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FRP-REINFORCED
CONCRETE DESIGN
Mahmoud Sayed Ahmed, Ph.D.
Table of Contents
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Introduction
 FRP Reinforcing Materials
 Design Process
 Flexure Design

Construction Issues
 Structural Applications

 Prefabricated Bridge
Elements and Systems
(PBES).
 Parking Garages
 Mode of failure

Shear Design
 Mode of failure


 Thermoset FRP
Serviceability Limit State
 Thermoplastic FRP
 Deflection
 Cracking

Bond and Anchorage of
Reinforcement
On-going Research
On-going Research

FRP Resources
Introduction
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
Introduction
 Corrosion
 Accelerated Construction
 Durability
American Galvanizers Association
http://stainlessrebar.com/stainless-rebar-info/a-look-at-corrosion/
FRP Manufacturers
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Aslan FRP
 B&B Manufacturing Inc.
 BP Composites
 Composite Rebar Technologies Inc
 Fiberline (Schoeck Combar)
 Hughes Brothers Inc
 Marshall Composite Technologies Inc
 Pultrall Inc

N.B. In USA 15 states (CO, FL, IA, IN, KY, MO, NC, NY, OH, OR, TX, UT, VT, WI, WV)
uses FRP bars in bridge decks
FRP Reinforcing Materials
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Fibers are arranged into different orientations:

Anisotropic

Unidirectional

Bias – Tailored direction

FRP composed of:
Fibers
Resins



0o – flexural strength
90o – columns wraps
+/- 45o – shear strength
Angle varies by application
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
FRP is anisotropic
 High strength in direction of fibers
 Anisotropic behaviour affects shear strength, dowel
action and bond performance

FRP doesn’t exhibit yielding: the material is linear
elastic until failure
 Design should account for lack of ductility
 Member does have substantial deformability
Manufacturing Methods for FRP Composites
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
Predominate Processes
 Pultrusion
 Vacuum Infusion (VIP)

Other processes
 Bladder Molding
 Compression Molding
 Thermoplastic Extrusion
 Filament winding
 Wet Layup
 Resin Transfer Molding (RTM)
Pultrusion
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Plastic resins
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Thermoset resin : polymer transformed into an infusible and
insoluble product after a thermal (heat, radiation) or physicochemical (catalysis, hardener) treatment.
 Thermoplastic resin : polymer capable of being alternatively
softened by heating and hardened by cooling in a temperature
scale that is proper to the polymer at issue. Thermoplastic resins are
able to be easily moulded by plasticity in their soft state.
 Thermostable resin : polymer with stable mechanical features under
high pressure and temperature (< 200°C) applied in a continuous
way. This property is measured by determining the temperature that
the resin can handle for 2000 hours without losing half of its
mechanical features.
 Thermoplastic elastomer : highly elastic polymer.

Thermoset versus Thermoplastic resins
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Thermoset maintain their molded shape at higher
temperatures and cannot be melted and reshaped
 Thermoplastics will melt at a given temperature and
can be solidified into new shapes by cooling to
ambient temperatures.

http://training.pluscomposites.eu/courses/matrixes
Thermoset resins
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Typical main mechanical features of the thermoset resins
Resin Type
Density
E
[kg/M^3]
Modulus of
Young
[MPa]
DELTA
R (MPa) :
(m/m°C) :
υ
Elasticity limit
Poisson's ratio
Thermal
in traction
expansion
Price [€/KG]
Polyester
1300
3800
0,37
88
100
3
Vinyl ester
1200
3500
0,35
81
65
4
Epoxide
1220
5200
0,38
122
40
7
Silicone
1550
1000
0,45
3
30
30
Polyamide
1217
3450
0,35
80
36
25
Phenol
1350
1350
0,36
70
80
3
Reinforcing fibers
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Fibers provide strength, dimensional stability

Glass




Carbon





Other man-made




Pan
Pitch
Kevlar 29, 49, 129, 149
Twaron
Technora
EC-Polyethylene
Polyvinyl Alcohol Fibre
Steel Fibre
natural materials
Tensile Compressive
Strength Strength
Density
Thermal Softening
expansion
Temp.
(MPa)
(g/cm3)
(µm/m·°C)
Fiber type
Aramid


