Experimental Study on Interfacial Shear Performance of RC Beams Added to Existing RC Columns

Abstract

The primary objectives of this study were to experimentally investigate the shear characteristicsof the interface between an existing RC column and a reinforced concrete (RC) beam added to the existing RC column, and to propose a formula for estimating the shear capacity of the beam-column interface. The major test variables consisted of concrete strength, added steel reinforcement ratio and shear span to depth ratio. Failure characteristics, displacements at the loading point, slips of the beam-column interface, and shear capacities of the beam-column interface were analyzed. Test results indicate that both the shear capacity of the beam-column interface and the corresponding interfacial slip increased with a decrease in shear span to depth ratio. In addition, as concrete strength grew, the shear capacity of the beam-column interface increased, but the interfacial slip corresponding to the interfacial shear capacity remained almost unchanged. Moreover, both the shear capacity of the beam-column interface and the corresponding interfacial slip increased with an increase in the longitudinal steel reinforcement ratio of the added RC beam. A formula for predicting the shear capacity of the beam-column interface was developed. The test results validate the proposed formula and provide important guidance for the design of the RC beam added to the existing RC column.