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Design of Columns and Beam-Columns in Timber Slide 2 Column failures Material failure (crushing) Elastic buckling (Euler) Inelastic buckling (combination of buckling and material failure) P P L eff Slide 3 Truss compression members Fraser Bridge, Quesnel Slide 4 Column behaviour Displacement (mm) Axial load P (kN) P cr P P Perfectly straight and elastic column Crooked elastic column Crooked column with material failure L eff Slide 5 Pin-ended struts Shadbolt Centre, Burnaby Slide 6 Column design equation P r = F c A K Zc K C where = 0.8 and F c = f c (K D K H K Sc K T ) size factor K Zc = 6.3 (dL) -0.13 1.3 d L axis of buckling P Slide 7 Glulam arches and cross-bracing UNBC, Prince George, BC Slide 8 Capacity of a column LeLe PrPr combination of material failure and buckling elastic buckling material failure FcA FcA 2 EI/L 2 (Euler equation) Slide 9 Pin-ended columns in restroom building North Cascades Highway, WA Actual pin connections Non-prismatic round columns Slide 10 Column buckling factor K C C C = L e /d KCKC 1.0 50 limit 0.15 Slide 11 What is an acceptable l/d ratio ?? Clustered columns Forest Sciences Centre, UBC L/d ration of individual columns ~ 30 Slide 12 Effective length L eff = length of half sine-wave = k L k (theory)1.00.50.7> 1 k (design)1.00.650.8> 1 non-sway sway* P PP PP P PPPP LeLe LeLe LeLe LeLe * Sway cases should be treated with frame stability approach Slide 13 Glulam and steel trusses Velodrome, Bordeaux, France All end connections are assumed to be pin-ended Slide 14 Pin connected column base Note: water damage Slide 15 Column base: fixed or pin connected ?? Slide 16 Effective length L ex L ey Slide 17 Round poles in a marine structure Slide 18 Partially braced columns in a post- and-beam structure FERIC Building, Vancouver, BC Slide 19 L/d ratios LeLe L ey L ex d dydy dxdx x x y y y y Slide 20 Stud wall axis of buckling d L ignore sheathing contribution when calculating stud wall resistance Slide 21 Stud wall construction Slide 22 Fixed or pinned connection ? Note: bearing block from hard wood Slide 23 An interesting connection between column and truss (combined steel and glulam truss) Slide 24 Slightly over-designed truss member (Architectural features) Slide 25 Effective length (sway cases) L eff = length of half sine-wave = k L k (theory)1.02.0 1.0