考虑层板脱落影响的正交胶合木楼板炭化速度试验研究

Experimental study on charring rate of cross-laminated timber floor considering the effect of delamination

为研究国产正交胶合木(CLT)楼板受火条件下的层板脱落情况及其对炭化速度的影响,开展了6组试件在给定时间下的炭化速度试验,研究了受火时间、层板厚度和层板脱落对CLT板炭化速度的影响规律,提出了考虑层板脱落影响的炭化深度计算方法.研究结果表明:当CLT楼板受火时间较短、炭化层未发展至层板胶缝处时,未发生层板脱落,其炭化速度与实木、层板胶合木等构件的炭化速度基本相同;当受火时间较长、炭化层发展至层板胶缝处时,采用单组分聚氨酯(PUR)作为胶黏剂压制而成的CLT板将发生层板脱落;且受火时间越长,脱落情况越严重,平均炭化速度越快;对比相同厚度不同层数的CLT板,层板数较多且单层层板厚度较薄的CLT脱落情况更严重,平均炭化速度更快.提出的炭化深度计算方法有效地考虑了受火时CLT楼板层板脱落带来的炭化速度加快的影响,计算结果与试验结果吻合良好,可供工程设计人员参考.

To study the delamination of cross-laminated timber (CLT) floor under fire and its influence on the charring rate,fire tests were carried out on six specimens at different given times.The effects of fire duration,the thickness of CLT floor,and falling off of charred layers on the charring rate of CLT floor were studied.The charring depth calculation method considering the influence of falling off of charred layers was established.The results show that when the CLT floor is exposed to fire within a short time and the char line does not develop to the glue line,the charred layer will not fall off.The charring rate will remain basically the same as that of the solid wood,glue-laminated timber and other engineered timber products.CLT bonded with one-component polyurethane (PUR) adhesive will fall off when the char line develops to the glue line after longer fire exposure.In addition,the longer the fire exposure time,the more serious the falling off and the faster the average charring rate.Compared the results of CLT with different layers,the falling off of the charred layers is found to be more serious and the average charring rate is higher when the number of layers is larger and the lamella is thinner.The proposed charring depth calculation model effectively takes into account the influence of accelerated charring rate caused by falling off of the charred layers under fire.The calculational results are in good agreement with the test ones and can provide a reference for engineers.