Analysis Of Fire Resistance Performance Of Reinforced Concrete Haunched Slab Under Fire

Fire brings convenience to people,but also endangers people's life and property safety.Every year,the number of building fire incidents in China is huge,the number of casualties is large,and the economic losses are heavy.The research on building fire prevention and fire resistance is a hot topic today.Reinforced concrete with axils around axils can be regarded as arch-shell structure with better mechanical performance than plane structure.The load is transmitted to the frame beam in the form of uniform distribution load,which is more reasonable and economical than the traditional load transfer mode of concentrated force on the floor,and the floor is an essential part of the fire resistance of the whole building,which can block the heat flow and prevent the flow of heat to other buildings floors,causing greater casualties,improving the fire resistance of the floor to prevent buildings from collapsing by fire,in order to reduce casualties and economic losses.reinforced concrete with axil slabs studied in this paper has been used in many buildings,but its fire resistance is rarely studied.in this paper,with the help of ABAQUS finite element software,the fire resistance of reinforced concrete slabs is modeled and analyzed,which can provide reference for the fire resistance design of axil slabs in the future,enhance the fire resistance of buildings and reduce the fire damage of buildings.The validity of the data model is proved by the experimental verification of the model.The following conclusions are obtained by using these validated data models based on finite element analysis of the heat-resistance performance of axillary plate modeling with different protective layer thickness,different axillary thickness and different axillary length:(1)Through the calculation of temperature field,the temperature-time curve of plate neutralization edge is obtained.Whether in plate edge or plate,there is a great temperature gradient between the bottom surface and the inner part of the plate with large haunched slab.From the model analysis of five different protective layer thickness plus axillary plate,the thickness of protective layer has no effect on the temperature field of axillary plate.The distribution of temperature field in reinforcedconcrete and axillary slab has a large temperature gradient,and the distribution of temperature field in slab is only related to the distance from the fire surface of the slab the slab,and is subjected to fire.The surface temperature is the highest and the temperature is the fastest.As the concrete inside is far away from the fire surface,the heating rate slows down,and the temperature gap between the back fire surface and the fire surface increases gradually.(2)By modeling and analyzing the axillary plate with five different thickness of protective layer,the deformation in the plate is obtained.The vertical displacement deformation in the plate is divided into three stages: the first stage is that the deformation in the plate decreases slowly,the deformation rate is very slow,and the vertical displacement increases very little;the second stage is that the deformation rate increases sharply,and in a short time,the vertical deformation increases sharply,which is the fire resistance limit stage;the third stage is that the deformation in the plate decreases slowly,the deformation rate is about 1/2 of the second deformation rate.Different thickness of the protective layer has a great influence on the deformation of the span plate,and the greater the thickness of the protective layer,the greater the fire resistance limit,which is because of the thermal inertia of concrete.Sometimes,however,the effect of increasing the thickness of the protective layer on increasing the fire resistance limit is not obvious,and the plate phase of 30 mm of the thickness of the protective layer is only increased by 2 minutes compared with the plate resistance limit of 25 mm in this paper Changing the thickness of the protective layer in this interval has little effect on the fire resistance limit of the axillary plate.(3)Through the thermal coupling analysis of three different axillary plates with150 mm?250mm and 350 mm,the vertical displacement cloud map of the three plates was obtained.By comparison,the fire resistance limit of the axillary plate with larger axillary thickness was significantly larger than that of the plate with larger thickness.From the deformation diagram of the plate with 150 mm axillary thickness,the vertical displacement and instability of the plate with smaller axillary thickness after the fire,and the fire resistance limit is small,give the building belt come uncertainty,more dangerous.In the design of axillary plate,the thickness of axillary plate can be increased to increased to increase the fire resistance limit of the axillary plate,and the fire resistance grade of the building can be increased.In the preliminary design,the thickness of the axillary plate should not be too small,otherwise it can not meet the fire resistance requirements.(4)Through the simulation analysis of three different axillary length plates of1000 mm?1500mm and 2000 mm,it is concluded that increasing axillary length can increase the fire resistance limit of axillary plate,the effect is very remarkable,and the deformation also accords with the law of three stages.Excessive increase in axillary length leads to fire resistance The limit is too large,which creates waste.