.2(7)).
10 Fatigue
10.1 General
(1) The structural design should ensure that stress concentrations are avoided or minimized by
appropriate detailing of geometrical changes in sections or changes in materials.
(2) Since fatigue failure, in most cases, occurs in singular areas where a stress-based verification is
difficult (e.g. in a web-flange junction), the fatigue verification, including testing, may be performed at the
structural member or joint level (e.g. for a bridge deck or a deck-to-girder joint), based on the action
effects, i.e. internal forces and/or moments.
NOTE Testing at the member and joint level also takes into account geometrical and material imperfections and
size effects.
(3) A fatigue verification should be performed for a structural member or joint if the condition in Formula
(10.1) is fulfilled:
E d ( γ Ff ⋅ Qfat ) / Rd > 1,6 − 0,18 ⋅ lg N
where
134
E d ( γ Ff ⋅ Qfat )
(10.1)
is the design value of an action effect in the structural member or joint (an internal
force and/or moment), caused by the fatigue action model;
CEN/TS 19101:2022 (E)
γ Ff
is the partial factor for the fatigue action (according to EN 1990);
Rd
is the design value of the corresponding static resistance of the member or joint,
according to 4.4.4(3);
Qfat
is the relevant constant amplitude fatigue action;
N
is the number of cycles of the fatigue action, i.e. the number of axle loads.
10.2 Fatigue actions
(1) The fatigue action model should take into account the mean stress level or the R -ratio, exhibited by
the actual actions. The R -ratio should be obtained from Formula (10.2):
R = E d,min / E d,max
where
(10.2)
E d,min , E d,max
are the minimum and maximum design values of an action effect in the member or
joint, obtained from the permanent and/or fatigue actions.
(2) The fatigue action model for traffic loads should be derived in accordance with EN 1991-2 and as
specified by the relevant authority or, where not specified, agreed for the specific project by the relevant
parties.
NOTE 1 Bridge exposure to braking and acceleration actions can induce fatigue effects in cellular bridge decks,
particularly in those of short-span bridges.
NOTE 2 The Palmgren-Miner linear damage hypothesis is not considered applicable for composites.
(3) Fatigue actions due to wind excitations should be selected in accordance with EN 1991-1-4.
(4) Fatigue actions due to temperature variations should be defined in accordance with EN 1990:—,
6.1.3.3(4).
(5) Fatigue action models for traffic loads, wind and temperature should not be combined.
10.3 Fatigue verification
(1) The fatigue verification should be performed at the structural member or joint level and be based on
an internal force and/or moment, as indicated in Formula (10.3):
E d ( γ Ff ⋅ Qfat ) ≤
where
ηc
⋅R
γ Mf f, k
E d ( γ Ff ⋅ Qfat )
Rf, k
γ Mf
ηc
(10.3)
is defined according to 10.1(2);
is the characteristic value of the corresponding fatigue resistance of the member
or joint, which should be obtained from member or joint testing, at constant
amplitude (10.4);
is the partial factor for the fatigue resistance;
is defined in 4.4.7 (to be selected for the material property which causes failure).
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CEN/TS 19101:2022 (E)
NOTE 1 The partial factor for fatigue resistance
different values.
γ Mf is given in Table 10.1(NDP), unless the National Annex gives
Table 10.1(NDP) — Partial factors for fatigue resistance, γ Mf
Inspection and access
Fail-safe
Non-fail-safe
Member or joint subjected to periodic
inspection and maintenance a;
detail accessible.
1,5
2,0
2,0
2,5
2,5
3,0
Member or joint subjected to periodic
inspection and maintenance a;
limited accessibility.
Member or joint not subjected to
periodic inspection and maintenance.
a
according to maintenance plan.
NOTE 2 The partial factor for the fatigue resistance depends on (i) the type of inspection and maintenance and
accessibility of the critical details, and (ii) the consequences of failure, i.e. whether a member or joint is fail-safe or
not, in accordance with EN 1990:—, 8.3.5.4(1), Note 2.
NOTE 3 In fail-safe structural members or joints local failure of the member or joint does not result in failure of the
structure or critical parts thereof. In non-fail-safe members or joints local failure of the member or joint could lead
to failure of the structure or critical parts thereof.
10.4 Fatigue testing
10.4.1 General
(1) Fatigue testing should be performed at the structural member or joint level.
(2) The test specimen should correspond to the structural member or joint or a representative segment
thereof.
(3) The fatigue test set-up, i.e. the specimen segment, boundary conditions and fatigue test load, should
be designed to reproduce the action effects (internal forces and/or moments) in the actual structural
member or joint caused by the selected fatigue action model.
(4) The fatigue test load should take into account (i) conversion and partial factors according to 10.3(1),
in order to obtain the characteristic value of the fatigue resistance from the test, as well as (ii) the mean
stress level or the R -ratio.
(5) In the case of a variable amplitude fatigue action model being selected, a corresponding spectrum
fatigue test load may be applied.
(6) The selected test frequency should not cause inadmissible heating effects.
(7) Representative environmental conditions should be applied during fatigue testing if the
environmental conditions are not taken into account by conversion factors.
(8) Qualification and proof testing should be performed, analogously to that specified in 10.4.2 for bridge
decks and slab bridges. Similar protocols may be derived for other types of composite members or
products, as specified by the relevant authority or, where not specified, agreed for a specific project by
the relevant parties.
NOTE
136
Qualification testing refers to EN 1990:—, D.3(1a), while proof testing refers to EN 1990:—, D.3(1e).
CEN/TS 19101:2022 (E)
10.4.2 Bridge decks and slab bridges
(1) If the surfacing layer has a significant stiffness, e.g. in the case of polymer concrete, the surfacing layer
may be taken into account in the design and fatigue testing. If this applies, the effects of temperature and
load rate on the surfacing layer stiffness should be considered.
NOTE 1 If the effect of elevated temperature on the stiffness of the surfacing material is significant, tests with and
without surfacing layer can be performed.
NOTE 2 If the fatigue life of the surfacing is inferior to that of the composite deck, fracture of the surfacing can cause
abrasion of the deck.
(2) The loading device configuration should induce the contact pressure distribution produced by the
tyre fatigue load and take into account the effects of the member or joint configuration and surfacing
layer.
(3) The induced contact pressure distribution of the loading device should not exhibit concentrations
towards the edges of the loading device.
NOTE
A soft pad between a steel plate and the deck can prevent pressure concentrations towards the edges.
(4) Finite element analysis may be used to design the loading device configuration.
(5) Qualification testing should be applied for each new product or design and may be performed only
once for a specific product.
(6) Qualification testing to approve a product or design should include:
— at least three static tests to determine the characteristic value of the static resistance; the coefficient
of variation, Vx , of the static resistance should be lower than 0,10;
— a minimum number of fatigue tests, as specified in Table 10.2;
— after concluding the fatigue loading with the number of cycles specified in Table 10.2, on each
specimen, a post-fatigue static test run to failure under the same conditions as the static tests.
Table 10.2 — Required number of fatigue tests and fatigue cycles in qualification testing for
bridges of 50 and 100 years of design service life
Number of fatigue cycles (×106)
Traffic
category a
Minimum
number of
fatigue tests
Local traffica
Long-distance
traffica
Local traffica
Long-distance
traffica
1
3
10
15
15
50
3 and 4
2
2
2
2
2
2
a
3
According to EN 1991-2.
50 years
2
100 years
5
5
10
(7) The result of qualification testing should be deemed a "pass" if, for each test:
— the required number of cycles is completed without failure;
— the stiffness reduction is less than 5%, to prevent excessive micro-cracking;
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CEN/TS 19101:2022 (E)
— detectable damage, i.e. macro-cracks, debonding, delamination, that could affect durability due to
moisture ingress does not occur;
— the result of the post-fatigue static test is within two standard deviations of the mean value of the
static resistance achieved in the static tests.
(8) In the case of a constant amplitude fatigue load and if a "pass" is obtained in all fatigue tests, the action
effect derived from the fatigue test load (internal force and/or moment) should be used as the
characteristic value of the fatigue resistance, Rf,k .
(9) In the case of a variable amplitude fatigue test load, 10.4.2(6) and (7) may be applied analogously.
(10) Proof testing should be applied for each application of a product, to verify that the properties are
achieved on site.
(11) Proof testing may be applied to project-specific adaptations of a product, i.e. adaptation of geometry
or configuration. Qualification testing is not required in these cases if the basic fatigue behaviour is not
changed.
NOTE
The consistency of the fatigue behaviour can be evaluated by numerical modelling.
(12) The proof testing protocol should be as specified by the relevant authority or, where not specified,
agreed for a specific project by the relevant parties.
(13) Proof testing may be unnecessary, when agreed for a specific project by the relevant parties.
11 Detailing
11.1 General
(1) The detailing of members and joints should be consistent with the design models adopted.
(2) The detailing of members and joints should ensure that stress concentrations are avoided or
minimized.
NOTE Stress concentrations can occur at locations of geometrical or material changes, holes and cut-outs, joints
and connections on the member and laminate level, and concentrated load introductions.
(3) The detailing should ensure that effects of environmental conditions are minimized, e.g. by
appropriate protection and dewatering systems.
NOTE Typical details for bridges, such as bearings, expansion joints, parapets and crash barrier fixations, are
shown in Annex E.
(4) The possible effects of tolerances and imperfections, such as eccentricities or thickness variations,
should be taken into account in the design of details.
11.2 Profiles
(1) In cases of possible exposure to local impact, closed-member sections should be selected.
NOTE
Outstanding flanges of open sections can be more easily damaged by local impact.
11.3 Sandwich panels and member laminates
(1) The minimum thickness of sandwich face sheets, excluding the thickness of any protective coatings
applied, should be 1,0 mm.
(2) Thickness changes of face sheets or laminates should be tapered transitions to reduce stress
concentration and avoid premature failure due to induced out-of-plane stresses. A tapering angle of
between 2 ° and 10 ° should be applied.
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CEN/TS 19101:2022 (E)
(3) In cores of sandwich panels consisting of dissimilar materials, stress concentrations in the face sheets
and core may be reduced by using scarf connections between the two core materials in lieu of butt
connections. The scarf angle should be between 30 ° and 60 °.
(4) Scarf, step-lap or single-strap connections may be used to connect face sheets (Figure 11.1) or
laminates; butt connections (i.e. connections of the face sheet or laminate ends) should not be used. For
a face sheet or laminate thickness greater than 5 mm, scarf or step-lap connections should be used instead
of single-strap connections in order to reduce eccentricities. For a face sheet or laminate thickness of less
than 5 mm, single-strap connections should be used.
(5) In scarf connections of face sheets (Figure 11.1a) or laminates, the scarf angle, α , should be at least
2 °; the scarf angle should not be greater than 10 ° for laminated connections or greater than 20 ° for
adhesive connections. Knife edges should not be used; the thickness at the adherend ends should be at
least 1,0 mm.
(6) In step-lap (Figure 11.1b) and single-strap (Figure 11.1c) connections, a minimum overlap length
equal to 10 times the step/laminate thickness and not less than 50 mm should be used.
(7) Inserts may be used to introduce concentrated loads into the sandwich panel. Local changes in the
geometry, stiffness and strength of the panel due to the presence of the insert should not prevent the
sandwich panel from bearing the stresses arising from the other applied loads.
139
CEN/TS 19101:2022 (E)
a) Scarf joint
b) Step-lap joint
a
c) Single-strap joint
α = 2 ° – 10 ° for laminated connections; α = 2 ° – 20 ° for adhesive connections
Key
1
face sheet
3
scarf connection
2
4
5
core
adhesive or gap
bonded or laminated plate
Figure 11.1 — Face sheet connections
11.4 Bolted connections
(1) The nominal bolt diameter, d , should not be less than the thickness of the thinnest connected
composite component, t min .
(2) The nominal bolt hole clearance (difference between the nominal bolt hole diameter, d0 , and
d ) should fulfil the 1,0 mm limit requirement specified in Table 11.1.
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CEN/TS 19101:2022 (E)
(3) Geometric requirements for bolted connections given in Table 11.1 should be followed, with symbols
defined in Figures 11.2 and 11.3. The end edge distance for single- or multi-row bolted connections may
be reduced when design is by testing (see 4.5(1)).
Table 11.1 — Minimum geometry requirements for bolted connections
Geometrical parameter
Nominal bolt diameter ( d )
(recommended range)
Nominal bolt hole clearance
Distances between holes
Distances from edges
single row
multi-rows
Requirement
d ≥ t min
( t min ≤ d ≤ 1,5t min )
d0 − d ≥ 1,0 mm
p1 ≥ 4d
p2 ≥ 4d
L ≥ 4,4d
side e2 ≥ 2d
end e1 ≥ 2,5d and e1 ≥ 30 mm
end e1 ≥ 2d
Key
1
Row No. (i)
Figure 11.2 —Double-lap bolted joint with symbols for bolts and no staggered bolting
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CEN/TS 19101:2022 (E)
Figure 11.3 — Double-lap bolted joint with symbols for staggered bolts
(4) Distances between the centres of the holes in a composite component for p1 (the spacing between
centres of bolts in a line in the direction of load transfer) and p2 (the spacing measured perpendicular to
the load transfer direction between adjacent lines of bolts) should not be less than 4d , as shown in
Figures 11.2 and 11.3.
(5) When bolts are staggered (Figure 11.3), the spacing, p2 , and the stagger distance, L , should be
selected from Table 11.1.
(6) A bolted connection with connection geometries that do not fulfil the geometry requirements defined
in Table 11.1 shall be designed by testing (see 4.5(1)).
(7) Spacer tubes should be used in bolted joints of closed-member sections, as shown in Figure 11.4, in
order not to crush the latter during tightening of the bolts.
Key
1
142
spacer tube
Figure 11.4 — Spacer tube insert in the case of closed-member sections
CEN/TS 19101:2022 (E)
11.5 Adhesive connections
(1) A minimum overlap length of 50 mm should be selected in double-lap and double-strap joints (Figure
11.5).
(2) Geometric deviations due to adherend tolerances may be compensated by selecting an appropriate
adhesive layer thickness.
(3) A minimum adhesive layer thickness, t a , of 1,0 mm should be selected in the case of on-site bonding.
Figure 11.5 — Double-lap and double-strap joints
12 Connections and joints
12.1 General rules
(1) All connections and joints of composite members and components shall have a design resistance such
that the structure is capable of satisfying all the requirements given in this document.
(2) Subclauses 12.1 to 12.5 are for the design of connections and joints between members that are bolted
(12.2 and 12.3), or bonded (12.4), or with a hybrid combination (12.5) of these two methods of connection.
(3) Composite material joints that are subjected to significant moment shall be permitted when joints
(for example, having composite or steel flange cleats) or connections (for example, having adhesive
bonding) are designed by either using 12.2 for bolting or 12.4 for bonding.
NOTE A significant moment exists, for example, in a beam-to-column joint configuration when the classification
of the joint is for semi-rigid or rigid in accordance with the requirements of EN 1993-1-8. Web-cleated beam-tocolumn bolted joints (12.3.1 to 12.3.3) are generally classified as simple joints in accordance with the requirements
of EN 1993-1-8, and thereby such joints cannot be subjected to significant moment in the plane of the joint. Webplated beam-to-column joints can be subjected to significant moment in the plane of the joint.
(4) The connection method of mechanical interlocking between composite members and components
should be designed by testing (see 4.5(1)).
(5) Joints shall be designed so that each connection and its parts are capable of resisting the design forces
and moments.
(6) When appropriate, configurations for connections in joints should be detailed so that the longitudinal axes
(in the x direction) of the connected members converge to a single point. Where there is eccentricity at
intersections, the joints and members should be designed for the resulting moments and forces.
(7) Eccentricity in forces shall be taken into account when determining the design forces and moments
within connections and joints.
(8) Verification of connection or joint resistances should take into account the actual stress distribution
including all stress concentrations due to the influences of geometry, materials, and internal forces and
moments.
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CEN/TS 19101:2022 (E)
(9) The effects of loading and thermal actions on the internal stress distributions in connections and
joints should be determined by structural analysis in accordance with the requirements of 7.1.5 and 7.2.1.
(10) Joint resistance should be verified by taking into account the different stages in execution.
(11) Verification of connection or joint resistances should be carried out by taking into account all
possible failure modes.
(12) The effects of environmental conditions on composite members, components and materials should be
considered in the design of connections and joints, in accordance with the requirements of 4.4.7.
(13) The fire resistance of the connections and joints in composite structures should be considered in a
way that they maintain the required structural resistance for the specific combination of fire and other
actions during the specified fire exposure, see Annex D.
12.2 Bolted connections
12.2.1 General
(1) Subclauses 12.2.1 to 12.2.4 scope the resistance of plate-to-plate bolted connections of composite
members and components subjected to in-plane and out-of-plane actions. The basic joint configuration
is for a double lap-shear joint that is constructed of two bolted connections, as shown in Figure 11.2.
(2) In composite members and components, bolted connections should be designed for pin-bearing
failure (12.2.3.2).
NOTE Designing for pin-bearing failure provides a level of damage tolerance. All other failure modes in bolted
connections have a higher probability of giving connections and/or joints a brittle failure mode with no damage
tolerance.
(3) Bolted connections with clearance holes shall be treated as "bearing-type" or "tension-type"
connections in accordance with the requirements of EN 1993-1-8:—, 5.4.1.
NOTE Subclause 12.2.3.6 is for "slip resistant-type" connections where the bolt clearance voiding is either filled
with an injected (cured) resin or a metal insert.
(4) Bolts and nuts of structural grade steels should be in accordance with the requirements of
EN 1993-1-8 and those of structural grade stainless steel should be in accordance with the requirements
of EN 1993-1-4.
(5) The bolt diameter should be in accordance with the requirements of 11.4(1) and should not be less
than 6 mm.
(6) Bolts made with composite material shall not be used.
(7) For bolting with a smooth shank, the length of thread in contact with any laminate should not exceed
1/3 of that laminate thickness.
(8) Steel or stainless steel washers of uniform diameter dw > 2d (where d is the nominal bolt diameter)
and conforming to ISO 7093 should be inserted under each bolt head as well as under each nut (see Figure
11.2 and Figure 11.3).
(9) For large series plain washers conforming to ISO 7093 the preferred nominal dimensions of diameters
for M6 to M20 bolt sizes may be selected as 2,82 ≤ nw ≤ 3,13.
(10) Plate-to-plate connections that subject the bolting to shear (for a "bearing-type" bolted connection)
in the plane of the connection (see Figure 11.2) should have bolts with the same nominal diameter, d ,
and of the same grade of steel.
NOTE The resistance formulae in 12.2.3 when a group of bolts is involved are for bolted connections having
constant diameter bolts.
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CEN/TS 19101:2022 (E)
(11) When bolts of varying diameters are used in a bolt group, the resistance should be determined by
testing or by numerical modelling, which should be verified by testing.
NOTE
Guidance on design assisted by testing is provided in EN 1990:—, Annex D.
(12) Holes for clearance in laminates should be drilled (or reamed, not punched) to have nominal diameter,
d0 , in accordance with the requirements of 11.4(2), that allows the nominal bolt diameter, d , to pass
through the laminate thickness without force being applied.
(13) Bolted connections of composite members and components shall be designed on the assumption
that the through thickness restraint from bolt torque is not beneficial to connection resistance and that
the in-plane connection force (12.2.3(4)) is transferred only in bearing between the bolts and the
composite members and components.
(14) The geometry of bolted connections and joints should be selected according to the requirements
given in Table 11.1 and 11.4, with symbols defined in Figures 11.2 and 11.3.
(15) Bolts should not be over-tightened to prevent compressive crushing failure of laminates in the outof-plane (z) direction. For non-greased steel bolts, the maximum tightening torque, T , should satisfy the
condition in Formula (12.1):
T ≤ 0,15 ⋅ ( nw2 − 1,2) ⋅ d 3 ⋅ fz,c,lim
where
nw
d2
d1
d
fz,c,lim
is
(12.1)
d2
;
d1
is outside diameter of washer;
is clearance hole (inner diameter) of washer;
is nominal bolt diameter;
is the limiting out-of-plane compressive strength of the laminate, which can be
taken as 25 MPa.
(16) The value of fz,c,lim for laminates may be determined by testing.
NOTE
Guidance on design assisted by testing is provided in EN 1990:—, Annex D.
12.2.2 Design criteria for bolted connections
(1) Static equilibrium shall be satisfied for the determination of the distribution of the:
— forces transferred by the bolt group in a connection;
— stresses in the laminate or other construction material adjacent to the bolts and bolt holes;
— stress field distant from the influence of the bolts and bolt holes.
(2) For bolted connections subjected to in-plane forces the resistances for the following four failure
modes of the laminate shall be verified:
— net-tension (12.2.3.1);
— pin-bearing (12.2.3.2);
— shear-out (12.2.3.3);
— block-shear (12.2.3.4).
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CEN/TS 19101:2022 (E)
(3) Subclauses 12.2.3.1 to 12.2.3.4 give formulae to verify the failure modes in 12.2.2(2), which are only
valid for the double-lap joint configuration.
(4) When bolted connections are for the single lap-shear joint configuration, the resistance calculated by
subclauses 12.2.3.1 to 12.2.3.4 shall be multiplied by a factor of 0,6 to take into account the effect of load
eccentricity on the internal forces and moments.
(5) For bolted connections not covered by subclauses 12.2.3.1 to 12.2.3.4, design by testing should be
used (see 4.5(1)).
(6) For bolted connections subjected to out-of-plane tensile force (in the z direction), the following failure
modes at the bolt locations shall be accounted for:
— pull-out failure through laminate (12.2.4.1);
— bolt failure in tension (12.2.4.2);
— failure of the laminate at a bolt owing to interaction of in- and out-of-plane forces (12.2.4.3).
12.2.3 Bolted connections subjected to in-plane actions
(1) Subclause 12.2.3 applies to bolted connections in which, at least, one joining part (e.g. member or web
cleat) in a connection is of composite material and is of constant material thickness.
(2) The number of bolts in each row, nb , shall be between 1 and 4 (see Figures 11.2 and 12.1).
(3) It is assumed that each bolt in the i -bolt row transfers an equal part of the design value of the
th
connection force, NEd,i , transferred at the i -bolt row’s section.
th
NOTE Figure 12.1 shows that for a multi-bolted joint having four rows ( i = 4) of three bolts the first row of bolts
for the composite material on the left-side is Row 1 ( i = 1) (numbering below the connection illustration), whereas
for the composite or steel material on the right-side it is also Row 1 (number above the connection illustration).
Row 1 is the bolt row that first resists the connection force (the furthest away from the free-end of the
corresponding side). The number of bolts per row of bolts does not have to be constant.
Key
1
2
3
4
146
composite
row number ordering for composite
composite or steel
row number ordering for composite or steel
Figure 12.1 — Layout of a multi-bolted lap-shear connection in which at least one side
(on left-side) is of composite material
CEN/TS 19101:2022 (E)
(4) The design value of the connection force per bolt at the i th -row of bolts, Vb,i ,Ed , should satisfy the
condition in Formula (12.2):
Vb,i =
,Ed
where
cr,i
nb,i
NEd
⋅ NEd
(12.2)
is the design value of the axial force for the connection force (tension or compression);
cr,i
is the bolt row load distribution coefficient listed in Table 12.1 for the i th -bolt row,
with reference to Figure 12.1;
nb,i
is the number of bolts at the i th bolt row.
(5) For bolted connections joining composite with structural grade steel members and components (see
Figure 12.1), the steel connection side may be designed in accordance with the requirements of
EN 1993-1-1, EN 1993-1-4 and EN 1993-1-12, taking into account the distribution of force per rows in
accordance with the requirements of 12.2.3(3) and (4).
(6) For connections joining composite with another construction material (other than steel), the design
value of the connection force per bolt at a row of bolts, Vb,i ,Ed , should be determined by numerical
modelling and, for the connection side of the other construction material, design should be in accordance
with the relevant material EN standard or by testing (see 4.5(1)).
Table 12.1 — Load distribution coefficients, cr,i , for the rows in a multi-bolted lap-shear
connection of composite materials of constant thickness components
Row number
ordering
(composite)
Plate combination
Row 1
cr,1
Row 2
cr,2
Row 3
cr,3
Row 4
cr,4
1
composite/composite
composite/steel
1
1
-
-
-
3
composite/composite
composite/steel
0,4
0,2
-
2
4
>4
composite/composite
composite/steel
0,5
0,6
0,5
0,4
composite/composite
composite/steel
0,3
0,4
0,2
0,3
12.2.3.1 Net-tension failure
0,4
0,5
0,2
0,3
Not permitted
-
0,2
0,2
-
0,3
0,1
(1) When the net-tension force is oriented at an angle 0o ≤ θ ≤ ±5o to the x direction of pultruded profiles
or pultruded flat laminates of constant thickness (see Figures 12.2 and 12.3), its design value, NEd , for
net-tension failure should satisfy the condition in Formula (12.3):
147
CEN/TS 19101:2022 (E)
NEd ≤ Nx,nt,Rd
where
Nx,nt,Rd
Nx,nt,Rd=
where
w
nb,1
d0
t
ktc
f x,t,d
=
f x,t,d
where
is the design value of the net-tension resistance in the x direction, given by
Formula (12.4),
1
⋅ ( w − nb,1 ⋅ d0 ) ⋅ t ⋅ f x,t,d
ktc
is the number of bolts across the first bolt row (Row 1) where the net-tension failure
mode occurs (see Figures 12.2 and 12.3);
is the nominal bolt hole diameter;
is the laminate thickness;
is a stress concentration factor that should be taken from Table 12.2 for specific bolted
connection configurations that satisfy the geometry requirements in Table 11.1; for
other bolted connection configurations, ktc should be taken equal to 3,0;
is the design value of the tensile strength of the pultruded laminate in the x direction,
given by Formula (12.5),
ηc
⋅f
γ m ⋅ γ Rd x,t,k
is defined in 4.4.5 (to be selected for f x,t,k );
ηc
is defined in 4.4.7 (to be selected for f x,t,k );
f x,t,k
(12.4)
is the width of the component ( w ≥ 4d , from Table 11.1), see also 12.2.3.1(5);
γm
γ Rd
148
(12.3)
(12.5)
is defined in 4.4.6 (Table 4.5, Net-tension failure);
is the characteristic value of the tensile strength of the pultruded laminate material in
the x direction.
CEN/TS 19101:2022 (E)
Key
1
principal direction of laminate or direction of pultrusion
Figure 12.2 — Net-tension failure mode illustrated with a single bolt, nb,1 = 1
Key
1
row No. (i)
Figure 12.3 — Net-tension failure mode illustrated with a 2 × 2 multi-bolted connection, nb,1 = 2
149
CEN/TS 19101:2022 (E)
Table 12.2 — Values of stress concentration factor ktc for specified bolted connection
configurations when NEd is oriented with an angle 0o ≤ θ ≤ ±5o to the major principal axis
(x direction) of pultruded laminates with glass fibres
Bolted connection configuration
ktc
Single
2,0
1 × 2 (single row)
2,5
1× 3
2,5
2× 2
2,0
2 × 1 (single column)
3× 1
3× 3
1 × 1 (staggered)
2 × 2 (staggered)
2,5
2,5
1,5
2,0
2,0
NOTE For staggered bolted configurations there is one bolt per bolt row. Configuration 1 × 1 (staggered) means
there is a total of two bolts and two bolt rows, with distance between holes L > 2,8d (Table 11.1 and Figure 11.3).
(2) When the net-tension force is oriented at an angle ±5o < θ ≤ ±90o to the x direction of pultruded
profiles or pultruded flat laminates of constant thickness (see Figures 12.2 and 12.3), its design value,
NEd , for net-tension failure should satisfy the condition in Formula (12.6):
NEd ≤ Ny,nt,Rd
where
where
Ny,nt,Rd
Ny,nt,Rd
=
where
w
nb,1
d0
