360R-06 Design of Slabs-on-Ground
DESIGN OF SLABS-ON-GROUND
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| DESIGN OF SLABS-ON-GROUND
360R-57 DESIGN DETAILS • Calculate the slab thickness, and consider thickening slab edges in terms of load-carrying ability and slab restraint. • Where random cracking is acceptable, specify distributed reinforcement in the upper half of the slab to minimize or eliminate sawcut contraction joints. Shrinkage reinforcement is not needed in the bottom half of slabs- on-ground. • If reinforcement is used, select practical spacings and diameters of wires and bars, considering at least 14 in. (350 mm) spacing and 3/8 in. (9 mm) diameter. • Consider square, diamond-plate, or rectangular-plate dowel systems that eliminate restraint longitudinally and transversely while transferring vertical load. • Eliminate as many slab restraints as possible, and isolate those that remain. • Specify largest practical size of base plate for rack posts. Include the base plate size in the slab thickness design process (baseplate thickness must be adequate to distribute post load over area of plate). • Consider shrinkage-compensating concrete or post- tensioning as design options. CONTROL OF CONCRETE MIXTURE • Specify workable concrete with the largest practical maximum size of coarse aggregate and with aggregate gap-grading minimized. • Specify concrete design strength and the age at which it is to be achieved. Consider using 60- or 90-day strengths in slab thickness design to permit the use of concrete with lower shrinkage than could be obtained with the same compressive strength at 28 days. Use lowest compressive strength and corresponding minimum cement content feasible; use mineral or metallic hardener or topping if surface durability is a concern. • Before slab installation, consider shrinkage testing of various cements (mortars), aggregate gradations, and concrete mixtures. • Specify the cement type and brand. • Consider a daily check of aggregate gradation to ensure uniform water demand and shrinkage of concrete. • Consider plant inspection to perform the aforemen- tioned testing and to monitor batching for uniformity (refer to ACI 311.5 for guidance). tải về 2.35 Mb. Chia sẻ với bạn bè của bạn:
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