Strengthening of precast RC beam-column connections for progressive collapse mitigation using bolted steel plates

Being one of the most critical scenarios in extreme events such as blast attacks, the progressive collapse of reinforced concrete (RC) structures has attracted the attention of structural engineering community. As precast concrete buildings are deficient in structural continuity, they are more vulnerable to progressive collapse than cast-in-situ RC buildings. Hence, effective rehabilitation techniques to upgrade beam-column joints in existing precast RC buildings for progressive collapse mitigation are needed. The goal of this study is to investigate the effectiveness of using bolted steel plates on the behavior of precast beam-column connections under sudden column-loss scenario. This study presents experiments involving one half-scale precast RC beam-column assembly, which represented the most prevalent types of existing precast beam-column joints in Saudi Arabia. One monolithic test specimen having continuity of top and bottom beam rebars was used for the sake of comparison. Another precast specimen similar to the control one was strengthened using bolted steel plates within the connection region. The progressive collapse scenario was simulated by removing the central column support and applying a sudden vertical load on this column at a rate of 100 mm/s until failure. The collapse load of both monolithic and strengthened specimens was predicted using a simplified section analysis procedure. The analysis was then used for some useful parametric studies in which the effect of different steel plate parameters on the response of test frames under middle column-loss scenario was investigated.