design of columns and beam columns in timber n.
Download
Skip this Video
Loading SlideShow in 5 Seconds..
Design of Columns and Beam-Columns in Timber PowerPoint Presentation
Download Presentation
Design of Columns and Beam-Columns in Timber

Loading in 2 Seconds...

play fullscreen
1 / 41

Design of Columns and Beam-Columns in Timber - PowerPoint PPT Presentation


  • 899 Views
  • Uploaded on

Design of Columns and Beam-Columns in Timber. Column failures. Material failure (crushing) Elastic buckling (Euler) Inelastic buckling (combination of buckling and material failure). P. L eff. Δ. P. Truss compression members Fraser Bridge, Quesnel. Column behaviour.

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about 'Design of Columns and Beam-Columns in Timber' - Leo


Download Now An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
column failures
Column failures
  • Material failure (crushing)
  • Elastic buckling (Euler)
  • Inelastic buckling (combination of buckling and material failure)

P

Leff

Δ

P

slide3

Truss compression members

Fraser Bridge, Quesnel

column behaviour
Column behaviour

Perfectly straight and elastic column

Pcr

P

Crooked elastic column

Leff

Δ

Axial load P (kN)

Crooked column with material failure

P

Displacement Δ (mm)

slide5

Pin-ended struts

Shadbolt Centre,

Burnaby

column design equation
Column design equation

P

axis of buckling

Pr =  Fc A KZc KC

where  = 0.8

and Fc = fc (KD KH KSc KT)

size factor KZc = 6.3 (dL)-0.13≤ 1.3

d

L

slide7

Glulam arches and cross-bracing

UNBC, Prince George, BC

capacity of a column

material failure

Capacity of a column

FcA

Pr

combination of material failure and buckling

π2EI/L2 (Euler equation)

elastic buckling

Le

slide9

Pin-ended columns in

restroom building

North Cascades Highway, WA

Non-prismatic round columns

Actual pin connections

column buckling factor k c
Column buckling factor KC

1.0

KC

limit

 0.15

CC = Le/d

50

slide11

What is an acceptable l/d ratio ??

Clustered columns

Forest Sciences Centre, UBC

L/d ration of individual columns ~ 30

effective length l eff length of half sine wave k l

P

P

P

P

P

P

P

P

P

P

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

Le

Le

Le

Le

* Sway cases should be treated with frame stability approach

slide13

Glulam and steel trusses

Velodrome, Bordeaux, France

All end connections are assumed to be pin-ended

slide14

Pin connected column base

Note: water damage

l d ratios

Le

Ley

Lex

L/d ratios

y

y

x

x

y

y

d

dx

dy

stud wall
Stud wall

axis of buckling

d

L

ignore sheathing contribution when calculating stud wall resistance

slide22

Fixed or pinned connection ?

Note: bearing block from hard wood

slide23

An interesting connection between column and truss

(combined steel and glulam truss)

slide24

Slightly over-designed truss member

(Architectural features)

effective length sway cases l eff length of half sine wave k l

P

P

P

P

P

P

P

P

P

P

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

Le

Le

Le

Le

Note: Sway cases should only be designed this way when all the columns are equally loaded and all columns contribute equally to the lateral sway resistance of a building

slide27

Sway permitted columns

….or aren’t they ??

slide28

Haunched columns

UNBC, Prince George, BC

frame stability
Frame stability
  • Columns carry axial forces from gravity loads
  • Effective length based on sway-prevented case
  • Sway effects included in applied moments
    • When no applied moments, assume frame to be out-of-plumb by 0.5% drift
    • Applied horizontal forces (wind, earthquake) get amplified
  • Design as beam-column
frame stability p effects

Note: This column does not contribute to the stability of the frame

Frame stability(P- Δ effects)

Htotal = H

 = amplification factor

H = applied hor. load

W

H

Δ

h

Δ = 1st order displacement

slide31

Minimal bracing, combined with roof diaphragm in lateral direction

Haunched frame in longitudinal direction

Sway frame for a small covered road bridge

combined stresses
Combined stresses

Bi-axial bending

Bending and compression

slide33

Heavy timber trusses

Abbotsford arena

slide35

Pf

fa = Pf / A

neutral axis

x

fbx = Mfx / Sx

Mfx

x

y

fby = Mfy / Sy

Mfy

y

fmax = fa + fbx + fby < fdes

( Pf / A ) + ( Mfx /Sx ) + ( Mfy / Sy ) < fdes

(Pf / Afdes) + (Mfx /Sxfdes) + (Mfy / Syfdes) < 1.0

(Pf / Pr) + (Mfx /Mr) + ( Mfy / Mr) < 1.0

The only fly in the pie is that fdes is not the same for the three cases

moment amplification
Moment amplification

P

Δo

Δmax

PE = Euler load

P

interaction equation
Interaction equation

Axial load

Bending about x-axis

Bending about y-axis

slide41

wall and top plate help to distribute loads into studs

joists

top plate

wall plate

d

L

studs

sill plate

check compression perp.