Kinked rebar configurations for improving the progressive collapse behaviours of RC frames under middle column removal scenarios

For reinforced concrete (RC) frame structures, applying more continuous longitudinal bars in the beams is the most effective way to improve the progressive collapse resistance. However, an RC frame has the possibility to experience multiple collapse mechanisms. An RC frame may not only experience progressive collapse caused by critical column removal but may also experience lateral collapse under strong earthquakes. The strong column-weak beam (SCWB) requirement in seismic design does not allow excessive longitudinal reinforcement in the beams. To solve this contradiction, a previous study proposed a novel kinked rebar (KB) configuration to enhance both the seismic and progressive collapse resistances of RC frames. This study was carried out to conduct further experimental validation and investigation of progressive collapse behaviours of RC frames with KB configurations. First, a quasi-static progressive collapse test involving 9 RC frame substructures was carried out. The test results indicated that the application of KBs could increase both the loading and deformation capacities under the catenary mechanism of RC substructures. For RC substructures, the influences on progressive collapse behaviours from various structural parameters were also investigated. Second, finite-element simulations were carried out to model the behaviours of the test specimens. This study experimentally verified that the KB configuration can improve the progressive collapse resistances of RC frame structures and clarified the progressive collapse mechanism of novel RC frame substructures with KB configurations.