360R-06 Design of Slabs-on-Ground
DESIGN OF SLABS-ON-GROUND 360R-71
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| DESIGN OF SLABS-ON-GROUND 360R-71
P r = W slab μ = = 9375 lb/ft Calculate final effective force in P-T tendon (friction and long-term losses). Assume P e = 26,000 lb Calculate the required spacing of the P-T tendons using Eq. (9-2) S ten = = = 0.95 ft or 11.4 in. Use 11 in. to provide more than 250 psi compression. Twelve inch spacing would provide a compression of approxi- mately 230 psi, which may be adequate. Use groups of two cables 22 in. on center (or groups of three at 33 in. on center) The type and magnitude of loading and other service- ability criteria will help determine the final spacing. If there is rack loading with post far apart or other concen- trated loading spaced sufficiently far apart as to not signifi- cantly influence each other, then check with the Westergaard Eq. (6-4) f b = 0.316[ – 4 log( – log(k) + 6.48] where f b = tensile stresses at the bottom of the concrete slab; P = concentrated load; h = slab thickness; a = radius of a equivalent circular load contact area; and k = modulus of subgrade reaction. Assume: P = 15,000 lb; h = 6 in.; a = 4.5 in. (base plate 8 x 8 in.); k = 150 lb/in. 3 ; and f b = 545 psi. Cracking of concrete: 7.5 × = 474 psi P-T to provide necessary precompression of: 545 – 474 = 71 psi P-T providing 250 psi is adequate. In the case of two or more placements post-tensioned together across the joint and creating a continuous slab, the following guidance can be used: Case 1: Multiple (12) strips 30 ft wide post-tensioned tải về 2.35 Mb. Chia sẻ với bạn bè của bạn:
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