Experimental study and analytical modeling on dynamic compressive behavior of BFRP-confined concrete under high strain rates

The dynamic compressive behavior of FRP-confined concrete (FCC) is particularly important for its application in impact-related structures. In this paper, sperate Hopkinson pressure bar (SHPB) tests were conducted to study the dynamic compressive behavior of FCC. Experimental results show that the maximum strength and maximum axial strain of FCC are sensitive to the strain rate effect. Moreover, the axial stress-strain curves are analyzed and divided into three branches based on their trend (i.e., the initial ascending branch, the descending branch, and the second ascending branch). The strain rate histories are plotted to show that the unsynchronized change in the axial and lateral strain rate effects leads to the descending branch and the second ascending branch. The test data indicate that the dynamic confinement ratio should be larger than 0.045 to ensure sufficient confinement for the concrete. A formula is developed for the lateral and axial average strain rate relationship. Enlightened by the test results, an analytical model for dynamically loaded FCC is proposed by incorporating the concrete's strain rate effect, the inertial confinement effect, and the FRP's strain rate effect into a well-recognized stress-strain model of static compression.