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wood design
Timber Design according to EC5
Timber Design according to EC5EN 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
Bending strength fm,k
Tensile strength parallel to grain ft,0,k
Tensile strength perpendicular to grain ft,90,k
Compression strength parallel to grain fc,0,k
Compression strength perependicular to grain
fc,90,k
Shear strength perpendicular to the grain in y direction
fv,k,y
Shear strength perpendicular to the grain in z direction
fv,k,z
Modulus of elasticity Notation
Mean value parallel to grain E0,mean
Mean value perpendicular to grain E90,mean
5% value of modulus parallel to grain
E0,05
Mean value of shear modulus Gmean
Density Notation
Characteristic value of density ρk
Mean value of density ρmean
Timber Design according to EC5
Partial factor (γM )
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 ModulusSLS
ModulusULS
First-order linear elastic analysis(*)
(*)
Second-order linear elastic analysis
Vibration analysis
M
meand
EEγ
=
)1( 2,
def
meanfinmean k
EE⋅+
=ψ
)1( 2,
def
meanfinmean k
GG⋅+
=ψ
)1(,def
meanfinmean k
EE+
=
)1(,def
meanfinmean k
GG+
=
M
meand
GGγ
=
M
meand
EEγ
=
M
meand
GGγ
=
meanE meanG meanE meanG
(*) conservative way ψ2 = 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
y
z
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 Longterm
Mediumterm
Shortterm
Instant.
Solid timber 123
0,600,600,50
0,700,700,55
0,800,800,65
0,900,900,70
1,101,100,90
Glued laminated timber (Glulam)
123
0,600,600,50
0,700,700,55
0,800,800,65
0,900,900,70
1,101,100,90
Laminated veneer lumber (LVL)
123
0,600,600,50
0,700,700,55
0,800,800,65
0,900,900,70
1,101,100,90
Timber Design according to EC5
Design strength of timber materials
• kh modification factor
Material type kh
Solid timber(if h < 150 mm)
Glued laminated timber (Glulam)(if h < 600 mm)
Laminated veneer lumber (LVL)
⎪⎩
⎪⎨⎧
⎟⎠⎞
⎜⎝⎛= 3,1 150min
2,0
orh
kh
⎪⎩
⎪⎨⎧
⎟⎠⎞
⎜⎝⎛= 1,1 600min
1,0
orh
kh
⎪⎩
⎪⎨⎧
⎟⎠⎞
⎜⎝⎛= 2,1 300min or
hk
S
h
Timber Design according to EC5
Design strength of timber materials
• kl modification factor
Material type kl
Laminated veneer lumber (LVL) ⎪⎩
⎪⎨⎧
⎟⎠⎞
⎜⎝⎛= 1,1 3000min
2/
orl
kS
l
Timber Design according to EC5
Design strength of timber materials
• kvol modification factor
Material type kvol
Solid timber 1,0
Glued laminated timber (Glulam)
Laminated veneer lumber (LVL)
2,00 ⎟⎠⎞
⎜⎝⎛=
VVkvol
where,
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
Glued laminated timber (Glulam)
Laminated veneer lumber (LVL)
M
kd
fkfγ⋅
= mod
M
kmhdm
fkkf
γ,mod
,
⋅⋅=
M
kthdt
fkkf
γ,0,mod
,0,
⋅⋅=
M
ktldt
fkkf
γ,0,mod
,0,
⋅⋅=
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 Compression and moment
1,,
,,
,,
,,
,0,
,0, ≤++dzm
dzmm
dym
dym
dt
dt
fk
ffσσσ
1,,
,,
,,
,,
,0,
,0, ≤++dzm
dzm
dym
dymm
dt
dt
ffk
fσσσ
1,,
,,
,,
,,
2
,0,
,0, ≤++⎟⎟⎠
⎞⎜⎜⎝
⎛
dzm
dzmm
dym
dym
dc
dc
fk
ffσσσ
1,,
,,
,,
,,
2
,0,
,0, ≤++⎟⎟⎠
⎞⎜⎜⎝
⎛
dzm
dzm
dym
dymm
dc
dc
ffk
fσσσ
where, km = 0,7 for rectangular sectionskm = 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
where, km = 0,7 for rectangular sectionskm = 1,0 for other cross-sectionskc,y = buckling reduction factor kc,z = buckling reduction factor
1,,
,,
,,
,,
,0,,
,0, ≤++⋅ dzm
dzmm
dym
dym
dcyc
dc
fk
ffkσσσ
1,,
,,
,,
,,
,0,,
,0, ≤++⋅ dzm
dzm
dym
dymm
dczc
dc
ffk
fkσσσ
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
where, kc,z is the buckling reduction factorkcrit is the lateral torsional buckling reduction factor:
where,
1,0,,
,
2
,
, ≤⋅
+⎟⎟⎠
⎞⎜⎜⎝
⎛
⋅ dczc
dc
dmcrit
dm
fkfkσσ
1,
, ≤⋅ dmcrit
dmc
fkσ
0, <+=AN
WM d
y
ddmcσ
λrel,m
≤
0,75 kcrit
= 1,0
0,75 < λrel,m
≤
1,4 kcrit
= 1,56-0,75
λrel,mλrel,m
≤
0,75 kcrit = 1/ l2rel,m
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
where,
kshape is the cross-section shape factor:
kshape = 1,2 for circular cross-section
for rectangular cross-sections
12
,
,,
,
, ≤⎟⎟⎠
⎞⎜⎜⎝
⎛+
⋅ dv
dyv
dvshape
dtor
ffkττ
{ }0,2; /15,01min bhkshape +=
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
where,
kshape is the cross-section shape factor:
kshape = 1,2 for circular cross-section
for rectangular cross-sections
12
,
,,
,
, ≤⎟⎟⎠
⎞⎜⎜⎝
⎛+
⋅ dv
dzv
dvshape
dtor
ffkττ
{ }0,2; /15,01min bhkshape +=
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)
where,
kdis is the stress distribution factor in apex zone factor (kdis =1,4)
kvol is the volume modifiction factor in the apex zone
1,90,
,90, ≤⋅⋅ dtvoldis
dt
fkkσ
Timber Design according to EC5
Timber structure design in seismic enviroment
(Response-spectrum analysis)
Ductility class Criteria γM
Low (DCL) q =< 1,5Solid timber: γM = 1,30
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