Title: Improved Shear Reinforcement for Footings— Punching Strength inside Shear-Reinforced Zone

Author(s): Dominik Kueres, Marcus Ricker, and Josef Hegger

Publication: Structural Journal

Volume: 114

Issue: 6

Appears on pages(s): 1445-1456

Keywords: column perimeter-depth ratio; footings; inclined punching shear reinforcement; punching shear; reinforced concrete; shear span-depth ratio

DOI: 10.14359/51689499

Date: 11/1/2017

Abstract:
Due to a smaller shear span-depth ratio and soil-structure interaction, footings and ground slabs achieve significantly higher punching shear capacities than flat plates. Because the inclination of shear cracks is steeper in footings, punching shear reinforcement elements with inclined bars seem to be more efficient than vertical bars. On the basis of previous experimental investigations on footings with punching shear reinforcement, a new punching shear reinforcement element with inclined bars was developed. To evaluate the efficiency of the punching shear reinforcement element, seven tests on reinforced concrete footings with uniform soil pressure and a failure within the shear-reinforced zone were conducted. The tests were planned considering the results of a previous systematic test series on reinforced concrete footings without and with stirrups as punching shear reinforcement. The main parameters investigated in the present test series were the shear span-depth ratio, the ratio of column perimeter and effective depth, the number and layout of punching shear reinforcement elements, and the effect of longitudinal reinforcement at the compression side. The comparison of the results of the new test series with the previous test series proves a significant increase in punching shear capacity with the newly developed punching shear reinforcement.