Analysis Of Mechanical Behavior Of Cross-shape Concrete-filled Steel Columns Under High Temperature

With the continuous progressWith the continuous progress and development of science and technology,more and more new technologies,new structures,new materials have been widely used in the field of engineering technology,among which,steel and concrete composite structures have been widely used.Concrete filled steel tube(CFST)composite structure has the advantages of high strength,good plasticity and good seismic performance,so that the integrity of the structure has been strengthened.Because of its superior characteristics,the steel and concrete composite structure has been widely used in practical engineering.Because of the increasing safety awareness and the improvement of living environment quality,concrete filled steel tube(CFST)composite frame structure has been widely recognized for its advantages such as flexible separation of space,saving of resources,good seismic performance and so on.At the same time,due to the rapid growth of the contemporary population,especially the continuous development of the diversified types of urban buildings,people's requirements for the safety of the living environment are becoming higher and higher,with regard to casualties and property losses caused by fire,Researchers and designers are becoming more and more concerned about the fire resistance of concrete filled steel tube(CFST)composite frame because of the multi-factor coupling research.In this paper,the mechanical properties of concrete-filled steel tube composite frame under high temperature fire are studied as follows:Through a large number of documents and field investigation,It is concluded that the research on mechanical characteristic plasticity analysis of concrete filled steel tube composite frame at high temperature has important application value and popularization significance in practical engineering field.2.Through summarizing the plastic analysis theory of concrete-filled steel tube composite frame at high temperature,this paper introduces the plastic analysis theory of concrete-filled steel tube composite frame at room temperature and high temperature,and expounds the concrete steps.3.By analyzing the influence parameters of the bearing capacity of concrete-filled steel tube composite frame at high temperature,the plastic mechanical characteristics of single-story concrete-filled steel tube composite frame at room temperature and high temperature are studied.Different theoretical calculation methods and corresponding steps are used to analyze the number and sequence of plastic hinges of concrete-filled steel tubecomposite frames under different fire conditions.4.The mechanical characteristics of concrete-filled steel tube composite frame under different working conditions and the accuracy of the theoretical calculation method are compared and analyzed by the finite element numerical analysis method.The determination of plastic hinge and out-hinge sequence of single-story concrete-filled steel tube composite frame and two-story two-span concrete-filled steel tube composite frame under thermal-mechanical coupling is discussed in detail,and the calculation of plastic ultimate bearing capacity and deformation of concrete-filled steel tube composite frame at high temperature is carried out.The mechanical properties of concrete-filled steel tubular composite frame under different fire time are reflected by the indexes of horizontal plastic strain,vertical displacement and local plastic region range of the structure.5.The theoretical and numerical analysis of the single-story concrete-filled steel tube composite frame is carried out,and the mechanical characteristics of the two-story and two-span concrete-filled steel tube composite frame are analyzed by using the finite element numerical analysis method.It is concluded that the theoretical calculation is consistent with the numerical results under different operating conditions,and the accuracy of the results is further verified.