Axial and lateral compression behavior of fiber‐reinforced polymer and aluminum expanded grid‐reinforced high‐performance concrete hollow tubular columns

In this study, the mechanical behavior of high‐performance concrete (HPC) hollow tubular columns reinforced with fiber‐reinforced polymer (FRP) grids and aluminum‐expanded grids under axial and lateral compression is experimentally investigated. A total of 16 specimens were fabricated by varying the outer diameter, inner diameter, and length‐to‐diameter ( L / D ) ratio. Of these, eight specimens were tested under axial compression, while the remaining eight were subjected to lateral compression. Two diameter configurations reinforced with either FRP grids or aluminum‐expanded grids were considered to evaluate the influence of column geometry and reinforcement type on the ultimate load‐carrying capacity, stiffness, and failure modes. The experimental results revealed that the aluminum‐expanded grid‐reinforced specimens exhibited higher ultimate strength, greater stiffness, and a more ductile failure behavior than the FRP grid‐reinforced specimens owing to the superior ductility and tensile strength of the aluminum grid. Finite element analysis was performed using ANSYS (2025), and the finite element model was validated against the experimental results. The validated model was subsequently employed to conduct a parametric study comprising 60 numerical models with varying diameter, length, length‐to‐diameter ( L / D ) ratio, and grid type. The numerical predictions showed excellent agreement with the design provisions of ACI 318, with an average ratio of P ACI / P FEA = 0.968, demonstrating the accuracy of the adopted design equation. Overall, the results confirm that the use of aluminum‐expanded grids significantly enhances the structural efficiency and load‐carrying capacity of HPC hollow tubular columns subjected to axial and lateral compression.