Effects of shear reinforcement on the impact behavior of reinforced concrete slabs

Abstract

Design of reinforced concrete (RC) members against impact loads is required for many structures such as industrial facilities, military protective structures, and infrastructures. This study presents experimental investigation for strengthening RC slabs under impact loads using shear reinforcement. Slabs were strengthened against punching shear with two methods: using shear studs as shear reinforcement and using steel fiber reinforced concrete (SFRC) instead of plain concrete. Eight RC slabs with dimensions of 2150x2150x150 mm were tested. Four of the specimens, two identical pairs, were cast with shear studs around the point of impact. Remaining four specimens, again two identical pairs, were cast with 1% steel fibers. Pairs in each group contained two different levels of longitudinal reinforcement. For each pair, one specimen was tested under static loading, whereas its identical twin was tested under impact loads. Specimens were tested with a test setup that provides simply supported conditions. Support loads, displacements, accelerations, and strains on bars were measured during the tests. The study revealed that using shear studs and SFRC prevents brittle punching shear failure for both static and impact loading. Specimens with steel fibers reached the highest load carrying capacity for static test while specimens with shear reinforcement carried a smaller load for large deformations. Specimens with SFRC displayed a close to static behavior under impact loading, influenced only slightly by inertial forces due to impact. Specimens with shear studs were largely influenced by inertial forces and scabbing occurred at some areas. Specimens with steel fibers endured more impacts compared to control specimens and specimens with shear studs due to their higher energy dissipating capabilities.