Experimental Study of the Seismic Behavior of Predamaged Reinforced-Concrete Columns Retrofitted with Basalt Fiber–Reinforced Polymer

Abstract

Reinforced concrete (RC) frame structures are widely used in earthquake regions, and damage to these structures has been reported after many earthquakes. Small parts of seriously damaged RC frames should be demolished and reconstructed, and a large number of earthquake-damaged RC frames can be retrofitted and used again. In this paper, the seismic behavior of predamaged reinforced concrete columns repaired using early-strength cement mortar and basalt fiber–reinforced polymer (BFRP) has been investigated through lateral reversed cyclic tests on seven large-sized RC columns. Two predamage levels [(1) moderate damage, and (2) severe damage] were assigned to the RC columns through cyclic loading. The axial load and residual displacement were kept constant during the retrofitting process, and the retrofitted columns were retested after 6 days of mortar and epoxy curing at room temperature. The ductility and energy dissipation capacities of the fiber-reinforced polymer (FRP)-retrofitted predamaged RC columns were greatly improved after early-strength cement mortar perfusion and BFRP wrapping compared with the original intact columns. The flexural capacity could be fully restored for the moderately predamaged RC column and partially restored for the severely predamaged column, whereas the initial elastic stiffness of the BFRP-retrofitted predamaged RC columns was lower than that of the original intact columns and deceased with increased predamage level. The influences of axial load, residual displacement, and predamage level on the repair effect of FRP-retrofitted predamaged RC columns were analyzed, and the predamage level was the main influencing factor.