Structural behavior of reinforced concrete frames subjected to progressive collapse

This paper presents an experimental program on structural behavior of four reinforced concrete frames under column removal scenarios, simulating progressive collapse. The specimens were designed with conventional non-seismic and seismic detailing in terms of stirrup arrangement and different boundary conditions. Each specimen, consisting of a two-bay beam, a middle joint, and two side columns, was quasi-statically tested by increasing the beam deflection until the complete failure. The load-deflection relationships show the sequential mobilization of compressive arch action and catenary action in the beams. Test results indicate that beam-column connections are the most critical components in developing catenary action, and confirmed the concern in current engineering practice that the longitudinal reinforcement in beams may fail to function as effective ties due to fracture of bars under large rotations. The bar fracture was ascribed to local rotations at the connections heavily dependent on the development of fixed-end rotation.