E-Glass
E-CR Glass (Alkali Resistant Glass
S-2 Glass
(MPa)
(°C)
E-glass
3445
1080
2.58
5.4
846
S-2 glass
4890
1600
2.46
2.9
1056
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Properties of various FRP composites and other materials
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Thermal Properties of various FRPs and other materials at room temperature
Kodur and
Baingo. 1998
FRP Composites
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Highly resistant to chloride ion and chemical attack
 High Strength-to-weight ratio
 Low electrical and thermal conductivity
 High Dielectric Strength and Low Moisture Absorption
 Transparent to magnetic fields and radar frequencies
 Design Flexibility

Limiting physical and
mechanical properties
of FRP rebar
Berg. Et al. 2006
FRP Bars
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Bar Type
 Straight Bar
 Bent Bar
 Headed-end Bar
Bar Surface
 Ribbed-Surface
 Sand-Coated
 Wrapped
 Wrapped and sandcoated
 Deformed
 Helical
Design Standards
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Mechanical and bond properties for straight bars required by the design standards
Property
Minimum Tensile strength, MPa
CSA S807
MTO NSSP (Grade III)
15 mm
650 MPa
15 mm
1000 MPa
20 mm
600 MPa
20 mm
1000 MPa
25 mm
550 MPa
25 mm
960 MPa
Minimum Modulus of Elasticity, GPa
>60 for GIII
>50 for GII
>40 for GI
>60 for GIII
>50 for GII
>40 for GI
Min. Transverse Shear Strength, MPa
>160
>180
Minimum Bond Strength, MPa
>8
>8
Minimum Strain, %
>1.2
>1.2
Not less than 5% as
compared to RT
Not less than 5% as
compared to RT
Tensile Properties at Cold Temperature
(-40oC)
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Kodur and
Baingo. 1998
Longitudinal tensile loading of a continuous parallel fibre lamina
Fire Rating
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Kodur and
Baingo.
1998
Variation of strength with temperature for different materials
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Kodur and
Baingo. 1998
325–degree C
Comparison of predicted temperature from the model with test data
Slab thickness 120 mml concrete cover thickness 15 and 30 mm
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Kodur and Baingo. 1998. Fire Resistance of FRP Reinforced Concrete Slabs, Internal Report No.
758. National Research Council Canada
Design Process
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Axial Capacity
 Flexural Capacity
 Shear Capacity
 Combined shear, bending and torsion
 Combined axial and bending

