Compressive stress-strain behavior and model for geometrical-similar BFRP RC square columns

Abstract

This paper presents experimental, numerical and analytical investigations to evaluate the compressive behavior and size effect of square concrete columns internally reinforced with basalt fiber-reinforced polymer (BFRP) bars and ties. Nine BFRP reinforced concrete (RC) square columns were tested under axial compression. The main parameters included cross-sectional heights, transverse reinforcement ratios, and configuration of transverse BFRP ties. The compressive behaviors of BFRP RC columns were discussed in terms of axial load-strain response, confined strength, and ductility index. The results revealed that there was significant size effect on the confined efficiency and ductility. With the increasing cross-sectional height, the maximum decreases of confined efficiency and ductility index were 16.0% and 18.9% respectively. Moreover, a meso-scale numerical model considering the heterogeneity of concrete was developed and verified using the test results. A parametric analysis was then performed to evaluate the effects of cross-sectional height and transverse reinforcement ratio on the compressive performance of BFRP tie-confined concrete. Finally, a design-oriented stress-strain model was proposed considering the effect of cross-sectional height and transverse reinforcement ratio. The proposed model was validated using the test results in the present study and literature.