Transcript Slide 1

T4. DESIGN OF TIMBER COLUMN (axial compression)
Floor plan
Timber framed building
Section
Column: Linear member subjected to axial compression (N0).
Axially compressed if M=0 és V=0 (Eccentrically compressed if M0 és V0)
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 N0 and M0 (and V0),
the combination of effect of normal force and moment should be checked.
N
M 
f  Ed , Ed   1 )
 N b, Rd M b, Rd 
page 4.
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 
wk 
h
wk 
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