Axial Capacity
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
Currently, CSA S806-12 permits the use of FRP bars
as longitudinal reinforcement in columns subjected to
axial load only, ignoring the contribution of FRP
bars in the ultimate capacity of the columns,
Afifi et al. 2013
The axial capacities of the GFRP RC columns were on average 7.0% lower
than their steel RC counterparts.
Flexure Design
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Mode of Failure
 Concrete Crushing
 Balanced Failure
 FRP rupture
In Canadian Code CSA S80602 (Clause 8.2.1(, it is
specified that the FRPReinforced Concrete section
shall be over-reinforced
Compression failure
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Whitney rectangular stress distribution for flexural design
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1 Determine the concrete cover and the effective
depth of the section
2 Calculate the FRP reinforcement ratio
𝐴𝑓𝑟𝑝
𝜌𝑓𝑟𝑝 =
𝑏𝑑
3 Calculate the balanced FRP reinforcement
ratio
′
𝜌𝑓𝑟𝑝𝑏 =
𝐴𝑓𝑟𝑝
𝜙𝑐 𝑓𝑐
Є𝑐𝑢
= 𝛼1 𝛽1
(
)
𝑏𝑑
𝜙𝑓𝑟𝑝 𝑓𝑓𝑟𝑝𝑢 Є𝑐𝑢 + Є𝑓𝑟𝑝𝑢
4 Check if the section will fail by tension failure or
compression failure
𝜌𝑓𝑟𝑝 > 𝜌𝑓𝑟𝑝𝑏
should have COMPRESSION FAILURE
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5 Determine the tensile stress in the FRP reinforcement
at compressive failure of the section
4 𝛼1 𝛽1 𝜙𝑐 𝑓𝑐′
𝑓𝑓𝑟𝑝 = 0.5 𝐸𝑓𝑟𝑝 Є𝑐𝑢 [ 1 +
− 1]
𝜌𝑓𝑟𝑝 𝜙𝑓𝑟𝑝 𝐸𝑓𝑟𝑝 Є𝑐𝑢
6 Determine the stress block depth, a
𝜙𝑓𝑟𝑝 𝐴𝑓𝑟𝑝 𝑓𝑓𝑟𝑝
𝛽1 𝑐 = 𝑎 =
𝛼1 𝜙𝑐 𝑓𝑐′ 𝑏
7 Determine the flexural capacity
𝑀𝑟 = 𝜙𝑓𝑟𝑝 𝐴𝑓𝑟𝑝 𝑓𝑓𝑟𝑝 [𝑑 −
𝑎
]
2
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8 Finally, we must check that the minimum flexural
capacity requirements are satisfied
𝑀𝑟 ≥ 1.5 𝑀𝑐𝑟
The cracking moment is determined by
𝑓𝑟 𝐼𝑡
𝑀𝑐𝑟 =
𝑦𝑡
fiber
Where 𝑓𝑟 = 0.6 𝑓𝑐′
𝐼𝑡 = transformed section moment of inertia
𝑦𝑡 = distance from N.A. to extreme tension
Shear Design
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Shear failure of reinforced
concrete beam and one-way
slab is usually sudden failure
happen due to “diagonal tension
failure”
Shear failure mode in two-way
lab subjected to point loading
fails under “Punching Shear”
Punching Shear
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Shear resistance provided by concrete (ISIS Canada Research
Network’s Design Manual, 2007)
𝑉𝑐 = 0.2 𝜆𝜙𝑐
𝑓𝑐′ 𝑏𝑤 𝑑
𝐸𝑓𝑟𝑝
𝐸𝑠
The punching strength of the two way slabs were verified using the
new punching equations that are being incorporated in the new
version of the S806-12 Standards
𝑉𝑐 = 𝑚𝑖𝑛
2
1/3
0.028 𝜆𝜙𝑐 1 +
𝐸𝑓 𝜌𝑓 𝑓𝑐′
𝑏0.5𝑑 𝑑
𝛽𝑐
𝛼𝑠 𝑑
1/3
0.147𝜆𝜙𝑐
+ 0.19 𝐸𝑓 𝜌𝑓 𝑓𝑐′
𝑏0.5𝑑 𝑑
𝑏0.5𝑑
0.056𝜆𝜙𝑐 𝐸𝑓 𝜌𝑓 𝑓𝑐′
1/3
𝑏0.5𝑑 𝑑
Serviceability Limit State
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Deflection
 Crack width less than 0.5 mm

Bond and Anchorage of Reinforcement
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The guaranteed bond strength shall be above the
specified limit of 8 MPa as set by CSA S807-15
Bond force transfer mechanisms.
(Source: ACI 408R-03)
Structural Applications
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Cast-In-Place Bridge Slab Deck
 Cast-In-Place Parking Garage Slabs
 Precast Full Depth Deck Panel (precast FDDP)
 Bridge Barriers and Road Barriers
 Sidewalk
 Slab Cantilever
 Grade Beams

