Cyclic loading behaviors of novel RC beams with kinked rebar configuration

Abstract

Lateral collapses due to earthquakes and progressive collapses due to the sudden destruction of columns are two of the most commonly encountered failure mechanisms for buildings. In a previous study, a novel kinked rebar (KB) configuration was proposed by the authors to simultaneously improve the seismic performance and the progressive collapse resistance of reinforced concrete (RC) frame structures. This configuration works because KB has a weaker initial yielding capacity and larger tensile deformability, and almost the same ultimate tensile capacity compared to ordinary steel rebar. This paper aims to provide further experimental validation and enhance the understanding of the seismic performance of RC beams with KB configurations. First, to overcome the disadvantages of the application of KB found in a previous study, the middle longitudinal bars in an RC beam were proposed to further improve the KB configuration. Second, cyclic loading tests of bare KB specimens were conducted to investigate the hysteresis equivalent stress-equivalent strain curves and failure modes of KB. Third, a cyclic loading test of RC beams with KB was performed. The test results showed that the application of KB could help relocate the plastic hinges to protect the RC column and joint, weaken the yielding loading capacity of the beams to increase the strong column-weak beam (SCWB) ratio, and increase the loading capacity of the beam again at large rotations to maintain a certain lateral load resistance at large deformation of the frame structure. An interesting “two-hinge” behavior was also found in the tests for RC beams with the KB configuration.