مقاله انگلیسی رایگان در مورد ارزیابی مقاومت قاب مهاربندی شده در برابر فروپاشی – اسپرینگر 2017

Structural safety has always been one of the main concerns for the design of civil engineering projects. One of the mechanisms of structural failure which has attracted much attention in recent decades is progressive collapse. Progressive collapse is defined as the spread of an initial local failure from element to element, resulting eventually in the collapse of an entire structure or a disproportionately large part of it. The phenomenon of progressive collapse under the influence of various factors occurs in structures. Plane impact, car collision and gas explosions are a few examples of the hazards which can produce such an event. An effect of this localized failure is that, without an increase in external load, redistribution emerges in internal forces of structures, and other parts are placed under additional forces, with a consequence of one or more other parts being damaged and more redistribution in forces occurring. Thus the damage spreads throughout the entire structure and may lead to collapse of the entire structure. The progressive collapse phenomenon, because of its catastrophic consequences and the high probability of its occurrence, is gradually taken into consideration in the design standards. The attention of engineers were drawn to the progressive collapse by destruction of a part of Ronan Point building located in London in the year 1968. The context of structural response to abnormal events drew more attention after the collapse of the World Trade Center towers on September 11, 2001. Rethinking and revising standards related to the design process of progressive collapse drew the attention of researchers at different institutions. For example, technical studies in this regard were conducted by the United States Department of Defense DOD or UFC (2010) and GSA (2005) and editors of European regulations. Kim and Kim (2009) studied the progressive collapseresisting capacity of steel moment frames by using alternate path method (APM) recommended in the GSA and UFC guidelines and observed that when a nonlinear dynamic analysis was conducted, it led to larger structural responses. Furthermore, they observed that the potential for progressive collapse was highest when a corner column was suddenly removed. The research also concluded that the progressive collapse potential decreased as the number of stories increased. Kim and Kim (2009) suggested that the performance of buildings using cover plate connections turned out to be most effective in resisting progressive collapse, especially in structures located in moderate-seismic regions. Fu (2009) declared that under the same general conditions, a column removal at an upper story will induce larger vertical displacement than a column removal at ground level. Khandelwal et al. (2009) in a study reviewed the progressive collapse strength in two different bracing system, including eccentrically braced frames (EBF) and special concentrically braced frame (SCBF), using simulation software. Simulation results revealed that although both models used seismic resistant frame around the building, eccentrically braced frames had less destruction against progressive collapse in comparison to Frames with special CBF system. Kim et al. (2011) reviewed the probability of progressive collapse occurrence in a variety of concentrically braced steel frames using GSA guidelines in two methods of nonlinear static and nonlinear dynamic. For this purpose, 8 different types of frame bracing system were designed and their performances were compared with a special moment frame that was designed for the same amount of loads. The results of the nonlinear static analysis showed that in case of removing the column from braced span on the first floor, apart from the frame with K-shaped bracing, most braced frames designed based on criteria of current regulations were able to resist progressive collapse. However, most of the modeled structures possessed brittle behavior because of buckling of braces and columns in the event of collapse. Among the braced frames, only -shaped braced frame (chevron) exhibited a ductile behavior in the event of a progressive collapse.