Study On Mechanical Behavior Of The Second Shaped Steel And Concrete Composite Beam Under Secondary Load

With the continuous development and progress of society and economy,people pay more and more attention to the rationality of building space and the reliability of building quality.Among many methods of reinforcement and reconstruction,using the section steel to reinforce concrete bending members can improve the bearing capacity greatly and take advantages of simple method,less wet operation and short construction period,so this method has been applied widely.However,in the actual reinforcement process,concrete bending members often can not be unloaded or can not be completely unloaded because of various reasons,the structure will appear the phenomenon of secondary load.The existence of secondary load will lead to the strain of the added steel lag behind the strain of the original concrete bending member,which will result in the decrease of the use efficiency of the section steel and the influence on the ultimate bearing capacity of the structure.Aiming at the existing problems,this article will focus on the rigidity and ultimate bearing capacity of composite beams formed by concrete bending members with the reinforcenment of section steel under the condition of primary load and secondary load.The results of this study not only improve the reinforcement theory of reinforced concrete structure,but also have practical value for the application of using section steel to reinforce concrete bending members.This article is divided into five chapters.The first chapter briefly introduces the research background,the research status,the construction technology,the research purpose and the mentality of concrete bending members with the reinforcement of section steel.The second chapter introduces the test process,including the design and production of the specimens,the arrangement of measuring points and loading method.Besides,this chapter introduces the phenomenon the failure characteristics and the results of the data processing.The third chapter uses the finite element analysis software ABAQUS to establish the finite element models of concrete bending members with the reinforcement of section steel.Through the comparison of numerical simulation results and test results,determining the feasibility of the finite element model preliminarily.Besides,on the basis of the finite element model,this chapter expands the analysis by using steel strength,concrete strength,the thickness of concrete bending members and the reinforcement ratio of the concrete bending members as variables.The fourth chapter on the basis of the test and the existing theory,conducting a theoretical analysis on concrete bending members with the reinforcement of section steel,establishing a reasonable mathematical model getting the computational formula of stiffness and ultimate bearing capacity of the second shaped steel and concrete composite beam under the primary load and secondary load.The fifth chapter summarizes the main content and conclusion of chapter one to chapter four and points out the attention points in the application of concrete bending members with the reinforcement of section steel.Besides,this chapter prospects the further research and application prospect of the concrete bending members with the reinforcement of section steel.