工程竹柱四面受火后力学性能的试验研究

Experimental study on mechanical behavior of engineered bamboo columns after being exposed to four-side fire

考虑目前常用的工程竹类型胶合竹和重组竹，通过2组10根工程竹柱四面受火后力学性能的对比试验，研究了不同受火时间后工程竹柱剩余承载力、破坏形态和炭化速度的变化。结果表明：不同受火时间后工程竹柱的剩余承载力明显降低，受火10～20min后降低幅度达29．0％～83．1％。四面受火后工程竹柱剩余承载力下降程度随受火时间增加而增加，随截面尺寸增加而减小。剩余承载力下降主要是由于四面受火后工程竹柱表面炭化引起的有效截面面积减少，以及四面受火后靠近炭化层的高温分解层强度明显劣化所致。各组对比试件的初始刚度均明显大于不同受火时间后试件。由于角部遭受两个方向的热传递，四面受火后工程竹柱角部炭化后变为弧形，等效成矩形截面后的等效炭化速度比非角部影响区的平均炭化速度大；胶合竹柱的炭化速度比重组竹柱的炭化速度略高。

Considering the common used engineered bamboo products of laminated bamboo and bamboo scrimber, through the comparative test on the mechanical properties of the two groups of ten engineered bamboo columns after being exposed to four-side fire, the variation of the residual bearing capacity, failure mode and charring rate of the engineered bamboo columns after being exposed to different times of fire were studied. The results show that the residual bearing capacity of the engineered bamboo column is significantly reduced after being exposed to four-side fire, and the reduction rate reaches 29% 83. 1% after being exposed to 10-20 minutes fire. The degree of decline in the residual bearing capacity of engineered bamboo columns after being exposed to four-side fire increases with the increase of the fire time and decreases with the increase of the section size. The decrease in the residual bearing capacity is mainly due to the reduction of the effective cross-sectional area caused by the charring of the surface of the engineered bamboo column after being exposed to four-side fire, and the significant deterioration of the strength of the pyrolysis layer close to the char layer after being exposed to four-side fire. The initial stiffness of the comparative specimens of each group is significantly greater than that of the specimens after being exposed to different times of fire. Because the corners are subjected to heat transfer in both directions, the comers of the engineered bamboo columns after being exposed to four-side fire become round after charring, and the equivalent charring rate after equivalent to rectangular section is greater than the average charring rate in non-comer affected areas. The charring rate of laminated bamboo columns is slightly higher than that of bamboo scrimber columns.