t
150
(12.6)
is the design value of the net-tension resistance in the y direction, given by
Formula (12.7),
1
( w − nb,1 ⋅ d0 ) ⋅ t ⋅ fy,t,d
ktc
is the width of the component ( w ≥ 4d , from Table 11.1), see also 12.2.3.1(5);
(12.7)
is the number of bolts across the first bolt row where the net-tension failure mode
occurs (see Figures 12.2 and 12.3);
is the nominal bolt hole diameter;
is the laminate thickness;
CEN/TS 19101:2022 (E)
ktc
f y,t,d
f y,t,d
=
where
is a stress concentration factor that should be from Table 12.3 for specific bolted
connection configurations that satisfy the geometry requirements in Table 11.1. For
other bolted connection configurations, ktc should be taken equal to 3,0;
is the design value of the tensile strength of the pultruded laminate in the y direction,
given by Formula (12.8),
ηc
⋅f
γ m ⋅ γ Rd y,t,k
(12.8)
γm
is defined in 4.4.5 (to be selected for f y,t,k );
ηc
is defined in 4.4.7 (to be selected for f y,t,k );
γ Rd
f y,t,k
is defined in 4.4.6 (Table 4.5, Net-tension failure);
is the characteristic value of the tensile strength of the pultruded laminate material in
the y direction.
Table 12.3 — Values of stress concentration factor ktc for specified bolted connection
configurations when NEd is oriented with an angle +5o ≤ θ ≤ ±90o to the major principal axis
(x direction) of pultruded laminates with glass fibres
Bolted connection configuration
ktc
Single
2,5
2 × 1 (single column)
2,0
1 × 2 (single row)
2,0
1× 3
2,0
2× 2
2,0
3× 1
3× 3
1 × 1 (staggered)
2 × 2 (staggered)
2,0
1,5
2,0
2,0
NOTE For staggered bolted configurations, there is one bolt per bolt row. Configuration 1 × 1 (staggered) means
there is a total of two bolts and two bolt rows, with distance between holes L > 2,8d (Table 11.1 and Figure 11.3).
(3) For balanced symmetrical flat laminates, regardless of the composite manufacturing process, of
constant thickness having plies with continuous glass fibres arranged in the two orthogonal directions x
and y, Formulae (12.4) and (12.7) may be used:
151
CEN/TS 19101:2022 (E)
— For NEd acting at an angle 0o ≤ θ ≤ ±5o to the laminate’s x direction, Formula (12.4) should be used
with f x,t,k ; the stress concentration factor ktc should be taken from Table 12.2 or, for other bolted
connection configurations, ktc should be taken equal to 3,0.
— For NEd acting at an angle of between ±5o ≤ θ ≤ ±90o to the laminate’s x–direction, Formula (12.7)
should be used with f y,t,k ; the stress concentration factor ktc should be taken from Table 12.3 or, for
other bolted connection configurations, ktc should be taken equal to 3,0.
(4) For multi-row bolted connections having a different lamination arrangement or/and having fibres
that are not glass, the value of stress concentration factor ktc should be determined by testing (see 4.5(1))
or by numerical modelling.
(5) When laminates in bolted connections have a flange outstand or web (often perpendicular to the plane
of the laminate with the bolting) it may increase side distance e2 (see Figures 12.2 and 12.3), to be
included in establishing the width w in Formula (12.4) or Formula (12.7). Distance e2 should be taken
from the centre of the hole to the nearest outstand or web edge plus 0,5 times the depth of the outstand
height or of the web height.
12.2.3.2 Pin-bearing failure
(1) When the connection force per bolt is oriented at an angle 0o ≤ θ ≤ ±5o to the x direction of the
laminate (see Figure 12.4), the design value of the connection force transferred per bolt (bearing force
per bolt) at the i th -bolt row, Vb,i ,Ed , for pin-bearing failure should satisfy the condition in Formula (12.9):
Vb,i ,Ed ≤ Vx,br,Rd
where
Vb,i ,Ed
Vx,br,Rd
= 1,5
Vx,br,Rd
where
kcc
d
is given by Formula (12.2);
is the design value of the pin-bearing resistance per bolt in the x direction, given by
Formula (12.10),
1
⋅ d ⋅t ⋅ f x,br,d
kcc
(12.10)
2
d 
is the reduction factor  0  accounting for the bearing compressive stress
d 
concentration in front of the bolt from having a clearance hole with limit on
dimension as specified in Table 11.1;
is the nominal bolt diameter;
d0
is the nominal bolt hole diameter;
f x,br,d
is the design value of the pin-bearing strength in the x direction of the laminate,
given by Formula (12.11),
t
152
(12.9)
is the thickness of the laminate resisting Vbr,i ,Ed ;
CEN/TS 19101:2022 (E)
f x,br,d
=
where
ηc
⋅f
γ m ⋅ γ Rd x,br,k
γm
is defined in 4.4.5 (to be selected for f x,br,k );
ηc
is defined in 4.4.7 (to be selected for f x,br,k );
γ Rd
(12.11)
is defined in 4.4.6 (Table 4.5, Pin-bearing failure);
f x,br,k
is the characteristic value of the pin-bearing strength in the x direction of the laminate
that may be determined in accordance with the requirements of procedure C in
ASTM D953, but allowing to consider testing with bolt diameters different to the
laminate thickness.
Key
1
principal direction of laminate or direction of pultrusion
Figure 12.4 — Pin-bearing failure mode for a single bolt
(2) The pin-bearing strength may be determined by testing at the sub-laminate level, when the thickness
of the laminate does not permit application of the standard test method (see 5.2.2(7)).
(3) When the connection force per bolt is oriented at an angle of ±5o < θ ≤ ±90o to the x direction of the
laminate (see Figure 12.4), the design value of the connection force transferred per bolt (bearing force
per bolt) at the i th -bolt row, Vbr,i ,Ed , for pin-bearing failure should satisfy the condition in Formula
(12.12):
Vb,i ,Ed ≤ Vy,br,Rd
where
Vb,i ,Ed
Vy,br,Rd
Vy,br,Rd
= 1,5
where
(12.12)
is given by Formula (12.2);
is the design value of the pin-bearing resistance per bolt in the y direction, given by
Formula (12.13),
1
⋅ d ⋅t ⋅ f y,br,d
kcc
(12.13)
153
CEN/TS 19101:2022 (E)
kcc
2
d 
is the reduction factor  0  accounting for the bearing compressive stress
d 
concentration in front of the bolt from having a clearance hole with limit on
dimension as specified in Table 11.1;
d
is the nominal bolt diameter;
d0
is the nominal bolt hole diameter;
f y,br,d
is the design value of the pin-bearing strength in the y direction of the laminate,
given by Formula (12.14),
t
=
f y,br,d
where
is the thickness of the laminate resisting Vbr,i ,Ed ;
ηc
⋅f
γ m ⋅ γ Rd y,br,k
(12.14)
γm
is defined in 4.4.5 (to be selected for f y,br,k );
ηc
is defined in 4.4.7 (to be selected for f y,br,k );
γ Rd
f y,br,k
is defined in 4.4.6 (Table 4.5, Pin-bearing failure);
is the characteristic value of the pin-bearing strength in the y direction of the laminate
that may be determined in accordance with the requirements of procedure C in
ASTM D953, but allowing to consider testing with bolt diameters different to the
laminate thickness.
(4) When there is consideration of bolt flexure (e.g., with the detailing in Figure 11.4) the design value of
the pin-bearing strength f x,br,d in Formula (12.10) or f y,br,d in Formula (12.13) should be reduced by a
factor of 0,5.
12.2.3.3 Shear-out failure
(1) For laminates of constant thickness, the design value of the bearing force transferred by a bolt at the
first row of bolts, Vso,1,Ed , for shear-out failure should satisfy the condition in Formula (12.15):
Vso,1,Ed ≤ Vso,1,Rd
where
Vso,1,Ed
Vso,1,Rd
154
(12.15)
is taken equal to Vb,i =1,Ed =
NEd
(in Figure 12.5 nb,1 is taken equal to 1);
nb,1
is the design value of the shear-out failure resistance, given by Formula (12.16),
CEN/TS 19101:2022 (E)
Vso,1,Rd
= 1,5 ( e1 − 0,5d0 ) ⋅ t ⋅ f xy,v,d
e1
is the end edge distance from the first row of bolts (Table 11.1 and 12.2.3.3(3));
d0
is the nominal bolt hole diameter;
f xy,v,d
is the design value of the in-plane shear strength of the laminate, given by Formula
(12.17),
t
=
f xy,v,d
where
(12.16)
is the thickness of the laminate resisting Vso,1,Ed ;
ηc
⋅f
γ m ⋅ γ Rd xy,v,k
(12.17)
γm
is defined in 4.4.5 (to be selected for f xy,v,k );
ηc
is defined in 4.4.7 (to be selected for f xy,v,k );
γ Rd
f xy,v,k
is defined in 4.4.6 (Table 4.5, Shear-out failure);
is the characteristic value of the in-plane shear strength of the laminate.
Key
1
principal direction of laminate or direction of pultrusion
Figure 12.5 — Shear-out failure mode for a single row of bolts
(2) For a laminate of constant thickness, for two rows of aligned bolts ( i = 2), separated by spacing p1
(distance between centres of holes in a line in the direction of load transfer, see Figures 11.2 and 12.6),
the design value of the bearing force transferred by a column line of two bolts, Vso,2,Ed , for shear-out failure
should satisfy the condition in Formula (12.18):
Vso,2,Ed ≤ Vso,2,Rd
where
Vso,2,Ed
(12.18)
is taken equal to
N1,Ed
nb,1
+
N2,Ed
nb,2
;
155
CEN/TS 19101:2022 (E)
N1,Ed
is the contribution of NEd at the first row of bolts ( i = 1);
nb,1
is the number of bolts at the first row of bolts ( i = 1) (see Figure 12.6);
N2,Ed
nb,2
and where
Vso,2,Rd
is the contribution of NEd at the second row of bolts ( i = 2);
is the number of bolts at the second row of bolts ( i = 2) (see Figure 12.6);
is the design value of the shear-out resistance per column line of bolts, given by
Formula (12.19),
Vso,2,Rd
= 0,9 ( e1 − 0,5d0 + p1 ) ⋅ t ⋅ f xy,v,d
where
e1
(12.19)
is the end edge distance from the first row of bolts (Table 11.1 and 12.2.3.3(3));
d0
is the nominal bolt hole diameter;
f xy,v,d
is the design value of the in-plane shear strength of the laminate, obtained from
Formula (12.17).
t
is the thickness of the laminate resisting Vso,2,Ed ;
Key
1
2
principal direction of laminate or direction of pultrusion
row No. (i)
Figure 12.6 — Shear-out failure mode for a multi-bolted connection having two rows of a single bolt
(3) When laminates in bolted connections have a flange outstand or web at the free end, the end distance
e1 to be included in Formula (12.16) or Formula (12.19) should be taken from the centre of the hole to
the outstand or web edge plus 0,5 times the depth of the outstand height or of the web height (see Figures
12.5 and 12.6).
(4) For three or four rows of aligned bolts ( i = 3 or 4) separated by spacing p1 , the design value of the
bearing force transferred by a column line of bolts, Vso,i ,Ed , for shear-out failure should satisfy the
condition in Formula (12.20):
156
CEN/TS 19101:2022 (E)
Vso,i ,Ed ≤ Vso,i ,Rd
where
Vso,i ,Ed
Vso,i ,Rd
(12.20)
is given by
∑
i =1 to j
Vi ,Ed
ni
, where i is either 3 or 4 (see Figure 12.1);
is the shear-out resistance per column line of bolts, Vso,3,Rd or Vso,4,Rd , in the laminate
of constant thickness, given by Formula (12.21),
Vso,=
1,3 ( i − 1) ⋅ p1  ⋅ t ⋅ f xy,v,d
i ,Rd
where
t
(12.21)
is the thickness of the laminate resisting Vso,i ,Ed ;
p1
is the spacing between centres of holes in a line in the direction of load transfer, see
Figure 11.2;
f xy,v,d
is the design value of the in-plane shear strength of the laminate, obtained from
Formula (12.17).
12.2.3.4 Block-shear failure
(1) When the connection force is transferred in tension, is concentric to a symmetric group of bolts, and
parallel to the x or y direction of laminates of constant thickness, its design value, NEd , for block-shear
failure should satisfy the condition in Formula (12.22):
NEd ≤ Nbs,Rd
where
Nbs,Rd
(12.22)
is the design value of the block-shear resistance for a multi-bolted connection, given
by Formula (12.23),
Nbs,Rd
= 0,5 ( Ans ⋅ f xy,v,d + Ant ⋅ fi ,t,d )
where
Ans
is the net area of the laminate subjected to shear;
f xy,v,d
is the design value of the in-plane shear strength of the laminate, given by Formula
(12.24),
Ant
=
f xy,v,d
where
(12.23)
γm
is the net area of the laminate subjected to tension, which should be taken as the
gross area of the laminate less appropriate deductions of area for all holes, in
accordance with the requirements of 12.2.3.4(2) or (3);
ηc
⋅f
γ m ⋅ γ Rd xy,v,k
(12.24)
is defined in 4.4.5 (to be selected for f xy,v,k );
157
CEN/TS 19101:2022 (E)
γ Rd
is defined in 4.4.6 (Table 4.5, Block-shear failure);
ηc
is defined in 4.4.7 (to be selected for f xy,v,k );
f xy,v,k
is the characteristic value of the in-plane shear strength of the laminate;
and where
is f x,t,d when NEd is parallel to x direction and is f y,t,d when NEd is parallel to
fi ,t,d
f x,t,d
=
f y,t,d
=
where
y direction, given by Formulae (12.25) and (12.26),
ηc
⋅f
γ m ⋅ γ Rd x,t,k
ηc
⋅f
γ m ⋅ γ Rd y,t,k
γm
is defined in 4.4.5 (to be selected for f x,t,k or f y,t,k );
ηc
is defined in 4.4.7 (to be selected for f x,t,k or f y,t,k );
γ Rd
(12.25)
(12.26)
is defined in 4.4.6 (Table 4.5, Block-shear failure);
f x,t,k , f y,t,k
are the characteristic values of the tensile strength of the laminate in the x and
y directions.
(2) Provided that the holes are not staggered (see Figure 11.2), the total area to be deducted for holes
should be the maximum sum of the sectional areas of the holes in a cross-section perpendicular to the
direction of tensile connection force.
(3) For a row of holes extending across a plate in any diagonal or zigzag pattern, the net width for
staggered bolting (with L= p22 + s 2 > 4,4d , see Figure 11.3) shall be determined by deducting from the
gross width of the part the sum of all hole widths in the pattern and adding, for each p2 spacing (see
s2
,
Figure 11.3), the quantity
4p2
where
s
p2
is the staggered pitch, the spacing of the centres of two consecutive holes in the chain
measured parallel to the member axis, see Figure 11.3;
is the spacing measured perpendicular to the load transfer direction between adjacent lines
of bolts, see Figure 11.3.
(4) The p2 spacing for holes in adjacent legs of angles shall be taken as the sum of the values of spacing
p2 from the back of the angles less the thickness of the fibre polymer composite angle.
(5) For a group of bolts subjected to eccentric in-plane tensile force (see Figure 12.7), its design value,
NEd , for block-shear failure should satisfy the condition in Formula (12.27):
NEd ≤ Nbs,Rd
158
(12.27)
CEN/TS 19101:2022 (E)
where
Nbs,Rd
is the design value of the block-shear resistance of the multi-bolted connection with
laminate of constant thickness, given by Formula (12.28),
Nbs,Rd= 0,5 ( Ans ⋅ f xy,v,d + 0,5 Ant ⋅ fi ,t,d )
where
Ans
is the net area of the laminate subjected to shear;
f xy,v,d
is the design value of the in-plane shear strength of the laminate, given by Formula
(12.29),
Ant
is the net area of the laminate subjected to tension, which should be taken as the
gross area of the laminate less appropriate deductions of area for all holes, in
accordance with the requirements of 12.2.3.4(2) or (3);
ηc
⋅f
γ m ⋅ γ Rd xy,v,k
f xy,v,d
=
where
γm
is defined in 4.4.5 (to be selected for f xy,v,k );
ηc
is defined in 4.4.7 (to be selected for f xy,v,k );
γ Rd
and where
=
f y,t,d
is the characteristic value of the in-plane shear strength of the laminate;
is f x,t,d when NEd is parallel to x direction and is f y,t,d when NEd is parallel to
fi ,t,d
=
f x,t,d
(12.29)
is defined in 4.4.6 (Table 4.5, Block-shear failure);
f xy,v,k
where
(12.28)
y direction, given by Formulae (12.30) and (12.31),
ηc
⋅f
γ m ⋅ γ Rd x,t,k
ηc
⋅f
γ m ⋅ γ Rd y,t,k
γm
is defined in 4.4.5 (to be selected for f x,t,k or f y,t,k );
ηc
is defined in 4.4.7 (to be selected for f x,t,k or f y,t,k );
γ Rd
f x,t,k , f y,t,k
(12.30)
(12.31)
is defined in 4.4.6 (Table 4.5, Block-shear failure);
are the characteristic values of the tensile strength of the laminate in the x and
y directions.
159
CEN/TS 19101:2022 (E)
Key
1
2
flange outstand
block shear failure
Figure 12.7 — Illustrative example for a situation with eccentric tensile load
(6) For multi-row bolted connections not scoped by 12.2.3.4(1) to (5), the design value of the block-shear
resistance should be verified by testing (see 4.5(1)).
12.2.3.5 Bolt shear failure
(1) The shear resistance for steel or stainless steel bolts shall be designed in accordance with the
requirements of EN 1993-1-8 or EN 1993-1-4.
12.2.3.6 Slip resistant bolted connections
(1) Resin injection bolts having a matrix material (e.g. of a polymer resin) filling the voiding between a
bolt and the laminates (owing to presence of hole clearance, see Table 11.1) should make the bolted
connection slip resistant.
(2) Information on resin injection bolts in steelwork is given in Annex J to EN 1090-2 and this information
may be used in the execution of a composite structure requiring slip resistant bolted connections.
(3) The design resistance of the resin injection bolted connection shall be determined by applying 12.1
to 12.2.3.5. In either 12.2.3.2(1) or (3) the reduction factor kcc shall be taken equal to 1,0.
(4) The mechanical properties for the resin injection bolted connection, such as slip resistance and fatigue
resistance, shall be determined by testing (see 4.5(1)).
(5) As an alternative to resin injection bolts, a snug-fitting metal bushing or sleeve may be inserted in an
over-sized hole.
12.2.4 Bolted connections subjected to out-of-plane actions
12.2.4.1 Pull-out failure
(1) For out-of-plane (z direction) shear failure (see Figure 12.8) of laminates, the design value of the outof-plane tensile force transferred at the bolt, Nz,Ed , for out-of-plane failure should satisfy the condition in
Formula (12.32):
160
CEN/TS 19101:2022 (E)
Nz,Ed ≤ Npo,Rd
where,
Npo,Rd
(12.32)
is the design value of the pull-out resistance per bolt, given by Formula (12.33),
Npo,Rd = Nz,Rd = π ⋅ dw ⋅ t ⋅ f xz,v,d
where
dw
is the diameter of the washer;
t
f xz,v,d
f xz,v,d
=
where
(12.33)
is the total thickness of the laminate resisting Nz,Ed ;
is the design value of the out-of-plane shear strength (xz plane) of the laminate, given by
Formula (12.34),
ηc
⋅f
γ m ⋅ γ Rd xz,v,k
γm
is defined in 4.4.5 (to be selected for f xz,v,k );
ηc
is defined in 4.4.7 (to be selected for f xz,v,k );
γ Rd
f xz,v,k
(12.34)
is defined in 4.4.6 (Table 4.5, Pull-out failure);
is the characteristic value of the out-of-plane shear strength (xz plane) of the laminate,
which can be taken as the characteristic value of the interlaminar shear strength, f xz,ILS,k .
NOTE Formula (12.33) applies only if the material through the thickness t (see Figure 12.8) of the connection is
of composite and is not applicable to sandwich panels.
Figure 12.8 — Pull-out failure caused by bolt tension force
(2) If through the thickness of the connection there are two of more different laminates, the value of f xz,v,k
should be taken as the lowest for the laminates present.
(3) Washers should be sized to transfer and resist the pull-out force at a bolt.
161
CEN/TS 19101:2022 (E)
12.2.4.2 Bolt failure in tension
(1) Steel or stainless steel bolts subjected to a design value of tensile force in the z direction (see Figure
12.9), Nz,Ed , shall be designed for the design value of the bolt tension resistance, Nz,Rd , in accordance with
the requirements of EN 1993-1-8 or EN 1993-1-4.
Figure 12.9 — Bolt failure due to bolt tension force
12.2.4.3 Bolted connections subjected to in- and out-of-plane forces
(1) In presence of combined in-plane shear force and out-of-plane tensile force, the resistance at a single
bolt should satisfy the linear interaction failure criterion given in Formula (12.35):
Vb,i ,Ed
Vbr,Rd
where
+
Vb,i ,Ed
Vbr,Rd
Nz,Ed
Nz,Rd
NOTE
Nz,Ed
Nz,Rd
≤ 1,0
(12.35)
is the design value of the connection force per bolt (bearing force transferred per bolt)
at the i th -bolt row from Formula (12.2);
is the design value of the pin-bearing resistance per bolt from 12.2.3.2 or from testing in
accordance with the requirements of 12.2.3.2;
is the design value of the out-of-plane tensile force transferred at the bolt (see Figures
12.8 and 12.9);
is the design value for the resistance for the out-of-plane tension force from 12.2.4 or
from testing.
Guidance on design assisted by testing is provided in EN 1990:—, Annex D.
(2) 12.2.4.3(1) applies only if the connection is composed of composite material through the total
thickness. Otherwise, connections shall be designed by testing (see 4.5(1)).
(3) In presence of combined in-plane shear and out-of-plane forces, the resistance of steel or stainless
steel bolts shall be designed in accordance with the requirements of EN 1993-1-8 or EN 1993-1-4.
162
CEN/TS 19101:2022 (E)
12.3 Bolted joints
12.3.1 General
(1) Where groups of bolts are to transfer tensile forces in the out-of-plane direction between joined
components in bolted joints, the connection shall be designed to resist the presence of prying action.
NOTE
For resistance owing to tying force failure of web cleat joints, see 12.3.3.
(2) In beam-to-column bolted joints having negligible ultimate joint moments and adequate joint
rotations, web cleat joints, consisting of a pair of leg-angles of composite material of constant thickness,
shall be designed in accordance with 12.1, 12.2 and 12.3.
12.3.2 Shear failure of web cleat joints
(1) The design value of the shear force acting over the area of a laminate at the fillet radius junction
between two legs of leg-angles of composite material, Vwc,Ed , in a web cleated beam-to-column joint, for
shear failure should satisfy the condition given in Formula (12.36):
Vwc,Ed ≤ Vwc,Rd
(12.36)
where
Vwc,Rd
is the design value of the shear resistance at the fillet radius junction between two legs
of leg-angles of composite material, given by Formula (12.37),
Vwc,Rd =2 ⋅ hr ⋅ t min ⋅ f xy,v,d
where
hr
is the depth of the shear plane at the fillet radius of the leg-angle;
f xy,v,d
is the design value of the in-plane shear strength (xy plane) of the laminate, given by
Formula (12.38),
t min
=
f xy,v,d
where
(12.37)
is the total minimum thickness from the pair of web cleats subjected to Vwc,Ed ;
ηc
⋅f
γ m ⋅ γ Rd xy,v,k
γm
is defined in 4.4.5 (to be selected for f xy,v,k );
ηc
is defined in 4.4.7 (to be selected for f xy,v,k );
γ Rd
f xy,v,k
(12.38)
is defined in 4.4.6 (Table 4.3, Material failure);
is the characteristic value of the in-plane shear strength (xy plane) of the laminate.
12.3.3 Tying force failure of web cleat joints
(1) In a web cleated beam-to-column joints of two leg-angles (see Figure 12.10) having constant thickness
outstands, the design value of the tensile force or prying action, Nty,Ed , for tying force failure should satisfy
the condition given in Formula (12.39):
163
CEN/TS 19101:2022 (E)
Nty,Ed ≤ Nty,Rd
where
Nty,Rd
Nty,Rd =
is the design value of the tying force resistance of a web cleated beam-to-column joint
of two leg-angles having constant thickness outstands, given by Formula (12.40),
2
h ⋅ t l-a
⋅ f y,f,d
3⋅ e
h
is the depth of the leg-angle;
e
is the lever arm distance from the centre of the nearest line of bolt holes to the centre of
the beam’s web, as shown in Figure 12.10;
f y,f,d
where
is the design value of the flexural strength of the laminate in the y direction, given by
Formula (12.41),
ηc
⋅f
γ m ⋅ γ Rd y,f,k
γm
is defined in 4.4.5 (to be selected for f y,f,k );
ηc
is defined in 4.4.7 (to be selected for f y,f,k );
γ Rd
is the characteristic value of the flexural strength of the laminate in the y direction.
Key
2
3
164
(12.41)
is defined in 4.4.6 (Table 4.3, Material failure);
f y,f,k
1
(12.40)
is the thickness of a leg-angle cleat, as shown in Figure 12.10;
t l-a
f y,f,d
=
(12.39)
beam web
composite web cleat
delamination failure location
Figure 12.10 — Tying force failure mode for pair of composite web cleats
CEN/TS 19101:2022 (E)
12.4 Adhesive joints and connections
12.4.1 General
(1) The rules for adhesive joints and connections may also be applied for laminated connections.
12.4.2 Design principles
(1) A composite structure comprising adhesive joints shall be designed as fail-safe, i.e. joint failure shall
not result in failure of the structure or critical parts thereof.
(2) Failure of an adhesive joint shall be considered as an accidental situation in accordance with EN 1990.
(3) The failure modes of adhesive connections shall be either cohesive failure in the adhesive or fibretear failure in the adherend, defined in accordance with Figure 12.11.
NOTE 1 The environmental conditions can change the failure mode.
NOTE 2 Further details about failure modes in adhesive connections can be found in ASTM D5573.
Key
1
adherend
3
fibre-tear failure (inside composite adherend)
2
4
5
adhesive layer
cohesive failure (inside adhesive layer)
adhesive failure (in adherend-adhesive layer interface)
Figure 12.11 — Failure modes in adhesive connections
(4) Pure adhesive failure, i.e. complete failure in the adherend-adhesive interface, shall be avoided.
(5) Adhesive failure may be prevented by an appropriate material selection and surface preparation and
the use of primers if necessary.
(6) In a mixed-mode failure, adhesive failure should cover less than 10% of the failure surface.
(7) The failure mode of adhesive connections shall be validated by tests.
12.4.3 Joint and connection design
(1) Adhesive joints should preferably be designed to be symmetrical with regard to the load axis and with
minimized eccentricities; examples are shown in Figure 11.5.
NOTE 1 Tapering of the adherends and the addition of adhesive fillets can reduce stress peaks.
NOTE 2 The effectiveness of tapering of adherends and adding adhesive fillets to reduce stress peaks in lap-shear
connections depends on the adhesive/adherend stiffness ratio and decreases with decreasing ratio.
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CEN/TS 19101:2022 (E)
NOTE 3 Size effects on strength can counteract the effect of reduced stress peaks on the connection resistance and
thus limit the effectiveness of tapering and adhesive fillets in lap-shear connections. Reducing the stress peaks can
however improve fatigue life.
(2) With regard to the connection dimensions, the adhesive layer thickness should be specified and
verified with particular attention.
12.4.4 Analysis
(1) The stiffness of the adhesive layer should be taken into account in the calculation of the stiffness and
deformation of the adhesive connection.
(2) The effect of the loading rate on the adhesive and connection responses should be taken into account
in the adhesive connection design.
NOTE An increasing loading rate can result in a stiffer material and adhesive connection response, and an
increased material strength and adhesive connection resistance, but also in a more brittle failure behaviour.
(3) The loading rate in the connection and in corresponding tests to obtain the material or connection
properties should be in agreement, particularly in cases of (i) flexible adhesives, i.e. exhibiting a low
adhesive/adherend stiffness ratio, or (ii) taking static resistances into account in fatigue S − N curves.
(4) In the case of fatigue loading of an adhesive connection, the rules stipulated under Clause 10 shall be
applied.
(5) In the case of on-site bonding, the effect of low temperature on the adhesive curing process and
associated delayed development of the Tg and mechanical properties should be taken into account.
(6) The minimum application temperature and associated development of the physical and mechanical
properties should be based on adhesive supplier data or determined by testing.
12.4.5 Resistance verification
12.4.5.1 General
(1) Adhesive connections should fulfil the condition in Formula (12.42):
E d ≤ Rac ,Rd
where
Ed
Rac ,Rd
Rac=
,Rd
where
γ M,ac
ηc
Rac ,k
166
(12.42)
is the design value of an action effect transmitted by the connection;
is the design value of the corresponding adhesive connection resistance, given by
Formula (12.43),
ηc
⋅R
γ M,ac ac ,k
is the partial factor for the adhesive connection resistance;
(12.43)
is defined in 4.4.7 (to be selected for the material property which causes failure);
is the characteristic value of the adhesive connection resistance.
CEN/TS 19101:2022 (E)
NOTE 1 The values of the partial factor for the adhesive connection resistance, γ M,ac , are given in Table 12.4(NDP),
unless the National Annex gives different values.
Table 12.4(NDP) — Partial factors for adhesive connection resistance, γ M,ac
Fully
controlled
application
Partially
controlled
application
Connection subjected to periodic
inspection and maintenance a;
adhesive connection accessible
1,5
2,0
Connection not subjected to
periodic inspection and
maintenance
1,7
2,2
2,0
2,5
Inspection and access
Connection subjected to periodic
inspection and maintenance a;
limited accessibility
a
according to maintenance plan.
NOTE 2 The partial factor for the adhesive connection resistance, γ M,ac , depends on (i) the type of inspection and
maintenance and accessibility of the adhesive connection, and (ii) the application conditions, either with fully
controlled, i.e. reproducible process parameters, or with only partially controlled parameters.
(2) The effect of unforeseen eccentricities in the joint due to manufacturing tolerances should be taken
into account in the joint design and structural verifications.
(3) Adhesive joints and connections may be designed based on the following methods: (i) design assisted
by testing, according to 12.4.5.2, (ii) design based on stress analysis, according to 12.4.5.3, and (iii) design
based on fracture mechanics, according to 12.4.5.4.
12.4.5.2 Design assisted by testing
(1) A design assisted by testing should follow the rules established in EN 1990 to derive characteristic
values of the adhesive connection resistance.
NOTE
Guidance on design assisted by testing is provided in EN 1990:—, Annex D.
(2) The test specimens should be conceived (i) full-scale, (ii) composed of the same materials and
geometrical configuration, (iii) manufactured and cured by the same processes, and (iv) subjected to the
same boundary conditions and action effects as the actual connection.
(3) Smaller scale specimens and adaptations in the geometrical configuration may be used if the
specimens (i) are subjected to the same stress state, (ii) exhibit only limited size effects and (iii) exhibit
the same failure mode as in the actual connection.
12.4.5.3 Design based on stress analysis
(1) Stress analysis should be conducted by finite element modelling (FEM); an appropriate mesh to obtain
consistent stress values, especially in zones of stress concentrations, should be used.
(2) For composite adherends, homogenized material properties may be used in FEM and material
orthotropy should be taken into account.
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CEN/TS 19101:2022 (E)
(3) An appropriate failure criterion should be applied in the failure plane to estimate the connection
resistance. In lap-shear connections exhibiting fibre-tear failure, the failure criterion may be defined as
in Formula (12.44):
2
  τ xy,Ed
 + 
  f xy,v,d
 σ z,t,Ed

