Experimental and numerical study on the axial compression behavior of circular concrete columns confined by BFRP spirals and ties

Abstract This study investigates the compression behavior of circular concrete columns confined with basalt fiber-reinforced polymer (BFRP) stirrups, comparing their performance with traditional steel-reinforced columns. The objective of the study is to assess the impact of the BFRP transverse reinforcements and concrete mix design (CMD) codes on the compressive strength (CS), energy accumulation (G Acc ), fracture energy (G F ), and ductility of RC cylinders. A total of 81 reinforced concrete (RC) cylinders were prepared using three distinct CMD codes and tested under axial compression. The specimens were confined with 6 mm and 8 mm BFRP and steel spirals/ties at varying rib spacings (45 mm, 60 mm, and 90 mm). The experimental results revealed that closer BFRP spiral/tie spacings (45 mm) significantly enhanced the CS by 7–15 % and G Acc by up to 59 % of the columns due to improved confinement effect, compared to those with larger spacings (60 mm and 90 mm). BFRP ties demonstrated superior performance in terms of CS, G Acc , and G F compared to BFRP spirals, particularly at moderate and larger spacings. Finite element model (FEM) simulations validated the experimental results with less than 8 % deviation and demonstrate a high degree of correlation between predicted and observed failure behaviors. The study suggests that BFRP spirals/ties reinforcements with optimal spacing can effectively replace steel in structural applications, offering comparable performance in strength, ductility, and energy absorption. These findings encourage the use of BFRP-based reinforcements in durable, lightweight, and eco-friendly concrete constructions.