Ultra-high strength concrete (UHSC) with compressive strength greater than 100 MPa at room temperature has been developed for concrete filled square steel tubular column for use in high-rise buildings. The fire resistance of UHSC filled protected square steel tubular columns exposed to the standard ISO fire is investigated in this paper. For this purpose, numerical heat transfer analysis and nonlinear thermal stress analysis were conducted by taking into account the existing material properties, such as the thermal and mechanical properties of UHSC and high strength steel. The numerical analyses were carried out and the results were validated against the test results in terms of heat distribution and mechanical behavior. Comparison with the test results showed a reasonable agreement with finite element results in terms of temperature field prediction and load displacement behavior during the fire. Finally, based on the validated finite element model, the effects of fire protection thickness, load ratio, the strengths of concrete and steel, steel contribution ratio, and relative slenderness ratio on the fire resistance of UHSC filled square steel tubular columns were carried out and discussed.

已开发出用于高层建筑中的方形钢管混凝土柱的室温下抗压强度大于100 MPa的超高强度混凝土（UHSC）。本文研究了UHSC填充的保护方形钢管柱在标准ISO防火下的耐火性。为此，考虑到现有的材料特性，例如UHSC和高强度钢的热和机械特性，进行了数值传热分析和非线性热应力分析。进行了数值分析，并根据热分布和机械性能对测试结果进行了验证。与测试结果的比较表明，在火灾期间的温度场预测和负载位移行为方面，有限元结果与合理结果吻合。最后，在验证的有限元模型的基础上，研究了防火厚度，荷载比，混凝土和钢的强度，钢的贡献率以及相对细长比对UHSC填充方形钢管柱的耐火性的影响，并讨论过。