Strengthening of Multibay Reinforced Concrete Flat Slabs to Mitigate Progressive Collapse

Abstract

Unable to generate sufficient ductility and continuity, RC flat slab structures are vulnerable to progressive collapse, in which the relatively brittle failure mechanism attributable to punching shear failure may lead to catastrophic consequences. Thus, it is necessary to evaluate the effectiveness of approaches for improving the ability of flat slabs to mitigate progressive collapse. Previous studies have indicated that integrity reinforcement may enhance the behavior, particularly postpunching behavior, of newly designed flat slab structures. However, limited tests have been conducted to determine reliable approaches for strengthening existing flat slab structures to resist progressive collapse. In this study, a series of seven multibay flat slab substructures were cast and tested to assess the effectiveness of proposed glass fiber-reinforced polymer (GFRP) strengthening schemes for improving the progressive collapse behavior of existing flat slab structures, owing to its low density, high strength, rigidity, and excellent resistance to corrosion. Three specimens without strengthening were used as control specimens and the remaining four specimens were strengthened by GFRP strips. Test results indicated that proposed strengthening schemes effectively improved the initial stiffness and flexural resistance of flat slab structures. However, they did not sufficiently enhance the postfailure resistance and deformation capacity: there was significant debonding of the GFRP strips from the concrete interface in the large displacement stage, even when specially designed fiber anchors were employed.