Experimental study and calculation method for axial compressive behavior of carbon fiber‐reinforced polymer bar‐reinforced ultra‐high performance concrete columns

Abstract

Fiber‐reinforced polymer‐reinforced ultra‐high performance concrete (UHPC) structures exhibit outstanding durability and mechanical properties. In this study, an experimental investigation was conducted on the axial compression behavior of carbon fiber‐reinforced polymer (CFRP) bar‐reinforced UHPC columns, focusing on the influence of the slenderness ratio on their structural response. The results indicated that the UHPC strain distribution along the column height remained uniform throughout loading, and all specimens reached failure under axial compression without exhibiting spalling. The ultimate compressive strain of UHPC was approximately 2500 με. Strains in the longitudinal CFRP bars were close to those in the surrounding UHPC, demonstrating effective composite action. However, the maximum strain in the CFRP bars did not reach their ultimate strain. The confinement provided by glass fiber‐reinforced polymer (GFRP) stirrups was minimal, with a maximum recorded strain of about 600 με. Subsequently, a finite element parametric analysis was performed to evaluate the effects of aspect ratio and reinforcement ratio. The numerical results revealed that increasing the aspect ratio reduced the load capacity and increased the vertical deformation of the columns, whereas the reinforcement ratio had a marginal effect on axial performance. Finally, based on section equilibrium, deformation compatibility, and the experimental and numerical results, an ultimate load capacity formula for CFRP bar‐reinforced UHPC columns was developed, incorporating the contribution of CFRP bars and a reduction factor for the aspect ratio. In comparison with existing formulas from previous studies, the proposed formula demonstrates superior precision and robustness.