Effect of construction joint on the shear behavior of reinforced concrete beams

Abstract

Construction joints are inevitable because of different intentional and unplanned factors that interrupt the continuous concrete placing process. Several measures are taken on the construction sites regarding the inclination and location of the construction joints. Since these practices are not based on comprehensive researches, it’s necessary to comparatively investigate the performance of the different types of practices. In this study, the effects of construction joints on the shear capacity of reinforced concrete (RC) beams without shear reinforcement is experimentally studied. Five slender RC beams without shear reinforcements were cast with varying interface type. The experimental program indicated the presence of construction joint highly affects the shear behavior of the RC beam. For the specimen with a vertical construction joint near the mid-span, a shear capacity reduction close to 10% was observed. For the specimen with an interface aligned in the major shear crack direction, the interface dictated the path of the diagonal shear crack. Although there was no significant capacity reduction, the failure type of the beam was much more brittle than the control specimen. Surprisingly, a notable increase of more than 30% in the shear capacity was observed for the specimen with interface placed perpendicular to the direction of the major shear crack. Additionally, due to the disturbance caused by the interface, the beam behaved like a deep beam. This change in the failure mode is believed to be the reason for the increase in the shear capacity of the specimen.