Abstract:

This study conducted a comparative test on the seismic performance of steel-reinforced ultra-high strength concrete (SRUHSC) columns and frame structures under reciprocating cyclic loads, focusing on exploring the influence mechanism of axial compression ratio on the seismic performance of the two and revealing the essential differences in seismic behavior between single columns and integral frames. Three sets of comparative tests between SRUHSC columns and frames under different axial pressure ratios were designed in the experiment. The key indicators such as failure mode, hysteresis curve, skeleton curve, stiffness degradation law, energy dissipation capacity and ductility coefficient were systematically analyzed. The test results show that as the axial compression ratio increases, the SRUHSC column alone mainly presents bending failure characteristics, manifested as the crushing of concrete at the end of the component and the yield of longitudinal reinforcing bars. However, the SRUHSC frame is mainly characterized by bending-shear-bond failure, accompanied by intensified bond sliding between the reinforcing bars and concrete in the node areas and restricted development of plastic hinges at the beam ends. A comparative analysis reveals that, compared with individual columns, frame structures exhibit more pronounced advantages in overall seismic behavior. In addition, the increase in the axial compression ratio has a significant impact on the mechanical performance of the two types of structures: it not only accelerates the propagation rate and distribution range of cracks, resulting in an increase in initial stiffness but also a faster degradation of stiffness in the later stage, but also significantly reduces the ductility and energy dissipation coefficient of the structure, and has an adverse effect on the ultimate bearing capacity. This study clarified the differentiation of axial compression ratio in the seismic performance of SRUHSC columns and frames, and confirmed that the seismic performance of individual columns decreases when they enter the overall frame structure. It provides important experimental data and theoretical basis for the seismic design optimization and performance improvement of SRUHSC structures.

Key words: SRUHSC frame, SRUHSC column, seismic behavior, axial compression ratio