Author: Abdy Kermani Its a comprehensive textbook which provides in depth guidance on design methods of structural timber to BS 5268 Part 2 and proposed Eurocode 5.Deskripsi lengkap
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Timber floor joist design ULS and SLSFull description
Full description
wood design
Descripción completa
Full description
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Beam, Column, Purlin, Truss, and Connections Design
Design of steel and timber structure
Design of steel and timber structure
Structural Design of Timber to BS 5268 Timber engineering Design of timber beams Design of timber joists Design of timber columnsFull description
Design of Timber StructuresDeskripsi lengkap
this example will guiding student to calculate timber structure.Deskripsi lengkap
Descripción: Design of Timber Structures
PRACTICE PROBLEMS IN TIMBER DESIGN
STRUCFull description
Descripción: h
Design of Bending Members in Timber
An Example of Timber Beams
What can go wrong ? TIMBER BEAMS:
• Lateral torsional buckling • Shear failure • No Notc tch h fa fail ilur ure e • Bearing failure • Excessive deflections
max
y
M
=
y
=
I S M = σ max S
for rectangular sections
=
bh
Design Equation: r
= ϕ
b
Where F is the characteristic bendin stren th For timber it is Fb = f b (KDKHKSbKT)
6
2
Bending failure in compression • • Benign failure mode
Logging bridge near Pemberton, BC Glulam I-beam
• • Brittle •
om na on o ens on an s ear, although tension fracture is the n a ng mo e
Mr = φ Fb S KZb KL where
φ
and
Fb = f b (KD KH KSb KT )
= 0.9
Lateral torsional buckling
Glulam beams in a Gerber system
-
20f-E and 24f-E grades
-
better
20f-EX and 24f-EX grades
Lateral torsional buckling of Elastic buckling: cr = π e Torsional stiffness
y Lateral bending stiffness y y
Le
∆x
x
y x
o e: e warp ng s ness or rectangular shapes is small compared to the torsional and bending stiffness
y y
θ
x
Lateral torsional buckling of -
Capacity of a timber beam subject
Mr = φ Fb S KZb material failure
u
Mr = φ Fb S KZb KL
r combination of material failure and lateral torsional buckling
elastic lateral torsional buckling
Le
Lateral torsional buckling factor KL
L 1.0
KL = 1 L
=
–
B
K
0.67
prac ca
m
0.5 KL = (0.65 E KSE KT) / (CB2 Fb KX)
CK = ( 0.97 E KSE KT / Fb )0.5 0
0
10
20
30
40
50
C
Slenderness ratio CB = ( Le d / b2 )0.5
Deep glulam beam
d/b
Lateral support
d b
of lateral ors ona
at spacing:
purlins or tie rods
KL = 1.0 when lateral support is prov e as shown
< 610 mm
< .
compression edge held by
decking or joists < 610 mm
< 7.5 <9
op e ge < 8d
plus bridging
both edges
A y
d
max
N.A.
= V(0.5A)(d/4) (bd3/12)b =1.5 V/A
b
τ
=
τ
VAy Ib
=
VQ Ib
s
σv(max)
Vr = φ Fv 2/3 A KZv where
φ
= 0.9
and
F
=f
K K K
σv(avg)
K
σv(max)
= . σv(avg) = 1.5 V / A
UNBC Prince Geor e, BC
• • Shrinkage cracks often occur at the ends of beams in the zone of maximum shear stress This part of the load transferred in
• transfer of loads in the end zones reduces the total shear force to be carr e .
compression
45o critical section
volume < 2.0 m3: Vr = φ Fv 2/3 A KN where
φ
and
Fv = f v (KD KH KSv KT )
= 0.9
KN = notch factor (see next section)
For larger beams this is usually quite approach is used (see clause 6.5.7.3)
n
d dn
e
KN = ( 1 – dn /d )2
For e > d : KN = ( 1 – dn /d ) For e < d : KN = 1 – dne/[d(d – dn)]
• For notches on the tension side of supports (sawn lumber)
Notch effect in sawn um er
• In new code: Reaction calculation Fr =
NEW !!
Ft A KN
= 0.9
Area A
Ft = f t (KD KH KSt KT) where f t = specified reaction force strength = 0.5 MPa for sawn lumber K = 1.0 for dr and 0.7 for wet service conditions A = gross cross-section area KN = notch factor
Notch factor KN
d1
e
d
dn
Mechanics theory
⎛ N
⎝ α = −
⎛
. n
⎛ 1 ⎞ . − ⎝ ⎝ α ⎠ an η = e
2
⎛ 1 ⎞ ⎞ ⎞ − 3 ⎝ α ⎠ ⎠ ⎠
−0.5
•
“
”
• Often governs • y u grain but also tension of the fibres
compression perpendicular to grain tension of fibres along the edges
