Study On Fire Resistance Of Composite Brace Strengthened Wooden Frames In Rural Buildings

The architectural form of China rural areas is mainly timber structure.In recent years,fires have occurred frequently.In particular,the rural areas account for a large proportion of casualties and property losses,mainly due to the lack of house spacing,a large number of hidden fire hazards,and the impact of geographic location.The rescue was not timely.The initial stage of large-scale fires in some villages and towns is usually caused by a fire in a certain part of the house,and then the timber roof truss is in a fire state.When the fire resistance limit is reached,the roof truss collapses,and the flame is exposed to the outdoors due to the influence of the wind to ignite the surrounding buildings,causing a collateral effect.Cause greater losses.There are few studies on the fire resistance of timber structures in our country,especially in the fire resistance of timber structures in villages and towns.Therefore,the research on the fire of timber structures needs to be more in-depth.According to the basic principles of heat transfer,this paper uses ABAQUS finite element software to analyze various aspects of timber beams.The work done is divided into the following aspects:(1)Introduced a component suitable for the reinforcement of timber structures in villages and towns,mainly composed of timber,steel and fire-resistant insulation materials.The purpose is to improve the fire resistance limit time of the timber frame structure under fire and the overall safety of the house.It has the characteristics of easy construction and installation,low cost,convenient use and good effect.(2)Summarize the current research status of thermal properties and mechanical properties of timber and steel,introduce the constitutive relationship of timber,and aim at the characteristics of timber anisotropy.When the ABAQUS finite element software simulates,the timber constitutive model is Use ABAQUS associated Vumat subroutine for analysis at room temperature,and use engineering constants to define timber properties for analysis at high temperature.(3)Establish a model corresponding to the test.Through the finite element numerical analysis of the temperature field of the timber beam section,the ultimate bearing capacity of the timber beam at room temperature,and the fire resistance limit time of the timber beam at high temperatures,the simulation results and the test results are carried out.Compare to verify effectiveness.The conclusion is: the higher the moisture content of the timber beam under fire on three sides,the slower the temperature rise and the slower the carbonization speed,but the effect is small.The higher the density,the slower the temperature rise at the same side point and the slower the carbonization speed.The impact of density on the carbonization speed of timber is less at the beginning stage.As time increases,the difference between temperature and carbonization speed becomes more and more obvious.(4)Use ABAQUS to conduct sequential thermo-mechanical coupling analysis of pure timber frame and reinforced frame,first simulate the temperature field,then simulate the structure field,and study the influence of different parameters on the fire resistance limit.Through the reinforcement of the timber frame,under normal temperature The ultimate bearing capacity and the fire resistance limit time under high temperature are obviously improved,and the effect is very good.The thickness of the channel steel in the bracing and the size of the timber square section were changed to study its influence on the ultimate bearing capacity,and an actual project was selected for simulation to provide a reference for the reinforcement of timber houses in villages and towns.