State-of-the-art review: Analysis and rehabilitation of existing masonry walls against progressive collapse

In masonry wall buildings, masonry walls constitute the building envelope, gravity load resisting system, and the lateral load resisting system at the same time. Therefore, major damage or a loss of integrity on the building envelope directly affects the integrity of the entire structural system; the loss of load-bearing members can cause catastrophic failures without much warning or time for evacuation of the building. The brittle, heterogeneous, and anisotropic properties of masonry make masonry structures susceptible to such failures, when certain causes and failure mechanisms were not considered in the original design. Codes and specifications that relate to progressive collapse analysis, such as the Unified Facilities Criteria (UFC) 04-023-03, cover steel and concrete structures in more depth and detail than masonry structures, making the analysis of existing masonry structures challenging. This paper reviews the available literature related to the assessment and retrofit of masonry structures against progressive collapse to showcase the insufficiency of available information in this topic. The paper also looks at current codes and standards, and compare practices between the U.S. and Europe. Results of the review suggest that there is need for further research in the topic and a need for increased detail in the provisions for masonry in the applicable codes.