design of timber columns and beam-columns

8/9/2019 Design of Timber Columns and Beam-Columns

1/41

Design of

Beam-Columnsin Timber


2/41

• a er a a ure crus ng•

• Inelastic bucklin combination of

buckling and material failure) ∆Leff

P


3/41


4/41

2 EI

P

π

= eff

cr L

Pcr P

er ec y s ra g an e as c co umn

Crooked elastic column

( k N

)

a l l o a d P

∆

Crooked column with material failure

Leff

A x

Displacement ∆ (mm)

P


5/41

-

Shadbolt Centre,

Burnaby


6/41

axis of

bucklingP

Pr = Fc A KZc KC

where = 0.8d

and Fc = f c (KD KH KSc KT)

size factor K = 6.3 dL -0.13 ≤ 1.3

L


7/41

Glulam arches and

cross-bracing

UNBC, Prince George, BC


8/41

Ca acit of a column

material failure

FcA

r

combination of

material failure and

buckling

π u er equa on

elastic buckling

Le


9/41


10/41

1

3 −

1.0

05350.1 ⎥⎢ += T SE

C ZccC

K K E K

KC

limit

± 0.15

CC = Le /d50


11/41

What is an acceptable

ra o

Clustered columns

Forest Sciences Centre, UBC


12/41

Effective lengthLeff = length of half sine-wave = k L

P PP P P

e e e e

k theor 1.0 0.5 0.7 > 1

P P PPP

k (design) 1.0 0.65 0.8 > 1

non-sway non-sway non-sway sway*

* Sway cases should be treated with frame stability approach


13/41

Glulam and steel trusses

Velodrome, Bordeaux, France

All end connections are assumed to

be pin-ended


14/41

Pin connected column base

Note: water damage


15/41

Column base: fixed or pin connected ??


16/41

length

Lex

Ley


17/41

Round poles in a marine structure


18/41

Partiall braced

columns in a post-and-beam structure

u ng,

Vancouver, BC


19/41

L/d ratiosx

yy

x

yy

L

ey

Lex

d

dd

x


20/41

buckling

d

Lgnore s ea ng

contribution

when calculating

stud wall

resistance


21/41

Stud wall construction


22/41

Fixed or pinned

connection ?

Note: bearing block from hard

wood


23/41

An interesting

connection between

column and truss

(combined steel and glulam truss)


24/41

Slightly over-designed truss member

(Architectural features)


25/41

Effective length (sway cases)Leff = length of half sine-wave = k L

P PP P P

Le

Le

Le

Le

k theor 1.0 2.0 2.0 1.0


26/41

Sway frame for a

bridge


27/41

Sway permitted columns

….or aren’t they ??


28/41

Haunched columns

UNBC, Prince George, BC


29/41

•

• Effective length based on sway-prevented case•

– When no applied moments, assume frame to be out-

of-plumb by 0.5% drift – Applied horizontal forces (wind, earthquake) get

amplified

• es gn as eam-co umn


30/41

Frame stability(P- ∆ effects)Htotal = H

= amplification factor

H

W .

∆

h

W Δ−

=1

α

Note: This column does

∆ = 1st order displacement

not contribute to the

stability of the frame


31/41

Sway frame for a

bridge

Minimal bracing,combined with roof

diaphragm in lateral

Haunched frame in


32/41

Bi-axial bending

Bending and


33/41

Heavy timber trusses

Abbotsford arena


34/41

Roundhouse Lodge, Whistler Mountain


35/41

Pf a = Pf / A

neu ra ax s

xmax a bx by des

( Pf / A ) + ( Mfx / Sx ) + ( Mfy / Sy ) < f des

f bx = Mfx / SxMfx

(Pf / Af des) + (Mfx / Sxf des) + (Mfy / Syf des) < 1.0

x

(Pf / Pr ) + (Mfx / Mr ) + ( Mfy / Mr ) < 1.0by fy y

Mfy

ye on y y n e p e s a des s

not the same for the three cases


36/41

P

0max1 Δ⎟⎜⎛ =Δ

∆o

∆max

E −

0max

1 PP E ⎟⎜

⎝ −=

=


37/41

0.111 ≤⎟⎟⎜⎜ −+⎟⎟⎜⎜ −+ r

fy

E rx

fx

Exr

f

M PP M PPP

Axial BendinBendinload about y-axisabout x-axis


38/41

3 storey walk-up (woodframe construction)


39/41

New Forestry Building, UBC, Vancouver


40/41

Stud wall construction


41/41

wall and top plate

o s s loads into studs

d

op p a e

wall plate

L

studs

check

compression perp.

design of timber columns and beam-columns

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