Axial Compressive Behavior of CFRP-Confined Concrete Columns Subject to Short-Term Preloading

Abstract

Twenty-nine circular specimens in four groups were tested to investigate the effect of short-term preloading on axial compressive behavior of CFRP-confined concrete. The results indicate that short-term preloading generally put a slight positive effect on the axial resistance of pure axial compressive members. As the preloading stress level index increases, the elastic segments of the load-strain curves of confined plain specimens, with or without preloading, firstly increase and then decrease. The influence of short-term preloading on the load-strain responses of confined reinforced concrete specimens is found to be insignificant. The elastic stiffness of all confined specimens does not seem to be affected by the index, but it would be increased by the introduction of longitudinal reinforcement. The results also indicate that the ultimate expansion ratio of a confined concrete column is related to the index and confinement ratio. As the ratio of the index to confinement ratio increases, the ultimate expansion ratio firstly decreases slightly and then increases rapidly. The regressive expression has also revealed that the influence of short-term preloading could be ignored if a column is extremely heavily confined with CFRP materials.