Analysis-oriented model for FRP confined high-strength concrete: 3D interpretation of path dependency

Various analysis-oriented models have been developed over the past decades to predict the stress-strain relationship of fibre-reinforced polymer (FRP) confined concrete. Most of these models are built based on the path-independent assumption, and the mechanism of this kind of model has been revealed by the authors based on a 3D geometrical approach. However, it is widely recognized that FRP confined high-strength concrete (HSC) is path dependent, which means that the stress of passively confined HSC deviates from the actively confined test results. Most of the existing solutions for this problem employ an alternative stress-strain relationship instead of the original actively confined HSC model for FRP confined HSC. In this paper, the mechanism of the path-dependency of confined HSC is revealed based on the 3D geometrical method. In addition, a corresponding analysis-oriented model for confined HSC considering path dependency is proposed. This model includes an actively confined concrete model, a damage criterion and post-damaged HSC behaviours. The proposed model can identify the confining mode from the load path and can select a proper stress-strain relationship for confined HSC without artificial intervention. Finally, the proposed model is calibrated and verified by test data collected from the literature. The results show that the proposed model has better accuracy than existing path-dependent models.