Timber Design according to EC5
Timber Design according to EC5
EN 1995-1-1:2004
Summary of the AxisVM implementation
• sturctural timber materials, partial factors
• load duration classes, service classes
• material properties for global analysis
• cross-sections, design elements
• design strength of timber materials (modification factors)
• checks of timber elements
• design in seismic enviroment
Timber Design according to EC5
Sturctural timber materials EN 338, EN 1194
• Solid timber /softwood(C), hardwood(D)/
• Glued-laminated timber (Glulam)
• Laminated veneer lumber (LVL)
Characteristic strength
Notation
Modulus of elasticity
Notation
Mean value parallel to grain
E0,mean
E90,mean
Bending strength
fm,k
Mean value perpendicular to grain
Tensile strength parallel to grain
ft,0,k
E0,05
Tensile strength perpendicular to grain
ft,90,k
5% value of modulus parallel to
grain
Compression strength parallel to grain
fc,0,k
Mean value of shear modulus
Gmean
Compression strength perependicular
to grain
fc,90,k
Density
Shear strength perpendicular to the
grain in y direction
fv,k,y
Characteristic value of density
Shear strength perpendicular to the
grain in z direction
fv,k,z
Mean value of density
Notation
ρk
ρmean
Timber Design according to EC5
Partial factor (γγM)
Timber type
Fundamental
combination
Accidental
combination
Solid timber
1,30
1,0
Glued laminated timber (Glulam)
1,25
1,0
Laminated veneer lumber (LVL)
1,20
1,0
Timber Design according to EC5
Load duration classes and service classes
Load duration class
Order of accumulated
duration of characteristic
load
Examples of loading
Permanent
more than 10 years
self-weight
Long-term
6 months – 10 years
storage
Medium-term
1 week – 6 months
imposed floor load, snow
Short-term
less than one week
snow, wind
Instantaneous
wind, accidental load
Service class
Environmental condition
1
the relative humidity in the surrounding air only exceeding 65% for a
few weeks per year*
2
the relative humidity in the surrounding air only exceeding 85% for a
few weeks per year*
3
The climatic condition leading to higher moisture contents than
Service Class 2
(*) the moisture content in the materials corresponding to a temperature of 20 Co
Timber Design according to EC5
Material properties for global analysis
Analysis type
Modulus
SLS
First-order linear elastic analysis
Second-order linear elastic analysis
Vibration analysis
Modulus
ULS
Emean, fin =
Emean
(1 + k def )
Emean, fin =
Emean
(*)
(1 + ψ 2 ⋅ k def )
Gmean, fin =
Gmean
(1 + k def )
Gmean, fin =
Gmean
(*)
(1 +ψ 2 ⋅ k def )
Ed =
Emean
Ed =
Emean
Gd =
Gmean
Gd =
Gmean
Emean
γM
γM
Gmean
Emean
γM
γM
Gmean
(*) conservative way ψ 2 = 1,0 is used
Material type
kdef
Service class 1
Service class 2
Service class 3
Solid timber
0,60
0,80
2,0
Glued laminated timber (Glulam)
0,60
0,80
2,0
Laminated veneer lumber (LVL)
0,60
0,80
2,0
Timber Design according to EC5
Cross-sections, design elements
Design assumptions:
• the grain parallel with the member x axis
• there is no hole or other weaking in the members
• the dominant bending plane is the x-z plane of the member (moment about y axis)
• Iy >= Iz
• in case of Glued-laminated timber (Glulam) the laminates are parallel with the y axis
• in case of Laminated veneer lumber (LVL) the laminates are parallel with the z axis
x
z
y
y
Timber Design according to EC5
Cross-sections, design elements
Solid timber
(softwood, hardwood)
Glued-laminated timber
(Glulam)
Laminated veneer lumber
(LVL)
Timber Design according to EC5
Design strength of timber materials
Strength modification factors
• kmod factor depending on the duration of load and the moisture content
• kh factor depending on the cross-section size and the reference depth size
• kl factor depending on the member length and the reference length
• kvol factor depending on the apex zone volume and the reference volume
Timber Design according to EC5
Design strength of timber materials
• kmod modification factor
Material type
Service
class
kmod
Permanent
Long
term
Medium
term
Short
term
Instant.
Solid timber
1
2
3
0,60
0,60
0,50
0,70
0,70
0,55
0,80
0,80
0,65
0,90
0,90
0,70
1,10
1,10
0,90
Glued laminated timber
(Glulam)
1
2
3
0,60
0,60
0,50
0,70
0,70
0,55
0,80
0,80
0,65
0,90
0,90
0,70
1,10
1,10
0,90
Laminated veneer lumber
(LVL)
1
2
3
0,60
0,60
0,50
0,70
0,70
0,55
0,80
0,80
0,65
0,90
0,90
0,70
1,10
1,10
0,90
Timber Design according to EC5
Design strength of timber materials
• kh modification factor
Material type
Solid timber
(if h < 150 mm)
Glued laminated timber
(Glulam)
(if h < 600 mm)
Laminated veneer lumber
(LVL)
kh
 150  0 , 2
k h = min 
 or 1,3
 h 
 600  0 ,1
k h = min 
 or 1,1
 h 
 300  S
k h = min 
 or 1,2
 h 
Timber Design according to EC5
Design strength of timber materials
• kl modification factor
Material type
kl
Laminated veneer lumber
(LVL)
 3000  S / 2
kl = min 
 or 1,1
 l 
Timber Design according to EC5
Design strength of timber materials
• kvol modification factor
Material type
Solid timber
kvol
1,0
where,
Glued laminated timber
(Glulam)
Laminated veneer lumber
(LVL)
k vol
V 
= 0
V 
0,2
V0 is the reference volume (0,01 m3)
V is the stressed volume of the apex zone,
and V < 0,67Vb (total volume of the beam)
Timber Design according to EC5
Design strength of timber materials
• Design strength calculation
Material type
fm,k
ft,0,k
ft,90,k , fc,0,k
fc,90,k , fv,k
Solid timber
f t ,0, d =
Glued laminated timber
(Glulam)
Laminated veneer lumber
(LVL)
f m ,d =
k mod ⋅ k h ⋅ f m , k
k mod ⋅ k h ⋅ f t , 0,k
γM
fd =
γM
f t ,0, d =
k mod ⋅ k l ⋅ f t ,0 ,k
γM
k mod ⋅ f k
γM
Timber Design according to EC5
Checks of timber elements
(interaction formulas for different design situation)
• Normal force, Moments (stress check parallel to the grain)
• Compression force, Moments (in plane buckling check)
• Moment (y), Normal force (lateral torsional buckling check)
• Shear (y), Torsion (shear check)
• Shear (z), Torsion (shear check)
• Moment (y), (tension stress perpendicular to the grain check)
Timber Design according to EC5
Checks of timber elements
(interaction formulas for different design situation)
Normal force, Moments (stress check)
Tension and moment
σt,0,d σm,y,d
ft,0,d
σt,0,d
ft,0,d
+
fm,y,d
+km
+km
σm,z,d
fm,z,d
σm,y,d σm,z,d
fm,y,d
+
fm,z,d
Compression and moment
2
≤1
σc,0,d  σm,y,d σm,z,d


