TwoWay PostTensioned Design The Portland （TwoWay PostTensioned设计波特兰）.pdf

TIME SAVING DESIGN AIDS Page 1 of 9 Two-Way Post-Tensioned Design The following example illustrates the design methods presented in ACI 318-05 and IBC 2003. Unless otherwise noted, all referenced table, figure, and equation numbers are from these books. The example presented here is for Two-Way Post-Tensioned Design. Loads: Framing Dead Load = selfweight Superrimposed Dead Load = 25 psf partitions, M/E, misc. Live Load = 40 psf residential 2 hour fire-rating Materials: Concrete: Normal weight 150 pcf fc = 5,000 psi fci = 3,000 psi Rebar: fy = 60,000 psi PT: Unbonded tendons 1/2”ϕ, 7-wire strands, A = 0.153 in2 f = 270 ksi pu Estimated prestress losses = 15 ksi (ACI 18.6) fse = 0.7 (270 ksi) - 15 ksi = 174 ksi (ACI 18.5.1) Peff = A*fse = (0.153)(174 ksi) = 26.6 kips/tendon Determine Preliminary Slab Thickness Start with L/h = 45 Longest span = 30 ft h = (30 ft)(12)/45 = 8.0” preliminary slab thickness Loading DL = Selfweight = (8in)(150 pcf) = 100 psf SIDL = 25 psf LLo = 40 psf IBC 1607.9.1 allows for LL reduction Exterior bay: AT = (25 ft)(27 ft) = 675 ft2 K = 1 LL LL = 0.83 LLo = 33 psf Interior bay: AT = (25 ft)(30 ft) = 750 ft2 K = 1 LL LL = 0.80 LLo = 32 psf TIME SAVING DESIGN AIDS Page 2 of 9 Two-Way Post-Tensioned Design DESIGN OF EAST-WEST INTERIO