Confinement Model for FRP-Confined High-Strength Concrete

It is well understood that confining concrete with fiber-reinforced polymer (FRP) composites can significantly enhance its strength and deformability. However, the confinement demand of concrete increases proportionally with its strength, resulting in higher confinement requirements for high-strength concrete (HSC). This paper reports on a study on the axial compressive behavior of FRP-confined HSC. A large experimental test database, which consists of 237 axial compression tests results for FRP-confined HSC, was assembled from the published literature and presented in this paper. This database was augmented with another database of FRP-confined normal-strength concrete (NSC), which consists of 739 test results. The combined database of 1063 test results, which cover specimens with unconfined concrete strengths ranging from 6.2 to 169.7 MPa, was used to investigate and quantify the factors that influence the compressive behavior of FRP-confined HSC. Analysis of the test results reported in the database indicates that the confinement requirement increases significantly with an increase in concrete strength, which adversely affects the observed strength enhancement through confinement. In addition, it was also observed that the hoop rupture strain of the FRP shell decreases as the concrete strength increases. Many existing stress-strain models developed for FRP-confined concrete were assessed by using the HSC database. A close examination of the results of the model assessment led to many important conclusions regarding the strengths and weaknesses of existing stress-strain models. Finally, a novel design-oriented model for FRP-confined concrete is presented that was developed on the basis of the database summarized in the paper. It is shown that the proposed model performs significantly better than any of the existing stress-strain models of FRP-confined concrete in predicting the ultimate conditions of FRP-confined HSC.