Shear strength of reinforced concrete beams: Concrete volumetric change effects

Abstract

Volumetric changes in concrete may affect the structural performance of reinforced concrete structures and their durability. It has been revealed that autogenous shrinkage of high-strength concrete decreases reinforced concrete beam's shear strength compared with low-shrinkage concrete. High-drying shrinkage of concrete may also decrease the shear strength of reinforced concrete beams using normal-strength concrete. In this study, the effects of drying shrinkage and expansion of normal-strength concrete on the shear strength of reinforced concrete beams with/without stirrups were investigated. Six concrete mix proportions, using different aggregates and admixtures, were used to control concrete volumetric changes. The used concrete showed a large range in volumetric change and high-shrinkage concrete caused shrinkage-induced cracking in the beams before loading. Loading test results showed that drying shrinkage and expansion decreased and increased the shear strength, respectively. The decrease or increase in measured shear strength as a result of volumetric changes was well reproduced by the proposed equation. The equation included the new concept of strain change in tension reinforcement caused by concrete shrinkage or expansion, which was proposed previously for autogenous shrinkage of high-strength concrete.