型钢-钢管混凝土柱耐火性能试验研究

Experimental research on fire resistance of steel tubular columns filled with steel reinforced concrete

通过8个组合柱短试件的温度场测试和10个组合柱长试件的耐火性能试验,研究了ISO 834标准升温曲线下型钢-钢管混凝土柱的温度场分布和耐火极限。试验参数包括截面形状、受火方式、轴压比和配骨率。试验结果表明:配置型钢后钢管混凝土柱截面内升温速率会略有提高,内置型钢对截面温度场分布影响不大,但是钢管混凝土柱的耐火极限会大幅度提高;以四面受火的方形截面试件的耐火极限为参照,三面受火时耐火极限变化不大,两面受火和单面受火时耐火极限大幅度提高,圆形截面试件1/2表面受火时耐火极限亦明显提高;轴压比从0.3增大到0.4时,试件耐火极限显著降低。经过合理的设计,无防火保护的型钢-钢管混凝土柱可以达到3 h的一级耐火极限要求。

Ten composite column specimens were tested under the axial load and ISO 834 standard fire to investigate the fire resistance of steel tubular columns filled with steel reinforced concrete. The cross-sectional temperature distributions were measured for eight short composite column specimens. Test parameters included the section form, fire exposure method, axial compression ratio and ratio of steel section. Test results show that the encased steel section can slightly improve the heating rate in the cross section, and has little effect on the cross-sectional temperature distribution. Meanwhile, the encased steel section can remarkably improve the fire endurance of the composite columns. Compared with the fire endurance of specimen in uniform fire, the fire endurance of square specimen in three-surface fire is almost the same. In the cases of two-surface and one-surface fires for the square specimens and one half surface fire for the circular specimen, the fire endurances increase significantly. The fire endurance decreases greatly when the axial compression ratio increases from 0.3 to 0. d. Unprotected steel tubular columns filled with steel reinforced concrete can reach 3 h fire resistance demand specified for load-bearing columns with reasonable design.