Study On Fire Separation Of Rural Residential Timber-structure-buildings In Southwest China

In southwest China,timber-structure-buildings are adopted widely in townships.Once a fire breaks out,it is easy to cause the serious fire consequence among timber-structurebuildings.At present,the domestic and foreign scholars’ research on the fire resistance performance of timber-structure-buildings mainly focuses on the material level and the component level,but the researches on the fire resistance performance of the whole structure and the fire prevention measures among timber-structure-buildings are weak comparatively.Most of the rural residential timber-structure-buildings in China do not meet the safety and fire protection standards,and there are hidden dangers of fire safety.In this paper,the typical rural residential timber-structure-building in southwest China was taken as the research object,the numerical simulation research on its fire disaster evolution mechanism was carried out,and the suitability fire prevention measures were put forward,so as to further improve the fire resistance performance of rural residential timber-structure-buildings.The main research contents of this paper are described as follows.(1)Taking a timber-structure-building in the ancient city of Lijiang as the research object,by FDS software,the numerical simulation research on its fire development process,heat transfer process and fire disaster evolution mechanism was carried out,and compared with the relevant test data to verify the effectiveness of the numerical model.At the same time,the influence rule of reference temperature and reaction heat on the results of numerical simulation was discussed,and the reasonable values of reference temperature and reaction heat in the numerical model were determined.(2)Taking a typical rural residential timber-structure-building in southwest China as the research object,PyroSim software was used to build three groups of fire numerical models representing different working conditions,and the influence rules of wind speed,window size and open-close state,and firewall setting between buildings on the thermal radiation flux were explored.Furthermore,the influence law of the above factors on the fire spreading process among the timber-structure-buildings was discussed,and the suitability fire prevention measures of the rural residential timber-structure-buildings were proposed.According to the results of numerical simulation,the following conclusions are proposed in this paper.(1)Two basic parameters,reference temperature and reaction heat,have significant effects on the accuracy of numerical simulation results.The maximum value of thermal radiation flux decreases with the increase of reaction heat,and the reaction heat has no significant effect on the time of the structure reaching flashover.The time of the structure reaching flashover is prolonged with the increase of the reference temperature,but the influence of the reference temperature on the maximum thermal radiation flux is not obvious.When the reaction heat is 5000 k J/kg and the reference temperature is 150℃,the actual pyrolysis of wood can be well reflected in the process of establishing the numerical model of timber-structure-building.(2)Wind speed has a great influence on fire spread among timber-structure-buildings.With the increase of wind speed,the thermal radiation flux around the perimeter of the burning building will increase,and the fire separation will increase.When the wind speed is0m/s,1m/s,2m/s,3m/s,4m/s and 5m/s,the fire separation between timber-structure-buildings is 5.4m,5.76 m,6.12 m,6.52 m,6.88 m and 6.54 m correspondingly.(3)The closed state of the window of the burning building and the shielding between the buildings can effectively delay the fire spread time between the buildings,and can effectively reduce the fire separation between the buildings.Under the wind speed of 4m/s,the fire separation between buildings can be reduced from 6.88 m to 4.91m;Under the wind speed of5m/s,the fire separation between buildings can be reduced from 6.54 m to 4.87 m,a decrease of 25%.Based on this,in this paper,the automatic window closing device in fire was proposed,and the suitability fire prevention measures by planting Shima superba as firewall between timber-structure-buildings was proposed,and the reasonable planting distance between Shima superba firewall and timber-structure-building was put forward.