Detailed numerical research on the performance of unbonded prestressed SRC frame beam under vertical cyclic load

Prestress tendons can be used to improve the serviceable performance of steel reinforced concrete (SRC) beam members. To have a comprehensive understanding of the seismic behaviors of unbonded prestressed SRC beam members, fifteen frame beam specimens, including thirteen unbonded prestressed SRC ones and two ordinary SRC ones, were designed to make the numerical multi-parameter analysis. The parameters considered were the amount of unbonded tendons, rebar, flange and web thickness of steel shape. In the paper, the load-carrying capacity, strain of steels and concrete, ductility, energy dissipation, deformation restoring capacity, stiffness and strength degradation were detailed analyzed and discussed. The results indicated that increase the amount of unbonded tendons would lower the utilization efficiency of steel and decrease the energy dissipation capacity. Raising the amounts of tendons, rebar or steel shape would reduce the specimen's ductility and the ductility coefficient had a good linear relationship with the introduced integrate reinforcement index. According to the numerical analysis, several brief design suggestions were provided for reference. Moreover, compared with the ordinary SRC specimens, it could be observed that the energy dissipation capacity of prestressed SRC members was relatively lower, while its deformation capacity was as good as ordinary SRC ones. The application of unbonded tendons in SRC beam members greatly improved its serviceability and deformation restoring capacity.