Experimental Study On Seismic Performance Of Shaped Steel Reactive Powder Concrete Columns After High Temperature

In recent years,reactive powder concrete(RPC)structures and steel reinforced concrete(SRC)structures with good mechanical properties have been more and more widely used in the field of building structures.The combination of RPC and SRC structure to form the steel reinforced reactive powder concrete structure can not only give full play to the excellent mechanical properties of RPC material,but also make it have the higher strength and better seismic performance than the ordinary steel reinforced concrete structure.In addition,in the case of building fire occurring frequently today,the possibility of fire damage to steel reinforced reactive powder concrete structures is increasing.Due to the high steel content of steel reinforced reactive powder concrete structures,the damage of steel reinforced reactive powder concrete structures after fire is more seriously than other structures under the same fire conditions.Moreover,the damage caused by fire and earthquake simultaneously will be much greater than the damage caused by each of them.Therefore,the impact of multiple hazards on the behavior of steel reinforced reactive powder concrete structures has attracted more attention.Researchers have studied various mechanical properties of steel reinforced reactive powder concrete structures at room temperature,and have achieved many achievements.However,there are relatively few studies on its performance in high temperature and after high temperature at home and abroad,and even fewer studies on its seismic performance after high temperature.Therefore,it has certain guiding significance to study the seismic performance of steel reinforced reactive powder concrete structures after high temperature.In this thesis,seven steel reinforced reactive powder concrete were designed and manufactured.One steel reinforced reactive powder concrete column was subjected to low cyclic loading test at room temperature,and six steel reinforced reactive powder concrete columns were subjected to low cyclic loading test after high temperature.The effects of constant temperature time(30 min,60 min,90 min)and axial compression ratio(0.2,0.3,0.4,0.5)on the seismic performance of the specimens were studied and investigated.The temperature field,axial displacement,failure modes,hysteresis curve characteristics,bearing capacity,ductility and stiffness degradation of the specimens were analyzed.Through the analysis of the test results,the following main conclusions can be obtained.(1)The surface of the specimens was grayish white after high temperature.Several transverse cracks and longitudinal cracks were detected on the fire surface of the specimen,and the specimen showed different degrees of concrete peeling and bursting phenomenon.The constant temperature time has a greater impact on the damage of concrete after high temperature of the specimen,the longer the constant temperature time,the more obvious the specimen burst phenomenon and the larger the burst area.The axial pressure ratio has little effect on the degree of concrete bursting and peeling of the specimens.(2)According to the temperature rise curve of the specimens,it can be seen that the internal temperature of the specimen decreases with the increase of the distance from the fire surface.The concrete temperature in the core area of the specimen is significantly lower than the edge temperature of the specimen.The temperature of the section steel of the specimen is lower than that of the longitudinal reinforcement and stirrup.(3)From the axial displacement-time curves of the specimens,it can be seen that the ultimate axial displacement of the specimen increases with the increase of the constant temperature time,and the ultimate axial displacement of the specimen decreases with the increase of the axial compression ratio.The results show that the constant temperature time and axial compression ratio have significant effects on the deformation of the specimens,and increasing the axial compression ratio can limit the axial displacement of the specimen.(4)The hysteresis curves of the specimens are plump,and the specimens have relatively large energy dissipation coefficient when the specimens are damaged after high temperature,indicating that the specimens still have good seismic resistance after high temperature.(5)With the increase of constant temperature time,the yield load and peak load of the specimen decreased by 20.6%?30.0% and 21.6%?33.8%,respectively.With the increase of axial compression ratio,the yield load and peak load increased by 9.0%?24.1% and11.5%?25.8%,respectively.(6)With the increase of constant temperature time,the ductility coefficient,initial stiffness and energy dissipation capacity of the specimen decreases by 16.0%?28.5%,7.2%?33.2% and 33.0%?45.5%,respectively.(7)With the increase of axial compression ratio,the ductility coefficient of the specimen decreases by 2.0%?10.2%.The initial stiffness and energy dissipation capacity of the specimens increased by 6.9%?13.9% and 11.1%?16.6%,respectively,with the increase of axial compression ratio.(8)The temperature field and thermal coupling model of steel reinforced reactive powder concrete columns were established by finite element software ABAQUS,and the results showed that the simulation results of the temperature field and axial displacement of the specimens at high temperature were basically consistent with the test results,which can provide a reference for the seismic performance analysis of steel reinforced reactive powder concrete columns after high temperature.