轴向往复荷载作用下钢管混凝土柱抗震性能试验研究

为了探究斜交网格结构体系中外筒斜柱的破坏机制，对8个钢管混凝土柱和2个钢管柱试件进行了轴向往复加载试验，研究加载路径、长径比、混凝土强度和含钢率对其抗震性能的影响，分析了钢管混凝土柱的破坏机制、破坏形态和滞回性能，并讨论了钢管与混凝土间的相互作用。结果表明：轴向往复荷载下钢管混凝土柱的破坏均由钢管断裂引起，核心混凝土整体保持完好，只在钢管屈曲处存在混凝土压碎现象；相比于空钢管柱，钢管混凝土柱受拉时混凝土对钢管的支撑作用，以及受压时钢管对混凝土的约束作用，保证了其具有更高的承载力、变形能力和耗能能力；钢管混凝土柱在轴压和轴拉荷载下的抗震性能存在显著差别，在轴拉荷载下具有更好的延性和耗能能力，而在轴压荷载下具有更高的承载力和刚度。钢管混凝土柱屈服后钢管对混凝土的约束作用持续增强，并当钢管纵向应变达到8×10^-3时，不同参数对其约束效应的影响达到最大。

Experimental research on seismic behavior of concrete-filled steel tube columns under cyclic axial loading

To investigate the failure mechanism of the inclined columns in a diagonal grid structure system, cyclic axial loading tests of eight concrete-filled steel tube (CFST) columns and two steel tube columns were carried out. The influences of loading path, length to diameter ratio, concrete strength and steel ratio on seismic performance of the specimens were studied. The mechanical behavior, failure mode and hysteretic behavior of CFST columns were investigated, and the interaction between the steel tube and concrete was discussed as well. The results indicate that failure of CFST columns under cyclic axial loading is caused by fracture of steel tubes, while the core concrete remains intact except for some concrete crushing at the buckling point of steel tube. Compared to the hollow steel tube columns, the supporting effect of concrete on steel tube when the CFST column is in tension and the restraining effect of steel tube on concrete when the CFST column is in compression ensure their higher capacity, deformability and energy dissipation capacity. Significant differences exist in the seismic behavior of CFST columns under axial compressive loads and axial tensile loads, better ductility and energy dissipation capacity are achieved in the tension direction, whereas higher bearing capacity and stiffness are achieved in the compression direction. The restraint effect of steel tube on concrete keeps increasing after yielding of CFST columns, and when the longitudinal strain of steel tube reaches 8×10^-3, the influence of different parameters on the restraint effect reaches the maximum.