Effects of High-Strength Concrete on Progressive Collapse Resistance of Reinforced Concrete Frame

The application of extreme loads, such as impact and blast, may lead to progressive collapse and the robustness of a structure must be considered in this context. Although extensive studies have been carried out in recent decades to investigate the load-resisting mechanism of RC frames to prevent progressive collapse, the effects of high-strength concrete (HSC) on progressive collapse resistance capacity remain unclear. Therefore, six tests of RC frames with different span-to-depth ratios and concrete strengths were conducted in present study. Among them, three are HSC frames and the others are normal-strength concrete (NSC) frames. It was found that the use of HSC could further enhance the compressive arch action (CAA) capacity, especially for frames with a low span-to-depth ratio. On the other hand, HSC can reduce the tensile catenary action (TCA) capacity at a large deformation stage, primarily because of the higher bond stress between concrete and rebar, leading to earlier fracture of the rebar. The analytical results from the model were compared with the test results. It was found that the refined CAA model could accurately predict the CAA capacity of NSC frames, but not of HSC frames. Moreover, using the existing model it is hard to accurately predict the CAA capacity of frames with relatively small span-to-depth ratios (less than 7). (C) 2020 American Society of Civil Engineers.