Nonlinear Axial Compressive Behavior of Concrete-Filled Filament-Wound GFRP Tubes

Utilizing multidirectional filament-wound glass fiber-reinforced polymer (GFRP) tubes instead of uniaxial GFRP wraps as a confinement mechanism can be shown to promote a recognizable degree of both axial and circumferential resistance against the concrete core against applied axial loads. This composite system is recognized as concrete-filled GFRP tubes (CFFTs). For this study, the CFFTs axial compressive behavior is investigated using low strength concrete that is encased by thin-walled and thick-walled GFRP tubes with a multidirectional fiber orientation. A total of 10 CFFTs and 5 unconfined cylinders are produced using normal density concrete. The filament-wound GFRP tubes in consideration have an off-axis fiber orientation of ±55°, promoting significant biaxial resistance to concrete core deformation. The classical lamination theory is adopted to estimate the GFRP tube’s enhanced material properties. The CFFTs possess a notable degree of nonlinear biaxial behavior at higher axial loads, attributed to nonlinear characteristics associated with the GFRP tubes. A modified prediction model, originally proposed by Xie et al., is adopted to predict the CFFTs nonlinear stress–strain response to ultimate failure. The experimental results are compared to the model output to verify its accuracy.