1 / 41

Design of Columns and Beam-Columns in Timber

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.

phillip-tassos
Download Presentation

Design of Columns and Beam-Columns in Timber

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. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Design of Columns and Beam-Columns in Timber

  2. Column failures • Material failure (crushing) • Elastic buckling (Euler) • Inelastic buckling (combination of buckling and material failure) P Leff Δ P

  3. Truss compression members Fraser Bridge, Quesnel

  4. 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)

  5. Pin-ended struts Shadbolt Centre, Burnaby

  6. 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

  7. Glulam arches and cross-bracing UNBC, Prince George, BC

  8. material failure Capacity of a column FcA Pr combination of material failure and buckling π2EI/L2 (Euler equation) elastic buckling Le

  9. Pin-ended columns in restroom building North Cascades Highway, WA Non-prismatic round columns Actual pin connections

  10. Column buckling factor KC 1.0 KC limit  0.15 CC = Le/d 50

  11. What is an acceptable l/d ratio ?? Clustered columns Forest Sciences Centre, UBC L/d ration of individual columns ~ 30

  12. 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

  13. Glulam and steel trusses Velodrome, Bordeaux, France All end connections are assumed to be pin-ended

  14. Pin connected column base Note: water damage

  15. Column base: fixed or pin connected ??

  16. Ley Lex Effective length

  17. Round poles in a marine structure

  18. Partially braced columns in a post-and-beam structure FERIC Building, Vancouver, BC

  19. Le Ley Lex L/d ratios y y x x y y d dx dy

  20. Stud wall axis of buckling d L ignore sheathing contribution when calculating stud wall resistance

  21. Stud wall construction

  22. Fixed or pinned connection ? Note: bearing block from hard wood

  23. An interesting connection between column and truss (combined steel and glulam truss)

  24. Slightly over-designed truss member (Architectural features)

  25. 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

  26. Sway frame for a small covered road bridge

  27. Sway permitted columns ….or aren’t they ??

  28. Haunched columns UNBC, Prince George, BC

  29. 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

  30. 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

  31. Minimal bracing, combined with roof diaphragm in lateral direction Haunched frame in longitudinal direction Sway frame for a small covered road bridge

  32. Combined stresses Bi-axial bending Bending and compression

  33. Heavy timber trusses Abbotsford arena

  34. Roundhouse Lodge, Whistler Mountain

  35. 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

  36. Moment amplification P Δo Δmax PE = Euler load P

  37. Interaction equation Axial load Bending about x-axis Bending about y-axis

  38. 3 storey walk-up (woodframe construction)

  39. New Forestry Building, UBC, Vancouver

  40. Stud wall construction

  41. wall and top plate help to distribute loads into studs joists top plate wall plate d L studs sill plate check compression perp.

More Related