Analytical and experimental evaluation of progressive collapse resistance of reinforced concrete structures

Experimental and analytical studies are carried out on three full-scale actual reinforced concrete (RC) buildings to characterize system level resisting mechanisms against progressive collapse following an initial local damage. The results obtained from the analytical models are verified with the experimental data and important modeling issues, assumptions, and requirements for structural elements as well as infill walls are identified and discussed. In order to evaluate the effects of initial damage location on progressive collapse of structures, a seven-story RC building structure is designed. Using an analytical model of the structure based on the knowledge gained in this study, the structure is analyzed under 15 different initial damage scenarios.;None of the experimentally evaluated structures experienced full or partial collapse. Vierendeel frame action is found to be the dominant progressive collapse resisting mechanism following element removal in all evaluated structures. The seven-story building designed in this study is found to be susceptible to collapse under the initial damage scenario of top floor corner column removal and top floor middle column removal on its short edge. The capability of the structure to develop Vierendeel Frame Action is crucial in resisting progressive collapse. Structures are less susceptible to collapse if there are at least two floors (and connecting columns) above the removed column such that Vierendeel frame action can effectively develop. Vierendeel frame action can be characterized by double curvature deformations of beams, slabs, and columns. Such a deformed shape provides shear forces in beams and slabs required to redistribute gravity loads following column removal. The direction of bending moments in the elements in the vicinity of the removed column changes after column removal. A potential brittle failure mechanism is identified and described which can develop due to insufficient reinforcement and the change in the moment direction. It is shown that axial compressive force develops in beams and slabs due to their growth at small displacements. This axial force enhances the flexural capacities of floor elements (beams and slabs) and in turn improves the performance of the Vierendeel frame action considerably. In the building structures discussed above, the level of displacements and deformations were not large enough to develop Catenary action.;In order to study Catenary action response in RC structures, progressive collapse resistance of a scaled two-dimensional frame structure is studied experimentally and analytically. The frame experienced small deformations and resisted collapse after being subjected a column removal on its first floor. Following this test, the frame was also subjected to monotonically increasing displacement at the top of the removed column to further study the resisting mechanism(s). The Catenary action was observed experimentally and evaluated analytically.