Seismic performance of reinforced concrete building exterior joints with substandard details

Abstract

Beam-column joints are important components of the seismic-force-resisting system in reinforced concrete (RC) frame buildings. A majority of older buildings have serious structural deficiencies and are substandard according to current seismic design criteria. Failure of beam-column joints with substandard details has caused building collapse during strong earthquakes. This paper evaluates the seismic performance of exterior beam-column joints with three different details of beam reinforcement; no transverse reinforcement was used in the beam-column joints. A total of six RC exterior joints with substandard details were tested under quasi-static cyclic loads and their performance was examined in terms of plastic rotation, joint shear strength and strain, and residual strength. Two levels of column axial compression were investigated and the influence of the axial load level on the performance of the joints is evaluated; in addition, the bond-slip behavior of the bottom beam bars is discussed. Joint shear failure and bond-slip failure were observed. The joint shear strength of the tested subassemblies exceeded the performance criteria stated in ASCE 41 for all test units with joint shear failure; however, joint shear strength was found to be lower than the requirements for Type 2 joints per ACI 352.