The Analysis Of Hysteretic Behavior And Failure Mechanism For Special Truss Moment Frames With Weak X-diagonals

Using trusses to take the place of solid-web girders in traditional 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. Setting energy dissipation segment near the mid-span of trusses, special truss moment frames with weak X-diagonals let it shear yielding under a certain horizontal earthquake that 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. Nonetheless, researches about this structure are rare. So the study of special truss moment frames with weak X-diagonals in the hysteretic behavior and failure mechanism has some engineering significance.In this paper two calculation methods for special truss moment frames with weak X-diagonals are introduced in details:one ordinary method basing on limit-state and one new method basing on structure performance. The finite analysis is finished mainly by using ANSYS with some preliminary verifications of this software.A standard level of the calculation model is mainly analyzed with ANSYS. Five parameters are studied in this paper:the shear resistance percent of weak X-diagonals, the panel’s depth-width ratio, the length of the energy dissipation segment, span of special truss moment frames and the number of spans. The results indicate that the shear resistance percent of weak X-diagonals affects the hysteretic behavior of the structure a lot, and the lateral stiffness and energy dissipation capacity could improve greatly with increasing the resistance percent of weak X-diagonals properly. In addition, the panel’s depth-width ratio has little effects on the structure performances. The length of the energy dissipation segment has big implications for the structure, and the hysteretic behavior could be improved with designing the length of the energy dissipation segment and the area of the truss properly. Span of the truss also affects greatly, and larger span behaves better under the same conditions. Multi spans could obtain outstanding performances familiar to the single pan frame, and multi spans should be the priority choice.In the end, a conclusion about the characteristics of special truss moment frames with weak X-diagonals is given. And this paper also provides some advices to later research according basing on the shortages of this paper.