Issue 78

D. D. Joshi et alii, Fracture and Structural Integrity, 78 (2026) 315-345; DOI: 10.3221/IGF-ESIS.78-19

K EYWORDS . Progressive collapse, Concrete structures, Strengthening techniques, Fiber-reinforced polymer, Stainless-steel wire mesh.

I NTRODUCTION rogressive collapse is defined as “the spread of an initial local failure from element to element resulting in the collapse of an entire structure or a disproportionately large part of it” [1] . Progressive collapse in building structures is typically initiated when one or more primary vertical load-carrying members are severely damaged or failed due to abnormal events. As a result, building’s gravity loads are redistributed to adjacent structural members. If these members are not adequately designed to resist and redistribute the additional forces through alternate load paths, that part of structure also fails. This chain reaction continues until redistribution of additional forces is stabilized, causing greater damage to the structure than the initial local failure. Progressive collapse can cause catastrophic structural failure, which may result in considerable loss of human lives and resources. In order to reduce the risk of progressive collapse, it is necessary to design and detail structures to develop alternate paths through adequate redundancy, ductility and continuity, particularly under extreme loading events. Progressive collapse is not a new phenomenon in the structural engineering community. It has been a concern since the collapse of the 21-storey Ronan Point Tower in London in 1968. The partial collapse of a corner of the entire building, triggered by a gas explosion in a kitchen on the 18 th floor, highlighted the vulnerability of precast concrete structures, particularly the susceptibility of connections between precast elements to disproportionate collapse. The Collapse of Skyline Plaza in Virginia in 1973, collapse of Kansas City Hyatt Regency Hotel in 1981 and collapse of U.S. Marine Barracks Lebanon in 1983 further attracted the attention of people to the issue of progressive collapse. Subsequently in 1987, a 16 storey under construction building L’Ambiance Plaza in Connecticut showed the features of progressive collapse due to construction error. Several buildings have experienced progressive collapse as a result of terrorist attacks. These include the Murrah Federal Building, Oklahoma City in 1995, the Khobar Towers, Saudi Arabia in 1996, the U.S. embassies in Kenya and Tanzania in 1998. Since then, several studies have been conducted and few guidelines have also been developed to address the issue of progressive collapse. However, research activities related to progressive collapse in structures increased significantly after the infamous collapse of the World Trade Center towers in New York, United States in 2001. Subsequently, detailed guidelines were developed by agencies such as the U.S. General Services Administration (GSA), Unified Facilities Criteria (UFC) by U.S. Department of Defense (DoD) and National Institute of Standard and Technology (NIST), to reduce the progressive collapse potential of structures by enhancing their resistance against progressive collapse [2-4]. Several buildings have continued to experience progressive collapse across different parts of the world such as the Windsor Tower in Spain in 2005, the Pyne Gould Corporation Building in New Zealand in 2011, Rana Plaza in Bangladesh in 2013, the Plasco Building in Iran in 2017 and the Surfside condominium in Florida in 2021, each triggered by different causes [5-7]. S IGNIFICANCE OF THIS REVIEW umerous experimental, analytical and numerical studies have been conducted to evaluate the progressive collapse potential of reinforced concrete (RC), steel and precast concrete structures as reported in the technical literature. With the advancement of research in this field, design guidelines for progressive collapse mitigation have also been periodically updated and published. Several aspects related to progressive collapse studies, such as, bibliometric details, terminologies and definitions, historical events and major failures, as well as types and causes, different mechanisms and loading actions, are not incorporated in this paper. Researchers have already consolidated these contributions in previous review papers, summarizing key findings and current state of the art [5-9]. This review paper primarily focuses on strengthening techniques employed to enhance progressive collapse resistance of RC and precast structures. Additionally, the potential of stainless-steel wire mesh (SSWM) as an alternative material for structural strengthening is highlighted and key research gaps are identified for possible future studies in those directions. P N

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