Maximum usable strain of FRP-confined concrete

This study investigates the progressive failure of FRP-confined concrete. Ten FRP-confined concrete specimens were divided into two groups with different jacket stiffness. One specimen in each group was tested until failure while the others were loaded to target strains and then unloaded in order to monitor the residual strength of the concrete cores. At 1% axial strain of FRP-confined concrete, the residual strength of the concrete cores were reduced more than 56% compared to the reference specimens. Experimental results have shown that the maximum usable strain of 1% is unconservative for FRP-confined concrete. A model is proposed to estimate the residual strength of concrete cores. Predictions from the proposed model fit the experimental results well. In addition, a new procedure is proposed to determine the maximum usable strain of FRP-confined concrete based on the maximum usable strain of unconfined concrete.