 fz,t,d
where
(12.44)
σ z,t,Ed
is the design value of the out-of-plane tensile (peeling) stress;
fz,t,d
is the design value of the out-of-plane tensile (peeling) strength, given by Formula
(12.45),
τ xy,Ed
f=
z,t,d
ηc
⋅f
γ M,ac z,t,k
f xy,v,d
f xy,v,d
=
where
2

 ≤ 1,0

γ M,ac
ηc
fz,t,k
f xy,v,k
is the design value of the in-plane shear stress;
is the design value of the in-plane shear strength, given by Formula (12.46),
ηc
⋅f
γ M,ac xy,v,k
(12.45)
(12.46)
is defined in Table 12.4(NDP);
is defined in 4.4.7 (to be selected for matrix-dominated composite properties (fibretear failure));
is the characteristic value of the out-of-plane tensile (peeling) strength;
is the characteristic value of the in-plane shear strength.
(4) The strength values indicated in failure criterion (12.44) should take into account the statistical size
effect resulting from the type of stress distribution in the failure plane.
NOTE 1 The strength depends on the stressed material volume, i.e. stress peaks increase and uniform stress
distributions lower the strength.
NOTE 2 In preliminary design and in the case of fibre-tear failure, the matrix strength can be assumed in the outof-plane direction.
(5) In the case of cohesive failure (see 12.4.2(3)), adhesive properties shall be determined by testing in
accordance with 5.4.
(6) Results obtained from stress analysis shall be validated by tests. The failure mode obtained from tests
and stress analysis, in particular, i.e. the depth of the failure plane and the adjacent materials, shall be
identical.
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CEN/TS 19101:2022 (E)
12.4.5.4 Design based on fracture mechanics
(1) A design based on fracture mechanics should be applied for crack initiation and may be based on the
criterion in Formula (12.47):
 GI,Ed

 GIc ,Rd
where
m
  GII,Ed
 + 
  GIIc ,Rd
(12.47)
GI,Ed , GII,Ed
are the design values of the strain energy release rate for crack initiation in Mode I
and Mode II respectively, obtained from FEM;
GIc ,Rd , GIIc ,Rd
are the design values of the critical strain energy release rate for crack initiation
in Mode I and Mode II respectively, given by Formula (12.48),
m, n
G=
ic ,Rd
where
n

