Numerical Investigation into the Strengthening of Concrete-Filled Steel Tube Composite Columns Using Carbon Fiber-Reinforced Polymers

Hollow and concrete-filled steel tubes (CFSTs) are extensively employed as columns in various structural systems, yet they are susceptible to local buckling under axial compression loading. Local buckling tends to manifest near the column ends where moments are the highest. To address this issue and enhance the strength and ductility of CFSTs, carbon fiber-reinforced polymers (CFRPs) emerge as a simple and effective solution, having been successfully utilized in prior studies. This investigation focuses on assessing the axial load behavior of CFRP-strengthened CFST slender columns using the finite element (FE) method. The study begins with a verification phase, followed by comprehensive parametric studies exploring the impact of CFRP layers, numbers, confinement lengths, and positions. The FE results demonstrate that a single CFRP sheet, with a thickness of 1.2 mm, enhances the composite column's axial load resistance by 8.5%. Doubling the CFRP sheets to a total thickness of 2.4 mm increases the resistance to 23.5%, while three sheets totaling 3.6 mm and four sheets totaling 4.8 mm result in axial load resistances of 35.1% and 44.5%, respectively. Furthermore, the study reveals that varying the lengths of CFRP sheets improves axial load resistance by 8.5%, 4.6%, 0.1%, and 0.5% for length percentages of 100%, 75%, 50%, and 25%, respectively. These findings underscore the efficacy of CFRP in strengthening CFST columns and provide valuable insights into optimizing the design parameters for an enhanced structural performance.