Influence of longitudinal reinforcement strength on one-way slab deflection

Abstract

The CSA A23.3 standard for reinforced concrete design provides both an implicit check of deflection control based on minimum member thickness requirements and a direct computation method for deflection. This paper reports on an analytical study that compared maximum span-to-depth ratios from the implicit deflection provisions against ratios determined from direct deflection calculations. Emphasis was placed on the deflection performance of lightly reinforced one-way slabs, including those with high-strength steel reinforcement. The results indicated that maximum span-to-depth ratios should decrease as the span length increases, as the design load increases or as the cracking moment decreases. In contrast to the current implicit provisions, the design strength of the longitudinal reinforcement did not have a significant effect on the minimum slab thickness required to satisfy common deflection criterion. Design aids were proposed, with implications for design presented through a case study of a multispan one-way slab system.