Progressive collapse resistance of RC T-beam cable subassemblages under a middle-column-removal scenario

Abstract

A straightforward method for progressive collapse design has been proposed using relaxed cables underneath reinforced concrete frame beams. In this method, cables are initially relaxed and preset to a specific original length larger than the beam spans. The initially relaxed cables enable the structural behavior to remain unchanged under conventional and seismic loads. However, when the structures are subjected to large deformation under progressive collapse, the cables are tensioned and provide resistance. Previous experimental studies have confirmed the feasibility of the proposed method using beam–column subassemblages. To further investigate the behavior of beams with flanges using the proposed method, six ¼-scale T-beam cable subassemblages with different flange widths were quasi-statically and monotonically loaded to simulate a middle-column-removal situation. The experimental results revealed that the resistance mechanism of the T-beam cable subassemblages consisted of flexural and compressive arch actions, the catenary action, and the cable tension. When using 14-mm diameter cables, the ultimate resistances of the subassemblages with different flange widths improved by 237%–349% compared with those of the subassemblages without cables. Finite element models were developed and validated as having an insight into the responses of the T-beam cable subassemblages with different original cable lengths, flange widths, and slab reinforcement ratios. Numerical results found that the proper original length of the relaxed cables was proven to range from 0.1% to 1.0% larger than the beam span. Based on the experimental and numerical results, the presetting of relaxed cables can be a solid step for the solution of multi-hazard design.