Collapse resistance of composite framed-structures considering effects of slab boundary restraints

Abstract

This paper analytically deals with the collapse resistance of composite framed-structures considering effects of slab boundary restraints. The collapse resistance of composite framed-structures due to different interior-edge (IE) column losses are investigated. The IE columns refer to the interior columns directly adjacent to the exterior columns, among which those nearest to corner columns are defined as interior-edge-corner (IEC) columns and the rests are interior-edge-intermediate (IEI) columns. The responses of main structural members including reinforced concrete slabs, steel beams and steel columns at large deflections are fully accounted for. The collapse resistance of composite framed-structures for a general interior (GI) column loss scenario has been previously studied. Three contributions to internal energy dissipations were considered, including the elongations of rebar and steel beams, the tensile force-induced additional bending moments, and the bending moments along yield lines of the slab. For IE column loss scenarios, however, besides the original three energy dissipations, contributions due to the deformation of the peripheral beams and edge columns are included. The detrimental effect of the lateral displacement at the top of edge columns on the energy dissipations due to the elongation of rebar and steel beams is also accounted for. The reasonability and reliability of the analytical method are verified against validated numerical analyses. The resistance-displacement curves of structures due to IEI and IEC column losses are compared. It is confirmed that for the IEC column loss scenario, a structure has the least progressive collapse resistance due to its weakest boundary conditions. Due to the existence of the concrete slab, the differences between the progressive collapse resistance of structures for IEI and IEC column loss scenarios are mitigated.