 ≤ 1,0

i
γ M,ac
ηc
Gic ,k
ηc
⋅G
γ M,ac ic ,k
are exponents that depend on the actual connection configuration and are
obtained from the fitting of theoretical and experimental results based on
criterion (12.47) for crack initiation;
(12.48)
is Mode I or Mode II;
is defined in Table 12.4(NDP);
is defined in 4.4.7 (to be selected for matrix-dominated composite properties (fibretear failure) or adhesive material, depending on the location of the failure plane);
are the characteristic values of the critical strain energy release rate for crack
initiation, obtained from Mode I and Mode II standard fracture mechanics tests
respectively, e.g. double cantilever beam (DCB, Mode I, ASTM D5528) and endnotched flexure specimen (ENF, Mode II, ASTM D7905/D7905M) can be used.
(2) Formula (12.47) should be applied for crack initiation. It may also be applicable for stable crack
propagation within a damage-tolerant design, e.g. to take the positive contribution of fibre-bridging into
account. GIc ,Rd and GIIc ,Rd are then the critical strain energy release rates for crack propagation.
NOTE While the critical strain energy release rate for crack initiation can be considered as a material parameter,
the critical strain energy release rate for crack propagation, i.e. the contribution of fibre-bridging, depends on the
joint geometry and the stiffnesses of the adherends.
(3) To obtain GI,Ed and GII,Ed from FEM, the virtual crack closure technique (VCCT) or cohesive zone
modelling (CZM) may be applied, the former for crack initiation and the latter for both crack initiation
and propagation.
NOTE VCCT does not take fibre-bridging into account and its application is limited to linear-elastic fracture
mechanics.
(4) The failure modes of the actual connection and the fracture mechanics specimens shall be identical
and verified by testing, i.e. the failure plane shall be located between or within the same materials.
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CEN/TS 19101:2022 (E)
12.5 Hybrid joints and connections
(1) The resistances of the adhesive bond and bolting should not be summed in hybrid, i.e. combined,
adhesive-bolted joints and connections.
(2) In the case of flexible adhesives, the resistances of the adhesive bond and bolting may be summed, if
confirmed by testing.
(3) The possible positive effect of pre-tensioned bolting on the stress distribution in the adhesive layer
shall be neglected in the design of hybrid joints and connections.
(4) Bolting may be used as a back-up system in adhesive joints and connections to maintain the fail-safe
condition.
(5) In the case of a sudden adhesive bond failure, the possible dynamic amplification of the static action
should be considered in the design of a bolted back-up system. The dynamic amplification effect can be
determined by testing.
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CEN/TS 19101:2022 (E)
Annex A
(informative)
Creep coefficients
A.1 Use of this annex
(1) This informative Annex provides supplementary guidance to that given in 4.4.8(5) for the values for
the creep coefficient, φ(t ) .
NOTE National choice on the application of this informative Annex is given in the National Annex. If the National
Annex contains no information on the application of this informative annex, it can be used.
A.2 Scope and field of application
(1) This informative Annex applies to specific composite and core materials, namely those defined in
Table A.1 (pultruded composite profiles), Table A.2 (composite laminates) and Table A.3 (PUR and PET
foams, and balsa wood), providing values for the creep coefficient, φ(t ) , for different elastic moduli, for
specific environmental conditions and for different periods.
(2) As an alternative to the values provided in this Annex, the creep coefficients may be determined by
testing, as defined in 4.4.8(6).
(3) For materials, properties and environmental conditions not covered by this Annex, the creep
coefficients should be determined by testing, according to 4.4.8(6).
A.3 Pultruded composite profiles
(1) The values for the creep coefficient φ(t ) given in Table A.1 for different elastic moduli of pultruded
composite profiles should be used.
NOTE The values given in Table A.1 are valid for linear viscoelasticity and the materials environmental conditions
indicated in the table.
Table A.1 — Values for the creep coefficient, φ (t ) , for different elastic moduli of pultruded
composite profiles (glass, carbon or basalt fibres; fibre volume fraction of at least 35%;
temperature up to 25 °C; relative humidity up to 65%)
Property
Period of time (years)
1
5
10
15
20
25
30
40
50
75
100
E xfull
0,25
0,38
0,46
0,51
0,55
0,58
0,61
0,66
0,70
0,78
0,84
E x,t
0,20
0,22
0,24
0,24
0,25
0,25
0,25
0,26
0,26
0,27
0,28
Gxyfull
E x,c
0,57
0,20
0,98
0,23
1,23
0,27
1,40
0,30
1,54
0,32
1,66
0,34
1,76
0,36
1,94
0,38
2,09
0,41
2,39
0,45
2,62
0,48
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CEN/TS 19101:2022 (E)
A.4 Composite laminates
(1) The values for the creep coefficient φ(t ) given in Table A.2 for different elastic moduli of composite
laminates/plies, comprising (i) unidirectional fibres (UD), (ii) woven bi-directional fabrics (0/90°) or
(iii) chopped strand mats (CSM), should be used.
NOTE 1 The values given in Table A.2 are valid for linear viscoelasticity and the materials environmental conditions
indicated in the table.
NOTE 2 For woven (0/90°) laminates/plies, the creep coefficient for Gxy given in Table A.2 for UD laminates/plies
can be considered as a conservative assumption.
NOTE 3 For woven ( ± 45°) laminates/plies, the creep coefficient for Gxy can be considered to be similar to the
creep coefficient given in Table A.2 for woven (0/90°) laminates/plies for E x,t and E x,c .
Table A.2 — Values for the creep coefficient, φ (t ) , for different elastic moduli of composite
laminates/plies (glass, carbon or basalt fibres; fibre volume fraction of at least 35%;
temperature up to 25 °C; relative humidity up to 65%)
Type of fibres
UD
Woven (0/90°)
CSM
Property
Period of time (years)
1
5
10
15
20
25
30
40
50
75
100
E x,t
0,10 0,11 0,12 0,13 0,13 0,13 0,13 0,14 0,14 0,14
0,15
Gxy
1,13 1,55 1,78 1,94 2,06 2,16 2,25 2,40 2,52 2,78
2,94
E x,c
E x,t , E x,c
E x,t , E x,c
A.5 Core materials
0,15 0,23 0,27 0,30 0,32 0,34 0,36 0,38 0,41 0,45
0,44 0,53 0,58 0,60 0,62 0,64 0,65 0,67 0,68 0,71
1,48 1,91 2,12 2,25 2,34 2,42 2,48 2,58 2,67 2,82
0,48
0,73
2,93
(1) The values for the creep coefficient φ(t ) given in Table A.3 for the out-of-plane shear modulus, Gxz ,
of different core materials should be used.
NOTE 1 The values given in Table A.3 are valid for linear viscoelasticity and the materials environmental conditions
indicated in the table.
NOTE 2 The creep coefficients given in Table A.3 can be used for core materials with densities higher than
100 kg/m3, for which they are expected to provide conservative estimates of creep deformations.
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CEN/TS 19101:2022 (E)
Table A.3 — Values for the creep coefficient, φ (t ) , for the out-of-plane shear modulus, Gxz , of
different core materials (temperature up to 22 °C for polymeric foams and up to 25 °C for balsa
wood; relative humidity up to 65%)
Material
Property
PUR foam
(up to 100 kg/m3)
PET foam
(up to 100 kg/m3)
End-grain balsa
(up to 100 kg/m3)
Gxz
Gxz
Gxz
Period of time (years)
1
5
10
15
20
25
30
40
50
75
100
3,34 4,19 4,60 4,86 5,05 5,20 5,33 5,54 5,70 6,01
6,24
0,70 1,59 2,11 2,47 2,74 2,97 3,16 3,49 3,75 4,28
4,69
0,03 0,21 0,31 0,38 0,44 0,49 0,53 0,60 0,65 0,77
0,86
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CEN/TS 19101:2022 (E)
Annex B
(informative)
Indicative values of material properties for preliminary design
B.1 Use of this annex
(1) This informative Annex provides supplementary guidance to that given in the Note to 4.3.2(1) and
Clause 5 for the physical and mechanical properties of fibres, resins, core materials, composite plies and
laminates that can be used for the preliminary design of fibre-polymer composite structures.
NOTE National choice on the application of this informative Annex is given in the National Annex. If the National
Annex contains no information on the application of this informative annex, it can be used.
B.2 Scope and field of application
(1) This informative Annex applies to the physical and mechanical properties of fibres, resins, core
materials, composite plies and laminates (for specific combinations of fibres and resins), giving indicative
values for material properties that can be used for the preliminary design of composite structures.
NOTE 1 According to this document, design verifications are made using characteristic values of material properties
determined by testing; however, indicative values of material properties can be used as a reference for an initial
assessment of the feasibility of a specific design.
NOTE 2 Indicative values of material properties provided in this Annex can be considered as mean values.
Characteristic values can be obtained by assuming appropriate values of coefficients of variation.
NOTE 3 For combinations of fibres and resins not included in this Annex, material properties to be used for the
preliminary design of composite structures can be taken from the literature.
B.3 General
(1) In the following, the symbol Vf denotes the fibre volume fraction (or content), the subscripts “1” and
“2” refer to the material principal directions of a ply (Figure 3.2), and the subscripts “ f ” and “ r ” refer to
fibre and resin, respectively.
B.4 Fibres
(1) The indicative values given in Table B.1 for the physical and mechanical properties of different types
of fibres may be used for preliminary design.
NOTE 1 The values included in Table B.1 are within the range of material properties reported in the literature.
NOTE 2 The values of elastic modulus, tensile strength and tensile strain at failure in the longitudinal direction
included in Table B.1, obtained from different tests, are not necessarily concomitant.
NOTE 3 Glass and basalt fibres are isotropic, while carbon and aramid fibres are orthotropic.
NOTE 4 The compressive strength of carbon and aramid fibres is significantly lower than their tensile strength.
NOTE 5 Aramid fibres are well suited for energy absorption applications.
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CEN/TS 19101:2022 (E)
Table B.1 — Indicative values for the physical and mechanical properties of different types of
fibres
Property
Elastic modulus in longitudinal direction, E f,1
[GPa]
Tensile strength in longitudinal direction, σ f,1
[MPa]
Tensile strain at failure in longitudinal
direction, ε f,1 [%]
Elastic modulus in transverse direction, E f,2
[GPa]
Shear modulus, Gf [GPa]
Poisson's ratio, ν f [-]
Density, ρ f [kg/m3]
Coefficient of linear thermal expansion in
longitudinal direction, α f,1 [10-6 K-1]
Coefficient of linear thermal expansion in
transverse direction, α f,2 [10-6 K-1]
Thermal conductivity in longitudinal direction,
λf,1 [Wm-1K-1]
a
b
HS – High strength.
HM – High modulus.
Glass
E-glass R-glass
Basalt
Carbon
Aramid
HS a
HM b
HM b
74
86
90
230
450
130
2500
3200
3000
4900
4400
3600
3,5
4,0
3,2
2,1
1,2
2,3
74
86
90
20
120
10
0,25
0,20
0,20
0,20
30
-
22
0,31
16
20
12
0,35
2600
2500
2700
1800
1770
1450
5,0
3,0
8,0
10,0
10,0
54,0
1,0
1,0
0,04
24
105
0,04
5,0
3,0
8,0
-0,4
-0,8
-2,0
B.5 Resins
(1) The indicative values given in Table B.2 for the physical and mechanical properties of different types
of thermoset resins may be used for preliminary design.
NOTE 1 The values included in Table B.2 are within the range of material properties reported in the literature.
NOTE 2 The actual value of Tg depends on the degree of polymerisation and, consequently, on the curing conditions.
NOTE 3 Resin properties mainly affect resin-dominated properties of composite laminates, such as interlaminar
shear strength (ILSS), compressive strength, shear strength, curing shrinkage and out-of-plane tensile strength
(resistance to delamination). The influence of the resin on fibre-dominated properties of composite laminates is
limited.
NOTE 4 The physical properties of resins can vary widely depending on their composition.
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CEN/TS 19101:2022 (E)
Table B.2 — Indicative values for the physical and mechanical properties of different types of
thermoset resins
Property
Polyester Vinylester
Elastic modulus, E r [GPa]
3,4 - 4,0
3,3 - 3,5
Maximum tensile elongation, ε r [%]
2,0 - 2,5
4,0 - 6,0
1,4
1,3
Tensile strength, σ r,t [MPa]
Compressive strength, σ r,c [MPa]
Shear modulus, Gr [GPa]
Shear strength, τ r [MPa]
Poisson's ratio, ν r [-]
Density, ρ r [kg/m3]
40 - 90
117
76 a
0,40
1200
Glass transition temperature, Tg [°C]
40 - 110
Thermal conductivity, λr [Wm-1K-1]
0,20
Coefficient of linear thermal expansion, α r [10-6 K-1]
a
b
Back-calculated from laminate data.
n/a – not available.
30 - 200
Epoxy
Phenolic
3,0 - 4,0
2,5 - 3,0
2,0 - 6,0
1,8 - 2,5
1,6
1,1
75 – 82
35 - 130
117
80 - 120
83 a
n/a b
n/a b
1150
1200
1300
0,38
40 - 120
30 - 50
0,40
40 - 300
50 - 110
0,18 - 0,20 0,10 - 0,20
40 - 70
n/a b
0,40
120 - 250
10
0,30
B.6 Core materials
(1) The indicative values given in Table B.3 for the physical and mechanical properties of different types
of core materials may be used for preliminary design.
NOTE Core materials frequently used in sandwich panels include polymeric foams (e.g. polyurethane (PUR),
polyethylene terephthalate (PET), polyvinyl chloride (PVC)) and balsa wood.
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CEN/TS 19101:2022 (E)
Table B.3 — Indicative values for the physical and mechanical properties of different types of
core materials
Property
Density, ρ [kg/m3]
Out-of-plane compressive
modulus in z direction,
E z,c [MPa]
PUR
50
PET
100
75
PVC
140
80
Balsa
250
100
250
6-12
29-30
50-70
110140
80-90
350-400
16002200
43007500
0,3-0,5
0,6-1,0
0,8-1,0
2,2-2,4
1,2–1,4
6,1-7,2
5,0-6,5
20-26
4-5
Out-of-plane shear
strengths (xz and yz
0,2-0,3
planes), perpendicular to
face sheets, f xz,v , fyz,v [MPa]
9-11
12-17
29-30
23-27
81-97
200-220
270350
0,3-0,5
0,4-0,6
1,1-1,2
1,0-1,2
3,9-4,5
1,4-1,6
3,4-4,0
0,2-0,3
0,3-0,5
0,5-0,7
1,2-1,4
1,0-1,2
3,9-4,5
1,4-1,8
3,0-4,0
6-12
In-plane compressive
strength in x and y direction, 0,3-0,5
f x,c , f y,c [MPa]
29-30
15-25
40-50
48
n/a a
70-80
220230
0,6-1,0
0,3-0,4
0,8-0,9
n/a a
n/a a
0,4-0,5
1,1-1,3
Thermal conductivity, λ
[W/m.K]
9-11
0,033
15-20
30-35
19
n/a a
110-150
Out-of-plane compressive
strength in z direction, fz,c
[MPa]
Out-of-plane shear moduli
(xz and yz planes), Gxz , Gyz
[MPa]
Out-of-plane shear
strengths (xz and yz
planes), parallel to face
sheets, fzx,v , fzy,v [MPa]
In-plane compressive
modulus in x and y
direction, E x,c , E y,c [MPa]
In-plane shear moduli (xy
plane), Gxy , Gyx [MPa]
a
n/a – not available
4-5
0,028
0,035
0,037
0,031
0,049
0,050
310400
0,085
NOTE 1 xyz axes are defined in Figure 3.4.
NOTE 2 For balsa core, the z direction is the end-grain direction. For PET foam, the z direction is the extrusion
direction.
NOTE 3 When compared to polymeric foam cores, the material properties of natural core materials, such as balsa
wood, exhibit higher scatter owing to variations in material density and the intrinsic nature of such core materials.
NOTE 4 In general, core materials are anisotropic. PUR foam can be anisotropic for densities below approximately
80 kg/m3.
177
CEN/TS 19101:2022 (E)
B.7 Ply properties
B.7.1 General
(1) A ply should be classified on the basis of the orientation of its fibres using the following distinction:
— unidirectional (UD) plies (UD roving, UD tape, UD non-woven fabric);
— bi-directional plies (woven fabric, non-woven fabric);
— mat plies (discontinuous or chopped strand mat (CSM), continuous fibre mat (CFM)).
NOTE 1 Micromechanics formulae for the determination of the ply stiffness properties are given in B.7.2.1, B.7.2.2
and B.7.2.3.
NOTE 2 While micromechanics formulae are effective in predicting the ply stiffness properties, they are not equally
accurate in predicting ply strength properties. For this reason, experimental values are provided as reference for
ply strength properties (B.7.3).
NOTE 3 The values of the ply and laminate material properties given in Tables B.4 to B.16 and calculated using the
formulae given in this Annex, are obtained using the constituent material properties of fibres and resins given in
Tables B.1 and B.2, respectively. The same formulae can be applied to filled thermoset resin based matrix plies and
laminates, if the material properties of the resin mixed with additives and fillers are known.
B.7.2 Indicative values for ply stiffness properties
B.7.2.1 UD plies
(1) The elastic properties of UD plies may be calculated from Formula (B.1) to (B.4):
E1 = E r + ( E f,1 − E r ) ⋅ Vf 
 1 + ξ2 ⋅η2 ⋅Vf 
E2 
=
 ⋅ Er
 1 −η2 ⋅Vf 
 1 + ξG ⋅ηG ⋅ Vf 
G12 = 
 ⋅ Gr
⋅
−
η
V
1
G
f


ν 12 =ν r − (ν r −ν f ) ⋅Vf
where
 E f,2

−1

E
 , with ξ = 2
η2 =  r
2
 E f,2

ξ
+

2
 Er

 Gf

 −1
G
 , with ξ = 1
ηG =  r
G
 Gf

 + ξG 
 Gr

178
(B.1)
(B.2)
(B.3)
(B.4)
(B.5)
(B.6)
CEN/TS 19101:2022 (E)
where
E1 , E 2
is the in-plane elastic modulus of the ply in the 1 and 2 direction;
G12
is the in-plane shear modulus of the ply;
νr
is the Poisson’s ratio of the resin;
ν 12
νf
Er
E f,1 , E f,2
Gr
Vf
is the Poisson’s ratio of the ply;
is the Poisson’s ratio of the fibres;
is the elastic modulus of the resin;
is the elastic modulus of the fibres in the 1 and 2 direction;
is the shear modulus of the resin;
is the fibre volume fraction of the ply.
(2) The indicative values given in Table B.4 for the elastic moduli of UD plies made of E-glass fibres and
unsaturated polyester resin may be used for preliminary design.
Table B.4 — Indicative values for the elastic moduli of UD plies made of E-glass fibres and
polyester resin
Vf [%]
E1 [GPa]
E2 [GPa]
G12 [GPa]
ν 12 [-]
40
32
9
3,0
0,34
50
39
12
3,7
0,33
45
55
60
65
70
B.7.2.2 Bi-directional plies
35
10
42
13
46
49
53
15
17
20
3,3
4,2
4,8
5,5
6,3
0,33
0,32
0,31
0,30
0,30
(1) The elastic properties of balanced bi-directional plies (0/90° orientation) may be calculated from
Formulae (B.7) to (B.9):
 1 + ξ2 ⋅η2 ⋅ Vf  
1 
E1 =E2 = ⋅ E r + ( E f,1 − E r ) ⋅ Vf + E r ⋅ 

2 
 1 − η2 ⋅ Vf  
 1 + ξG ⋅ηG ⋅Vf 
G12 
=
 ⋅ Gr
 1 − ηG ⋅Vf 
(B.7)
(B.8)
179
CEN/TS 19101:2022 (E)
ν 12 =
where
ν r − (ν r −ν f ) ⋅Vf
(B.9)


 E + E − E ⋅V  
1   r ( f,1
r)
f 
⋅ 1 +

2 
 1 + ξ2 ⋅η2 ⋅ Vf 

E
⋅

 r 

 1 − η2 ⋅ Vf 


 E f,2

−1

E
 , with ξ = 2
η2 =  r
2
 E f,2

+
ξ

2
 Er

(B.10)
 Gf

 −1
G
 , with ξ = 1
ηG =  r
G
 Gf

+
ξ

G 
 Gr

(B.11)
(2) The indicative values given in Table B.5 for the elastic moduli of balanced bi-directional plies made of
E-glass fibres and polyester resin may be used for preliminary design.
Table B.5 — Indicative values for the elastic moduli of balanced bi-directional plies made of
E-glass fibres and polyester resin
Vf [%]
E1 = E2 [GPa]
G12 [GPa]
ν 12 [-]
25
14
2,2
0,17
35
18
2,7
0,16
30
40
45
50
B.7.2.3 Mat plies
55
16
20
23
25
28
2,5
3,0
3,3
3,7
4,2
0,16
0,15
0,15
0,15
0,15
(1) The elastic properties of mat plies may be calculated from Formulae (B.12) to (B.14):
3 UD 5 UD
=
E E1 + E 2
8
8
1 UD 1 UD
=
G E1 + E 2
8
4
180
(B.12)
(B.13)
CEN/TS 19101:2022 (E)
E
=
ν 1
−
2G
where
E1UD , E2UD
(B.14)
are the longitudinal and transverse moduli of a fictitious unidirectional ply of the
same fibre volume fraction as the mat ply.
(2) The indicative values given in Table B.6 for the elastic moduli of mat plies made of E-glass fibres and
unsaturated polyester resin may be used for preliminary design.
Table B.6 — Indicative values for the elastic moduli of mat plies made of E-glass fibres and
polyester resin
Vf [%]
E1 = E2 [GPa]
G12 [GPa]
ν 12 [-]
15
8
3,0
0,40
20
10
3,6
0,40
30
14
17,5
25
9
12
B.7.3 Indicative values for ply strength properties
3,3
4,2
4,9
0,40
0,41
0,41
(1) The indicative values given in Tables B.7, B.8 and B.9 for the strength of UD plies, bi-directional plies
and mat plies, respectively, for various combinations of reinforcing fibres and resins may be used for
preliminary design.
NOTE
The values given in Tables B.7 to B.9 are based on experimental data.
181
CEN/TS 19101:2022 (E)
Table B.7 — Indicative values for the strength properties of UD plies for combinations of
reinforcing fibres and resins
E-glass,
epoxy,
Vf = 60%
S-glass,
epoxy,
Vf = 60%
E-glass,
isophthalic
polyester,
Vf = 60%
Carbon
(AS4/3501-6),
epoxy,
Vf = 60%
Longitudinal tensile
strength, f1,t [MPa]
1020
1620
900
1830
Longitudinal compressive
strength, f1,c [MPa]
40
40
40
57
620
690
360
1100
In-plane shear strength,
f12,v [MPa]
140
140
68
230
60
60
40
71
60
80
76
n/a a
Property
Transverse tensile
strength, f2,t [MPa]
Transverse compressive
strength, f2,c [MPa]
Intralaminar shear
strength, f13,v , f23,v [MPa]
a
n/a – not available.
Table B.8 — Indicative values for the strength properties of balanced bi-directional plies for
combinations of reinforcing fibres and resins
Property
Longitudinal tensile strength, f1,t [MPa]
E-glass, epoxy,
Vf = 50%
Carbon (HS), epoxy,
Vf = 45%
400
420
Transverse tensile strength, f2,t [MPa]
400
420
Transverse compressive strength, f2,c [MPa]
390
360
Longitudinal compressive strength, f1,c [MPa]
In-plane shear strength, f12,v [MPa]
a
n/a – not available.
182
390
n/a a
360
55
CEN/TS 19101:2022 (E)
Table B.9 — Indicative values for the strength properties of mat plies made of E-glass and epoxy
Property
Longitudinal tensile strength, f1,t [MPa]
E-glass, epoxy,
Vf = 17%
130
Transverse tensile strength, f2,t [MPa]
130
Transverse compressive strength, f2,c [MPa]
180
Longitudinal compressive strength, f1,c [MPa]
Intralaminar shear strength, f13,v , f23,v [MPa]
180
25
(2) For the strength properties of plies with basalt reinforcing fibres, the indicative values for E-glass
reinforcing fibres given in Tables B.7 to B.9 may be used as a conservative approximation.
B.7.4 Coefficient of linear thermal expansion for plies
(1) The coefficient of linear thermal expansion in the longitudinal and transverse directions of UD plies,
respectively, α1 and α 2 , may be calculated from Formulae (B.15) and (B.16):
α1 =
Vf ⋅ α f,1 ⋅ E f,1 + Vr ⋅ α r ⋅ E r
E1
α2 =
(1 +ν f ) ⋅α f,2 ⋅Vf + (1 +ν r ) ⋅α r ⋅Vr − α1 ⋅ν 12
where
(B.15)
(B.16)
E f,1
is the elastic modulus of the fibres in their longitudinal direction;
α f,2
is the coefficient of linear thermal expansion of the fibres in their transverse direction;
α f,1
ν 12
is the coefficient of linear thermal expansion of the fibres in their longitudinal direction;
is the Poisson’s ratio of the UD ply.
(2) The coefficient of linear thermal expansion of a mat ply with randomly oriented fibres, α q , may be
calculated from Formula (B.17):
αq =
α1UD + α 2UD α1UD − α 2UD
E1UD − E2UD
+
⋅ UD
2
2
E1 + (1 + 2 ⋅ν 21UD ) ⋅ E2UD
(B.17)
where α 1UD , α 2UD , E1UD , E2UD are the properties of a fictitious UD ply with the same fibre volume fraction as
UD
the mat ply, calculated using the formulae from B.7.2.1 and Formulae (B.15) and (B.16), and in which ν 12
UD
may be calculated from Formula (B.18):
corresponds to ν 12 , defined in B.7.4(1), and ν 21
183
CEN/TS 19101:2022 (E)
ν 12UD ν 21UD
=
E1UD E2UD
(B.18)
(3) The indicative values given in Tables B.10, B.11 and B.12 for the coefficient of linear thermal
expansion of UD plies, balanced bi-directional plies and mat-plies, respectively, made of E-glass fibres
and polyester resin may be used for preliminary design.
Table B.10 — Indicative values for the coefficient of linear thermal expansion of UD plies made
of E-glass fibres and polyester resin
α r = 30 × 10-6 K-1
Vf [%]
α r = 200 × 10-6 K-1
α1 [10-6 K-1]
α 2 [10-6 K-1]
α1 [10-6 K-1]
α 2 [10-6 K-1]
40
6,7
25
18
164
50
6,1
22
14
139
45
6,4
55
24
5,9
60
21
5,8
65
19
5,6
70
17
5,5
15
16
152
12
126
11
112
9,8
99
8,9
86
Table B.11 — Indicative values for the coefficient of linear thermal expansion of balanced bidirectional plies made of E-glass fibres and polyester resin
α r = 30 × 10-6 K-1
α r = 200 × 10-6 K-1
α1 = α 2 [10-6 K-1]
α1 = α 2 [10-6 K-1]
25
19
115
35
17
99
Vf [%]
30
40
45
50
55
184
18
16
15
14
13
107
91
84
76
69
CEN/TS 19101:2022 (E)
Table B.12 — Indicative values for the coefficient of linear thermal expansion of mat plies made
of E-glass fibres and polyester resin
α r = 30 × 10-6 K-1
α r = 200 × 10-6 K-1
α1 = α 2 [10-6 K-1]
α1 = α 2 [10-6 K-1]
10
19
116
20
15
82
Vf [%]
15
25
30
B.7.5 Thermal conductivity of plies
17
14
13
96
72
64
(1) The thermal conductivity of UD plies may be calculated from Formulae (B.19) and (B.20):
=
λ1 Vf ⋅ λf,1 + Vr ⋅ λr
 1 + ξ ⋅η ⋅ Vf 

