Quasi-static and dynamic behavior of precast concrete frames with high performance dry connections subjected to loss of a penultimate column scenario

Unbonded post-tensioned precast concrete (UPPC) frame exhibits excellent performance in resisting seismic load from experimental tests and post-earthquake investigations. However, the behavior of UPPC frames subjected to extreme load such as the loss of a column due to explosion is still not well studied. To fill this knowledge gap, in this paper, four 1/2 scaled UPPC beam-column substructures were tested under both quasi-static and dynamic loading regimes. The comparative study between these two test-regimes were subsequently performed, which provides a clear understanding of the difference of these two test methods in progressive collapse studies for other researchers. The test results indicated that UPPC frames achieved required load redistribution capacity to mitigate progressive collapse. The failure modes of the frames observed in dynamic test were quite similar to that in quasi-static tests. Moreover, it was found that strain rate effects were insignificant for progressive collapse events caused by suddenly column removal. Based on the measured load resisting function from quasi-static tests, a single-degree-of-freedom (SDOF) model, with the consideration of strain hardening and softening, was developed. After validation, the proposed SDOF model was used to quantify the effects of service load, initial velocity, initial displacements, and damping ratio on the dynamic response. It was found that the damping ratio, non-zero initial velocity and initial displacement are the three most influential parameters.