Influence of aggregate size on shear mechanism of reinforced concrete beam subjected to impact load

Abstract

This study presents the influence of aggregate interlock, in terms of aggregate size, on shear mechanism of reinforced concrete beam under a drop-weight impact using a non-linear finite element model. Four aggregate sizes (8-, 16-, 24-, and 32-mm) were used to study the variation of the shear force at the critical section. Large shear force was recorded at the critical section for the specimens with the 32-mm aggregate size regardless of the impact mass and velocity. This is expected since larger aggregates create rougher surfaces and transfer larger shear forces than smaller ones. As the impact mass increased from 868 to 1700 kg, the critical section shear force decreased on average by 5.3%, regardless of aggregate size. Increasing the impact velocity by 41% decreased the critical section shear force by 58%, 56%, 45%, and 41.5% for the 8 mm, 16 mm, 24 mm, and 32 mm aggregate size specimens, respectively. The influence of aggregate size on the shear transfer mechanism was also studied in the presence of shear reinforcement and increased span-to-depth ratio. The difference in shear force at the critical section among the specimens with the different aggregate sizes is negligible in the presence of shear reinforcement indicating that the presence of stirrups reduced the contribution of aggregate interlock in shear resistance. Increasing the span length by 67% (from 3 to 5 m) decreased the effect of aggregate size by 95% on average.