室内火灾作用下正交胶合木结构受火性能研究

Experimental study on fire performance of cross laminated timber structure exposed to compartment fire

为了研究室内自然火灾作用下可燃的正交胶合木(cross laminated timber, CLT)对CLT房间火灾荷载的贡献和不同层板组成的CLT对火灾的动态影响,开展4次内表面受火面积不同、板材层板组成不同的CLT房间自然火灾试验,直接受火CLT面积占CLT房间内表面积百分比分别为0%、19.8%、36.4%和87.6%;并以双区域模型为基础,建立考虑炭化层脱落的CLT结构室内自然火灾温度场计算模型,对CLT房间火灾试验进行模拟,分析双区域模型应用于CLT结构自然火灾时的有效性及局限性。试验结果表明:CLT受火面积对室内自然火灾发展过程及热量释放影响显著,随着CLT受火面积的增大燃烧速率显著提高,火灾的热释放速率增大;炭化层是否脱落对火灾发展过程影响显著,炭化层脱落时间及区域存在随机性;CLT单层层板厚度越薄,炭化层越早发生脱落;考虑CLT燃烧及炭化层脱落的双区域模型可一定程度上准确模拟CLT房间自然火灾室内空气温度,但是火灾降温阶段双区域模型预测的温度始终低于试验温度。

To investigate the contribution of combustible cross laminated timber(CLT) to the fire load of CLT compartment and the dynamic impact of CLT lay-up for fire under the compartment fire, four CLT compartment fire tests with different fire areas on the inner surface and different CLT lay-ups were carried out. The area of the directly fired CLT accounted for 0%, 19.8%, 36.4% and 87.6% of the inner surface of the CLT compartment, respectively. Fire dynamic model for the CLT compartment considering fall-off of the charred layers was proposed based on the two-zone fire model. CLT compartment fire tests were analyzed and simulated, and the effectiveness and limitations of the two-zone model used in the analysis of CLT compartment fire were discussed. The tests results show that the fire area of CLT has a significant influence on the development and heat release of compartment fire. The combustibility of CLT significantly increases the burning rate and the heat release rate of the fire. Whether the charred layers fall off has a significant impact on the fire development. Randomness is found in terms of both time and area of the fall-off of charred layers. The thinner the CLT single layer is, the earlier the charred layers fall off. The two-zone model that considering CLT combustion and fall-off of the charred layers can simulate the air temperature of the CLT compartment fire to a certain extent, but the fire temperature predicted by the two-zone model in the cooling phase is always lower than the test temperature.