 1 − η ⋅ Vf 
λ2 = λr ⋅ 
where
 λf

 −1
λ

η= r
 λf

 +ξ 
 λr

ξ = 10
a
3 lg  
b
(B.19)
(B.20)
(B.21)
(B.22)
where a / b is the aspect ratio of the cross-sectional dimensions of the fibres, with a and b being the
cross-section dimensions respectively parallel and transverse to the direction of heat conduction. For
fibres with circular cross sections (e.g. glass and basalt fibres), a / b = 1 and ξ = 1 .
(2) The indicative values given in Tables B.13 and B.14 for the thermal conductivity of UD plies and
balanced bi-directional plies, respectively, made of E-glass fibres and polyester resin may be used for
preliminary design.
185
CEN/TS 19101:2022 (E)
Table B.13 — Indicative values for the thermal conductivity of UD plies made of E-glass fibres
and polyester resin
Vf [%]
λ1 [W/m.K]
λ2 [W/m.K]
40
0,52
0,35
50
0,60
0,40
45
0,56
55
0,37
0,64
60
0,43
0,68
65
0,47
0,72
70
0,51
0,76
0,55
Table B.14 — Indicative values for the thermal conductivity of balanced bi-directional plies
made of E-glass fibres and polyester resin
Vf [%]
λ1 = λ2 [W/m.K]
25
0,34
35
0,40
30
40
45
50
B.7.6 Swelling of plies
55
0,37
0,43
0,47
0,50
0,54
(1) For design situations where swelling can potentially occur, the coefficients of moisture expansion in
the longitudinal ( β1 ) and transverse ( β2 and β3 ) directions may be calculated from Formulae (B.23) and
(B.24):
β1 =
Er ρ
βr
E1 ρ r

β 2 = β3 = ( 1 +ν r ) −

 ρ
Er
ν 12  ⋅ β r
E1  ρ r
(B.23)
(B.24)
where ρ and ρ r are the densities of the ply and the resin, respectively, β r is the moisture expansion
coefficient of the resin, E1 is the elastic modulus of the ply in the 1 direction, E r is the elastic modulus of
the resin, ν 12 and ν r are the Poisson’s ratio of the ply and the resin, respectively.
186
CEN/TS 19101:2022 (E)
B.7.7 Failure criteria for plies
(1) Empirical failure criteria, which have been developed to represent experimental data for failure of
single plies of composite laminates under plane stress conditions, may be used.
NOTE Well-established failure criteria for plies of composite laminates include Maximum Stress, Maximum Strain,
Tsai-Hill, Tsai-Wu, Puck and Hashin.
(2) Failure of an orthotropic ply may be predicted applying the Tsai-Hill failure criterion, given in
Formula (B.25):
2
2
 σ 11   σ 22   τ 12

 + 
 + 
 f1,i   f2,i   f12,v
where
2
 σ 11 ⋅ σ 22
1
=
 −
f1,2i

(B.25)
σ 11
is the longitudinal stress in the ply resulting from the effect of the actions;
τ 12
is the transverse stress in the ply resulting from the effect of the actions;
f1,i ( i = t or c)
is the shear stress in the ply resulting from the effect of the actions;
is the longitudinal tensile (t) or compressive (c) strength of the ply;
σ 22
f2,i ( i = t or c)
f12,v
is the transverse tensile (t) or compressive (c) strength of the ply;
is the in-plane shear strength of the ply.
(3) Failure of an orthotropic ply may be predicted applying the Tsai-Wu failure criterion, given in Formula
(B.26):
2
2
2
+ F22 ⋅ σ 22
+ F66 ⋅τ 12
+ 2 ⋅ F12 ⋅ σ 11 ⋅ σ 22 =
F1 ⋅ σ 11 + F2 ⋅ σ 22 + F6 ⋅τ 12 + F11 ⋅ σ 11
1
(B.26)
where F1 , F2 , F6 , F11 , F22 , and F66 are the strength coefficients, which may be calculated from Formulae
(B.27) to (B.32) using the tensile, compressive, and shear strength properties of the ply in the principal
material directions:
=
F1
=
F2
1
1
−
f1,t f1,c
1
1
−
f2,t f2,c
F6 = 0
F11 =
F22 =
1
f1,t ⋅ f1,c
1
f2,t ⋅ f2,c
(B.27)
(B.28)
(B.29)
(B.30)
(B.31)
187
CEN/TS 19101:2022 (E)
F66 =
1
(f )
12,v
2
(B.32)
and where F12 is a strength interaction term between σ 11 and σ 22 ; since the experimental determination
of F12 requires a suitable biaxial test, experimental data are not easily available and an approximation can
be obtained from Formula (B.33):
1
F12 =− ⋅ F11 ⋅ F22
2
B.8 Laminate properties
(B.33)
B.8.1 General
(1) Stiffness properties of laminates may be predicted using the Classical Lamination Theory (CLT), based
on the ply properties.
(2) Strength properties of laminates may be determined analytically using the CLT based on the ply
properties and an appropriate failure criterion (B.7.7).
(3) The ultimate failure of a laminate may be estimated based on the following steps:
1. Calculate stresses and strains in each ply using CLT;
2. Apply an appropriate failure criterion to predict which ply fails first;
3. Assign reduced stiffness and strength to the failed ply;
4. Recalculate stresses and strains in each of the plies using CLT;
5. Repeat steps from 2 to 4 until ultimate failure of the laminate occurs.
NOTE 1 After the failure of a ply, the stresses and strains in the remaining plies increase and the laminate stiffness
decreases. The laminate often does not fail after the failure of the first ply and the failed ply can still carry part of
the load.
NOTE 2 Several analytical methods have been proposed to take into account the failed ply and simulate the
subsequent behaviour of the laminate, including the following:
—
Total discount method: zero stiffness and strength are assigned to the failed ply in all directions.
—
Residual property method: residual strength and stiffness are assigned to the failed ply.
—
Limited discount method: if the ply failure is in the matrix material, the transverse stiffness, the transverse
strength, the shear stiffness, and the shear strength of the failed ply are set to zero; if the ply fails by fibre
rupture, the total discount method is adopted.
B.8.2 Stiffness and strength
(1) The indicative values given in Tables B.15 and B.16 for the experimental and analytical values
(estimated with the analytical procedure described in B.8.1) of stiffness and strength properties of
balanced symmetrical bi-directional laminates made of glass fibres and epoxy resin may be used for
preliminary design.
188
CEN/TS 19101:2022 (E)
Table B.15 — Experimental (mean) and analytical values of stiffness properties of balanced
symmetrical bi-directional laminates made of glass fibres and epoxy resin ( Vf = 54%)
Stiffness properties
Glass fibre and epoxy laminate
[0/90/90/0]s a
Experimental values
Analytical values
E x [GPa]
26,8
26,2
Gxy [GPa]
4,7
3,3
E y [GPa]
ν xy [-]
23,7
0,15
26,2
0,1
Plain weave 50/50 fabrics were used to manufacture the sample: direction x corresponds to the warp and
direction y corresponds to the weft.
a
Table B.16 — Experimental (mean) and analytical values of strength properties of balanced
symmetrical bi-directional laminates made of glass fibres and epoxy resin ( Vf = 54%)
Strength properties
Glass fibre and epoxy laminate
[0/90/90/0]s balanced layup a
Experimental values
Analytical values
f x,t [MPa]
502
440
f y,t [MPa]
411
440
f x,c [MPa]
f y,c [MPa]
f xy,v [MPa]
348
321
64
300
300
n/a b
Plain weave 50/50 fabrics were used to manufacture the sample: direction x corresponds to the warp and
direction y corresponds to the weft.
a
b
n/a – not available.
(2) The indicative values given in Table B.17 for the ILSS of two epoxy resin laminates produced by
vacuum infusion may be used for preliminary design.
(3) The indicative values given in Table B.18 for the ILSS of polyester resin and vinylester resin laminates
produced by pultrusion may be used for preliminary design.
189
CEN/TS 19101:2022 (E)
Table B.17 — Experimental (mean) values of interlaminar shear strength for two epoxy resin
laminates produced by vacuum infusion
Strength properties
Glass fibre and epoxy laminate Glass fibre and epoxy laminate
[0/90/90/0]s balanced layup
UD layup
Vf = 54%
Vf = 62%
f yz,ILS [MPa]
a
45
f xz,ILS [MPa]
n/a a
45
n/a – not available.
53
Table B.18 — Experimental (mean) values of interlaminar shear strength for two polyester resin
and vinylester resin laminates produced by pultrusion
Strength properties
Glass fibre and polyester
laminate
Vf = 46%
Glass fibre and vinylester
laminate
Vf = 53%
f xz,ILS [MPa]
33
39
B.8.3 Coefficients of linear thermal expansion
(1) The coefficient of linear thermal expansion in x and y direction, α x and α y , for a laminate that consists
of several plies with different fibre directions may be calculated using CLT.
(2) For a laminate that consists of different plies ( n ) with different fibre directions, the coefficient of
thermal expansion along the two directions x and y, α x and α y , may be calculated from Formulae (B.34)
and (B.35):
αx =
αy =
α x,1 ⋅ t1 + α x,2 ⋅ t 2 +  + α x,n ⋅ t n
t1 + t 2 +  + t n
α y,1 ⋅ t1 + α y,2 ⋅ t 2 +  + α y,n ⋅ t n
t1 + t 2 +  + t n
(B.34)
(B.35)
where t i is the thickness of the ply i and α i , j is the value of the thermal expansion coefficient of the j th
ply along the assigned direction i (x or y).
190
CEN/TS 19101:2022 (E)
Annex C
(normative)
Buckling of orthotropic laminates and profiles
C.1 Use of this annex
(1) This Normative Annex contains additional provisions to Clause 8 for estimating the elastic buckling
resistances of orthotropic laminates and profiles.
C.2 Scope and field of application
(1) This Normative Annex applies to orthotropic laminates and profiles, providing formulae to estimate
their elastic buckling resistances. The member types and loading cases covered in this annex are:
—
—
Subclause C.4 is for orthotropic flat laminates with different boundary conditions and under various
loading cases;
Subclause C.5 is for profiles with different cross-sections subjected to compression or major-axis
bending: subclause C.5.2 is for profiles with double symmetric cross-sections subjected to
compression; subclause C.5.3 is for profiles with angle, cruciform and T cross-sections subjected to
compression; subclause C.5.4 is for profiles with double symmetric cross-section subjected to majoraxis bending; and subclause C.5.5 is for local buckling of profiles with double symmetric cross-section
considering the rotational restraint at web-flange junctions.
C.3 General
(1) In general, flexural stiffnesses should be calculated using Classical Laminate Theory (CLT). For
orthotropic, symmetric and balanced laminates (e.g., walls of pultruded profiles), when mechanical
properties are determined at the laminate level, such stiffnesses should be calculated from Formulae
(C.1) to (C.4):
D11 =
ηc ⋅ E x,c,k ⋅ t 3
12 (1 −ν xy,k ⋅ν yx,k )
D=
ν yx,k ⋅ D11
12
D22 =
D66 =
where
ηc ⋅ E y,c,k ⋅ t 3
12 (1 −ν xy,k ⋅ν yx,k )
ηc ⋅ Gxy,k ⋅ t 3
12
(C.1)
(C.2)
(C.3)
(C.4)
are the longitudinal, coupling, transverse and shear flexural stiffness, respectively;
D11 , D12 ,
D22 and D66
191
CEN/TS 19101:2022 (E)
t
E x,c,k
E y,c,k
Gxy,k
ν xy,k
ν yx,k
ηc
is the wall thickness (laminate, flange or web);
and are the characteristic values of the elastic moduli in compression in the x and y
directions;
is the characteristic value of the in-plane shear modulus;
and are the characteristic values of major and minor Poisson’s ratios, respectively;
is defined in 4.4.7 (to be selected for E x,c,k , E y,c,k or Gxy,k ).
NOTE 1 Some of the formulae in Annex C require the calculation of the flexural stiffnesses of orthotropic laminates,
which, in the case of profiles, correspond to the cross-section walls.
NOTE 2 Subscripts x and y are for longitudinal and transverse direction, respectively, and subscript c is for
compression force.
(2) When the in-plane moduli of a composite laminate in a given direction is significantly different from
the flexural moduli in the same direction, the flexural moduli should be considered in Formulae (C.1) to
(C.3).
NOTE 1 The fibre architecture affects the in-plane and flexural moduli of a composite laminate.
NOTE 2 The flexural modulus of a composite laminate can be determined by testing, according to EN ISO 14125.
C.4 Elastic buckling of orthotropic laminates
C.4.1 Scope
(1) Subclause C.4 provides formulae to estimate the critical elastic buckling stresses of flat rectangular
laminates that have orthotropic in-plane elastic constants, a balanced symmetrical lamination
configuration, width-to-thickness ratio higher than 20 and length-to-width ratio higher than 5, for
specific boundary conditions.
NOTE 1 The formulae in subclause C.4 are for elastic critical buckling stresses (bifurcation) of geometrically perfect
laminates.
NOTE 2 The formulae in subclause C.4 do not apply to curved laminates.
NOTE 3 For flat laminates having width-to-thickness ratio higher than 20 and length-to-width ratio lower than 5,
the formulae in subclause C.4 provide conservative estimates of elastic critical buckling stresses.
(2) The critical elastic buckling stresses of laminates (bifurcation) having (i) width-to-thickness ratio
lower than 20, or (ii) curvature should be determined by numerical modelling.
C.4.2 Orthotropic symmetrical laminates
C.4.2.1 Compression
(1) The characteristic value of the critical buckling compressive stress of a laminate under in-plane
compression loading for the different boundary conditions illustrated in Figure C.1, fi ,cr,k , should be calculated
from Formulae (C.5) to (C.10):
—
192
Both edges simply supported (SS) (Figure C.1a):
CEN/TS 19101:2022 (E)
=
fi ,cr,k
—
—
—
—
π2 
⋅ 2 D11 ⋅ D22 + 2( D12 + 2 ⋅ D66 )

t ⋅ b2 
One edge simply supported (SS) and one edge clamped (CL) (Figure C.1b):
=
fi ,cr,k
π2 
⋅ 3,13 D11 ⋅ D22 + 2,33( D12 + 2 ⋅ D66 )

t ⋅ b2 
(C.6)
π2 
⋅ 4,53 D11 ⋅ D22 + 2,44( D12 + 2 ⋅ D66 )
t ⋅ b2 
(C.7)
Both edges clamped (CL) (Figure C.1c):
=
fi ,cr,k
One edge free (Free) and one edge simply-supported (SS) (Figure C.1d):
f i,cr,k =
12 ⋅ D66
t ⋅ b2
One edge free (Free) and one edge clamped (CL) (Figure C.1e):
fi ,cr,k=
fi ,cr,k=
where
ρ=
where
1
⋅ D11 ⋅ D22 ⋅ 15,1 ⋅ K 1 − ρ + 7(1 − K ) , if K ≤ 1
t ⋅ b2
1
⋅ D11 ⋅ D22 ⋅ 15,1 ⋅ K ⋅ 1 − ρ + 6(K − 1) ⋅(1 − ρ ) , if K > 1


t ⋅ b2
2D66 + D12
K=
(C.5)
(C.8)
(C.9)
(C.10)
(C.11)
D11 ⋅ D22
D12
2D66 + D12
(C.12)
D11 , D12 , are the flexural stiffnesses defined in C.3(1);
D22 and
D66
t
b
is the thickness of the laminate;
is the width of the laminate (perpendicular to the compressive stress direction).
NOTE In Formulae (C.5) to (C.10) i is either for the x or y direction of the laminate (i.e. longitudinal or
perpendicular to the laminate width).
193
CEN/TS 19101:2022 (E)
a) Simply-supported (SS) - Simply-supported (SS)
b) Simply-supported (SS) – Clamped (CL)
c) Clamped (CL) - Clamped (CL)
d) Simply-supported (SS) - Free
e) Clamped (CL) - Free
Figure C.1 — Orthotropic laminate under in-plane compression with different boundary
conditions for the edge(s): Simply Supported (SS), Free (Free) or Clamped (CL)
C.4.2.2 Shear
(1) The characteristic value of the critical buckling shear stress of a laminate under in-plane shear loading
for the different boundary conditions illustrated in Figure C.2, f xy,cr,k , should be calculated from Formulae
(C.13) to (C.16):
—
Both edges simply supported (SS) (Figure C.2a):
f xy,cr,k =
=
f xy,cr,k
—
4 4
3
⋅ D11 ⋅ D22
⋅(8,13 + 5,05 ⋅ K )
2
t ⋅b
4
1,46 

⋅ D22 ⋅ ( D12 + 2 ⋅ D66 ) ⋅  11,7 + 2 
2
t ⋅b
K 

Both edges clamped (CL) (Figure C.2b):
f xy,cr,k =
f xy,cr,k
=
where
4 4
3
⋅ D11 ⋅ D22
⋅ (15,0 + 7,08 ⋅ K )
t ⋅ b2
, if K > 1
, if K ≤ 1
4
3,56 

⋅ D22 ⋅ ( D12 + 2 ⋅ D66 ) ⋅  18,6 + 2 
2
t ⋅b
K 

D11 , D12 ,
D22 and D66
194
, if K ≤ 1
, if K > 1
are the flexural stiffnesses defined in C.3(1);
(C.13)
(C.14)
(C.15)
(C.16)
CEN/TS 19101:2022 (E)
t
is the thickness of the laminate;
b
is the width of the laminate;
K
is given by Formula (C.11).
a) Simply-supported (SS) - Simply-supported (SS)
b) Clamped (CL) – Clamped (CL)
Figure C.2 — Orthotropic laminate under in-plane shear with different boundary conditions for
the edge(s): (a) Simply Supported (SS); and (b) Clamped (CL)
C.4.2.3 In-plane bending
(1) The characteristic value of the critical buckling bending stress of a laminate under in-plane bending
loading for the different boundary conditions illustrated in Figure C.3, fi ,b,cr,k , should be calculated from
Formulae (C.17) to (C.19):
—
—
Both edges simply supported (SS) (Figure C.3a):
=
fi ,b,cr,k
π2 
⋅ 13,4 ⋅ D11 ⋅ D22 + 10,4 ( D12 + 2 ⋅ D66 ) 

