Seismic retrofit of deficient exterior RC beam-column joints using steel plates and angles

Abstract

This paper proposes a simple and practical method for retrofitting deficient (non-seismic detailed) exterior beam-column joints based on fixing steel plates and angles around the joint with different configurations. Six half-scale exterior RC beam-column joints were tested under quasi-static cyclic loading with a constant axial load on the column. The experimental program included two control specimens representing code-detailed and deficient joints in addition to four retrofitted specimens. The proposed retrofit methods were designed to compensate the lack of joint transverse reinforcement using different steel arrangements (X-shape, horizontal plates) and the short development length of beam bars using angles tied by external or internal anchors. One of the retrofit methods is applicable in the presence of a transverse beam. The test results showed that the deficient joint exhibited brittle joint shear failure, unlike the code-detailed joint which failed by flexure in the beam. The proposed retrofitting methods effectively prevented the brittle joint shear failure and increased the joint strength, ductility, stiffness, and energy dissipation. A softened strut and tie model was applied and modified to predict the joint shear strength of control and retrofitted joints and it showed a good agreement when compared with the experimental results.