Two-Way Flat Slab

A flat slab structural system consists of a constant thickness of concrete slab with drop panels at the columns locations (see Fig­ure 5.2b). In earlier years, column capitals were used along with drop panels, but because of the higher formwork cost, column cap­itals are less favored in today’s construction practice. Flat slabs are used to resist heavier loads and longer spans than flat plates. Generally, the system is most suitable for square or nearly square panels.

Waffle Slab

Waffle slab construction is shown in Figure 5.2c. It consists of rows of concrete joists at right angles to solid heads at the columns. Waffle slabs can be used for spans up to about 50 ft (15.2 m), and they are used to obtain an attractive ceiling.