Experimental study on the flexural behavior of square high-strength concrete-filled steel tube beams with different CFRP wrapping schemes

Abstract

Recently, carbon fiber reinforced polymer (CFRP) materials have been recommended for strengthening concrete-filled steel tube (CFST) members. In this paper, experimental study is presented to further investigate the flexural behavior of square high-strength concrete-filled steel tube beams with different CFRP wrapping schemes. Results reveal that all of the specimens display the failure of longitudinal fibers at the bottom of the tensile zone when reaching the ultimate state. Meanwhile, the performance of CFRP confined CFST (CFRP-CFST) beams is improved significantly due to the transverse confinement and longitudinal reinforcement of CFRP sheets. For example, the moment capacity of CFST beams of fcu = 62.8 MPa and 128.2 MPa increased by up to 22 % and 34 %, respectively, strengthened with the full scheme. Moreover, for CFST beams of fcu = 128.2 MPa, the half scheme achieved the similar enhancement effect (29 %) in comparison with the full scheme. Based on the experimental results, a simplified approach using the fiber element method is proposed to predict the moment–curvature relationship and ultimate moment capacity of the CFRP-CFST beams. The predictions are validated with the experimental results from this paper and other study. A stepwise analytic approach is developed for designing CFRP-CFST flexural members.