t ⋅ b2 
Both edges clamped (CL) (Figure C.3b):
=
fi ,b,cr,k
fi ,b,cr,k
=
where
π2 
⋅ 26,8 ⋅ D11 ⋅ D22 + 12,9 ( D12 + 2 ⋅ D66 ) 
2 
t ⋅b
π2 
⋅ 30,1 ⋅ D11 ⋅ D22 + 11,5 ( D12 + 2 ⋅ D66 ) 
2 
t ⋅b
(C.17)
, if K ≤ 3
, if K > 3
(C.18)
(C.19)
D11 , D12 , D22 and D66
are the flexural stiffnesses defined in C.3(1);
b
is the width of the laminate (perpendicular to the bending stress direction);
t
K
is the thickness of the laminate;
is given by Formula (C.11).
NOTE In Formulae (C.17) to (C.19) i is either for the x or y direction of the laminate (i.e., longitudinal or
perpendicular to the plate width).
195
CEN/TS 19101:2022 (E)
a) Simply-supported (SS) - Simply-supported (SS)
b) Clamped (CL) – Clamped (CL)
Figure C.3 — Orthotropic laminate under in-plane bending with different boundary conditions
for the edge(s): (a) Simply Supported (SS); and (b) Clamped (CL)
C.5 Elastic buckling of profiles
C.5.1 Scope
(1) Subclause C.5.2 provides formulae to estimate the design value of the compressive resistance to local
buckling of profiles, Ncr,Rd , with double symmetric cross-sections (I-sections and single-cell tubular
sections - rectangular or square) subjected to axial compression, and the reduction factor, χ E , that takes
into account the interaction between local and flexural buckling.
(2) Subclause C.5.3 provides formulae to estimate the design values of the compressive resistance to
torsional buckling of profiles, NT,Rd , and to flexural-torsional buckling of profiles, NFT,Rd , with all section
walls sharing a common junction (the shear centre).
(3) Subclause C.5.4 provides formulae to estimate the design value of the bending moment resistance to
global buckling of profiles or local buckling of profiles, MRd2 , with double symmetric cross-sections (Isections and single-cell tubular sections - rectangular or square) subjected to major-axis bending (y-axis,
Figure 3.3), and the reduction factor, χ LT , that takes into account the interaction between local and
lateral-torsional buckling.
NOTE For profiles subjected to minor-axis bending (z-axis, Figure 3.3), flexural-torsional buckling does not occur
and χ LT = 1,0.
(4) Subclauses C.5.2 and C.5.4 do not take into account the beneficial effect on local buckling resistance
of elastic rotational restraint along the junctions between the walls in the cross-section. Subclause C.5.5
has formulae to determine resistance that include such effect.
C.5.2 Profiles with double symmetric cross-sections subjected to compression
(1) For profiles with double symmetric cross-sections, the design value of the compressive resistance to
local buckling of the profile, Ncr,Rd , should be determined from Formula (C.20):
N=
cr,Rd
where
γm
1
⋅ A ⋅ f x,cr,k
γ m ⋅ γ Rd
is defined in 4.4.5 (to be selected for E x,c,k , the characteristic value of the in-plane
compressive modulus in the longitudinal (x) direction, except for the conditions defined
in C.5.2(4) and C.5.5, for which Gxy,k , the characteristic value of the in-plane shear
modulus, should be considered instead);
196
(C.20)
CEN/TS 19101:2022 (E)
γ Rd
A
f x,cr,k
is defined in 4.4.6 (Table 4.3, Local buckling);
is the gross area of the cross-section;
is the characteristic value of the critical stress associated to local buckling of the profile
in compression, considering the appropriate values of the conversion factor, ηc , for the
relevant material properties (defined in 4.4.7).
(2) The value of f x,cr,k should be determined from Formula (C.21):
{
f x,cr,k = min ( f x,cr,k )f ; ( f x,cr,k )w
where
(f )
(C.21)
is the characteristic value of the critical stress of the compressed flange for a uniform
stress distribution over the flange width, considering the appropriate values of the
conversion factor, ηc , for the relevant material properties (defined in 4.4.7);
x,cr,k f
(f )
is the characteristic value of the critical stress of the compressed web for a uniform
stress distribution over the web width, considering the appropriate values of the
conversion factor, ηc , for the relevant material properties (defined in 4.4.7).
x,cr,k w
NOTE
}
Subscripts f and w refer to the flange and the web, respectively.
(3) The values of ( f x,cr,k )f and ( f x,cr,k )w may be obtained from C.5.2(4) to (7). As an alternative, they may be
obtained from C.5.5.2 (accounting for the elastic rotational restraint along the junctions between the
walls) or from numerical modelling.
(4) For profiles with I cross-sections, the characteristic value of the critical stress of the compressed
flange, assuming simply supported (SS) boundary condition along the junction with the web, ( f x,cr,k )f ,
SS
may be conservatively estimated using Formula (C.22):
f ) (=
f )
(=
x,cr,k f
where
NOTE
D66
SS
x,cr,k f
bf and t f
12 ( D 66 )f
b 
tf ⋅  f 
2
(C.22)
2
is the flexural stiffness defined in C.3(1);
are defined in Figure C.4a.
Subscript f refers to the flanges and superscript SS stands for simply supported.
(5) For profiles with I cross-sections, the characteristic value of the critical stress of the compressed web,
assuming simply supported (SS) boundary conditions along the junction with the flanges, ( f x,cr,k )w , may
be conservatively estimated using Formula (C.23):
( f ) =( f )
x,cr,k w
where
SS
x,cr,k w
=
{
}
π2
⋅ 2 ( D11 )w ⋅ ( D22 )w + 2 ( D12 )w + 2 ( D66 )w 
t w ⋅ bw2
SS
(C.23)
197
CEN/TS 19101:2022 (E)
D11 , D12 , D22 and D66
are the flexural stiffnesses defined in C.3(1);
bw and t w
NOTE
are defined in Figure C.4a.
Subscript w refers to the web and superscript SS stands for simply supported.
(6) For profiles with single-cell tubular cross-sections (rectangular or square), the characteristic value of
the critical stress of the compressed flange assuming simply supported (SS) boundary conditions along
the junction with the webs, ( f x,cr,k )f , may be conservatively estimated using Formula (C.24):
SS
( f ) =( f )
x,cr,k f
where
SS
x,cr,k f
π2
{
=
⋅ 2
t f ⋅ bf2
( D11 )f ⋅ ( D22 )f + 2 ( D12 )f + 2( D66 )f }
(C.24)
D11 , D12 , D22 and are the flexural stiffnesses defined in C.3(1);
D66
bf and t f
are defined in Figure C.4b.
(7) For profiles with single-cell tubular sections (rectangular or square), the characteristic value of the
critical stress of the compressed webs assuming simply supported (SS) boundary conditions along the
junction with the flanges, ( f x,cr,k )w , may be conservatively estimated using Formula (C.25):
SS
( fx,cr,k )w =( fx,cr,k )w =
SS
where
D11 , D12 , D22 and D66
bw and t w
{
}
π2
⋅ 2 ( D11 )w ⋅ ( D22 )w + 2 ( D12 )w + 2 ( D66 )w 
t w ⋅ bw2
(C.25)
are the flexural stiffnesses defined in C.3(1);
are defined in Figure C.4b.
a) I-section
b) single-cell tubular section
Figure C.4 — Symbols for geometrical dimensions of double symmetric cross-sections
(S – shear centre, and C – centroid)
198
CEN/TS 19101:2022 (E)
(8) The value of the reduction factor to take into account the interaction between local and flexural
buckling, χ E , should be determined from Formula (C.26):
χ=
E
where
cE
ΦE
and
(
ΦE =
(C.26)
is an empirical constant (equal to 0,65);
is an auxiliary coefficient, given by Formula (C.27),
1 + λE2
2
λE
λE =
where
)
1
⋅ ΦE − Φ2E − cE ⋅ λE2 , and χ E ≤ 1,0
cE ⋅ λE2
(C.27)
is the profile slenderness for interaction between local and flexural buckling, given by
Formula (C.28),
Ncr,Rd
(C.28)
NE,Rd
NE,Rd
is the design value of the flexural buckling resistance of the profile, which includes the
effects of shear deformation.
(9) The design value of the flexural buckling resistance of the profile, NE,Rd , should be determined from
Formula (C.29):
N=
E,Rd
where
1
⋅ A ⋅ fE,cr,k ⋅ χ E,shear
γ m ⋅ γ Rd
γm
γ Rd
A
fE,cr,k
χ E,shear
(C.29)
is defined in 4.4.5 (to be selected for E x,c,k , the characteristic value of the in-plane
compressive modulus in the longitudinal (x) direction);
is defined in 4.4.6 (Table 4.3, Global buckling – flexural);
is the gross-area of the cross-section;
is the characteristic value of the critical flexural buckling stress (without considering the
effects of shear deformation), and considering the appropriate values of the conversion
factor, ηc , for the relevant material properties (defined in 4.4.7);
is the reduction factor to take into account the influence of shear deformation.
NOTE The empirical constant cE was derived for members manufactured by pultrusion. It can be applied to
members manufactured by other processes, provided they guarantee equivalent or more stringent geometrical
tolerances.
(10) The value of fE,cr,k should be determined from Formula (C.30):
199
CEN/TS 19101:2022 (E)
π 2 ⋅ηc ⋅ E x,c,k
fE,cr,k =
where
 k ⋅L 
 i 


L
is the unbraced profile length;
k
E x,c,k
ηc
i
(C.30)
2
is the effective length parameter to take into account the restraining effects of end
supports to flexural buckling of the profile about the relevant axis of bending ( k ⋅ L is the
buckling length);
is the characteristic value of the in-plane compressive modulus in the longitudinal (x)
direction;
is defined in 4.4.7 (to be selected for E x,c,k );
is the radius of gyration about the relevant axis.
(11) The effective length parameter, k , may be different for flexural buckling about the major-axis and
minor-axis, depending on the restraints to elastic rotation provided by the end supports, and may be
taken as:
—
k = 1,0 , if both ends of the profile are simply supported;
—
k = 0,5 , if both ends of the profile are fully clamped.
—
k = 0,7 , if one end of the profile is simply supported and the other end is fully clamped;
(12) The reduction factor that accounts for the influence of shear deformation, χ E,shear , should be determined
from Formula (C.31):
χ E,shear
where
Gxy,k
ηc
Av

fE,cr,k
A
=
⋅ 
 1 +

 ηc ⋅ Gxy,k Av 
−1
(C.31)
is the characteristic value of the in-plane shear modulus;
is defined in 4.4.7 (to be selected for Gxy,k );
is the shear area of the cross-section, which is given in Table 8.1 for common thin-walled
cross-section shapes and shear force directions.
C.5.3 Profiles with angle, cruciform and tee cross-sections subjected to compression
(1) For thin-walled open section profiles subjected to compression, in particular with all walls sharing a
common junction (the shear centre, Figure C.5), the following buckling modes should be considered:
—
—
200
twisting about the shear centre for double-symmetric cruciform cross-sections (C.5.3(2));
combined twisting and bending about the axis of symmetry for single-symmetric angle, cruciform
and tee cross-sections (C.5.3(6)).
CEN/TS 19101:2022 (E)
a) double-symmetric cruciform crosssections
(b) single-symmetric angle, tee and cruciform crosssections
Figure C.5 — Symbols for geometrical dimensions (S – shear centre, and C – centroid)
(2) For profiles with double-symmetric cruciform cross-sections, the design value of the compressive
resistance to torsional buckling of the profile, NT,Rd , should be determined from Formula (C.32):
N=
T,Rd
where
1
⋅ A ⋅ f T,cr,k
γ m ⋅ γ Rd
γm
γ Rd
A
f T,cr,k
(C.32)
is defined in 4.4.5 (to be selected for Gxy,k , the characteristic value of the in-plane shear
modulus);
is defined in 4.4.6 (Table 4.3, Global buckling – flexural-torsional);
is the gross area of the cross-section;
is the characteristic value of the critical torsional buckling stress, considering the
appropriate values of the conversion factor, ηc , for the relevant material properties
(defined in 4.4.7).
(3) The value of f T,cr,k should be determined from Formula (C.33):
f T,cr,k =
where
L
kw
E x,c,k
Gxy,k
ηc
2

1  π ⋅ηc ⋅ E x,c,k ⋅ I w

⋅
+ ηc ⋅ Gxy,k ⋅ I t 
2
2
A ⋅ i0  ( kw ⋅ L )


(C.33)
is the unbraced profile length;
is the warping end restraint parameter for torsional buckling of the cross-section, which
refers to the effective length for warping of the profile ( kw ⋅ L ), assuming that both ends
cannot twist;
is the characteristic value of the in-plane compressive modulus in the longitudinal (x)
direction;
is the characteristic value of the in-plane shear modulus;
is defined in 4.4.7 (to be selected for E x,c,k or Gxy,k );
201
CEN/TS 19101:2022 (E)
i0
is the polar radius of gyration about the centre of twisting of the cross-section (the shear
centre);
It
is the torsional constant of the cross-section;
Iw
is the warping constant of the cross-section.
(4) The constants I t and I w should be determined, respectively, from Formulae (C.34) and (C.35):
1
I t =⋅
3
∑ b ⋅t
i
1
Iw = ⋅
36
where
i
3
i
∑ b ⋅t
3
i
i
bi and t i
3
i
(C.34)
(C.35)
are the width and thickness of the section wall i , respectively.
(5) The warping end restraint parameter, kw , may be taken as:
—
kw = 1,0 , if both ends of the profile are free to warp;
—
kw = 0,5 , if both ends of the profile have warping prevented.
—
kw = 0,7 , if one end of the profile is free to warp and the other has warping prevented;
Conservatively, it may always be assumed that kw = 1,0 .
(6) For profiles with single-symmetric angle, cruciform or tee cross-sections, the design value of the
compressive resistance to flexural-torsional buckling of the profile, NFT,R d , should be determined from
Formula (C.36):
N=
FT,Rd
where
1
⋅ A ⋅ fFT,cr,k
γ m ⋅ γ Rd
γm
γ Rd
A
fFT,cr,k
is defined in 4.4.5 (to be selected for Gxy,k , the characteristic value of the in-plane shear
modulus);
is defined in 4.4.6 (Table 4.3, Global buckling - flexural-torsional);
is the gross area of the cross-section;
is the characteristic value of the critical flexural-torsional buckling stress, considering
the appropriate values of the conversion factor, ηc , for the relevant material properties
(defined in 4.4.7).
(7) The value of fFT,cr,k should be determined from Formula (C.37):
202
(C.36)
CEN/TS 19101:2022 (E)
fFT,cr,k
=
where
fE,cr,k ⋅ χ E,shear + f T,cr,k 
4 ⋅ H ⋅ fE,cr,k ⋅ χ E,shear ⋅ f T,cr,k
⋅ 1 − 1 −
2

2⋅ H
( fE,cr,k ⋅ χE,shear + fT,cr,k )

fE,cr,k
χ E,shear
f T,cr,k
and where




is estimated in C.5.2(10) and should be detemined with respect to the axis of symmetry
of the cross-section (Figure C.5);
is estimated in C.5.2(12);
is estimated in C.5.3(3).
H= 1 − d02 i02
where
i0
d0
(C.37)
(C.38)
is the polar radius of gyration about the shear centre;
is the distance from the centroid to the shear centre of cross-section (Figure C.5).
(8) Profiles with angle cross-sections, where the connection to another profile is through one of the legs,
subjected to a combination of axial compression and bending, shall comply with 8.3.7.2.
NOTE
For such profiles, the compression force in the profile is eccentric with respect to the centroid axis.
NOTE
Such profiles buckle by combined twisting and bending about both principal axes of the cross-section.
(9) For profiles with angle cross-section without any symmetry (different leg properties), the critical load
may either be determined from analytical formulae available in the literature or from numerical
modelling verified by testing.
C.5.4 Profiles with double symmetric cross-sections subjected to major-axis bending
(1) For profiles with double symmetric cross-sections subjected to major-axis (y-axis, Figure 3.3)
bending, the design value of the bending moment resistance to local buckling of the profile, Mcr,Rd , should
be determined from Formula (C.39):
Mcr,Rd =
where
γm
γ Rd
Wy
1
⋅W ⋅ f
γ m ⋅ γ Rd y x,b,cr,k
(C.39)
is defined in 4.4.5 (to be selected for E x,c,k , the characteristic value of the in-plane
compressive modulus in the longitudinal (x) direction, except for the conditions defined
in C.5.4(4) and C.5.5.2(3), for which Gxy,k , the characteristic value of the in-plane shear
modulus, should be considered instead);
is defined in 4.4.6 (Table 4.3, Local buckling);
is the major-axis elastic modulus of the cross-section;
203
CEN/TS 19101:2022 (E)
f x,b,cr,k
is the characteristic value of the critical stress associated to local buckling of the profile
in bending, considering the appropriate values of the conversion factor, ηc , for the
relevant material properties (defined in 4.4.7).
(2) The value of f x,b,cr,k should be determined from Formula (C.40):
{
f x,b,cr,k = min ( f x,b,cr,k )f ; ( f x,b,cr,k )w
where
(f
(f
NOTE
)
x,b,cr,k f
)
x,b,cr,k w
}
(C.40)
is the characteristic value of the critical stress of the compressed flange (of a profile
in bending) for a uniform stress distribution over the flange width, considering the
appropriate values of the conversion factor, ηc , for the relevant material properties
(defined in 4.4.7);
is the characteristic value of the critical stress of the web (of a profile in bending) for
a linear stress distribution along the web height, considering the appropriate values
of the conversion factor, ηc , for the relevant material properties (defined in 4.4.7).
Subscripts f and w refer to the flange and the web, respectively.
(3) The values of ( f x,b,cr,k )f and ( f x,b,cr,k )w may be obtained from C.5.4(4) to (7). As an alternative, they may
be obtained from C.5.5 (accounting for the elastic rotational restraint along the junctions between the
walls) or from numerical modelling verified by testing.
(4) For profiles with I cross-sections, the value of ( f x,b,cr,k )f , neglecting the elastic rotational restraint from
the web to twisting in the compressed flange, should be determined from Formula (C.41):
12 ( D 66 )f
f
f
(=
) (=
)
x,b,cr,k f
where
NOTE
SS
x,b,cr,k f
D66
bf and t f
b 
tf ⋅  f 
2
2
is the flexural stiffness defined in C.3(1);
are defined in Figure C.4a.
Subscript f refers to the flanges and superscript SS stands for simply supported.
(5) For profiles with I cross-sections, the value of
(f
)
x,b,cr,k w
, neglecting the elastic rotational restraint
from the flanges to transverse bending of the web, should be determined from Formula (C.42):
(f
where
) =( f
x,b,cr,k w
)
SS
x,b,cr,k w
=
{
}
π2
⋅ 13,4 ( D11 )w ⋅ ( D22 )w + 10,4 ( D12 )w + 2 ( D66 )w 
t w ⋅ bw2
D11 , D12 , D22 and D66
bw and t w
204
(C.41)
are the flexural stiffnesses defined in C.3(1);
are defined in Figure C.4a.
(C.42)
CEN/TS 19101:2022 (E)
NOTE
Subscript w refers to the web and superscript SS stands for simply supported.
(6) For profiles with single-cell tubular sections (rectangular or square), the value of ( f x,b,cr,k )f , neglecting
the elastic rotational restraint from the webs to transverse bending of the flanges, should be determined
from Formula (C.43):
(f
where
) =( f
x,b,cr,k f
)
SS
x,b,cr,k f
{
}
π2
=
⋅ 2 ( D11 )f ⋅ ( D22 )f + 2 ( D12 )f + 2 ( D66 )f 
t f ⋅ bf2
D11 , D12 , D22 and D66
bf and t f
(C.43)
are the flexural stiffnesses defined in C.3(1);
are defined in Figure C.4b.
(7) For profiles with single-cell tubular sections (rectangular or square), the value of ( f x,b,cr,k )w , neglecting
the elastic rotational restraint from the flanges to transverse bending of the webs, should be determined
from Formula (C.44):
( fx,b,cr,k )w =( fx,b,cr,k )w =
SS
where
D11 , D12 , D22 and D66
bw and t w
{
}
π2
⋅ 13,4 ( D11 )w ⋅ ( D22 )w + 10,4 ( D12 )w + 2 ( D66 )w 
t w ⋅ bw2
(C.44)
are the flexural stiffnesses defined in C.3(1);
are defined in Figure C.4b.
(8) The reduction factor to take into account the interaction between local and lateral-torsional buckling
of the profile for double symmetric cross-sections, χ LT , should be determined from Formula (C.45):
=
χ LT
where
cLT
(
ΦLT
and
ΦLT =
λLT
λLT =
where
)
1
2
, and χ LT ≤ 1,0
ΦLT − Φ2LT − cLT ⋅ λLT
2
cLT ⋅ λLT
(C.45)
is an empirical constant (equal to 0,70);
is an auxiliary coefficient, given by Formula (C.46),
1 + λL2T
2
(C.46)
is the profile slenderness for interaction between local and lateral-torsional buckling, given
by Formula (C.47),
Mcr,Rd
MLT,Rd
(C.47)
205
CEN/TS 19101:2022 (E)
MLT,Rd
is design value of the bending moment resistance to lateral-torsional buckling of the
profile.
NOTE
The empirical constant cLT was derived for members manufactured by pultrusion.
NOTE
EN 13706-2:2002, Table B.1, gives geometrical tolerances for profiles produced by pultrusion.
(9) The empirical constant cLT given in C.5.4(8) may be applied to members manufactured by processes
other than pultrusion, provided they guarantee equivalent or more stringent geometrical tolerances.
(10) If sufficient restraint from lateral buckling is provided to the profile to prevent lateral-torsional
buckling, then the reduction factor χ LT may be taken equal to 1,0.
(11) The design value of the bending moment resistance to lateral-torsional buckling of the profile, MLT,Rd
, should be determined from Formula (C.48):
=
MLT,Rd
where
γm
1
⋅W ⋅ f
γ m ⋅ γ Rd y LT,cr,k
(C.48)
is defined in 4.4.5 (to be selected for E x,c,k , the characteristic value of the in-plane
compressive modulus in the longitudinal (x) direction);
γ Rd
is defined in 4.4.6 (Table 4.3, Global buckling – lateral-torsional);
fLT,cr,k
is the characteristic value of the critical lateral-torsional buckling stress, considering the
appropriate values of the conversion factor, ηc , for the relevant material properties
(defined in 4.4.7).
Wy
is the major-axis elastic modulus of the cross-section;
(12) For profiles with I cross-sections, the value of fLT,cr,k should be determined from Formula (C.49):
fLT,cr,k
where
2
π 2 ⋅ηc ⋅ E x,c,k ⋅ Iz   kz   I w
C1 ⋅
=
⋅   ⋅
2
Wy ⋅ ( kz ⋅ L )   kw   Iz

