Reinforced concrete beam-columns anchored with headed bars subjected to reversed cyclic loading: Experimental and numerical investigation

Past seismic events have shown poor performance of reinforced concrete (RC) moment resisting frames, due to failure of beam-column joints, attributed to insufficient anchorage and poor workmanship. Inadequate development length in beam-column joints may lead to joint strength deterioration due to detailing constraints and site errors. Alternatively, headed bars have potential to replace conventional anchorage system of development length in beam-column joint. The paper deals with extensive experimental and numerical program conducted on RC beam-column joints with plain and deformed (grooved and ribbed) headed bars and compared with the specimens with conventional development length. Effect of steel fibers on strength of RC beam-column joints is also investigated. The test specimens of beam-column joints were subjected to displacement-controlled reversed cyclic loading and structural behavior was assessed in terms of failure mode, load carrying capacity, stiffness, drift, ductility, and energy dissipation. The strength parameters of headed bar specimens were well comparable to that of conventional specimens. Grooved-headed and ribbed-headed bar specimens exhibited superior load resistance as compared with plain-headed bar specimens. Numerical analysis was carried out, whose results were in agreement with the experimental results, thus demonstrating the efficacy of headed bars as mechanical anchorage system for RC beam-column joints.