This paper presents the experimental findings on fire resistance of concrete encased steel (CES) composite columns made of C120 concrete and S500/S690 high-strength steel section. Eight full-scale CES columns were tested under concentrated load and heated under the ISO834 fire until failure. The fire performance of each CES column specimen was evaluated by analysing the fire resistance time, axial displacement-time curve, temperature-time curve, rotational angle of end support, post-fire conditions of the concrete surface and failure mode. The experimental study showed that the addition of polypropylene fibre was effective in minimizing explosive concrete spalling in high-strength CES columns to achieve comparable fire resistance time as those of normal-strength CES columns. A database containing 40 CES specimens was established to assess the accuracy of the current design methods in predicting the fire resistance of CES columns. The limitations of each design method were discussed based on whether they can provide safe and accurate predictions of the fire resistance of tested CES column specimens. Finally, recommendations were provided to modify the current methods for fire resistant design of CES columns made of high-strength concrete.

本文介绍了用C120混凝土和S500 / S690高强度钢截面制成的混凝土包裹钢（CES）复合柱的耐火性的实验结果。在集中负载下测试了八根全尺寸CES色谱柱，并在ISO834火焰下加热直至失效。通过分析耐火时间，轴向位移-时间曲线，温度-时间曲线，端部支撑的旋转角度，混凝土表面的后燃条件和破坏模式，评估了每个CES柱试样的耐火性能。实验研究表明，聚丙烯纤维的添加可有效减少高强度CES柱的爆炸性混凝土剥落，从而获得与普通强度CES柱相当的耐火时间。建立了包含40个CES标本的数据库，以评估当前设计方法在预测CES柱耐火性方面的准确性。讨论了每种设计方法的局限性，基于它们是否可以对测试的CES柱试样的耐火性提供安全，准确的预测。最后，提出了一些建议，以修改当前由高强度混凝土制成的CES柱的耐火设计方法。