Seismic damage evaluation of CFRP-strengthened columns in subway stations

FRP, fiber reinforced plastics, can be used to improve the lateral deformation capacity of reinforced concrete columns without remarkably changing their lateral stiffness. The intensity of seismic response of subway stations depends on the relative stiffness between surrounding soils and structures. Therefore, when using the FRP-strengthed columns of subway stations, the damage of columns can be decreased, but the seismic response of overall structures will not be influenced. The experimental analysis is conducted to study the lateral stiffness and deformation capacity of reinforced concrete columns strengthened by CFRP, i.e., carbon fiber-reinforced plastics. The test results are used to verify the reasonability of numerical models, then the deformation properties of CFRP-strengthened columns under different axial forces are discussed using the verified models. The 3D nonlinear time-domain explicit integration algorithim is employed to simulate the seismic response of subway stations strengthened by CFPR, and the deformation behaviours of columns during earthquakes are analyzed. The earthquake-induced damages of non-strengthened and CFRP-strengthened columns are evaluated by the improved Park-Ang model. It is found that under the earthquakes with PGA of 0.3g~0.4g, the CFRP-strengthened columns in bottom storey are in the easily repairable or repairable states, but the non-strengthened columns are in the difficultly repairable or irreparable states.