Collapse resistance of RC beam–slab subassemblies due to column loss at large deflections

This paper proposes an energy-based method to theoretically determine the collapse resistance of reinforced-concrete (RC) beam–slab subassemblies subject to a middle column loss at large deflection. It considers the contributions to internal energy dissipation due to extension of rebar in the slab and beams, the additional resultant bending moment from membrane forces in the slab and catenary tensile forces in beams, and the sectional bending moment at plastic hinges of beams and along yield lines of slabs. Furthermore, the effect of tensile forces on the sectional bending moment of the slab and beams is also accounted for. The effectiveness and accuracy of the proposed method are validated against available test results. The proposed method is found to produce accurate predictions on the collapse resistance of the subassemblies, as well as capture the main feature of mechanism of the subassembly at large deflections. It is concluded that the energy dissipation due to the extension of rebar and additional resultant bending moment significantly contribute to the resistance of subassemblies at large deflections. The interaction between membrane forces and bending moment of the beam and slab sections has a detrimental effect on the collapse resistance. Neglecting this effect will overestimate the collapse resistance for the subassembly.