 f  + f +km f ≤1
m,z,d
 c,0,d  m,y,d
2
≤1
σc,0,d 
σ
σ

 +km m,y,d + m,z,d ≤1
f 
fm,y,d fm,z,d
 c,0,d 
where,
km = 0,7 for rectangular sections
km = 1,0 for other cross-sections
Timber Design according to EC5
Checks of timber elements
(interaction formulas for different design situation)
Compression force, Moments (in plane buckling check)
Compression and moment
σc,0, d
kc, y ⋅ fc,0, d
σc,0, d
kc, z ⋅ fc,0,d
+
σ m, y,d
fm, y,d
+ km
+ km
σ m, z, d
σ m, y, d σm, z, d
fm, y, d
+
≤1
fm, z, d
fm, z, d
≤1
where,
km = 0,7 for rectangular sections
km = 1,0 for other cross-sections
kc,y = buckling reduction factor
kc,z = buckling reduction factor
Timber Design according to EC5
Checks of timber elements
(interaction formulas for different design situation)
Moment (y), Normal force (lateral torsional buckling check)
Moment and compression
Moment and small tension
2
σmc,d
 σm,d 
σc,d

 +
 k ⋅ f  k ⋅ f ≤1
c, z
c,0,d
 crit m,d 
where,
kc,z is the buckling reduction factor
kcrit is the lateral torsional buckling
reduction factor:
λrel,m ≤ 0,75
kcrit = 1,0
0,75 < λrel,m ≤ 1,4
kcrit = 1,56-0,75 λ rel,m
λrel,m ≤ 0,75
kcrit = 1/ l2rel,m
kcrit ⋅ fm,d
≤1
where,
σmc,d =
Md Nd
+ <0
Wy A
Timber Design according to EC5
Checks of timber elements
(interaction formulas for different design situation)
Shear (y), Torsion (shear check) SIA 265:2003
Shear(y) and Torsion
τ tor, d
k shape ⋅ f v , d
τ
+  v , y ,d
 f v, d
2

 ≤1


where,
kshape is the cross-section shape factor:
kshape = 1,2 for circular cross-section
kshape = min{1 + 0,15h / b; 2,0} for rectangular cross-sections
Timber Design according to EC5
Checks of timber elements
(interaction formulas for different design situation)
Shear (z), Torsion (shear check) SIA 265:2003
Shear(y) and Torsion
τ tor,d
k shape ⋅ f v,d
τ
+  v , z ,d
 f v ,d
2

 ≤1


where,
kshape is the cross-section shape factor:
kshape = 1,2 for circular cross-section
kshape = min{1 + 0,15h / b; 2,0} for rectangular cross-sections
Timber Design according to EC5
Checks of timber elements
(interaction formulas for different design situation)
Moment (y), (tension stress perpendicular to the grain check)
Moment(y)
σ t ,90,d
k dis ⋅ kvol ⋅ f t ,90, d
≤1
where,
kdis is the stress distribution factor in apex zone factor (k dis =1,4)
kvol is the volume modifiction factor in the apex zone
Timber Design according to EC5
Timber structure design in seismic enviroment
(Response-spectrum analysis)
Ductility class
γM
Criteria
Solid timber: γM = 1,30
Low (DCL)
q =< 1,5
Glulam:
γM = 1,25
LVL:
γM = 1,20
Medium (DCM)
1,5 < q =< 2,5
γM = 1,0
High (DCH)
2,5 < q
γM = 1,0
- The dissapitive zones have to be concentrated into the joints
- The timber elements works in elastic assuption