Thermal Stress And Flexural Behavior Of Reinforced Concrete Beam Under High Temperature

For nuclear power plants and high-temperature workshops of metallurgy and chemical industry,the internal reinforced concrete structure of the buildings is exposed to high-temperature radiation all year round,which causes its bearing capacity and stiffness at high temperatures to be significantly reduced.In order to further enrich the research methods and theories of structural performance at high temperatures and provide reference for the optimized design of reinforced concrete structures at high temperatures,relying on the project "Experimental Research on Reinforced Concrete Members under Extreme Temperatures" jointly conducted with China Universal Engineering Corporation and Wuhan University,taking the Reinforced concrete beam members under high temperature as research object,Systematic research is carried out on the loading and testing methods and the thermal and mechanical property of reinforced concrete materials at high temperatures.Based on this,the deformation and thermal stress analysis of flexural members under high temperature environments are performed.The specific research contents are as follows:(1)Research on test methods for mechanical properties of components during heating.Design and develop a high temperature mechanical property test system to achieve the simultaneous independent application of temperature and load,so that the mechanical performance test of bending,axial tension and axial compression members under high temperature environment can be realized.Utilizing the advantages of this test system to accurately control and monitor the temperature of the test specimen,an in-situ compensation concept,namely the self-compensation method of strain gauge temperature,is proposed to effectively distinguish the strain caused by heating and the strain caused by force.In addition,test analysis of coefficient linear thermal expansion of materials at different temperatures can be provided effective support.(2)Test and research on coefficient of linear thermal expansion of steel bars,mortar,and limestone and elastic modulus of mortar and limestone at high temperature.Relying on the in-situ compensation method,the coefficient of linear thermal expansion s of the steel bars,mortar,and limestone in the range of 30℃ to 300℃ are obtained through testing.Comparative analysis of the variation of test parameters with temperature can be used to verify the rationality of the test system and method,and provides a basis for the study of internal thermal stress and mechanical properties of reinforced concrete members at high temperatures.(3)Deformation test of reinforced concrete flexural members under high temperature.Using the high-temperature loading test system and in-situ compensation test method,the reinforced concrete beam specimens were subjected to a coupling test of heating and four-point bending load in the range of 30 ℃ ~ 300 ℃.The resistance strain gauge technology is used to measure the strain of the mid-span section of the reinforced concrete beam,and the strain caused by the heating and the strain caused by the load are separated,and the mechanical performance of the reinforced concrete beam under high temperature environment is analyzed and studied.It provides a reference for the analysis of mechanical properties of reinforced concrete under high temperature and the optimization of design.