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  1. More than 1.6 billion people worldwide live in informally constructed houses, many of which are reinforced with concrete. Patterns of past earthquake damage suggest that these homes have significant seismic vulnerabilities, endangering their occupants. The characteristics of these houses vary widely with local building practices. In addition, these vulnerabilities are potentially exacerbated by incremental construction practices and building practices that address wind/flood risk in multi-hazard environments. Yet, despite the ubiquity of this type of construction, there have not been efforts to systematically assess the seismic risks to support risk-reducing design and construction strategies. In this study, we developed a method to assess the seismic collapse capacity of informally constructed housing that accounts for local building practices and materials, quantifying the effect of building characteristics on collapse risk. We exercise the method to assess seismic performance of housing in the US. Caribbean Island of Puerto Rico, which has high seismic hazard and experiences frequent hurricanes. This analysis showed that heavy construction, often due to the addition of a second story, and the presence of an open ground story leads to a high collapse risk. Severely corroded steel bars could also worsen performance. Although houses with infill performed better than those with an open ground story, confined masonry construction techniques produced a major reduction in collapse risk when compared to infilled or open-frame construction. Infill construction with partial height walls performed very poorly. Well-built reinforced concrete column jackets and the addition of infill in open first-story bays can reduce the greater risks of openground- story houses. These findings, which are quantified in the results portion of this article, are intended to support the development of design and construction recommendations for safer housing.There is an urgent need to improve community capacity to recover more effectively after disasters through safer design and construction practices. To do this, training programs need to foster an improved understanding of shelter design and construction to withstand future wind and earthquake events. This project analyzed informal builders’ perceptions of housing safety in Puerto Rico (responding to 2017's Hurricane Maria and the 2019-2020 earthquake swarm) and homeowner’s perceptions of housing safety in Philippines (responding to 2013's Typhoon Haiyan and 2017's Ormoc earthquake) to: (1) assess local understanding of shelter safety in multiple hazards, including causal factors influencing this understanding, through a household survey in the Philippines and a survey to informal contractors in Puerto Rico; (2) assess the expected performance of various post-disaster shelter typologies to quantify safety during future earthquake and wind events using performance-based engineering methods, developing a rapid screening tool that can be used in design or evaluation; (3) identify conflicts between perceived and assessed safety of shelter, and why these conflicts exist, by comparing engineering assessments with local perceptions; and (4) create a communication design for organizations assisting with training for safer housing construction. 
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  2. More than 1.6 billion people worldwide live in informally constructed houses, many of which are reinforced with concrete. Patterns of past earthquake damage suggest that these homes have significant seismic vulnerabilities, endangering their occupants. The characteristics of these houses vary widely with local building practices. In addition, these vulnerabilities are potentially exacerbated by incremental construction practices and building practices that address wind/flood risk in multi-hazard environments. Yet, despite the ubiquity of this type of construction, there have not been efforts to systematically assess the seismic risks to support risk-reducing design and construction strategies. In this study, we developed a method to assess the seismic collapse capacity of informally constructed housing that accounts for local building practices and materials, quantifying the effect of building characteristics on collapse risk. We exercise the method to assess seismic performance of housing in the US. Caribbean Island of Puerto Rico, which has high seismic hazard and experiences frequent hurricanes. This analysis showed that heavy construction, often due to the addition of a second story, and the presence of an open ground story leads to a high collapse risk. Severely corroded steel bars could also worsen performance. Although houses with infill performed better than those with an open ground story, confined masonry construction techniques produced a major reduction in collapse risk when compared to infilled or open-frame construction. Infill construction with partial height walls performed very poorly. Well-built reinforced concrete column jackets and the addition of infill in open first-story bays can reduce the greater risks of open-ground-story houses. These findings, which are quantified in the results portion of this article, are intended to support the development of design and construction recommendations for safer housing.

     
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