自然老化对古建筑马尾松燃烧行为和力学性能的影响

The effect of natural aging on the combustion and mechanical properties of ancient architectural Pinus massoniana

选取距今约170年的清代木结构建筑屋内和屋外马尾松为研究对象,系统分析自然老化对马尾松微观结构、燃烧行为及力学性能的影响规律。结果表明,自然老化作用会显著破坏松木的细胞结构,其中屋内松木服役过程中易因虫蚁蛀蚀和真菌寄生而出现明显的表面虫洞现象,而屋外松木服役过程中易受紫外线作用而发生更显著的内部有机成分降解。相比于内部有机成分降解,表面虫洞现象会更大程度恶化松木的力学性能,其中屋外清代松木的抗拉强度和抗弯强度较现代松木下降了27.4%和10.8%,而屋内清代松木则分别下降了48.2%和31.6%。燃烧性能分析表明,自然老化作用削弱了木材的燃烧强度和热稳定性,其中屋内清代松木和屋外清代松木的峰值热释放速率较现代松木分别降低了8.4%和15.4%,初始分解温度(T5%)较现代松木分别降低了19.2、10.1℃。相比于屋外清代松木,屋内清代松木具有更低的T5%值与更高的CO_(2)与CO产生速率,这主要与屋内清代松木的细胞结构破坏程度较大有关,表现出较低的热稳定性和较强的火灾烟气毒性。

The Pinus massoniana inside and outside the Qing Dynasty wooden building from approximately 170 years ago was taken as the research object to systematically analyzes the effects and regulations of natural aging on the microstructure,combustion behavior and mechanical properties of the Pinus massoniana.The results show that natural aging can significantly damage the cellular structure of the pine,where indoor pine is susceptible to significant surface wormholes due to insect infestation and fungal parasitism during service,while outdoor pine is susceptible to more significant degradation of internal organic constituents due to UV light.Compared to the degradation of internal organic components,the surface wormholes can deteriorate the mechanical properties of the pine to a greater extent.The tensile and bending strengths of outdoor Qing Dynasty pine are lower than those of modern pine by 34.1%and 34.7%,respectively,while those of indoor Qing Dynasty pine are reduced by 48.2%and 31.6%,re⁃spectively.Combustion performance analysis reveals that the natu⁃ral aging effect weakens the combustion strength and thermal stability of the wood,with the peak heat release rate(PHRR)being reduced by 8.4%and 15.4%,and the initial decomposition temperature(T5%)being reduced by 19.2 and 10.1℃,for the indoor Qing Dynasty pine and outdoor Qing Dynasty pine,respectively,compared to the modern pine.In addition,compared with outdoor Qing Dynasty pine,the indoor Qing Dynasty pine has lower T5%and higher CO_(2) and CO production rate,which is mainly related to the greater destruction of cellular structure of indoor Qing Dy⁃nasty pine,thereby indicating that the indoor Qing Dynasty pine has lower thermal stability and stronger fire smoke toxicity.