L
kz
kw
E x,c,k
Gxy,k
ηc
Iz
206
2

2
 ( kz ⋅ L ) ⋅ηc ⋅ Gxy,k ⋅ I t

C
z
C
z
⋅
⋅
+
+
−
( 2 g) 2 g

π 2 ⋅ηc ⋅ E x,c,k ⋅ Iz


(C.49)
is the unbraced profile length;
is the effective length parameter allowing for the effect of minor-axis (z-axis, Figure 3.3)
rotation at supports ( kz ⋅ L is the buckling length);
is the warping end restraint parameter for torsional buckling (C.5.3(5));
is the characteristic value of the in-plane compressive modulus in the longitudinal (x)
direction;
is the characteristic value of the in-plane shear modulus;
is defined in 4.4.7 (to be selected for E x,c,k or Gxy,k );
is the minor-axis second moment of area of the cross-section;
CEN/TS 19101:2022 (E)
It
is the torsional constant of the cross-section (C.5.3(4));
zg
is the distance between the point of load application and the shear centre (Figure C.6);
Iw
C1
C2
is the warping constant of the cross-section, which, for I cross-sections, may be taken as
b2
I w= Iz ⋅ w ;
4
is the equivalent uniform moment coefficient that depends on the shape of the bending
moment diagram (Table C.1);
is the coefficient associated with load level and is dependent on the shape of the bending
moment diagram and out-of-plane restraint conditions (Table C.1).
(13) As an alternative to C.5.4(12), the value of fLT,cr,k may be determined by numerical modelling.
(14) For profiles with other cross sections (including without double symmetry), the value of MLT,Rd may
be determined by numerical modelling.
(15) For all types of support conditions, the effective length parameter, kz , may be taken conservatively
equal to 1,0.
(16) The effective length parameter, kz , may assume the following values:
—
—
—
kz = 1,0 , if the ends at both profile supports are free to rotate about the minor-axis;
kz = 0,7 , if one end cannot rotate about the minor-axis and the other end is free to rotate about the
minor-axis;
kz = 0,5 , if the ends at both profile supports cannot rotate about the minor-axis.
(17) The distance between the point of load application and the shear centre, zg (Figure C.6), should be
defined as:
—
—
—
zg > 0 , when the load is applied on the compressed part of the profile ( zg = + h / 2 , for top flange
loading);
zg = 0 , when the load is applied at the shear centre;
zg < 0 , when the load is applied on the tensioned part of the profile ( zg = −h / 2 , for bottom flange
loading).
207
CEN/TS 19101:2022 (E)
Key
1
a) top flange loading (positive values of zg )
b) bottom flange loading (negative values of zg )
Shear centre
Figure C.6 — Distance between the point of load application and the shear centre
(18) For different load and end support conditions, the values of the equivalent uniform moment
coefficient, C1 , should be taken from Table C.1.
NOTE The value of C1 depends on the out-of-plane support conditions (which also set the value of kz ) and either
on the ratio ψ = Mmin Mmax (for profiles loaded by moments at end supports) or the shape of the bending moment
diagram.
208
CEN/TS 19101:2022 (E)
Table C.1 — Values of C1 and C 2 coefficients for profiles with different loading and end support
conditions
Loading and end support conditions
Bending moment diagram
kz
C1
C2
1,0
0,5
1,00
1,00
0
0
1,0
0,5
1,31
1,37
0
0
1,0
0,5
1,0
0,5
1,0
0,5
1,0
0,5
1,0
0,5
1,14
1,19
1,52
1,60
1,77
1,86
2,06
2,15
2,35
2,42
0
0
0
0
0
0
0
0
0
0
1,0
0,5
2,60
2,45
0
0
1,0
0,5
2,60
2,45
0
0
1,0
0,5
1,12
0,97
0,45
0,36
1,0
0,5
1,35
1,05
0,59
0,48
1,0
0,5
1,04
0,95
0,42
0,31
209
CEN/TS 19101:2022 (E)
(19) For specific loading and end support conditions, values of the coefficient associated with the load
level, C2 , should be taken from Table C.1. For profiles loaded only by moments at the end supports, C2 = 0 .
(20) For other loading and end support conditions not covered in Table C.1, MLT,Rd may be estimated from
numerical methods, namely by using a linear elastic buckling analysis without imperfections.
C.5.5 Local buckling of double symmetric profiles considering the rotational restraint at
web-flange junctions
C.5.5.1 General
(1) Subclause C.5.5 provides formulae to determine the local buckling stresses for profiles with double
symmetric cross-sections (I-sections and single-cell tubular sections - rectangular or square) subjected
to either uniform compression or major-axis bending. These formulae include the effect of the elastic
rotational restraint along the junctions between web and flange walls.
C.5.5.2 Profiles subjected to compression
(1) For profiles subjected to uniform compression, the web or flange in the cross-section (I and singlecell tubular shapes) that first triggers local buckling may be identified by determining coefficient R , using
Formula (C.50):
( f ) ⋅(E )
R=
( f ) ⋅(E )
x,cr,k
x,cr,k
where
(f )
SS
x,cr,k f
(f )
x,cr,k
E x,c,k
SS
w
SS
f
SS
w
x,c,k
x,c,k
w
(C.50)
f
is the characteristic value of the critical stress of the compressed flange for a uniform
stress distribution over the flange width, corresponding to a simply supported (SS)
boundary condition along the web-flange junction;
is the characteristic value of the critical stress of the compressed web for a uniform
stress distribution over the web width, corresponding to a simply supported (SS)
boundary condition along the web-flange junction;
is the characteristic value of the in-plane compressive modulus in the longitudinal (x)
direction.
NOTE Subscripts f and w refer to the flanges and the webs, respectively, and the superscript SS stands for simply
supported.
(2) For profiles with I cross-sections subjected to uniform compression, the values of
(f )
x,cr,k
SS
w
(f )
SS
x,cr,k f
and
to calculate R by Formula (C.50) should be estimated by Formulae (C.22) and (C.23),
respectively.
(3) For profiles with I cross-sections subjected to compression, when R ≤ 1 , the flanges buckle first and
the value of ( f x,cr,k )f should be determined from Formulae (C.51) and (C.52):
=
( fx,cr,k )f
210
( D11 )f ⋅ ( D22 )f
b 
tf ⋅  f 
2
2

7 (1 − K )
⋅ K ⋅ 15,1 ⋅η ⋅ 1 − ρ + 6 (1 − ρ ) ⋅ (1 − η )  +
1 + 4,12 ⋅ ζ


 , if K ≤ 1

(C.51)
CEN/TS 19101:2022 (E)
=
( fx,cr,k )f
where
K=
ρ=
=
ζ
η=
( D11 )f ⋅ ( D22 )f
b 
tf ⋅  f 
2
2
⋅ 15,1 ⋅η ⋅ 1 − ρ + 6 (1 − ρ ) ⋅ ( K − η )  , if K > 1
(C.52)
2 ( D66 )f + ( D12 )f
(C.53)
( D11 )f ⋅ ( D22 )f
( D12 )f
2 ( D66 )f + ( D12 )f
2 ( D22 )f ⋅ bw
⋅
1 − R ( D22 )w ⋅ bf
(
(C.54)
1 + (7,22 − 3,55 ⋅ ρ ) ⋅ ζ
and where
D11 , D12 , D22 and D66
bf , t f , bw and t w
)
(C.55)
−1
(C.56)
are the flexural stiffnesses defined in C.3(1);
are defined in Figure C.4a.
(4) For profiles with I cross-sections subjected to compression, when R > 1 , the web buckles first and the
value of ( f x,cr,k )w should be determined from Formula (C.57):
(f =
)
x,cr,k w
where
{
}
π2
⋅ 2 (1 + 4,14 ⋅ ξ ) ⋅ ( D11 )w ⋅ ( D22 )w + ( 2,0 + 0,62 ⋅ ξ 2 ) ⋅ ( D12 )w + 2 ( D66 )w 
bw2 ⋅ t w


( D22 )w ⋅ bw
R
1 + 0,61 
ξ=
⋅


 4 ( R − 1) ( D66 )f ⋅ bf

and where
D11 , D12 , D22 and D66
bf , t f , bw and t w
1,2







(C.57)
−1
(C.58)
are the flexural stiffnesses defined in C.3(1);
are defined in Figure C.4a.
(5) For profiles with single-cell tubular sections (rectangular or square) subjected to uniform
compression, the values of ( f x,cr,k )f and ( f x,cr,k )w to calculate R by Formula (C.50) should be estimated by
SS
SS
Formulae (C.24) and (C.25), respectively.
(6) For profiles with single-cell tubular sections (rectangular or square) subjected to compression, when
R ≤ 1 , the flanges buckle first and the value of ( f x,cr,k )f should be determined from Formula (C.59):
211
CEN/TS 19101:2022 (E)
( f )=
x,cr,k f
where
{
}
π2
⋅ 2 (1 + 4,14 ⋅ ξ ) ⋅ ( D11 )f ⋅ ( D22 )f + ( 2,0 + 0,62 ⋅ ξ 2 ) ⋅ ( D12 )f + 2 ( D66 )f 
bf2 ⋅ t f

5 ( D22 )f ⋅ bw
⋅
ξ=
 1 +
 1 − R ( D22 )w ⋅ bf



(C.59)
−1
and where
D11 , D12 , D22 and D66
(C.60)
are the flexural stiffnesses defined in C.3(1);
bf , t f , bw and t w
are defined in Figure C.4b.
(7) For profiles with single-cell tubular sections (rectangular or square) subjected to uniform
compression, when R > 1 , the webs buckle first and the value of ( f x,cr,k )w should be determined from
Formula (C.61):
{
}
π2
⋅ 2 (1 + 4,14 ⋅ ξ ) ⋅ ( D11 )w ⋅ ( D22 )w + ( 2,0 + 0,62 ⋅ ξ 2 ) ⋅ ( D12 )w + 2 ( D66 )w 
2
bw ⋅ t w
(f =
)
x,cr,k w
where

5 ⋅ R ( D22 )w ⋅ bf
⋅
ξ=
 1 +
R − 1 ( D22 )f ⋅ bw

and where
D11 , D12 , D22 and D66
bf , t f , bw and t w



−1
(C.61)
(C.62)
are the flexural stiffnesses defined in C.3(1);
are defined in Figure C.4b.
C.5.5.3 Profiles subjected to major-axis bending
(1) For profiles subjected to major-axis bending, the web or flange in the cross-section (I and single-cell
tubular shapes) that first triggers local buckling may be identified by determining coefficient R , using
Formula (C.63):
(f
R=
(f
) ⋅(E )
) ⋅(E )
SS
x,b,cr,k f
SS
where
(f
(f
212
x,b,cr,k
x,b,cr,k
x,b,cr,k
)
SS
)
f
SS
w
w
x,c,k
w
x,c,k f
(C.63)
is the characteristic value of the critical stress of the compressed flange (of a profile
in bending) for a uniform stress distribution over the flange width, corresponding to
a simply supported (SS) boundary condition along the web-flange junction;
is the characteristic value of the critical stress of the web (of a profile in bending) for
a linear stress distribution along the web height, corresponding to a simply supported
(SS) boundary condition along the web-flange junction;
CEN/TS 19101:2022 (E)
E x,c,k
is the characteristic value of the in-plane compressive modulus in the longitudinal (x)
direction.
NOTE Subscripts f and w refer to the flanges and the webs, respectively, and the superscript SS stands for simply
supported.
(2) For profiles with I cross-sections subjected to major-axis bending, the values of
(f
x,b,cr,k
)
SS
w
(f
x,b,cr,k
)
SS
f
and
to calculate R by Formula (C.63) should be estimated by Formulae (C.41) and (C.42),
respectively.
(3) For profiles with I cross-sections subjected to major-axis bending, when R ≤ 1 , the flange buckles first
and the value of ( f x,b,cr,k )f should be determined from Formulae (C.64) and (C.65):
=
( fx,b,cr,k )f
=
( fx,b,cr,k )f
where
K=
ρ=
=
ζ
η=
( D11 )f ⋅ ( D22 )f
b 
tf ⋅  f 
2
2
( D11 )f ⋅ ( D22 )f
b 
tf ⋅  f 
2
2

7 (1 − K )
⋅ K ⋅ 15,1 ⋅η ⋅ 1 − ρ + 6 (1 − ρ ) ⋅ (1 − η )  +


1 + 4,12 ⋅ ζ

⋅ 15,1 ⋅η ⋅ 1 − ρ + 6 (1 − ρ ) ⋅ ( K − η )  , if K > 1
2 ( D66 )f + ( D12 )f
(C.64)
(C.65)
(C.66)
( D11 )f ⋅ ( D22 )f
( D12 )f
2 ( D66 )f + ( D12 )f
(C.67)
4 ( D22 )f ⋅ bw
⋅
1 − R ( D22 )w ⋅ bf
(

 , if K ≤ 1

1 + (7,22 − 3,55 ⋅ ρ ) ⋅ ζ
and where
D11 , D12 , D22 and D66
bf , t f , bw and t w
)
(C.68)
−1
(C.69)
are the flexural stiffnesses defined in C.3(1);
are defined in Figure C.4a.
(4) For profiles with I cross-sections subjected to major-axis bending, when R > 1 , the web buckles first
and the value of ( f x,b,cr,k )w may be conservatively estimated using Formula (C.42).
(5) For profiles with single-cell tubular sections (rectangular or square) subjected to major-axis bending,
the values of
(f
x,b,cr,k
)
SS
f
and
(f
x,b,cr,k
)
SS
w
to calculate R by Formula (C.63) should be estimated using
Formulae (C.43) and (C.44), respectively.
213
CEN/TS 19101:2022 (E)
(6) For profiles with single-cell tubular sections (rectangular or square) subjected to major-axis bending,
when R ≤ 1 , the flange buckles first and the value of ( f x,b,cr,k )f should be determined from Formula (C.70):
( fx,b,cr,k )=f
where
{
}
π2
⋅ 2 (1 + 4,14 ⋅ ξ ) ⋅ ( D11 )f ⋅ ( D22 )f + ( 2,0 + 0,62 ⋅ ξ 2 ) ⋅ ( D12 )f + 2 ( D66 )f 
bf2 ⋅ t f

