Prediction of nonlinear bending behavior for FRP concrete beams based on multi-axial constitutive laws

This study focuses on a predictive model of the flexural behavior of FRP-confined concrete structural members. A hypoelasticity-based constitutive law of concrete is presented on the basis of a three-dimensional stress state in order to model the compressive behavior of confined concrete wrapped with FRP jackets. The strength enhancement of concrete was determined by the failure surface of concrete in a triaxial stress state, and its corresponding peak strain was computed by the strain-enhancement factor also proposed in this study. The behavior of FRP jackets is modeled using two-dimensional orthotropic lamination theory. Therefore, the newly proposed model is a nonlinear load path-dependent confinement model of FRP-confined concrete. To model FRP-confined concrete bending members, a procedure is presented for the prediction of the flexural behavior of FRP-confined concrete structural members using a nonlinear fiber cross-sectional approach. The developed model is validated with test results obtained from several bending experiments. The results demonstrate that the proposed model is able to capture the flexural behavior of FRP-confined concrete structural members as well as the axial and lateral strains of the sections.