A Study Of Fire Resistance On New Timber-Steel Composite Floorslab In Rural Buildings

Wood is the main building material used in rural buildings in Northwest Guangxi and Southeast Guizhou.Due to the combustible wood and the close layout of rural buildings,the fire risk of rural buildings is high and the fire destructive power is strong.In addition,the rapid spread of fire and the shortened collapse time increase the difficulty to rescue.Based on the research background of rural wooden structure houses,this paper proposes a new type of wooden structure composite floor slab that adds a layer of thin steel plate and plank on the basis of ordinary floor slab.The main research contents and conclusions are as follows:(1)Using the finite element software ABAQUS,based on the standard heating curve,the temperature field of the ordinary floor slab,the proposed new composite floor slab and the wooden beams connected to it were analyzed.The results of the numerical simulation show that the temperature distribution changes in the cross-section at the junction of the floor and the wooden beam when the cross-section is exposed to fire,and the heating rate of the fire-back surface of the composite ones is much lower than that of the fire-back surface of the ordinary floor slab.(2)Carbonization rate analysis is carried out according to the carbonization part of the obtained temperature field Contour plots of the ordinary and composite floors.The results illustrates that the average carbonization rate in the vertical direction of the composite floor is0.51mm/min,and the average carbonization rate in the thickness direction of the composite floor is 0.65mm/min,and the carbonization rate decreases with the increase of density.(3)The static numerical simulation model of the floor with groove and tongue was established at room temperature.The results show that the ultimate bearing capacity and mid-span deflection of the floor with groove and tongue are in good agreement with the test results.The thermal stress-coupling model of the ordinary slab and the new composite slab is established.The ultimate fire resistance time of the two slab is analyzed from the perspective of bearing capacity and heat insulation.The results show that the ultimate fire resistance time of the ordinary slab and the composite slab is 11min36 s and 30min51 s,respectively.The thermal insulation ultimate fire resistance time of the ordinary and composite floors is13min23 s and 39min47 s respectively.Compared with the ordinary slab,the ultimate fire resistance time of the new composite slab is significantly improved.(4)According to the thermal-stress coupling model of the new composite floor,the factors affecting the ultimate fire resistance time of the new composite floor are analyzed.The results demonstrates that increasing the thickness of the upper board of the new composite floor slab can increase the ultimate fire resistance time,but increasing the thickness of the thin steel plate cannot increase the limit.