2,5 ( D22 )f ⋅ bw
⋅
ξ=
 1 +
−
1
R
( D22 )w ⋅ bf

and where
D11 , D12 , D22 and D66
bf , t f , bw and t w



−1
(C.70)
(C.71)
are the flexural stiffnesses defined in C.3(1);
are defined in Figure C.4b.
(7) For profiles with single-cell tubular sections (rectangular or square) subjected to major-axis bending,
when R > 1 , the webs buckle first and the value of ( f x,b,cr,k )w may be conservatively estimated by Formula
(C.44), considering the edges simply supported.
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Annex D
(normative)
Structural fire design
D.1 Use of this annex
(1) This Normative Annex contains provisions for structural fire design.
D.2 Scope and field of application
(1) This Normative Annex applies to composite structures, or parts of composite structures, that are
within the scope of this document (1.1) and are designed accordingly to fulfil a loadbearing function,
separating function or both.
(2) This Annex gives principles and applications rules for the design of composite structures for specified
requirements in respect of the aforementioned functions and levels of performance.
(3) This Annex applies to the design of composite structures for the accidental situation of fire exposure.
It only identifies differences from, or supplements to, normal temperature design.
D.3 Assumptions
(1) In addition to the general assumptions of this document (1.2), the following assumptions given in
EN 1991-1-2 apply:
—
—
the choice of the relevant fire scenario is made by appropriate qualified and experienced personnel,
or is given by the relevant national regulation;
any fire protection measure taken into account in the design will be adequately maintained.
D.4 Basis of design
D.4.1 General
(1) Where mechanical resistance in the case of fire is required, composite structures shall be designed
and constructed in such a way that they maintain their loadbearing function during the relevant fire
exposure.
(2) Where compartmentation is required, the elements forming the boundaries of the fire compartment,
including joints, shall be designed and constructed in such a way that they maintain their separating
function during the relevant fire exposure to ensure that:
—
—
integrity failure does not occur;
insulation failure does not occur.
NOTE 1 See EN 1991-1-2 for definitions.
NOTE 2 There is no risk of fire spread due to thermal radiation when an unexposed surface temperature is below
the ignition temperature. The ignition temperature is the same order of magnitude as is the decomposition
temperature.
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(3) Deformation criteria shall be applied where the means of fire protection require consideration of the
deformation of the loadbearing structure.
(4) Consideration of the deformation of the loadbearing structure may be omitted, when the efficiency of
the means of protection has been evaluated according to D.5.4.
(5) Deformation criteria shall be applied where the design criteria for separating elements require
consideration of the deformation of the loadbearing structure.
(6) Consideration of the deformation of the loadbearing structure may be neglected when the separating
elements fulfil requirements of a nominal fire exposure.
D.4.2 Nominal fire exposure
(1) For standard fire exposure, elements shall comply with the following functions defined in
EN 1991-1-2 during the required time of fire exposure:
—
loadbearing function: loadbearing capacity (R);
—
separating and loadbearing functions: R, E and, when requested, I.
—
separating function: integrity (E) and, when requested, insulation (I);
(2) The loadbearing function is assumed to be satisfied when loadbearing capacity is maintained.
(3) The separating function is assumed to be satisfied when integrity and, when requested, insulation are
maintained.
(4) Integrity is assumed to be maintained when a separating element of building construction, exposed
to fire on one side, prevents the passage through it of flames and hot gases and the occurrence of flames
on the unexposed side.
(5) Insulation is assumed to be maintained when the average temperature rise over the whole of the
unexposed surface is limited to 140 K, and the maximum temperature rise at any point of that surface
does not exceed 180 K.
(6) With the external fire exposure curve the same functions (R, E, I) apply, however the reference to this
specific curve shall be identified by the letters “ef”.
(7) With the hydrocarbon fire exposure curve the same functions (R, E, I) apply, however the reference
to this specific curve shall be identified by the letters “HC”.
(8) Where a vertical separating element with or without loadbearing function has to comply with impact
resistance requirement (function M), the element shall resist a horizontal concentrated load as specified
in EN 1363-2.
D.4.3 Physically based fire exposure
(1) The loadbearing function shall be maintained during the complete duration of the fire, including the
cooling phase or during a required period of time according to EN 1991-1-2:—, 4.4(4).
(2) For the verification of the separating function the following applies, assuming that the normal
temperature is 20 °C:
—
216
The average temperature rise of the unexposed side of the construction should be limited to 140 K
and the maximum temperature rise of the unexposed side should not exceed 180 K during the
heating phase until the maximum temperature in the fire compartment is reached;
CEN/TS 19101:2022 (E)
—
The average temperature rise of the unexposed side of the construction should be limited to 200 K
and the maximum temperature rise of the unexposed side should not exceed 240 K during the decay
phase.
D.4.4 Actions
(1) Thermal and mechanical actions shall be taken from EN 1991-1-2.
(2) The potential contribution of combustible composite material (polymer matrix, sandwich core
material) to the fire development should be considered when such contribution is relevant.
NOTE The contribution of combustible composite material can be relevant in unprotected all-composite
structures or in structures where the composite material experiences significant pyrolysis at any point during the
steady burning phase of a fire.
(3) Different methods available in the literature may be used to consider the increase of the fire load due
to combustible composite material.
NOTE For physically-based fire exposure, such methods (developed for timber structures) are based on the
design value of the fire load density and involve determining different thermo-physical parameters of the composite
materials (heat of combustion, density, decomposition rate).
(4) The heat of combustion may be measured based on the test procedures described in standards EN
ISO 1716, ISO 5660-1 and ASTM E1354.
(5) The change of density (or mass) of composite materials as a function of temperature may be measured
from thermogravimetric analysis, as described in standards EN ISO 11358-1 and ASTM E1131.
(6) The decomposition rate (speed of progress of isotherm corresponding to decomposition
temperature) may be determined from thermal analysis (D.8.2) or experiments.
D.4.5 Design values of materials properties
(1) Design values of mechanical (strength and stiffness) properties for the fire situation, X d,fi , should be
calculated from Formula (D.1):
X d,fi =
where
Xk
kθ
γ M,fi
kθ ⋅ X k
γ M,fi
(D.1)
is the characteristic value of a strength or stiffness property (generally f k or E k ) for
normal temperature design according to 4.3.2(1);
is the temperature-dependent reduction factor ( X k,θ / X k ) for a strength or stiffness
property, where X k,θ is the characteristic value of that property at temperature θ (D.5.3);
is the partial factor for the relevant mechanical material property for the fire situation.
NOTE
The value of γ M,fi is 1,0 unless the National Annex gives a different value.
NOTE
The characteristic values of thermal properties correspond to mean values.
(2) Design values of thermal properties for the fire situation should be taken equal to the characteristic
values.
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D.4.6 Verification methods
(1) The model of the structural system adopted for design shall reflect the performance of the structure
in the fire situation.
(2) Mechanical resistance shall be verified for the required duration of fire exposure t according to
Formula (D.2):
E d,fi ≤ Rd,t,fi
where
E d,fi
Rd,t,fi
(D.2)
is the design effect of actions for the fire situation, determined in accordance with
EN 1991-1-2, including effects of thermal expansions and deformations;
is the corresponding design resistance in the fire situation.
(3) The structural analysis for the fire situation should be carried out according to EN 1990:—, 7.1.5.
NOTE For verifying resistance requirements based on the standard fire curve, unless otherwise specified, a
member analysis is sufficient.
(4) The following design methods may be used in order to satisfy D.4.6(2):
—
use of tabulated data for specific types of members (D.6);
—
use of advanced design methods for the analysis of members, parts of the structure or the entire
structure (D.8).
—
use of simplified design methods for specific types of members (D.7);
(5) As an alternative to design by calculation, fire design may be based on the results of fire tests, or on
fire tests in combination with calculations.
D.4.7 Member analysis
(1) The design effect of actions for the fire situation should be determined for time t = 0 using
combination factors according to EN 1991-1-2:—, 6.3.
(2) As a simplification to D.4.7(1), the design effect of actions for the fire situation, E d,fi , may be obtained
from a structural analysis for normal temperature design as:
E d,fi= ηfi ⋅ E d
where
Ed
ηfi
(D.3)
is the design effect of actions for normal temperature design for the fundamental
combination of actions (EN 1990);
is the reduction factor applied to Ed in order to obtain E d,fi , as defined in EN 1991-1-2.
(3) The value of ηfi = 0,65 should be used, except for imposed loads according to load category E, as given
in EN 1991-1-1 (areas susceptible to accumulation of goods, including access areas), where the value
should be ηfi = 0,7.
(4) The effect of thermal deformations resulting from thermal gradients across the cross-section shall be
considered.
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NOTE Depending on the stiffness of member supports, restrained axial or in-plane thermal expansions can
increase acting loads considerably.
(5) The effects of axial or in-plane thermal expansions may be neglected.
(6) For sandwich panels, the differential thermal expansion between the face sheets and the core should
be considered.
(7) The kinematic boundary conditions at supports and ends of members, applicable at time t = 0 , may
be assumed to remain unchanged throughout the fire exposure.
(8) If the supports are not protected from fire exposure, the potential changes in kinematic boundary
conditions should be considered.
NOTE Protecting the supports from fire exposure allows for a proper anchoring of the fibres of parts subjected to
tensile stresses.
(9) Tabulated design data, simplified or advanced design methods given in D.6, D.7 and D.8, respectively,
are suitable for verifying members under fire conditions.
D.4.8 Analysis of parts of the structures
(1) The effect of actions should be determined for time t = 0 using combination factors according to
EN 1991-1-2:—, 6.3.
(2) Within the part of the structure to be analysed, the relevant failure mode in fire, the temperaturedependent material properties and member stiffness, and the effects of thermal expansions and
deformations (indirect fire actions) shall be taken into account.
(3) The part of the structure to be analysed should be specified on the basis of the potential thermal
expansions and deformations such that their interaction with other parts of the structure can be
approximated by time-independent support and boundary conditions during fire exposure.
(4) As an alternative to D.4.8(1), the reactions at supports and internal forces and moments at boundaries
of part of the structure may be obtained from structural analysis for normal temperature design as given
in D.4.7.
NOTE If stiffness reduction due to elevated temperature does not occur uniformly in the different composite
components, redistribution of forces and moments can occur.
D.4.9 Global structural analysis
(1) A global structural analysis for the fire situation shall take into account:
—
the relevant failure mode in fire exposure;
—
effects of thermal expansions and deformations (indirect fire actions).
—
the temperature-dependent material properties and member stiffness;
D.4.10 Fire protection measures
(1) Fire protection measures may be adopted to satisfy fire performance requirements.
NOTE 1 The fire resistance and fire reaction performance of composite structures can be significantly improved by
using passive fire protection systems (e.g. coatings or boards with an appropriate thickness) or active protection
systems (e.g. water cooling). Fire protection measures can also include the use of sprinklers.
NOTE 2 The fire reaction performance can also be improved by using flame retardant additives and inherently
flame retardant resins (e.g. phenolics).
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NOTE 3 Depending on the required fire resistance (and fire reaction performance), specific fire protection systems
can be considered for the connections between composite members.
(2) Fire protection systems developed for other structural materials (e.g. steel) should not be applied to
composite structures without consideration of their distinctive characteristics.
NOTE
Qualification and proof testing specific to protection of composite structures is likely to be required.
D.5 Material properties
D.5.1 General
(1) Unless given as design values, the values of material properties given in D.5 shall be treated as
characteristic values.
(2) The variation with temperature of the thermal and mechanical properties of composite materials
should be considered.
NOTE 1 The thermal and mechanical properties of composite materials change significantly at elevated
temperature. The variation with temperature of the thermal and mechanical properties of composite materials
depends on (i) the type of polymeric matrix, (ii) the fibres (type, content and architecture), and (iii) the
manufacturing process (including the processing temperature).
NOTE 2 The changes in thermal and mechanical properties of composite materials are mainly due to the glass
transition and decomposition processes experienced by their polymeric matrixes. In addition, elevated temperature
also changes the properties of the fibres, with glass and basalt fibres softening and melting, carbon fibres oxidizing
and aramid fibres decomposing.
NOTE 3 At elevated temperature, polymeric core materials and adhesives also experience the glass transition and
decomposition processes, while balsa core undergoes two-stage softening (hemicellulose and lignin) and then
decomposition.
NOTE 4 The changes that take place in material properties at elevated temperature can also be caused by time
effects due to the kinetics of the chemical and physical processes involved (such as glass transition and
decomposition).
(3) The variation with temperature of the thermal and mechanical properties of composite materials shall
be determined by testing.
NOTE Indicative design values of thermal and mechanical properties for specific materials are given in D.5.2 and
D.5.3, respectively. The indicative values for thermal properties result from tests and mechanism-based
thermophysical property models (some include multi-linear approximations rather than actual empirical data).
These properties are given as examples and cannot be generalized.
(4) The indicative design values of thermal and mechanical properties for specific materials given in D.5.2
and D.5.3 may be used in preliminary design of composite structures, provided that the materials being
used are sufficiently similar to those corresponding to the indicative properties.
NOTE The indicative values of material properties provided in this Annex can be considered as mean values.
Characteristic values can be obtained by assuming appropriate values of coefficients of variation.
(5) Where fire design is based on a combination of tests and calculations, where possible, the material
properties should be calibrated to the test results.
D.5.2 Thermal properties
D.5.2.1 Emissivity coefficient
(1) The emissivity related to the composite surface should be taken as 0,8, except for composites with
carbon or basalt fibres for which the emissivity should be taken as 0,9.
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D.5.2.2 Thermal conductivity
(1) The thermal conductivity of composite materials at a constant temperature may be measured using
the hot plate method (e.g. ISO 8302 or ASTM C177). The effective thermal conductivity of composite
materials at different temperatures may be measured using the hot disk method (e.g. EN ISO 22007-2) in
conjunction with a transient thermal analysis.
NOTE When the temperature increases, the thermal conductivities of the fibres and the resin within a composite
material can change. More significantly, when decomposition occurs, fibres can be debonded from the resin and
voids can be formed due to the decomposed gases. This can hamper the heat transfer within a composite material
thus considerably reducing its effective thermal conductivity (shielding effects).
(2) Indicative values of the ratio between the effective thermal conductivity as a function of temperature
θ ( λθ ) and the corresponding value at 20 °C ( λ20°C ) given in Figure D.1 may be used for specific
composite materials.
Key
1
2
Glass-polyester composite (fibre mass fraction, Mf = 61%, pultrusion, λ20°C = 0,35 W/m.K)
Carbon-epoxy composite ( Mf = 72%, λ20°C = 1,36 W/m.K)
Figure D.1 — Indicative values of the ratio between effective thermal conductivity as a function of
temperature θ ( λθ ) and corresponding value at 20 °C ( λ20°C ) for specific composite materials
D.5.2.3 Specific heat
(1) The specific heat of composite materials at a constant temperature may be quantified through a
calorimetry method (EN ISO 22007-2). As an alternative, the change of specific heat as a function of
temperature may be directly evaluated through differential scanning calorimetry (EN ISO 11357-4 or
ASTM E1269). In general, the tests to quantify the specific heat of composite materials should be
conducted in an inert environment.
NOTE 1 When the temperature increases, the specific heat of the fibres and the resin within a composite material
can change, generally increasing. When resin decomposition (an endothermic reaction) occurs, additional heat is
required to break the bonds within molecular chains; the resulting measured value of specific heat is often called
effective specific heat because it expresses the total energy needed for all the physical and chemical changes
involved.
NOTE 2 An oxidative environment is more representative of the surface of a composite laminate, whereas an inert
environment is more representative of its inner layers (i.e. of the bulk material).
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(2) Indicative values of the ratio between the effective specific heat as a function of temperature θ
( cp,θ ) and the corresponding value at 20 °C ( cp,20°C ) given in Figure D.2 may be used for specific composite
materials.
Key
1
2
Glass-polyester composite ( Mf = 61%, pultrusion, cp,20°C = 1136 J/kg.K)
Carbon-epoxy composite ( Mf = 72%, cp,20°C = 1287 J/kg.K)
Figure D.2 — Indicative values of the ratio between effective specific heat as a function of
temperature θ ( cp,θ ) and corresponding value at 20 °C ( cp,20° C ) for specific composite materials
D.5.2.4 Density
(1) The change of density (or mass) of composite materials as a function of temperature may be measured
from thermogravimetric analysis (e.g. EN ISO 11358-1 or ASTM E1131).
NOTE The mass (or density) of composite materials generally remains stable prior to the decomposition of its
polymer matrix. When decomposition occurs, the polymer material reacts into gases and char and this causes a
reduction in mass. With aramid fibres, a further reduction occurs due to the decomposition of the fibres.
(2) Indicative values of the ratio between the density as a function of temperature θ ( ρθ ) and the
corresponding value at 20 °C ( ρ20°C ) given in Figures D.3 and D.4 may be used for specific composite and
core materials, respectively.
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CEN/TS 19101:2022 (E)
Key
1
2
Glass-polyester composite ( Mf = 61%, pultrusion, ρ20°C = 1870 kg/m3)
Carbon-epoxy composite ( Mf = 72%, ρ20°C = 1600 kg/m3)
Figure D.3 — Indicative values of the ratio between density as a function of temperature θ ( ρ θ )
and corresponding value at 20 °C ( ρ 20° C ) for specific composite materials (tested in an inert
environment)
Key
1
Polyurethane (PUR) foam ( ρ20°C = 40 kg/m3)
3
End-grain balsa ( ρ20°C = 150 kg/m3)
2
End-grain balsa ( ρ20°C = 94 kg/m3)
Figure D.4 — Indicative values of the ratio between density as a function of temperature θ ( ρ θ )
and corresponding value at 20 °C ( ρ 20° C ) for specific core materials (tested in an inert
environment)
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D.5.3 Mechanical properties
D.5.3.1 Strength and stiffness properties
(1) The stress-strain relationship of composite, core and adhesive materials at elevated temperature shall
be determined by testing. The standard test methods given in Clause 5 should be used.
NOTE In general, when the glass transition temperature of the polymeric resin is approached, the stiffness and
strength properties of composite materials are notably reduced, with such reduction being more significant in
matrix-dominated properties than in fibre-dominated properties (see Notes 1 and 2 to 4.4.7.2(1)). A similar
reduction in stiffness and strength properties occurs with polymeric core materials and adhesives.
(2) Indicative values of reduction factors kθ (ratio between property as a function of temperature θ and
corresponding property at 20 °C) of different mechanical properties given in Figures D.5 to D.9 may be
used for specific composite materials.
Key
1
Glass-polyester composite laminates (pultrusion, Mf = 70%, Tg = 100 °C from DMA onset of storage modulus decay)
3
UD carbon-epoxy composite strips (pultrusion, Vf = 62%)
2
4
UD carbon-epoxy composite strips (pultrusion, Vf = 68%)
UD basalt-epoxy composite strips (pultrusion, Vf = 69%, Tg = 167 °C from DMA peak of loss factor)
Figure D.5 — Indicative values of the reduction factor kθ for longitudinal tensile strength as a
function of temperature θ for specific composite materials
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CEN/TS 19101:2022 (E)
Key
1
UD glass-vinylester composite bars, pultrusion, Mf = 87%, Tg = 157 °C from DMA onset of storage modulus decay)
3
UD carbon-epoxy composite bars (pultrusion, Vf = 60%)
2
4
UD carbon-epoxy composite strips (pultrusion, Vf = 62%)
UD basalt-epoxy composite strips (pultrusion, Vf = 69%, Tg = 167 °C from DMA peak of loss factor)
Figure D.6 — Indicative values of the reduction factor kθ for longitudinal tensile modulus as a
function of temperature θ for specific composite materials
Key
1
Glass-polyester composite profiles (pultrusion, Mf = 69%, Tg = 104 °C from DMA onset of storage modulus decay)
Figure D.7 — Indicative values of the reduction factor kθ for longitudinal compressive strength
as a function of temperature θ for specific composite materials
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Key
1
2
Glass-polyester composite laminates (pultrusion, Mf = 70%, Tg = 104 °C from DMA onset of storage
modulus decay) - in-plane shear strength
Basalt-epoxy composite laminates (pultrusion, Vf = 69%, Tg = 167 °C from DMA peak of loss factor) interlaminar shear strength
Figure D.8 — Indicative values of the reduction factor kθ for shear strength as a function of
temperature θ for specific composite materials
Key
1
2
Glass-polyester composite laminates (pultrusion, Mf =70%, Tg = 104 °C from DMA onset of storage modulus decay)
Basalt-epoxy composite laminates (pultrusion, Vf = 56%, Tg = 92 °C from DMA, curve not specified)
Figure D.9 — Indicative values of the reduction factor kθ for in-plane shear modulus as a
function of temperature θ for specific composite materials
(3) Indicative values of reduction factors kθ (ratio between property as a function of temperature θ and
corresponding property at 20 °C) of different mechanical properties given in Figures D.10 to D.13 may be
used for specific core materials.
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Key
1
End-grain balsa (150 kg/m3) in longitudinal (fibre) direction
3
PET foam (100 kg/m3) in out-of-plane (z) direction
2
4
End-grain balsa (150 kg/m3) in radial direction
PVC foam (75 kg/m3) in out-of-plane (z) direction
Figure D.10 — Indicative values of the reduction factor kθ for compressive strength as a function
of temperature θ for specific core materials
Key
1
2
3
PET foam (100 kg/m3) in out-of-plane (z) direction
PVC foam (100 kg/m3) in out-of-plane (z) direction
PVC foam (100 kg/m3) in in-plane (x or y) direction
Figure D.11 — Indicative values of the reduction factor kθ for compressive modulus as a
function of temperature θ for specific core materials
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Key
1
PUR foam (40 kg/m3)
4
End-grain balsa (94 kg/m3) with shear plane longitudinal to fibres
2
3
PVC foam (100 kg/m3)
End-grain balsa (94 kg/m3) with shear plane transverse to fibres
Figure D.12 — Indicative values of the reduction factor kθ for out-of-plane shear strength as a
function of temperature θ for specific core materials
Key
1
PUR foam (40 kg/m3)
3
PET foam (94 kg/m3, Tg = 65 °C from DMA onset of storage modulus decay)
2
PUR foam (68 kg/m3, Tg = 90 °C from DMA onset of storage modulus decay)
4
PVC foam (100 kg/m3, Tg = 70 °C from DMA onset of storage modulus decay)
6
End-grain balsa (94 kg/m3) with shear plane longitudinal to fibres
5
End-grain balsa (94 kg/m3) with shear plane transverse to fibres
Figure D.13 — Indicative values of the reduction factor kθ for out-of-plane shear modulus as a
function of temperature θ for specific core materials
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(4) Indicative values of reduction factors kθ (ratio between property as a function of temperature θ and
corresponding property at 20 °C) for the tensile and shear strengths and moduli given in Figure D.14 may
be used for a specific adhesive.
Key
1
tensile strength
3
tensile modulus
2
4
shear strength
shear modulus
Figure D.14 — Indicative values of the reduction factor kθ for tensile and shear properties as a
function of temperature θ for an epoxy adhesive (two-component, ambient cured, Tg = 47 °C
from DMA onset of storage modulus decay)
D.5.3.2 Thermal expansion coefficient
(1) The thermal expansion coefficient of composite, core and adhesive materials at elevated temperature
may be determined according to ISO 11359-2 or ASTM E831.
NOTE In composite materials, the thermal expansion coefficient is directionally dependent and can be
substantially different from more common structural materials, such as concrete or steel.
D.5.4 Fire protection materials
(1) The properties and performance of fire protection materials used in design should be assessed using
the test procedures given in the relevant parts of EN 13381 as appropriate.
NOTE These standards include a requirement that the fire protection materials have to remain coherent and
cohesive to their supports throughout the relevant fire exposure.
D.6 Tabulated design data
D.6.1 General
(1) Tabulated design data may be used to obtain recognised design solutions generally in relation to
member typology (dimensions) without recourse to any form of equilibrium equation.
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NOTE
There is no tabulated design data in this document.
(2) Tabulated data can be derived from tests, calculation models or some combination of the two and may
be presented either in the form of a table or an equation.
(3) Tabulated design data should give conservative results compared to relevant tests or simplified or
advanced design methods. They should be used only within their range of application, without
extrapolation outside.
D.7 Simplified design methods
D.7.1 General
(1) Simplified design methods, which are based on global equilibrium equations, may be used.
NOTE 1 Solving the global equilibrium equation of a simplified design method results in the determination of a single
quantity: e.g. the temperature in a section or part of it, the loadbearing capacity of a heated cross section or a member.
NOTE 2 There are no simplified design methods in this document.
(2) Simplified design methods should give conservative results compared to relevant tests or advanced
design methods.
D.8 Advanced design methods
D.8.1 General
(1) Advanced design methods shall be based on fundamental physical behaviour, employing local
equilibrium equations, which are satisfied at every point in the structure.
NOTE Calculations are undertaken using numerical models based on finite element analyses or other appropriate
advanced procedures. Solving the equations of an advanced design method results in the determination of a
quantity in a large number of points or nodes: e.g. the temperatures in a section, the displacements along a member.
(2) Any potential failure mode not covered by the advanced design method shall be prevented by
appropriate means.
(3) Advanced design methods may include separate calculation models for the determination of:
—
—
the development and distribution of the temperature within structural members (thermal response
model);
the mechanical behaviour of the structure or of any part of it (mechanical response model).
(4) Advanced design methods may be used in association with any thermal action, provided the material
properties are known for the relevant temperature history.
(5) Advanced design methods may be used with any type of composite component and cross-section.
(6) Advanced calculation models may be used when information concerning stress and strain evolution,
deformations and / or temperature fields are required.
D.8.2 Thermal analysis
(1) Advanced design methods for thermal response shall be based on the acknowledged principles and
assumptions of the theory of heat transfer.
(2) The thermal response model shall consider:
—
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the relevant thermal actions specified in EN 1991-1-2;
CEN/TS 19101:2022 (E)
—
the temperature dependent thermal properties of the materials (D.5.2).
(3) The effects of non-uniform thermal exposure and of heat transfer to adjacent building components
may be included where appropriate.
(4) The influence of moisture content and of migration of the moisture within the materials may be
conservatively neglected.
D.8.3 Mechanical analysis
(1) Advanced design methods for mechanical analysis shall be based on the acknowledged principles and
assumptions of the theory of structural mechanics.
(2) The mechanical response model shall consider:
—
—
the material temperatures calculated according to D.8.2;
the temperature dependent mechanical properties of the materials (D.5.3).
(3) The effects of thermally induced strains and stresses due to temperature rise and temperature
differentials shall be considered.
(4) The mechanical response model should also take account of:
—
geometrical imperfections;
—
the non-linear material behaviour, including the effects of loading and unloading and viscoelasticity
on the structural stiffness.
—
geometrical non-linear effects;
(5) The compatibility between all parts of the structure shall be taken into account by the design method.
(6) The deformations given by the design method shall not cause failure due to the loss of adequate
support to one of the members.
D.8.4 Validation of advanced design methods
(1) A verification of the accuracy of the design methods should be made on basis of relevant test results.
(2) Calculation results may refer to temperatures, deformations and fire resistance times.
(3) The critical parameters should be checked to ensure that the model complies with sound engineering
principles, by means of a sensitivity analysis.
NOTE
Critical parameters refer, for example, to the buckling length, the size of the elements and the load level.
231
CEN/TS 19101:2022 (E)
Annex E
(informative)
Bridge details
E.1 Use of this annex
(1) This informative Annex provides supplementary guidance to Clause 11 for the design of bridges.
NOTE National choice on the application of this informative Annex is given in the National Annex. If the National
Annex contains no information on the application of this informative annex, it can be used.
E.2 Scope and field of application
(1) This informative Annex applies to the design of bridge details, giving generic examples of selected
details.
(2) Details considered concern (i) composite bridge decks of hybrid composite-steel or compositeconcrete bridges, and (ii) composite bridge slabs.
NOTE Bridge details that are normally proprietary, i.e. specific to certain products, such as bridge deck panel
joints, are not considered.
E.3 General
(1) Bridge details should be appropriately designed to assure overall structural safety, serviceability and
durability.
(2) Details should be conceived in a way that they can be appropriately inspected and maintained.
E.4 Bridge bearings
(1) In the case of composite slab bridges, the bearing regions can be reinforced by concrete infills in deck
cavities (e.g. pultruded slabs) or high density/strength core inserts (sandwich slabs), as shown in
Figure E.1.
NOTE
The details shown in Figure E.1 do not take uplift forces into account.
E.5 Expansion joints
(1) Expansion joints should allow for bridge movements without compromising serviceability and
durability requirements.
(2) In addition to assuring the continuity of the surfacing, expansion joints should prevent moisture
ingress into the superstructure.
NOTE
232
Examples of details for fixed supports and small or large bridge movements are shown in Figure E.2.
CEN/TS 19101:2022 (E)
Key
1
face panel/sheet
(a) fixed
2
cavity (pultruded deck)
4
elastomer layer
3
5
6
7
8
9
(b) movable
reinforcing concrete infill
dowel
core (sandwich deck)
reinforcing high density/strength insert
movable bearing
abutment
Key
Figure E.1 — Bridge bearings
(a) fixed supports or small movements
1
surfacing layer
3
standard concrete bridge expansion joint
2
4
5
6
7
(b) large movements
elastomer plug joint
composite deck
steel girder
shear studs
abutment
Figure E.2 — Expansion joints
233
CEN/TS 19101:2022 (E)
E.6 Parapets
(1) Parapets, in addition to serving for the connection of railings or crash barriers (see E.8), should assure
the drainage of water (coming from the surfacing area) and prevent water from running along the bottom
of the deck by integrating appropriate drip edges, as shown in Figure E.3.
Key
(a) constant deck thickness
1
surfacing bulge
3
water flow
2
(b) variable deck thickness
drip edges
Figure E.3 — Parapets
E.7 Adhesive deck-girder connections
(1) The exposed edges of adhesive deck-girder connections should be properly sealed to prevent
moisture ingress.
NOTE
An example of an adhesive deck-to-steel girder connection is shown in Figure E.4.
(2) A proper sealing of the adhesive connection during its design service life should be required in the
maintenance plan.
E.8 Crash barrier fixations
(1) If the crash barriers are connected to the composite bridge deck or composite slab bridge, as shown
in Figure E.5a, the design value of the resistance to impact of the composite deck or composite slab
(including fixed inserts) should be higher than that of steel connecting elements, which should be
replaceable to facilitate repair.
(2) The regions of the crash barrier post connections in composite bridge decks or composite slab bridges
can be reinforced by high density/strength core inserts (sandwich decks), as shown in Figure E.5a, or
concrete infills in deck cavities (e.g. pultruded decks), also shown in Figure E.1a.
NOTE In composite sandwich decks or slabs, the core and core inserts can be protected from moisture by tube
inserts, as shown in Figure E.5a).
(3) If the composite deck resistance as specified in E.8(1) cannot be provided, the crash barriers may be
connected to steel cross-beams, as shown in Figure E.5b.
234
CEN/TS 19101:2022 (E)
Key
1
composite deck
4
spacer
2
3
5
6
7
8
9
(a) overview
adhesive connection
steel girder
blasted steel surface
corrosion protection steel
adhesive
rubber profile
sealing adhesive connection
Figure E.4 — Adhesive deck-to-steel girder connection
Key
(a) connected to composite deck or slab
1
reinforcing high density/strength insert
4
composite deck
2
3
5
6
(b) detail
(b) connected to steel
cross-beam
core (sandwich deck)
sealing tubes
steel cross-beam
crash barrier
Figure E.5 — Crash barrier fixations
235
CEN/TS 19101:2022 (E)
Bibliography
References contained in recommendations (i.e. “should” clauses)
The following documents are referred to in the text in such a way that some or all of their content
constitutes highly recommended choices or course of action of this document. Subject to national
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where technically justified. For dated references, only the edition cited applies. For undated references,
the latest edition of the referenced document (including any amendments) applies.
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236
CEN/TS 19101:2022 (E)
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237
CEN/TS 19101:2022 (E)
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238