重组竹材三面和四面受火炭化性能试验

Experimental study on charring properties of bamboo scrimber exposed to three-and four-side fire

摘要:

重组竹作为一种新型的建筑结构材料应用日益广泛,但同木材相似的可燃性导致重组竹结构抗火设计方法亟待补充和完善.为研究重组竹材多面受火炭化性能,依据ISO 834火灾试验方法进行了4组16根重组竹构件三面和四面受火试验,分析截面尺寸、受火时间以及不同受火面对炭化深度和炭化速度的影响.结果表明,由于炭化层隔热作用,随着受火时间增加重组竹构件炭化速度逐渐减小；火灾作用下构件截面有效面积减小,角部区域因承受双向热传递而由棱角变为圆角形,圆角区和非圆角区炭化深度差异明显；通过对比重组竹材多面炭化非圆角区炭化深度与单面受火炭化深度,前者较后者增加明显,引入多面炭化因子进一步修正计算模型；为简化抗火设计,通过对比多种木材,考虑圆角区影响提出重组竹材多面受火条件下名义炭化速度为0.7 mm/min,为重组竹结构灾后剩余截面计算提供重要参数依据.

Abstract:

As a new structural material, bamboo scrimber has been widely adopted in construction engineering. However, considering that bamboo scrimber is a combustible material similar to timber, it is urgent to complement and improve the fire resistance design of bamboo scrimber structures. To study the charring properties of bamboo scrimber, a total of 16 specimens in 4 groups exposed to three-and four-side fire were tested to analyze effects of section size, exposure time, and exposure surface number on charring depth and charring with furnace temperatures following the requirements of ISO 834. Results show that the charring rate decreases as the exposure time increases due to the thermal resistance of char layer. The effective section decreases and the cross-section changes to corner rounding due to the double heating process. The difference of the charring depth between the corner and non-corner areas is significant. Comparing with the charring properties of bamboo scrimber exposed to one side fire, the charring depth in multi-side fire is larger than that in one side fire. The simulation model of charring depth is further revised by considering multi-side charring factor. To simplify the fire resistance design, the notional charring rate is suggested to be 0.7 mm/min based on the corner rounding effect. Therefore, the reliable data can be used in residual cross-section simulation of bamboo scrimber structures after fire.