Experimentally and numerically testing the behavior of FRP structural bars in composite columns

The applications of basalt fiber-reinforced polymer (BFRP) bars in columns have gained attention due to their superior durability and corrosion resistance. However, their structural behavior in composite columns remains inadequately explored. This study experimentally and numerically investigates the performance of various BFRP reinforcement configurations, including plate sections, angle sections, circular tubes, and conventional circular rebars, in square columns. A total of eight examples were tested under axial compression, incorporating different reinforcement types and stirrup spacings (50 mm and 100 mm) to assess their impact on strength, ductility, and failure mechanisms. Experimental results revealed that BFRP tube-confined examples exhibited the highest peak load capacity, reaching up to 1150 kN, a 25% increase compared to steel-reinforced counterparts. The inclusion of stainless-steel stirrups enhanced the confinement effect, improving ductility by approximately 30% over BFRP-reinforced examples without stirrups. Finite element analysis (FEA) using the concrete damaged plasticity (CDP) model demonstrated strong agreement with experimental results, with an average error of less than 5% in peak load predictions. A detailed parametric study highlighted the influence of reinforcement geometry and spacing on load-carrying capacity and failure modes. These findings provide valuable insights for adopting BFRP reinforcement in concrete columns, offering a viable alternative to conventional steel reinforcement for enhanced durability and serviceability in structural applications.