Experimental study on the shear performance of RC beams reinforced with welded reinforcement grids

Abstract

The performance of welded reinforcement grids (WRGs) made of smooth rebar, as shear reinforcement for RC beams, was investigated through monotonic and cyclic loading tests, in comparison to conventional bent smooth and deformed stirrups. The influence of the two main differences of the WRG to the conventional bent stirrups, i.e. the low bond stress and the limited strength of weld, on the performance of specimens was analyzed, based on the test observations, load-displacement curves and strain in the shear reinforcement. Test results showed that the WRG-reinforced beams had similar behavior and failure modes to the specimens reinforced with bent smooth stirrups, in both monotonic and cyclic loading tests. However, under cyclic loads, the shear capacity of beams was negatively influenced by the insufficient bond stress between smooth rebar and concrete. To overcome this deficiency, a new type of WRG, with an additional horizontal rebar branch to provide mechanical anchorage, was proposed and its effectiveness was experimentally examined. Finally, modifications were made to an existing formula to predict the contribution of the WRG to the shear capacity, based on the actual strength of weld covered by the concrete, obtained using the an experimental method proposed in this study.