高温后方钢管型钢混凝土短柱轴向力学性能研究

The Axial Mechanical Behavior of Steel-Reinforced Concrete-Filled Square Steel Tubular Short Columns After Exposure to Elevated Temperature

为探究加热时间、钢管宽厚比和型钢含钢率等参数对火灾后方钢管型钢混凝土短柱力学性能的影响,对9根未经加热和12根加热不同时间后的短柱进行轴向静力荷载试验。通过分析荷载-轴向应变曲线,讨论了高温后试件的剩余承载力、延性及刚度退化的变化规律,最后提出了常温下方钢管型钢混凝土短柱极限承载力的计算公式。结果表明:所有试件均为鼓曲破坏,鼓曲处混凝土局部发生破碎,但其核心混凝土仍保持为一个整体。试件高温后的剩余承载力随加热时间先小幅增加后稳步下降;其下降幅度随着型钢含钢率的增加而减小,当含钢率接近9%时基本保持不变。延长加热时间可以提高试件的延性,试件加热130 min后延性系数约提高71%。增加内外含钢率比及加热时间能够减缓试件刚度退化的速率。基于提出公式所得的计算承载力与试验结果较为一致,可应用于工程实践。

In order to explore the axial mechanical behavior of steel-reinforced concrete-filled square steel tubular short columns after fire, 12 specimens heated with different times, along with nine unheated specimens for comparison, are designed with multiple parameters of the width-to-thickness ratio of the steel tube and steel ratio.The influence of load-strain curves, residual bearing capacity, ductility and stiffness degradation is analyzed.The calculation formula of the ultimate bearing capacity under ambient temperature is proposed.The experimental results show that the failure mode of all the specimens is buckling failure, and the core concrete remains integral despite of some local crushing at the bulge.The residual bearing capacity of specimens increases slightly at first and then decreases steadily with the heating time.When the steel ratio is close to 9%,the residual bearing capacity has barely fallen.Increasing the heating time can improve ductility.Especially when the specimens are heated to 130 mins, the ductility can be improved by 71%.Increasing the steel ratio and heating time can slow down the rate of stiffness degradation.The calculated bearing capacities based on the proposed formula are in a good agreement with the experimental results.