Progressive collapse resistance of exterior reinforced concrete frames and simplified method for catenary action

This paper investigated the progressive collapse resistance of exterior reinforced concrete frames under middle column removal scenarios. Five half-scale exterior frames comprising of a double-span beam, a middle beam-column joint and two side columns were tested under a concentrated point load on the middle joint. Different joint links and reinforcement ratios in beams and column sizes were used in frames. The resistances, deformation capacities and failure modes of frames were experimentally obtained. Test results showed that catenary action in bridging beams resulted in flexural failure of side columns, and thus the load capacity of frames depended highly on the moment capacity of column sections. A simplified method was also proposed based on the moment capacity of column sections and the axial force-bending moment interaction diagram of beams. The axial tension force in beams and the associated catenary action capacity were calculated by using the proposed method. Comparisons with test data suggest that the simplified method could predict the load capacity and tension force in beams under catenary action with reasonably good accuracy.