A path-dependent stress-strain model of FRP-confined circular concrete columns derived from an energy balance approach

Abstract

It is generally believed that the use of fibre-reinforced polymer (FRP) confinement can effectively improve the strength and ductility of concrete. Passive confinement is one of the key features of the behavior of FRP-confined concrete. Analysis-oriented models for passively confined concrete have been established on the base of the active confinement model by many researchers. Among them, a stress path-independent assumption was made for those passively confined concrete. However, in recent years, numerous researchers have found that the influence of stress path on the stress-strain relationship of confined concrete cannot be neglected. Therefore, in order to further understand and simulate the uniaxial behavior of FRP-confined concrete, this paper presents a stress path-dependent model of FRP-confined concrete based on an energy balance approach in which the extra work done by the active confining pressure in the stress path-independent model is considered. Firstly, experimental data comprising 341 sets of FRP jacket confined concrete tests and 28 sets of concrete-filled FRP tube (CFFT) tests were collected. Subsequently, the stress paths of the two types of specimens were identified based on the properties of FRP materials, and then the energy balance assumption was introduced, and finally a new stress path-dependent model was established using the energy balance approach. By comparing the predictions of the proposed model with collected experimental data and those of several existing models, it was observed that the proposed model can more accurately predict the ultimate stress of FRP-confined concrete and exhibit good agreement with the experimental stress-strain curves.