Numerical and analytical study on dynamic response of prestressed PC beam-column sub-assemblages under middle-joint drop-weight loading

This study numerically and analytically investigated the dynamic response of prestressed PC sub-assemblage under middle-joint drop-weight loading. A finite element model (FEM) of prestressed PC sub-assemblage with high fidelity was established using LS-DYNA software. The dynamic response of sub-assemblage was investigated under different impact velocities. The dynamic response mechanism was revealed according to damage mode and internal force distribution, followed by a parameter analysis on the dynamic response, including the effect of reinforcement ratio of steel strands and top energy-dissipated bars. An analytical method was further proposed to predict the plastic hinge distribution in the beam span. The research showed that with increase of impact velocity, the damage mode of the beam transferred from flexure to shear. At local response stage, two plastic hinges occurred in the beam under compression-flexure combined mechanical state. A stationary hinge was located at beam end near middle joint, but a traveling hinge emerged in beam span and moved toward side joint. At global response stage, the mechanical behavior of the beam was similar with that under quasi-static loading. Increasing the impact velocity can result in a plastic hinge of beam span emerging near the middle joint, thereby reducing the local dynamic response region within the beam. Furthermore, it expedited the shear damage of beam end near the middle joint. Increasing the reinforcement ratio of steel strands or top energy-dissipated rebar can effectively displace the plastic hinge away from middle joint, diminishing the effect of shear damage, and improving the ductility of sub-assemblage.