Compressive Behavior of Four Types FRP Tube Confined Ultra-high-performance Concrete

An axial compression test was conducted to investigate the performance of ultra-high performance concrete(UHPC) specimens confined with different types and thickness of fiber reinforced polymer(FRP) tubes.40 cylindrical specimens were prepared,of which 4 were non-confined while the rest were confined with FRP tubes.Stress-strain curves were produced,and the strength and ultimate strains obtained.The test results show significant enhancement in ultimate strength and strain of UHPC.The confinement effectiveness improves with increase in the FRP layers,and also with increase in strength of FRP.Axial compression stress-strain curves relationship exhibits bilinear characteristics.Under the same confinement ratio,the smaller the stiffness of FRP tube is,the greater the ultimate strain value of the confined specimen becomes.The predicted value of both ultimate strength and strain of existing models is higher than the tested value,and the predicted values of the ultimate strain are more higher than that of the experimental results.The accuracy of the formula for the prediction of strength and ultimate strain of FRP tube confined UHPC specimens suggested in this paper is higher.