Seismic performance assessment of flexure-dominate FRP-confined RC columns using plastic rotation angle

External wrapping of fiber reinforced polymer (FRP) materials is a widely applied method for the seismic retrofit of reinforced concrete (RC) columns. The seismic evaluation of conventional reinforced concrete columns prior to retrofit is presented in ASCE 41-13 although there is little available guidance for evaluating the deformation capacity of FRP-retrofitted reinforced concrete columns. In this paper, 77 FRP-retrofitted concrete columns with flexural deficiency were collected from the published literature. The yield and ultimate rotations of all specimens were obtained from backbone curves. The relationship between yield and ultimate rotation, and column parameters was analyzed. Consistent with the approach of ASCE 41, an empirical model, which considers the variation of axial force ratio, effective transverse reinforcement ratio and shear force ratio, was proposed to predict the plastic and ultimate rotations. Results were compared with other available models and were shown to be generally more accurate for both circular and rectilinear columns, which proved the efficiency of the proposed model. Finally, a reduction parameter for the expression of plastic rotation angle was adopted to obtain the model parameter a required for ASCE 41-compliant modelling of FRP-retrofitted reinforced concrete columns with flexural deficiency.