Strengthening and Retrofitting of RC Flat Slabs to Mitigate Progressive Collapse by Externally Bonded CFRP Laminates

Previous studies indicated that RC flat slabs, especially without drop panels, are of high vulnerability to progressive collapse because no beams could assist in redistributing the axial force previously carried by the lost columns. In order to reduce the likelihood of progressive collapse, necessary strengthening schemes should be applied. Six specimens of similar dimensions and reinforcement details were prepared, two of which were unstrengthened and served as control specimens, while the remaining four were strengthened with two different schemes: orthogonally (Scheme 1) or diagonally (Scheme 2) bonded carbon-fiber-reinforced polymer (CFRP) laminates on the top surface of the slab. The progressive collapse performance of the strengthened specimens was studied in terms of their load-displacement relationships, first peak strength, initial stiffness, and energy dissipation capacities. The dynamic ultimate strength and corresponding dynamic effects of flat slabs after the sudden removal of a corner column was also discussed due to the dynamic nature of progressive collapse. Test results indicated that both schemes were effective in improving the performance of RC flat slabs in resisting progressive collapse.