Rectangular Filament-Wound Glass Fiber Reinforced Polymer Tubes Filled with Concrete under Flexural and Axial Loading: Analytical Modeling

This paper presents an analytical model to predict the behavior of concrete-filled rectangular fiber reinforced polymer (FRP) tubes (CFRFTs), subjected to bending and axial loads. The model accounts for different laminate structures of the flange and web of the tube. Gradual reduction of stiffness, resulting from progressive failure of FRP layers oriented at various angles is considered through the ultimate laminate failure approach. The model adopts cracked section analysis, using layer-by-layer approach and accounts for totally and partially filled tubes. The model predicts the moment–curvature responses of beams, load–strain responses of columns, and complete interaction curves of beam–columns. The model is verified using experimental results and is used to study the effects of laminate structure, hybrid laminates, thickness of the tube and optimization of partially filled tubes. Comparisons of CFRFT with conventional reinforced concrete (RC) sections showed that CFRFT could provide axial load–bending moment interaction curves comparable to those of RC sections of similar reinforcement index. Also, providing a small fraction of carbon fibers in the flanges could substantially improve flexural performance. The first ply failure approach could highly underestimate the strength of CFRFT.