Minimum Steel for Reinforced Concrete Slabs

Reinforced concrete slabs are often exposed to rain and radiation from the sun, in addition to normal loads, and hence have to be provided with at least the minimum shrinkage and temperature reinforcement. Shrinkage and temperature reinforcement has traditionally been specified as a certain percentage of the cross-sectional area (about 0.12%-0.18%), which is often empirical. Moreover, this was specified when M20-M25 concrete and reinforcements of Grade Fe 415 were used, which have since been found to be inadequate by practicing engineers. Some researchers have found that the reinforcement prescribed in codes has to be increased considerably to avoid cracks due to shrinkage and temperature effects. Hence, a formula for minimum reinforcement has been developed for slabs, similar to that for beams, which provides consistent safety against collapse due to cracking. It takes into account factors that may affect the behavior of these slabs, such as concrete and steel strength and the ratio of depth to effective depth. (C) 2021 American Society of Civil Engineers.