木梁三面受火后力学性能的试验研究  

Experimental study of the mechanical behavior of timber beams exposed to three-side fire

作　　者：许清风[1,2] 李向民[1,2] 张晋[3] 穆保岗[3] 徐强[2] 李帅希[3] 

机构地区：[1]上海市工程结构新技术重点实验室,上海200032 [2]上海市建筑科学研究院,上海200032 [3]东南大学,江苏南京210096

出　　处：《土木工程学报》2011年第7期64-70,共7页China Civil Engineering Journal

基　　金：上海市科委青年科技启明星计划(07QB14031);国家"十一五"科技支撑计划(2006BAJ03A10-02)

摘　　要：木梁三面受火后截面分为三个区:外侧为炭化层,承载力完全丧失;中间为高温分解层,承载力明显劣化;内部为正常层,承载力无影响。通过4组15根木梁三面受火后力学性能的对比试验研究,了解不同受火时间后木梁剩余承载力、破坏形态和炭化速度的变化。研究结果表明,三面受火后木梁初始刚度明显降低,剩余承载力显著减小。三面受火后木梁承载力下降原因主要包括:受火后木梁表面炭化使有效面积减小,中和轴上升;受火后靠近炭化层的高温分解层木材强度明显劣化。由于角部遭受两个方向的热传递,使木梁下角部炭化加速后变为弧形。随着受火时间增加,木梁炭化速度有所降低;且竖向炭化速度略大于水平炭化速度。The cross-section of timber beams exposed to fire is divided into three parts： char layer with no strength,pyrolysis zone with decreasing strength,and the normal zone.To learn about the fire performance of timber beams,such as residual bearing capacity,failure mode and charring rate,15 specimens in 4 series were experimentally studied.It is found that the residual bearing capacity and initial stiffness of exposed specimens decrease obviously.The reasons for decreasing ultimate strength include： decrease of effective cross-section,rise of the neutral axis and obvious reduction of strength of the pyrolysis zone.Since the corners are subjected to heat transfer from two directions,faster charring at these corners led to a rounding effect.It is found that the charring rate will decrease with increasing exposed time,and the vertical charring rate is always larger than the horizontal charring rate.

关 键 词：木梁 三面受火 炭化速度 高温分解层 力学性能 剩余承载力 

分 类 号：TU352.5[建筑科学—结构工程] TU366.2