Study On The Influence Of Aging On Fire Characteristics Of Ancient Buildings With Pine Components

China is mostly pine components of ancient buildings,after a long period of natural aging effect,the wood moisture content is reduced,the wood is loose,easy to be ignited or even start a fire.In recent years,fires in ancient buildings have occurred frequently in China,causing serious economic and cultural losses,and the effective prevention and control of fire in ancient buildings have gradually become a research hotspot.Timber components of ancient buildings is the main body of burning ancient buildings fire,its burning properties significantly affect the development trend of the fire.However,the current research on the combustion performance of wood components is mainly focused on modern buildings,and there is less research on the material properties,combustion performance and indoor fire spread of wood components in ancient buildings.Therefore,it is important to research the effect of aging on the fire characteristics of pine components of ancient buildings,which has important practical significance and scientific research value.Taking four kinds of aged pine as the research object,this paper systematically explores the influence of aging on the material characteristics of pine by means of industrial analyzer,element analyzer,scanning electron microscope,laser flash device,Fourier transform infrared spectrometer(FTIR)and X-ray diffraction(XRD).The results showed that the thermal conductivity of pine wood increased with deepening aging,and the number of groups such as aromatic hydrocarbons,ethers and carboxyl groups and cellulose crystallinity decreased.Natural aging causes a reduction in the moisture content and severe damage to the intracellular structure of pine wood.The artificial accelerated aging makes the pine wood moisture content increase,and aging damage is mostly concentrated in the surface layer of pine wood.Research on the thermal behavior and thermodynamic characteristics of pine wood during oxidation by the simultaneous thermal analyzer(STA).The results show that with the deepening of aging,the dry cracking temperature of pine wood will increase,the ignition point and carbonization temperature will be reduced,the apparent activation energy will increase during combustion,and the combustion performance will be reduced.In addition,the thermodynamic mechanism function of aged wood in the combustion stage was changed from YM(logs)obeying the Valensi equation to obeying a first-order chemical reaction model.In the carbonized combustion stage,naturally aged pine and YM obeyed the same most probable mechanism function as in the combustion stage,but the most probable mechanism function of artificially aged pine shifted from the first-order chemical reaction model to obey the shrinkage reaction model.The combustion characteristics of four kinds of pine wood were tested by cone calorimetry(CONE).It is concluded that artificially accelerated and naturally aged pine tends to form a carbonized layer,which blocks the temperature transfer and gas exchange during combustion,retards the mass loss during combustion,reduces the rate of heat release during combustion,and reduces the release of smoke as well as the release of CO2.In addition,artificially accelerated aging results in increased CO production during its combustion due to its own high water content,while naturally aged pine reduces CO production due to the slow combustion process,which results in more complete combustion.Using FDS software(Fire Dynamics Simulator)to simulate the indoor fire spread characteristics of four kinds of aging pine characteristics of ancient buildings when the wind speed is 0 m/s,It is concluded that the fire simulation results of artificial accelerated aging of one hundred and twenty cycles of pine(YE120)can be an approximate substitute for the fire simulation results of ancient buildings(CQ).Due to the lower ignition point of aging timber,burning will quickly consume oxygen,so the ancient building interior boom combustion time in advance.Finally,the coupled model of the temperature field of underfire propagation under the effect of aging damage is established.