Size effect tests on axial compressive behavior of BFRP-reinforced concrete columns

Abstract

To explore the compressive behavior and corresponding size effect of concrete columns internally reinforced with basalt fiber‐reinforced polymer (BFRP) bars and stirrups, twelve geometrically similar columns were tested under axial compression. The test parameters included cross-sectional shapes, cross-sectional diameters/widths and stirrup ratios. The test results indicated that both the circular and square BFRP reinforced concrete (RC) columns presented a notable size effect on nominal compressive strength and ductility. As the cross-sectional size varied from 200 mm to 600 mm, the nominal compressive strength of circular and square columns exhibited maximum decreases of 11.0 % and 19.1 %, respectively, while the maximum decreases of ductility index were 66.2 % and 16.7 %, respectively. Moreover, increasing the stirrup ratio could effectively improve the confinement efficiency and ductility as well as weaken the size effect on nominal compressive strength of BFRP RC circular columns. The accuracy of available design equations was significantly influenced by the confinement effect of BFRP spirals in circular columns, while for square columns the specimen size was the most important factor. Finally, new equations were derived by considering the confinement effect of stirrups or size effect of concrete, and these equations showed satisfactory accuracy in predicting the axial load-carrying capacity of BFRP RC columns.