Experimental and theoretical analyses of the progressive collapse resistance of NSM strengthening RC frames after the failure of a corner column

When exposed to accidental loads, reinforced concrete (RC) frames are vulnerable to progressive collapse after the failure of a corner column, so necessary strengthening schemes should be employed for the frame. By strengthening the slab with near-surface-mounted (NSM) glass fiber-reinforced polymer (GFRP) bars and engineered cementitious composites (ECC) layer, this study experimentally revealed the effect of the strengthening method on the progressive collapse behavior of beam-slab systems after the removal of a corner column. Then, on the basis of experimental results, a theoretical analysis method of the peak capacity for the beam-slab system is proposed according to the principle of virtual work and the yield-line theory. The derived formula can accurately predict the progressive collapse resistance of the RC beam-slab system after the failure of a corner column and quantitatively evaluate the contribution of floor slabs to the structural capacity. The validity of the method is also proven by the application to the structural capacity of a flat-slab system and a beam-column system. Finally, according to the theoretical formula, the influence of several parameters on the structural capacity is investigated, such as the earthquake fortification intensity of the frame, the over-strength factors, the column spacing, and the depth-to-span ratio of the beam. The research results demonstrate that after considering the L-beam action, the capacities of the test specimens can be improved by 52%–65%. The capacity of the flat-slab system is the lowest among the above three structural systems. The structural progressive collapse resistance can be effectively improved through enhancing the constraint stiffness of the corner beam-column joint and utilizing building materials with high plastic development ability. •The effect of NSM GFRP bars and ECC layer on the enhancement of collapse resistance is explored.•A theoretical method of peak capacity under corner column-removal scenario is proposed and validated.•Up to 65% enhancement of peak capacity after considering the L-beam action is revealed.•Measures of enhancing the progressive collapse resistance after removing a corner column are analyzed.