Shear behavior of reinforced concrete beam with local enhancement in compression zone

Abstract

The stress conditions and material properties of the compression zone of reinforced concrete (RC) beam significantly influence the shear behavior. Using the highperformance engineered cementitious composite (ECC) to locally replace the compression zone concrete is a new pilot standpoint to enhance the shear performance of RC beams. Four full-scale RC beams are designed to investigate the effects of compression zone ECC on the shear behaviors of RC beams without and with stirrups. To accurately and directly obtain the shear contributions of stirrups and concrete, large numbers of strain gauges are installed inside each stirrup, rather than on the surface, aiming to eliminate the strain measurement error caused by the bond-slip effect. Digital image correlation (DIC) is adopted to monitor the strain fields of a concrete beam, based on which the flexural and shear deflections can be decoupled. The results indicate that the ECC changes the failure process of EC beams. For RC beams without stirrups, the inclusion of ECC increases the shear strength and deflection by 92.0% and 97.3%, respectively, and these two values are 5.2% and 26.8% for beams with stirrups. For beams with stirrups, from the occurrence of the critical diagonal crack to shear failure, the contribution of concrete of conventional RC beam decreases monotonically. However, for the beam with ECC, this component decreases first and increases again. Two methods are utilized to decouple the flexural and shear deflections, and the results matches well with each other. Some existing typical design codes cannot accurately predict the contribution of concrete and stirrups.