Experimental investigation and numerical simulation on progressive collapse resistance of RC frame structures considering beam flange effects

Abstract

In this paper, five 1/4-scaled reinforced concrete (RC) substructural specimens were tested under a middle-column-removal scenario to study the progressive collapse-resisting mechanisms of RC floor systems. This experimental set up includes two reinforced concrete beam-column subassemblies with different kinds of joints and three T-beam-column subassemblies with different beam flange widths. Test results indicated that the existence of a beam flange could obviously enhance the resistance of a specimen. Meanwhile, we also examined the splice length of the bottom bars in beams at the middle joint, as required in Chinese code specifications, designed to meet continuity requirements in progressive collapse-resistant design. Based on the compressive arch action (CAA) and catenary action observed in the tests, a simplified model was proposed and verified by calculating the nonlinear static load-deflection responses of RC two-span beams. Numerical simulation results indicated that the axial restraint of the beam had a significant positive effect on the progressive collapse resistance capacity in a beam-column subassembly; however, the capacity would remain unchanged when the ratio of the axial restraint stiffness to the axial stiffness of the beam exceeded 10. Meanwhile, the progressive collapse resistance capacity of a beam-column subassembly decreased with the increase of the span-to-height ratio.