The Analysis Of Hysteretic Behavior For Special Truss Moment Frames With Buckling Restrained Braces

Using trusses to take the place of solid-web girders in tradional steel frames is called truss moment frames, which has the advantages of large span and low steel consumption. However,the seismic performance of ordinary truss moment frames is poor. To set energy dissipation segment near the mid-span of trusses and let it shear yielding under a certain horizontal earthquake can not only improve the structural seismic behavior significantly, but also control its yield load and failure mode accurately to realize performance-based design. It is a new type of seismic structural system named special truss moment frames, and has wide application range, significant economic and social benefits.To set energy dissipation segment with buckling restrained braces in midspan of truss moment frames is a new kind of special truss moment frames. In order to study the seismic behavior of special truss moment frames, this program, is intended to carry out cyclic tests and hysteresis analysis, elasto-plastic are performed with simplified theoretical method and finite element method, and in which, all the possible influential factors are taking into consideration. The main purpose is to study the failure mechanism of the energy dissipation segments, the cooperative working mechanism and the dynamic characteristics of the structure, and the failure mechanism of connections. The analysis is focus on the strength, the stiffness, the ductility, the energy dissipation capacity and the failure mode of structure during different working stage. Based on that, the shear bearing capacity calculation method of energy dissipation segment, the calculation methods of structural dynamic characteristics, the theory calculation model will be presented, and the performance-based seismic design method are also brought at last. The results of this program will promote development of the relevant theory and engineering applications.Firstly, the ultimate shear bearing capacity of energy dissipation segment is derived. Secondly, methods to determine the design value of bearing capacity of buckling restrained brace and detailing requirements are also presented according to China’s seismic design code. The presented method can control the yield time and failure mode of special truss moment frames accurately, and achieve the target which all floor yield synchronously under the horizontal earthquake, so consume energy fully. Monotonic and cyclic test with finite element method are analyzed and confirmed. Results show that, reasonable bearing capacity of buckling restrained brace can significantly enhance the ductility, energy dissipation capacity, load carrying capacity and safety margin of special truss moment frames, and its seismic behavior is obviously superior to truss moment frames. This paper provided methods can realize structure optimization design in the premise of ensuring energy consumption of energy dissipation segment.Finally, this paper according to the theory research and results of ANSYS analysis, summarizes the influence of different parameters and seismic characteristics for the BRB truss framework. This paper analyzes the shortcomings and gives the measures for improving the later study.