Building Design: Slab Type
The construction cost of slabs is often more than half the cost of structural framing systems, except in extremely tall buildings. Therefore, selection of the slab formwork system deserves considerable attention to minimize cost.
The selection of a formwork system should be made on the basis of the selected floor system that satisfies the structural loading conditions. Floor slabs in concrete buildings are classified into two basic types, based on the load distribution applied on the slab:
1. Two-way slab, in which the rectangularity ratio (slab length/width) is between 1 and 2, and the slab load is transferred to the supporting beams in two directions. Two-way construction includes flat plate, flat slab, waffle slab, and two-way slabs supported by drop beams.
2. One-way slab, in which the rectangularity ratio (slab length/width) is more than 2, and the slab load is transferred to the supporting beams in one direction. One-way construction usually includes solid slabs on beams or walls, one-way joist (ribbed) slabs supported on beams or bearing walls.