دانلود رایگان مقاله انگلیسی ارزیابی مقاومت قاب مهاربندی شده غیرمعمول در برابر فروپاشی پیشرونده - اشپرینگر 2017

Abstract

One of the most important and effective factors of structural strength against the risk of progressive collapse is the type of lateral load bearing system of a building. In this research, strength of dual steel moment frames equipped with a variety of eccentric bracings against progressive collapse was evaluated by using nonlinear static alternate path method. 6-floored building samples were designed with steel frame using a dual steel moment system together with 3 different types of bracing, including inverted eccentrically V-shaped bracing (chevron bracing), eccentrically V-shaped bracing and eccentrically X-shaped bracing, each with two different kinds of arrangement of bracings in the structural plan, in form of alternate and neighbor. The effects of sudden removal of columns on different floors of these buildings were examined. These studies showed that dual steel moment frames equipped with eccentric bracings generally exhibited desirable strength against progressive collapse. A change in the type of bracing resulted in significant changes in the system capacity in the progressive collapse. Among the different types of braces assessed, chevron type eccentrically brace showed higher strength against progressive collapse. Also, that alternate arrangement of bracings in structure plan demonstrated better performance than neighboring arrangement.

5. Conclusion

In structures with eccentrically lateral seismic bracing system, by removing each of the critical elements determined by UFC progressive collapse instruction and by executing progressive collapse analysis via alternate path method on the reviewed samples, the following results have been obtained:

(1) Eccentrically inverted V type bracing system provided more ductile behavior and better performance compared to other systems against progressive collapse because of providing more suitable alternative paths and the ability of better distribution of plastic hinges in the structure. By changing the type of bracing system from inverted Vshape to V-shaped or X-shaped bracing, significant decline was observed in structures progressive collapse-resisting capacity.

(2) Among the type of arrangement of bracing, arrangement of alternate bracing supported more column removal compared to the arrangement of neighbor bracing against progressive collapse and demonstrated better performance. As a result, among these six types of analytical model structures, the building with dual special moment frame with inverted V type eccentrically bracing, with alternate arrangement of bracings demonstrated the best performance compared to the other structures.

(3) It was obvious that the removal of column with one braced span compared to its removal in situations with two neighbor braced spans because of the providing less alternative paths can lead to more critical situations in terms of the dangers of progressive collapse.