Research On The Seismic Behavior Of Concrete-filled Square Tubular Braced Frame Structures

China is the biggest country in steel product, but steel cost of buildings is limited. Furthermore, steel structure is seldom adopted in residences field, which is a vast area. So we should put great effort to develop steel structural residences, and the government pays much attention to it now. Steel structure have many advantages, such as lighter weight, better seismic behavior, quicker to build and more beneficial for environment protection. Therefore, developing steel structural residences is in accordance with the industrial policy of our country and strategy of sustainable development, and will put forward residences industrialization.Several demonstration projects of steel structural residences have been built, which are low-rise, multi-story, and high-rise residences. Base on a great deal of investigation, a new structure system is put forward, which is concrete-filled rectangular steel tubular(CRFT) braced frame structure system. This new system has two remarkable points: the first, CRFT column is introduced, it is small in size and can be hidden in walls, is more suitable for residences; the second, steel brace is used to resist lateral load, and it can avoid the problems caused by using steel-reinforced concrete shear wall to resist lateral load.In order to study the seismic behavior of this structure system, three frames are designed and they are subjected under cyclic reversed lateral load. We mainly study the strength, stiffness, ductility, energy absorption capacity and failure causation in the test. The results show that, compared with rectangular steel tubular frame, CRFT frame have higher lateral stiffness, bearing capacity and better behavior of ductility; CRFT braced frame has high lateral stiffness and bearing capacity, it's load bearing capacity doesn't have remarkable drop after bucking of brace, which indicates its good behavior of ductility.Besides, this paper makes nonlinear finite element analysis on concrete-filled CRFT frame and CRFT braced frame, then design methods on CRFT braced frame structure are introduced, proposed values of elastic and elastic-plastic story drift in CRFT braced frame structure are presented. This paper also finds out that the critical points in CRFT braced frame structure are joint and brace design, and detailed investigations on brace design are carried on.Energy-dissipation technology is a much more rational, effective, safe, economic earthquake resistant method, which develops quickly in recent years, and it is more suitable for high rise steel structure. A energy-dissipation braced frame is designed with viscous damper as energy-dissipation device. Test on the frame under cyclic reversed lateral load of various frequency and displacement is carried out to check its energy-dissipation capacity and structural measures. The results show that viscous damper possesses excellent energy-dissipation capacity, and the structural measures is adequate. Investigations in this paper provide a fully new way for the design of high-rise steel residences.