Analysis On The Damage Types And Chemical Composition Changes Of Wood Components In Ancient Buildings In Shanxi

The wooden ancient architecture not only represents the architectural culture of our country but also the inheritance of national culture.After several hundred years or even thousands of years of changes in the natural environment and the human environment,many ancient wooden buildings in China have suffered serious damage.One of the important aspects of repairing and protecting ancient wooden buildings is to comprehensively analyze the damage mechanism of the replaced ancient wood components,and then reasonably repair and protect the ancient wooden buildings,and to protect the original value of the ancient wooden buildings to the greatest extent.Therefore,it is very important to make full use of the replaced ancient wood components to understand the structural changes and damage of ancient wood components after many years of service.This paper collected some of the materials of the post-column and purlin components from the three thousand-year-old temples of Baitai Temple,Jinxi Tang Shu,and Daixian Confucian Temple in Xinyi County,Shanxi Province,and observed the macroscopic and microscopic scale features of ancient wood components.The physical and mechanical properties and chemical composition of the ancient wood components are measured from the outer to the inner layer,and the damage of the replaced ancient wood components is qualitatively and quantitatively evaluated,and the causes of structural damage and property changes are comprehensively analyzed.Through the analysis of the macroscopic and microscopic scales(SEM,LSCM)of the ancient elm posterior column of dates back to about 970 in Shanxi Baitai Temple,the part buried in the wall is hollow inside,the outer layer is missing,and the outer layer is visible.The late larvae were confirmed to have been attacked by stolen beetles during service;the components as a whole were eroded by soft rot fungi.The basic density of the components from the outer to the inner layer(0.46?0.53 g/cm3)is in the range of modem eucalyptus(0.46?0.54 g/cm3);the maximum saturated water content of the component from the outer to the inner layer is higher than 120?147%.The modem elm 112%,radial shrinkage ratio(5.99?6.96%)and tangential shrinkage ratio(8.2?10.82%)are close to the maximum radial shrinkage rate of 6.20%and tangential shrinkage rate of 9.0%.The content of healds in the inner layers of the ancient eucalyptus components is about 73%?76%,and the lignin content is about 21%?24%.There is no obvious change in the chemical composition between the inner layers.The above results indicated that the soft rot is from the outside to the external components.It is synchronous and has a low degree of decay.FTIR showed that the characteristic absorption peaks of hemicellulose and lignin in the outer layer of wood were slightly lower than that in the inner layer;XRD showed that the cellulose crystal form of the outer layer to the inner layer did not change,but the cellulose crystallinity of the outer layer of the member was slightly lower.It showed that over 900 years of aging has an impact on components.Shanxi Jinci Tang Shuzhu dates back to about 630 years old ancient spruce purlin components,its macroscopic and microscopic features(SEM)showed no obvious insects and decay.Radial cracks are visible in the cross-section of the member,and the crack depth is about 1/2 of the radius of the member.Cracking is the main type of damage.There is a pressed wood feature on the cell wall of the late material-thread crack.The growth width of the member from the outer to the inner layer is gradually increased(1.26?5.57mm).The basic density of the member from inner to outer layer is 0.29?0.31 g/cm3,the dynamic elastic modulus is 8.35?11.97GPa,and the radial shrinkage rate is 3.95?4.39%and tangential shrinkage rate of 7.11?8.47%gradually increased,indicating that the material properties of the member did not change significantly with the change of microstructure.The basic density of the outer layer of the member is 0.31 g/cm3 and the dynamic elastic modulus of 11.97 GPa is larger than the average value of the modern spruce,indicating that the wood member has good bending resistance.Chemical composition analysis,FTIR measurement results showed that the chemical composition and functional groups of the components from the outer to the inner layer are not significantly degraded.The XRD results showed that the cellulose of the outer layer of the member has a small erystallinity,indieating that the enamel member is affeeted by aging.Through the macroscopic observation of wood components of the Wen Temple of the County of Shanxi Province,dates back to about 470,the cross section of the wall was conical missing,and the long-column adult was found in the wormhole,indicating that it was long in service.The infestation of the beetle;the outer layer of the member has obvious square cracks.It is confirmed by microscopic observation(SEM)that the member is corroded by soft rot fungus and the outer layer is more decaying than the inner layer.The basic density of the part from the outer crack to the inner layer of the member is 0.39?0.41 g/cm3 and the maximum saturated water content is 182.90?176.41%.The radial and tangential shrinkage ratio of each layer of the member is slightly larger than the wet expansion ratio.After drying,it is saturated with water,and then dried again,and the wood can be basically restored to its original size.The above results showed that the internal portion of the member is less corroded than the square crack portion.Soft rot caused cellulose degradation,so the cellulose content of the outer layer of the member was 17.62%significantly lower than the internal 24.52%;FTIR showed that the outer lignin infrared absorption peak of the member was higher than the inner layer,and the XRD measurement showed the cellulose of the outer layer of the member.The crystallinity of 46.42%is significantly greater than the inner layer crystallinity of 53.80%.The above results indicated that the soft rot progresses from the outside to the inside in the member.Wood components are susceptible to insects and soft rot fungi.After several hundred years of use,the wood components change little from the outside to the inside.Aging leads to partial degradation of the outer layer of the component,but it has less influence on the component than the insect and decay.Therefore,the prevention and protection of the ancient building is the first to prevent insects and corrosion.