Transcript Slide 1
T4. DESIGN OF TIMBER COLUMN (axial compression)
Floor plan
Timber framed building
Section
Column: Linear member subjected to axial compression (N0).
Axially compressed if M=0 és V=0 (Eccentrically compressed if M0 és V0)
Example:
Checking column O1
T4. Design of timber column
page 1.
I.
Design of column O1
I.1. Geometry, model, loads
Profile
l =3.00m
Material properties: GL28h (glued-laminated)
f c , 0, k
M
kmod
f c , 0, d
f c,90,k
( ST )
kmod
M
( ST )
f c , 0, k
Loads: floor load (Practical T3):
( ST )
f c,90,d
kmod
M
f c,90,k
floor
pEd
G2
self-weight of double beam transferred to the columne: GEd
O1
self-weight of column: GEd
O2
reaction force of column O2 (approximately): N Ed
I.2. Calculation of internal forces
Reaction of column O1 approximately:
transferred floor load + self-weight of beams and columns + reaction of the column above
O2
NEd p Edfloor AO1 GOEd1 GGEd2 NEd
page 2.
T4. Design of timber column
I.3. Ultimate limit state: strength analysis
I.4. Stability analysis
(ST.)
f
St eel : N b, Rd min A y
M1
kc buckling reductionfactor kc min kc (max )
N Rd kc A f c ,0,d
analysis about y axis in the xz plane:
y
Lcr , y
iy
Iy
iy
A
yl
(ST)
analysis about z axis in the xy plane:
z
iy
h2
bh3
12
12bh
iz
Lcr , z
iz
zl
iz
Iz
A
against buckling about z axis it is supported along y
iy
axis:
against buckling about y axis it is supported
l
along z axis:
z
l
y 1
z 1
(ST)
(ST)
y
max z
y
page 3.
T4. Design of timber column
relativeslenderrness : rel , z
E
rel , z
GL28h
z
E
z
where E is theEuler slenderness
E
(ST)
kc
NRd kc Afc,0,d
(ST)
NEd
(In case of eccentric compression if N0 and M0 (and V0),
the combination of effect of normal force and moment should be checked.
N
M
f Ed , Ed 1 )
N b, Rd M b, Rd
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T4. Design of timber column
I.5. Checking column joint
GL28h: f c ,0,d
f c ,90,d
N
mm2
N
mm2
checking surface a: compression parallel to grain
The force acting at the joint is the reaction of column O2:
N (Eda ) N OEd 2
N (Rda ) f c,0,d A( a )
checking surface b: compression perpendicular to grain
Joint loaded by the support reaction of beam: (approximately)
N (Edb)
N (Rda ) kc,90 f c,90,d Aef (b)
Determination of modification factor of local compression (punching):
point support, for glued-laminated timber: kc,90
(ST)
)
N (a
Rd
page 5.
T4. Design of timber column
Complement I
I.7. Additional internal force on column O1 arising from horizontal load
wind load:
wk q p c
qp
wk
h
wk
wind compression
+
wind suction
w Ed
Static model: loads are transferred to the bracing by the rigid floor.
N Ed
N Rd
page 6.
T4. Design of timber column
Complement II