Mesoscale Modeling and Simulation of Size-Dependent Shear Response of Rectangular CFRP-Confined RC Columns

Reinforced concrete (RC) columns are prone to shear failure under seismic loads, particularly in the case of short columns. However, this brittle failure may have more adverse effects on large-sized columns. To address this issue, a common solution is to retrofit RC columns using fiber-reinforced polymer (FRP) laminates to improve seismic performance. The primary objective of this study is to assess the shear performance and size effect of rectangular RC columns confined using carbon fiber–reinforced polymer (CFRP). To account for the heterogeneity of concrete, a mesoscale numerical approach is developed using a random aggregate model. The investigation focuses on impacts of the axial compression ratio and CFRP volumetric ratio. Results show that the cross-sectional size has little effect on the final failure mode of the columns. However, the width of the main diagonal crack is reduced as the cross-sectional height increases. It can be observed that the size effect on the CFRP rupture hoop strain distribution is primarily manifested in the strain value rather than the shape of the distribution. The size effect is evident in the total shear strength of columns and in the CFRP shear contribution, with the effect becoming more pronounced with increasing axial compression ratio. Taking into account the influences of size on the CFRP shear contribution and shear strength of RC columns as well as the CFRP confinement effect on concrete, the calculation model of shear capacity is established based on a new proposed FRP effective strain model available for rectangular columns. The proposed model can provide a more accurate prediction on shear capacity of rectangular CFRP-confined RC columns compared with existing design codes.