Abstract Concrete-filled double-skin steel tubular (CFDST) specimens that exhibit lightweight, good ductility, and better bending resistance, can be used for beams. However, fire often causes great damage, and the flexural behavior of CFDST beams after subject to high-temperature has not been studied. To investigate the flexural behavior of CFDST beams after subject to high temperature, seven CFDST specimens after subject to high temperature were carried out four-point bending tests. The main parameters explored in the test include hollow ratio (0.31, 0.52, 0.72) and temperature (300 °C, 500 °C, 800 °C). The corresponding finite-element analysis (FEA) models were established, and the results showed good agreement with the test. The in-depth mechanism and systematic analysis including the influence of different hollow ratio, material property, and temperature on the whole process curve of CFDST after subject to high temperature are carried out using FEA models. It is found that the ultimate bending moment of CFDST after subject to high-temperature increases with hollow ratio and material property, but decreases with the temperature. The outer steel tube contributes the most to the ultimate bending moment, and the inner steel tube improves the ductility at a later stage. Specimens with a large hollow ratio (χ ≥ 0.52) have better bending capacity, and the ultimate bending moment of specimens with a small hollow ratio (χ

中文翻译：

---

双层钢管混凝土梁高温抗弯性能研究

摘要 混凝土填充双层钢管（CFDST）试件具有重量轻、延展性好、抗弯性能好等特点，可用于梁。然而，火灾往往会造成很大的破坏，CFDST梁在高温下的弯曲行为尚未得到研究。为了研究 CFDST 梁在高温后的弯曲行为，对七个 CFDST 试样进行了高温后的四点弯曲试验。测试中探索的主要参数包括空心比（0.31、0.52、0.72）和温度（300°C、500°C、800°C）。建立了相应的有限元分析（FEA）模型，结果与试验吻合良好。深入的机理和系统分析，包括不同空心比、材料性能、CFDST经过高温后的整个工艺曲线上的温度和温度是使用有限元模型进行的。结果表明，CFDST高温后的极限弯矩随空心比和材料特性而增加，随温度升高而减小。外钢管对极限弯矩贡献最大，内钢管在后期提高了延展性。空心比大(χ≥0.52)的试样具有较好的抗弯能力，空心比(χ≥0.52)小的试样的极限弯矩 但随着温度的升高而降低。外钢管对极限弯矩贡献最大，内钢管在后期提高了延展性。空心比大(χ≥0.52)的试样具有较好的抗弯能力，空心比(χ≥0.52)小的试样的极限弯矩 但随着温度的升高而降低。外钢管对极限弯矩贡献最大，内钢管在后期提高了延展性。空心比大(χ≥0.52)的试样具有较好的抗弯能力，空心比(χ≥0.52)小的试样的极限弯矩