Study On Fire Performance Of Two-way Concrete Slabs Supported Simply On Three Sides And Fixedly On One Side

As a common type of slab in engineering,the two-way concrete slab is an important horizontal bearing member.There are few full-scale two-way concrete slab tests which could not explain the impact of different support conditions in present domestic and foreign researches,so it is particularly necessary to research the fire performance of the two-way concrete slab under several typical different support conditions.The two-way slab with three sides simply supported and one side fixed is located in the edge of plate at both ends of the long building structure,which is one of the main areas for escape and rescue.This paper mainly carries out the fire performance test of the two-way concrete slab with simple support on three sides and fixed support on one side based on the above reasons.The main research contents are as follows:(1)The fire performance test of the full-scale two-way concrete slab with simple support on three sides and fixed support on one side was carried out under the condition of heating under constant load.The test designed related fixed end device and measured the temperature field distribution of the concrete and steel in the direction of section thickness,off-plane displacement,in-plane displacement and the angle of plate edges of the two-way concrete slab under fire,then the macro phenomena such as the cracks form,etc.and failure characteristics of the two-way slab under fire was analyzed.(2)The test results show that the cracks form of the slab surface,which presenting shallow bowl bottom shapes,consists of the two transverse cracks on the1/2 area of the medially fixed side and the intensively annular diagonal cracks on the corner side.There are several main transverse cracks in the central area of the slab surface.The whole slab is concave along the plastic line and its shape is similar to a basin.The crack on the slab bottom is obvious,and there are radial cracks in the no-fire area.There is obvious nonlinear temperature field in the direction of section thickness,and the temperature gradient is large and it occurs different degree of flat stage at about 100?.The tendency of temperature of steel is the same as that ofconcrete and there is little difference of the temperature between the steel and the concrete at the same position.During the heating process,the off-plane displacement was greatly affected by the fixed end,and gradually decreased from the middle to the four sides.The displacement at the same position from the central axis was less than that at the simple supporting edge,showing a nonlinear trend as a whole,and the maximum displacement reached-244.56 mm and-261.41 mm respectively.The fixed end has a certain inhibitory effect on the edge displacement and angle of the shorter simple supported edge.The whole slab was in the state of expansion and there was partial shrinkage in the process.During the cooling process,the off-plane displacement rebounded obviously,and the maximum displacement rebounded31.76% and 30.73% respectively,there was a stable level with the temperature decreasing.In the plane,the short side shrinks inward while the long side shrinks under the influence of the fixed end.(3)The temperature diagram,displacement diagram and failure area diagram can be obtained by establishing the two-way slab model with simple support on three sides and fixed support on one side.The temperature field and the deformation law of the slab could be proved secondarily by analyzing the data.The numerical simulation results of temperature field and off-plane displacement are in good agreement with the experimental results,and the model is relatively reliable.