Size effect on shear failure of CFRP-strengthened concrete beams without web reinforcement: Meso-scale simulation and formulation

The purpose of the present study is to explore the influence of fiber ratio on the shear failure and size effect of reinforced concrete (RC) beams strengthened in shear with externally bonded CFRP sheets. A three-dimensional meso-scale numerical model that can consider concrete heterogeneities and CFRP-concrete interactions was established. The influence of fiber ratio on size effect in shear failure was studied. Moreover, a size effect law is established and verified to predict the nominal shear strength of CFRP-strengthened concrete beams, in which the contribution of the CFRP fiber ratio is quantitatively considered. The simulation results indicate that, 1) The cross-section size has a great influence on the shear strength of CFRP-strengthened RC cantilever beams, and CFRP has a greater contribution to the shear capacity of small-sized beams; 2) The increase of fiber ratio strengthen the shear capacity of CFRP-strengthened RC cantilever beam and weakens the size effect on shear strength; 3) The existence of CFRP cannot increase the shear strength of RC beams indefinitely, and the increase of shear strength is obvious under the condition of small fiber ratio; 4) The proposed size effect law for shear failure of CFRP-strengthened RC beams can well describe the quantitative influence of fiber ratio, and it is consistent with the available test data.