Size effect in shear failure of lightweight concrete beams wrapped with CFRP without stirrups: Influence of fiber ratio

Lightweight aggregate concrete (LWAC) is a superior material due to its light weight and high strength. There however remain significant lacunae in engineering knowledge with regards to shear failure of LWAC beams. Focusing on exploring the shear resistance and the corresponding size effect in shear failure of LWAC beams wrapped with CFRP sheets, we propose a 3D meso-scale simulation method to evaluate the structural behavior of both LAWC and NWC (normal weight concrete) beams wrapped with CFRP sheets. The concrete material is viewed as a complex heterogeneous material consisting of mortar matrix in which are dispersed various aggregates with interface transition zone between them. It is hypothesized here the CFRP and the concrete beams are perfectly bonded and we investigate the effects of structural size, of CFRP ratio and of aggregate type on the shear failure of a CFRP-strengthened concrete beam. Besides, we analyze also the shear contribution by CFRP on the LWAC beams having different structural sizes (i.e. beam-depth) and the size effect on the nominal shear strength of CFRP-strengthened LWAC beams. Based on the numerical results via 3D mesoscale simulation, we propose a novel size effect law that can quantitatively describe the influence of CFRP fiber ratio on shear strength of the CFRP-strengthened concrete beam, and the newly proposed law is verified by experimental data and simulation results.