Experimental investigation of progressive collapse resistance of one-way reinforced concrete beam–slab substructures under a middle-column-removal scenario

Abstract

Floor systems composed of beams and slabs are critical structural elements of frame structures to resist progressive collapse. Previous experimental studies have focused mainly on beam–column or continuous-beam substructures and have ignored the influence of the slab. To study the progressive collapse-resisting mechanisms of reinforced concrete (RC) floor systems, seven 1/3-scaled one-way substructure specimens, including five beam–slab specimens and two continuous-beam specimens without slabs, were tested under a middle-column-removal scenario. The effects of various structural parameters, including sectional dimensions (beam height, slab width, and slab thickness) and seismic reinforcement, on the progressive collapse resistance were studied by analyzing material strains and load–displacement curves. Under small deformations, the progressive collapse resistance was largely affected by the beam height, slab width and seismic reinforcement in the beams. However, the effect of the slab width, upon exceeding the effective flange width, became insignificant. Note that increasing the slab thickness simultaneously increased the amount of slab reinforcement according to the minimum requirement of reinforcement ratio for slabs, such an increase will in turn enhanced the progressive collapse resistance. In addition, the existence of the slab led to an over-reinforced damage in the compressive zones of the beam ends, which accelerated the bending failure and the presence of the catenary action of the specimens. Under large deformations, the progressive collapse resistance was mainly influenced by the reinforcement area of the entire beam–slab section. The total reinforcement area of a beam–slab substructure designed to meet a higher seismic requirement was not significantly increased, and consequently, the progressive collapse resistance of the substructure under the catenary mechanism was not notably improved. This finding stands in stark contrast to those of previous tests of beam–column specimens without slabs.