Study on pure-torsional size effect of CFRP-strengthened RC beams using a 3D meso-scale numerical model

Abstract

In this paper, a 3D meso-scale numerical model for pure-torsional failure analysis of carbon fiber reinforced plastic (CFRP)-strengthened reinforced concrete (RC) beams is established. Three main aspects regarding the establishment of the numerical model are thoroughly considered, including the heterogeneity of concrete, the bond-slip relationship between steel bars and concrete, and the nonlinear interaction between CFRP and concrete. Effects of CFRP fiber ratio and span-height ratio on pure-torsional performances and size effect behaviors of CFRP-strengthened RC beams are analyzed. With the increase of CFRP fiber ratio, the cracks spacing decreases, the number of cracks increases, and the strain of CFRP decreases. With the increase of the span-height ratio, the inclination angle of the oblique crack decreases, and the strain of CFRP increases. It is found that CFRP-strengthened RC beams have an obvious torsional size effect. Furthermore, CFRP fiber ratio and span-height ratio not only have a coupling enhancement effect on the nominal torsional strength, but also have a coupling weakening effect on the size effect behavior. Based on the simulation results, a CFRP-related Torsional size effect law (SEL), which can quantitatively describe the influences of CFRP fiber ratio and span-height ratio on the size effect of nominal torsional strength of CFRP-strengthened RC beams, is established.