Contents lists available at ScienceDirect Structures journal homepage: www.elsevier.com/locate/structures Progressive collapse vulnerability assessment of irregular voided buildings located in Seismic-Prone areas Mohammad Soheil Ghobadi ⁎ , Hamed Yavari Department of Civil Engineering, Faculty of Engineering and Technology, Imam Khomeini International University, 34148-96818 Qazvin, Iran ARTICLEINFO Keywords: Progressive collapse Nonlinear dynamic analysis Alternate load path method Irregular voided structures Level of site seismicity Moment connection robustness Column removal scenario Spatially distributed damage Redundancy ABSTRACT Nowadays, many special architectural forms of voided buildings such as hotels, commercial complexes, etc. are constructed in famous cities. In this paper, the effects of opening in the volume of low- and mid-rise irregular voided structures with low to high seismic resistance on the progressive collapse vulnerability are investigated. The structures are three and nine stories high, seismically designed with a steel moment frame system based on the AISC seismic code, and are located in sites with high, moderate, and low levels of seismicity. Detailed three- dimensional nonlinear dynamic analysis is performed to investigate spatially distributed damage to frame members and the structural robustness against abnormal loads according to the GSA 2016 guidelines. The re- sponse quantities are expressed in the form of the displacement of the node above the removed column, the spatially distributed formation of plastic hinges, the stress growth in nearby columns after progressive collapse occurrence, and the connection robustness analysis. The results show moment connections that govern the ro- bustness of the structure and they are the most critical components in the structure. In addition, larger openings and proximity of the column removal scenario to position of the opening play a significant role in reducing the progressive collapse vulnerability of voided structures. However, in the scenarios of removing the internal column away from the opening, the progressive collapse mechanism of the structures with or without opening does not differ. Therefore, in the structural robustness analysis, internal columns away from opening of the voided buildings should be considered as critical and controllable elements in the progressive collapse capacity ofstructures.Amongthemodeledbuildings,onlythebuildingslocatedinhighseismicareascanpassprogressive collapse analyses and the seismicity level of the site is the most important parameter in robustness of the structure in comparison with the height or irregularity of the structure. Increasing the height of structures also reduces the amount of stress growth in the columns adjacent to the demolished column and the taller structures are safer structures in this regard. 1. Introduction The progressive collapse phenomenon is a series of consecutive failures that result in partial or total chain collapse of a structure and can be due to human created factors such as design error, construction error, fire, explosion, overload, or natural hazards such as earthquakes, winds, and so on. In recent decades, the progressive collapse phenom- enon has been the subject of much attention, as it can be a catastrophic disaster for a structure subjected to the mentioned factors. Research on progressive collapse in structures is generally focused on gravity loads; however, dynamic loads such as wind and earthquake loads can also be factors that cause progressive collapse. The American Society of Civil Engineering (ASCE) committee proposed the following definition for progressive collapse mentioned in the ASCE 7-05 [1] Standard: The spread of an initial local failure from element to element because of an initial accident, eventually resulting in the collapse of an entire struc- ture or a disproportionately large part of it. As an example of progressive collapse, the University of Zoology devastation in Scotland can be referred to [2–3].Thissteelbuildingwas completely destructed in 1966 during construction. The reason for the destruction of the building could be attributed to the defected welds of girders, which were substantially weakened by the fatigue phenom- enon. Five people were killed and three were injured in the incident. At that time, progressive collapse was the cause of destruction of struc- tures in various places, such as the 16-story building of L'Ambiance Plaza [4] and the building of the World Trade Center [5]. Total de- molition of the 8-story building of Rana Plaza Commercial Office Complex [6–7] in Bangladesh in 2013 (Fig. 1) was one of the deadliest https://doi.org/10.1016/j.istruc.2020.03.063 Received 16 January 2020; Received in revised form 29 February 2020; Accepted 28 March 2020 ⁎ Corresponding author. E-mail address: msghobadi@eng.ikiu.ac.ir (M.S. Ghobadi). Structures 25 (2020) 785–797 2352-0124/ © 2020 Institution of Structural Engineers. Published by Elsevier Ltd. All rights reserved. T