Cast-In-Place Bridge Slab Deck
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Sayed-Ahmed, M. 2016.
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Steel Reinforced Deck
Sayed-Ahmed, M. 2016.
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GFRP Reinforced Deck
Sayed-Ahmed, M. 2016.
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Bending Moment Values
Specimen
Load
w
L
a
b
c
R1
R2
kN
kN/b
m
m
m
m
kN
kN
Experimental resisting
moment
Mr.precast
kN.m/0.6 m
Mr.precast
kN.m/m
Steel Rft
163.11 652.44
2 0.875
0.25 0.875
81.55
81.55
76.45
127.42
GFRP Rft
137.22 548.88
2 0.875
0.25 0.875
68.61
68.61
64.32
107.20
Sayed-Ahmed, M. 2016
𝛽 = 𝑀𝑟,𝑒𝑥𝑝𝑒𝑟𝑖𝑚𝑒𝑛𝑡𝑎𝑙 𝑀𝑟,𝑡ℎ𝑒𝑜𝑟𝑒𝑡𝑖𝑐𝑎𝑙
The flexural capacities of the GFRP RC slab was 15.0% lower than their steel RC counterparts.
Cast-In-Place Parking Garage Slabs
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CSA S413-07, Parking Structures
CSA S806-12, Design by FRP…
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La Chancelière parking garage in
Quebec City, the site of the second
rehabilitation project. Source: Pultrall
Pultrall V-Rod rebar reinforcements for La
Chancelière parking garage rehabilitation.
Illustration: Karl Reque
Increasing the GIII - GFRP reinforcement ratio from 0.71 to 1.62 percent raised the punching shear capacities at failure significantly.
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Source: http://www.compositesworld.com/articles/(619)
Bridge Barriers
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PL-3 concrete bridge barrier
Khederzadeh, H., and K. Sennah. 2016
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Khaled Sennah, Ryerson University
Cast-In-Place Bridge Deck
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Empirical Method for FRP-Reinforced Bridge Deck, ISIS Manual
Precast FDDP
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Sayed-Ahmed. 2016
Sidewalk
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Slab Cantilever
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Azimi et al. 2014
Grade Beams
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On-going Research
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Concrete Reinforcing with composite bar (GFRP and/or CFRP)
 Approach Slabs
 Bridge Decks and Bridge Deck overlays
 Cast-in-Place Flat Slab Superstructures
 Pile Bent Caps not in direct contact with water
 Pier Columns and Caps not in direct contact with water
 Retaining Walls, Noise Walls, Perimeter Walls
 Pedestrian/Bicycle Railings
 Bulkheads and Bulkhead Copings
 MSE Wall Panels and Copings
 Drainage Structures
 Concrete Sheet Piles
 Noise Walls
http://www.fdot.gov/structures/innovation/FRP.shtm
References
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












AASHTO "AASHTO LRFD Bridge Design Guide Specifications for GFRP-Reinforced Concrete Bridge Decks
and Traffic Railings"
ACI 440.1R-15 "Guide for the Design and Construction of Structural Concrete Reinforced with FRP Bars"
ACI 440.4R-04 "Prestressing Concrete Structures with FRP Tendons"
ACI 440.5-08 "Specification for Construction with Fiber-Reinforced Polymer Reinforcing Bars"
ACI 440.6-08 "Specification for Carbon and Glass Fiber-Reinforced Polymer Bar Materials for Concrete
Reinforcement"
ACI 440R-07 "Report on Fiber-Reinforced Polymer (FRP) Reinforcement for Concrete Structures"
Azimi, Sennah, Sayed-Ahmed, Nikravan, Louie, Hassaan, Al-Bayati. 2014. Bridge Deck and Guardrail
Anchorage Detailing for Sustainable Construction. ASCE Journal of Bridge Engineering.
CSA S6-14. 2014. Canadian Highway Bridge Design Code. CSA.
CSA S806-12
CSA S807-15
FDOT. Structural Manual, Volume 4 Fiber Reinforced Polymer Guidelines
Khederzadeh, H., and K. Sennah. "Development of cost-effective PL-3 concrete bridge barrier reinforced
with sand-coated glass fibre reinforced polymer (GFRP) bars: static load tests." Canadian Journal of Civil
Engineering 41.4 (2014): 368+. Academic OneFile. Web. 22 Oct. 2016.
Sayed-Ahmed, M. 2016. Development and Study of Closure Strip Between Precast Deck Panels in
Accelerated Bridge Construction, PhD Dissertation. Ryerson University, Toronto, ON.
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Fiber Reinforced Polymer (FRP) bar is made
of composite corrosion-less materials, and
has high strength-to-weight ratio. FRP is used
as concrete reinforcements.
Mahmoud Sayed Ahmed, Ph.D.
mahmoud@megastone.ca