Study On Low Cycle Fatigue Performance Of Thin Steel-Concrete-Steel Composite Structure

With the development of composite structure in our country,the concrete filled steel tubular(CFST)structure has been used more and more frequently in practical engineering,and achieved satisfactory results.The double-wall hollow concrete-filled steel tube composite structure is a new type of structural member,which is developed from the traditional concrete filled steel tube.Not only inherited the advantages of a series of traditional solid concrete-filled steel tube,but also has a cross-section development,large bending stiffness,light weight,good seismic performance,better fireproof performance,and special environment has good corrosion resistance.This structure not only can be used as vertical compression members such as building structure frame column,pier column of bridge structure,pile foundation,as well as the main leg of the offshore platform but also can be used as underwater,submarine,leap of oil and gas pipeline system.The double-wall hollow concrete-filled steel tube composite structure because of its good mechanical properties and a wide range of applications prospects,it has received more and more attention.In recent years,experts and scholars have done some research on mechanical property of the double-wall hollow concrete-filled steel tube composite structure,some achievements have been made,but the research on the low cycle fatigue performance of the double-wall hollow concrete-filled steel tube composite structure is still relatively less.In particular,the strength,stiffness and energy dissipation capacity of this kind of structure will gradually degraded condition with the gradual increase in the level of displacement.The definition of the failure criterion and the damage law of the specimen need to be further studied.In this paper,the thin steel-concrete-steel double walled hollow tube,thin steel can adopt stainless steel material,with good corrosion resistance and mechanical properties.So it can be used for marine,underwater and corrosive environment of the force components,and economic and reasonable.The main contents of the study on the low cycle fatigue performance of the composite structure include the following aspects: 1.Experimental study on low cycle fatigue behavior of the thin steel-concrete-steel double walled hollow tube(1)According to the previous research methods,conclusions and related norms,three kinds of cross-section of the four double-wall hollow concrete-filled steel tube composite structure are designed and manufactured in this paper.Combined with the existing conditions of the laboratory,to determine the test loading system,the data acquisition scheme and the strain gauge layout scheme are determined.The experimental study on the low cycle fatigue behavior of double-wall hollow concrete-filled steel tube composite structure under the same loading system and the same axial compression ratio is carried out.The load-displacement hysteresis curve of the test column recorded by a data sensor.The destruction process of each test column in the test process is recorded in detail,and the resistance strain gauge reading.(2)According to the load-displacement curve of each specimen,extract the skeleton curve,and further analysis of test strain energy dissipation capacity,strength degradation,stiffness degradation and strain change under each target displacement point of each specimen are analyzed.2.Finite element analysis method on low cycle fatigue behavior of the thin steel-concrete-steel double walled hollow tubeThe finite element model of this experiment is established by using ABAQUS finite element software,and the material properties,meshing,loading system and boundary condition are defined.With the test results of the analysis and the contrast found that roughly matches.3.The results of the analysis of the thin steel-concrete-steel double walled hollow tube(1)Through the test and finite element analysis,it is found that the double-wall hollow concrete-filled steel tube composite structure has good low cycle fatigue performance.With the increase of target displacement,when traditional failure criterion has ruled specimen damage,the cumulative energy dissipation and equivalent viscous damping coefficient of the specimen are still increasing,indicating that the energy dissipation capacity of the specimen is increasing.This means that it can effectively resist the energy of the earthquake.Even in the case of lower concrete grades,the specimens still exhibit good energy dissipation capacity and ductilityIn addition,the increase of concrete strength grade as well as the increase of theconfinement factor can obviously improve the energy dissipation capacity of the specimen.(2)The study shows that,the failure criterion of the double-wall hollow concrete-filled steel tube composite structure when the bearing capacity of the skeleton curve drops to 80% of the peak bearing capacity,determination of specimen failure...