Fire Resistance Test Of Shaped Steel Reactive Powder Concrete Columns With Different Stirrup Ratios

Reactive Powder Concrete(RPC)is a kind of structure in which Reactive Powder Concrete(RPC)is replaced by the surrounding Concrete of SRC column structure.Because RPC structure has low porosity,good impermeability,excellent durability,and excellent mechanical properties,it has a broad application prospect in the future construction field.SRC structures with high bearing capacity,high ductility coefficient,strong resistance to transverse deformation,flexible section size and other advantages have been widely used in large span,heavy load,high-rise and earthquake prone areas.Therefore,with the frequent occurrence of fire in recent years,there are still insufficient fire resistance tests for the new structure of SRC.Therefore,it is of great significance to study the fire resistance of SRC structure.Combining with domestic and international research on high temperature mechanical properties of reactive powder concrete material,steel reinforced concrete structure under the influence of the high temperature performance research,design and casting steel reactive powder concrete column 5,the use of electric heating furnace for high temperature under constant load test research,mainly considering the influence of different reinforcement ratio,the phenomenon of experimental data and analysis,get the following conclusion:1)By comparing the damage phenomena of the five specimens,it is found that the concrete part of all RPC specimens becomes lighter in color and the steel fibers appear black under the action of high temperature,but they still maintain certain compactness and gripping property.The specimen with high stirrup ratio did not show large cracks and deformation,and no concrete burst phenomenon.The vertical cracks were the main failure of the specimen,which was the compression failure,regardless of the stirrup ratio.By observing the crack strike,the cracks of the specimen all developed from the axial compression of the calculation area.With the increase of the hoop ratio of steel RPC column specimens,the failure phenomenon of specimens becomes less and less obvious.The crack distribution varies from a large area in the calculation area of the specimens with low hoop ratio to a sporadic distribution in the center of the calculation area of the specimens with high hoop ratio,and the surface crack distribution tends to decrease.2)By sorting out and analyzing the time-temperature curves of the specimens,it is found that in the process of temperature increase,the temperature change of each measuring point in the early period of temperature rise is very small and the change trend is basically the same.With the increase of furnace temperature,the temperature of the outer measuring point rises faster than that of the inner measuring point,and the temperature of the same steel member inside the specimen is basically the same.3)By sorting out and analyzing the refractoriness time of the specimens,it is found that the displacements of all specimens remain basically unchanged in the stage of graded loading;At the beginning of loading and heating stage,when the temperature was low,the axial displacement of the specimen changed little,but when it reached a certain temperature,the axial displacement of the specimen began to increase gradually.The slope of the displacement change curve of the specimen with low hoop ratio was higher than that of the specimen with high hoop ratio.When the maximum fire resistance time is between 65% and 84%,the displacement rate of the specimen increases slowly with the fluctuation.4)Finite element analysis software ABAQUS was used to analyze the whole process of the test,and it was found that the numerical analysis results were in good agreement with the experimental research in the temperature field simulation.The longer the heating time is,the smaller the error between the surface concrete temperature and the simulated value will be.However,the longer the temperature of the internal concrete rises,the more the heat loss will be,and the larger the error will be with the simulated value.The distribution and development of cracks are verified in the thermodynamic coupling simulation,and the deformation and failure characteristics of the test specimen are verified.The general rule that the fire resistance time of the specimen lengthens with the increase of the stirrup ratio is verified in the thermodynamic coupling simulation.And it was further verified by parameter expansion.