Assessing the behavior of historic masonry buildings to tornadic events: A comparative study of code-based analysis and point cloud based simulation

During the Midwest Tornado outbreak in December 2021, the historic downtown of Mayfield, Kentucky was heavily impacted. Employing digital documentation, numerical analysis, and onsite wind speed estimations, this study evaluates the behavior of the impacted historic masonry buildings. It explores the structural damages and stress distributions observed in historic masonry buildings impacted by tornadoes, comparing them to predictions made by the ASCE 7-22 standard for tornado loads. Through this investigation, it becomes evident that the stress distribution and damages produced by the on-site tornado wind speeds were significantly different than those derived from the ASCE 7-22 standard. The current standard does not account for most historic structures, typically classified as Risk Category. II. Based on the results of this research, even when these structures are treated as Risk Category III, the stresses estimated by the standard are much lower than the ones experienced on-site. This disparity raises critical questions for preservationists evaluating similar masonry structures in tornado-prone regions. Historic preservation emphasizes minimal intervention, so understanding and addressing the specific vulnerabilities of historic masonry structures to tornadoes is crucial. The analysis in this study identified uplift forces on the roof and high stresses on windward walls as primary causes of damage in these structures, which aligned with the observed collapse mechanisms. Preservationists can use these insights to develop targeted retrofitting strategies that address these vulnerabilities while minimizing impact on the historic fabric. Recognizing these nuances and their impact on structural behavior is crucial for safeguarding the resilience and significance of historic civil structures. Thus, this study lays the groundwork for developing evidence-based, preservation-sensitive guidelines for mitigating tornado damage to irreplaceable historic masonry structures.