Behaviors of damaged GFRP-confined concrete columns subjected to eccentric compression

To investigate the mechanical response of a concrete-filled glass fiber-reinforced polymer (GFRP) tube with initial damage under eccentric compression, a total of 21 specimen types were designed and fabricated, incorporating slenderness ratio, eccentricity, damage length, and damage location as variable parameters. Static eccentric compression loading tests were performed. A comprehensive comparative study was undertaken focusing on the mechanisms of damage nucleation and evolution, load–displacement curves, and the variation patterns of ultimate load-bearing capacity. Additionally, the ultimate load-bearing capacity of GFRP-confined concrete columns with initial damage was calculated. The findings reveal that damage on the compression side is particularly detrimental, exerting a substantially greater adverse effect than damage on the tension side. Stress concentration at the damage tip initiates the propagation of complex cracks, forming plastic hinges and altering the stress transfer path. Despite the damage, the internal concrete retains partial confinement through the arching effect. The presented study introduces reduction coefficients for slenderness ratio and eccentricity, resulting in a formula for predicting the ultimate load-bearing capacity of GFRP-confined concrete columns, considering the influence of damage location on strength. The calculated results are generally consistent with the experimental results.