Test and modeling of ultra-high performance concrete confined by fiber reinforced polymer tube

The ultra-high performance concrete (UHPC) confined by fiber reinforced polymer (FRP) tube is a novel hybrid system with superior performance.Four unconfined UHPC cylindrical specimens and thirty-six FRP-confined UHPC specimens with four different types of fibers and three different tube thicknesses were tested under monotonic uniaxial compression.The influence of FRP tube types and thickness on the compressive behavior of confined UHPC was discussed.The FRP tube confinement was shown to significantly enhance both the ultimate strength and strain.The dilation rate of confined UHPC specimens equals to the Poisson's ratio of unconfined specimens at first.Once the FRP confinement becomes fully activated,the rate deduces to an asymptotic value that was larger than the value of conventional concrete.The test results were compared with a number of typical confinement models.A new stress-strain model was proposed based on the test results.Comparison of the models showed that the new model provides the most accurate prediction of the ultimate condition and the stress-strain behavior of FRP-confined UHPC specimens. © 2016, The Editorial Board of Journal of Basic Science and Engineering. All right reserved.