State-of-the-art Review of Seismic Behavior of Deficient and Retrofitted Reinforced Concrete Beam Column Joints

Beam-column joint is considered a critical region in a structure when subjected to seismic load. Past earthquakes have shown that many of these structures behaved poorly and exhibited a combination of brittle failure at the joint and pullout of the beam longitudinal steel, leading to a rapid degradation of the joint and a precursor to a catastrophic collapse of a structure. Review of existing structures built prior to 1976 have determined concrete joints typically have little or no transverse reinforcement, discontinuous bottom beam reinforcement with insufficient embedment depth, and a common occurrence of column lap splice above the beam-column interface. Previous studies of rebar bond slip behavior, joint shear response, and joint interface -- shear response were reviewed culminating in a study of various joint models simulating the behavior of deficient concrete beam-column joint subjected to a seismic load.;An experimental test program consisting of three specimens was developed to test the behavior of deficient concrete beam-column joints. Specimen AB1 consists of deficient shear reinforcement at the joint, and will be tested to evaluate the behavior of a deficient reinforced concrete beam-column joint solely on insufficient shear reinforcement. Specimen AB2 is designed according to pre-1976 building standard and lacks sufficient rebar embedment of longitudinal beam reinforcement at the joint and has no shear reinforcement within the joint area. Specimen ACI318 is designed per the specifications of ACI 318-08, and will be used as the control specimen. Experimental results of the test program will eventually be applied as a baseline comparison to proposed state-of-the-art retrofit schemes aimed at enhancing the overall seismic performance of deficient reinforced concrete beam-column joints.