This study investigates the seismic behavior of composite frames with initial heavy load conditions. Two frame specimens consisting of square concrete-filled steel tube (CFST) columns and steel-reinforced concrete (SRC) deep beams were fabricated and poured using ordinary concrete and high-strength concrete, respectively. Thereafter, the two specimens were tested under cyclic loadings, and the failure models, hysteretic behavior, bearing capacity, ductility, and accumulated energy dissipation of the specimens were investigated in detail. The experimental results revealed that both of the specimens failed owing to the local buckling at the column ends. This kind of composite frame has good seismic performance and can be regarded as a high-ductility structure. Moreover, a finite element (FE) model was developed and verified by the experimental results. The effects of the typical parameters, such as the material strength and axial compression ratio, were studied using the FE model. The parametric study demonstrates that increasing the yield strength of the steel tube can effectively improve the ultimate bearing capacity of the composite frame and that decreasing the axial compression ratio is a valid method for improving the ductility of the structure.

中文翻译：

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初始重载条件下复合框架抗震性能的试验和数值研究

本研究研究了复合框架在初始重载条件下的抗震性能。由方形钢管混凝土（CFST）柱和钢筋混凝土（SRC）深梁组成的两个框架试件分别使用普通混凝土和高强混凝土制作和浇筑。此后，对两个试件进行循环载荷试验，详细研究了试件的破坏模型、滞回行为、承载力、延展性和累积能量耗散。实验结果表明，由于柱端部的局部屈曲，两个试样都失败了。这种组合框架具有良好的抗震性能，可视为一种高延性结构。而且，有限元 (FE) 模型被开发并通过实验结果进行验证。使用有限元模型研究了材料强度和轴压比等典型参数的影响。参数研究表明，提高钢管的屈服强度可以有效提高组合框架的极限承载能力，降低轴压比是提高结构延性的有效方法。