Experimental Study On Residual Resistance Of Shaped Steel Reactive Powder Concrete Axial Compression Columns After High Temperature

With the rapid development of China's economic strength and scientific and technological level in recent years,the form of building structure has gradually developed to super high-rise structure and long-span spatial structure.The research and development of new materials has also become an inevitable trend in the development of China's building materials industry.Reactive powder concrete(RPC)has attracted the attention of scholars all over the world because of its superior performance.In addition,the combination of reactive powder concrete and section steel not only continues the advantages of high strength and good seismic performance of steel reinforced concrete(SRC)structure,but also has the advantages of high durability and corrosion resistance of RPC.Therefore,Steel Reinforced Reactive Powder Concrete(SRRPC)structure has entered the world of researchers and become a hot topic of scientific research.With the frequent occurrence of building fires in recent years,it has brought great harm to people's life safety and social environment.Domestic experts and scholars have done a lot of research on the mechanical properties,fire protection characteristics and seismic performance of steel reinforced concrete members under fire and after fire,and obtained many important results.Because of its high steel content,the damage of section steel reactive powder concrete structure caused by fire is more serious than that of ordinary SRC structure.Therefore,this thesis has a certain practical significance for the experimental research on the residual resistance of steel reactive powder concrete columns under axial compression after fire.In this experiment,six specimens of section steel reactive powder concrete columns were designed and made.Considering the thickness of section steel protective layer and constant temperature time,the constant load temperature rise test and axial compression test after high temperature were carried out.The residual resistance of section steel reactive powder concrete columns under axial compression after high temperature was studied,and the failure phenomenon,variation law of temperature field,load displacement curve,axial stiffness and other test results of the specimens were recorded and analyzed.The numerical analysis model is established by ABAQUS software to simulate the temperature field.The following conclusions are drawn:(1)Under the condition of fire on all sides,the column body of section steel reactive powder concrete column is gray white and cyan gray,and the color change is more obvious with the increase of fire time.Irregular cracks are evenly distributed in the column body on the fire surface,and the cracks are mainly vertical small cracks.With the increase of fire time,the more dense the cracks are and the more peeling on the concrete surface.At the same time,the more serious the burst of section steel RPC specimens,and the larger the burst range,area and depth are.(2)From the temperature field curve measured by the real test of each specimen,it can be seen that the variation law of the temperature field of the measuring points of the same section in each specimen tends to be consistent;The temperature variation law of each measuring point of all specimens is affected by the distance between the measuring point and the concrete surface.The closer the distance is,the higher the temperature is.(3)Under the same fire conditions,the thickness of the protective layer of the section steel can effectively affect the change of the internal temperature field and the axial displacement of the dead load.With the increase of the thickness of the protective layer,the slower the heat conduction rate is,the slower the temperature rise of the internal measuring points of the section steel is;The constant temperature duration at high temperature has a significant effect on the axial displacement of the specimen,and the axial displacement increases greatly with the increase of constant temperature duration.(4)The failure mode of axial compression test specimens is strength failure.The main failure reason is that the small vertical cracks left by high temperature gradually expand and extend to the column body.At this time,the section steel buckles,the specimen loses its bearing capacity,and the material reaches the strength limit.(5)The ultimate bearing capacity and axial stiffness of the specimens increased significantly with the increase of the thickness of the protective layer of the section steel,which increased by 8.24%?14.77% and 13.26%?30.54% respectively;The ultimate displacement of the specimen decreases by 9.63%?19.58% with the increase of the thickness of the protective layer.(6)The constant temperature time after high temperature has a great influence on the residual resistance of section steel RPC axial compression column.With the increase of constant temperature time,the ultimate bearing capacity and axial stiffness of the specimen are greatly reduced,which are reduced by 10.29%?49.98% and 19.90%?69.75% respectively;The ultimate displacement of the specimen increases by 8.50%?29.28% with the increase of constant temperature time.(7)After the numerical simulation test is carried out by using the finite element software ABAQUS,the temperature field curve and the axial displacement curve of the steel reactive powder concrete column after high temperature are obtained.The numerical simulation results are in good agreement with the real test results,which can provide a reference for the fire analysis of steel reactive powder concrete columns.