1. Engineering with Wood Presenters: David W. Boehm, P.E. Gary Sweeny, P.E. Gary Sweeny, P.E. Shear Walls and Diaphragms Why Buildings Don’t Fall Over

17. Plan View

19. Assume seismic load is also 200 plf

20. v eu l = 120’ DIAPHRAGM UNIT SHEARS w ew = 200#/FT b=40’ w ns = 200#/FT v ns = w ns x l 200 x 120 2 x 40 300 #/FT== v ns v ew = w ew x b 200 x 40 2 x 120 33 #/FT== 2 x l 2 x b

22. PANEL LAYOUT AND FASTENER SCHEDULE North-South Loading Case 1v = 300 #/FT Assume8 d nails 15/32 plywood 2” nominal framing Choose:Blocked Diaphragm 8 d nails @ 4” panel edges 8 d nails @ 6” interior East-West Loading Case 3v = 33 #/FT Unblocked 6” max spacing at panel edges

24. DIAPHRAGM CHORD SIZE Moment due to N-S wind m = w l 2 = 200 120 2 = 360,000 FT-LBS 8 8 Axial load in chords = C = T = M = 360,000 ft-lbs = 9,000 LBS b 40 ft Assume allowable ft = 1150 psi Area required = 9,000# = 7.8 in 2 Assume 2 x 8 wall plate, bolted Area of 2 x 8 with bolt hole A = 1.5 x (7.25 -.875) = 9.56 in 2 Use double 2 x 8 top plate / chord to allow for splice 1150 psi

25. Diaphragm layout

27. Shear Walls North wallv=33 #/ft North wallv=33 #/ft Nominal nailing required Nominal nailing required East and west walls v=300 #/ft East and west walls v=300 #/ft 20’ Shear wall elevationNailing pattern 7/16 sheathing 2 x studs 8d nails @ 4” required A 40’ TC V ns = 300#/ft(40’) = 12000#

29. Tiedown Force ΣM A = 0 0 = (12000 x 20) – (T x 40) T = 6,000#

31. WALL DESIGN WITH OPENINGS

32. DRAG STRUT / COLLECTOR FORCE

33. OVERTURNING FORCE