Two-Way Solid Flat Slab Design
Traditionally, the term “flat slab” has represented a solid uniform depth slab with thicker drop panels supported upon “mushroom head” conical capitals with round columns or various prismatic brackets with square columns. Early codes distinguished between four-way reinforcement and two-way reinforcement systems. The four-way system, intricate by today’s standards, was soon abandoned because of the excessive field labor required, particularly with the truss bar systems popular then. Also, effective depth was sacrificed when four layers of the reinforcement intersected at the columns. As forming costs increased, most flat slab design eliminated either the drop panels or the capitals and brackets. Today, the flat plate form is preferred for light loads and short spans; the flat slab with capitals and brackets only, in heavy duty designs where few partitions are used; and the flat slab with drop panels only, for heavy duty design with or without partitions. Edge beams can be used with all three forms of the solid flat slab, but they are usually avoided where not structurally required to avoid the added forming expense. The waffle flat slab (Chapter 7) extends both the span and load limits without excessive dead weight.
KeywordsLive Load Slab Thickness Factor Moment Flat Slab Edge Beam
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