Experimental Study On Low Cycle Reciprocating Performance Of Steel Reinforced Concrete L-Shaped Column After High Temperature

The steel reinforced concrete special-shaped column is a new type of combined structure.The concrete is filled with channel steel and angle steel and connected by steel bars or webs.The main section of the steel-reinforced concrete special-shaped column includes L-shaped,cross-shaped and T-shaped,which has the advantages of not occupying the room area,flexible building layout and space saving.In recent years,the frequency of fires has increased year by year,and fires have an important impact on the seismic performance of special-shaped columns.This paper mainly studies the seismic performance of steel-reinforced concrete L-shaped columns under fire conditions.The main work and conclusions of this paper are as follows:1.Analysis of temperature field of steel reinforced concrete L-shaped column.The steel-concrete L-shaped column was subjected to fire test under no-load conditions.Among them,the No.1 test piece was used as the comparative member at room temperature,and the No.2 test piece and the No.3 test piece were respectively subjected to the 120 min and 180 min fire test components.Thermocouples were pre-embedded in the same height section of the three test pieces to measure temperature changes and temperature field analysis was performed using finite element software.The results show that:(1)There is a difference in heating rate at different depths of the same section.The farther the temperature is from the fire,the slower the heating rate is.The temperature of the surface measuring point is similar to the heating process of the furnace temperature.(2)After the high temperature,the steel is high.The color of concrete on the surface of concrete L-shaped column changes.With the increase of high temperature time,the surface color changes from grayish white to dark red,and micro cracksappear in high temperature areas,and the boundary between unfired areas is obvious;(3)through finite element analysis Temperature field analysis of steel reinforced concrete L-shaped columns.2.Low-cycle reciprocating test of steel-concrete L-shaped column after high temperature.The effects of different fire times on the hysteretic behavior of steel reinforced concrete L-shaped columns were studied experimentally,and the skeleton curve,stiffness degradation,ductility development and energy dissipation capacity were analyzed.The test results show that:(1)The hysteretic curves of steel reinforced concrete L-shaped columns are fusiform,experiencing the elastic phase,plastic development stage and failure stage;(2)the fire time is suitable for the stiffness and ultimate load of the steel reinforced concrete L-shaped column.A certain impact,but the impact is not great,but the impact on the energy consumption and ductility of the specimen is obvious;(3)The hysteresis curve of the final failure of the L-shaped column of steel reinforced concrete converges to the pure steel skeleton,mainly because of the test When the loading is carried out,the concrete protective layer on the surface is seriously detached,the profile steel is relatively intact,and it has certain resistance to deformation under the action of earthquake;(4)The equivalent viscosity coefficient of the L-shaped column of steel reinforced concrete is between 0.2 and 0.4,indicating Steel-concrete L-shaped columns have better energy dissipation capacity.