Size effect on axial compressive failure of CFRP-wrapped square concrete columns: Tests and simulations

•30 CFRP-wrapped concrete columns under axial compression are tested.•Influences of CFRP and stirrup ratio on failure of CFRP-wrapped columns are studied.•3D meso-scale simulation method is utilized to furtherly explore the size effect.•An updated SEL is built for axial-compressive failure of CFRP-wrapped columns.•The test data and simulation results verify the updated size effect law. Carbon Fiber Reinforced Polymer (CFRP) has been widely utilized to wrap concrete column in order to improve the axial compressive bearing capacity. In this study, the size effect of CFRP-wrapped square concrete columns was investigated using both experimental and numerical approaches. A total of 30 geometrically-similar CFRP-wrapped concrete columns with a maximum cross-sectional width of 600 mm were designed and tested with repeated axial compression. The influences of loading type, structural size and reinforcement configuration on the failure of the columns were explored and measured. Moreover, a 3D meso-scale simulation approach considering the influence of concrete heterogeneity and CFRP-concrete interactions was utilized to furtherly investigate the size effect of CFRP-wrapped columns. In the 3D meso-scale simulations, the failure of columns with larger structural sizes and larger CFRP fiber ratios was analyzed. The size effect on the nominal compressive strength of CFRP-wrapped columns was examined and discussed in detail. Finally, an updated size effect law (SEL) was established to describe the size effect in CFRP-wrapped concrete columns. The updated SEL is proved to be reasonable, which shows good consistence with the present experimental data and simulation results.