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1. Informally-Constructed houses in Puerto Rico under Hurricane load:Building Capacity for Safer Post-disaster Shelter: Leveraging Local Understanding and Advanced Engineering Assessments

   https://doi.org/10.17603/ds2-2b49-dx51  

   Lochhead, Meredith; Goldwyn, Briar; Venable, Casie; Liel, Abbie; Javernick-Will, Amy (January 2024, Designsafe-CI)

   This study assesses the wind performance of various housing typologies representing informal construction practices in Puerto Rico to suggest modifications to enhance housing resilience in hurricanes. Based on fieldwork and interviews, the study defined four base housing typologies and possible variations in design and construction details. Each house was assessed using performance-based static wind analysis of potentially critical components. The results show that the initial governing failure mode in all base house typologies considered is roof panel loss due to tear-through at the fasteners, with subsequent governing failures being panel loss due to failures at the purlin-to-truss connections and failures of the truss-to-wall connections. In-plane wall failures and masonry uplift failures were both found to occur at much higher wind speeds than roof failures. To improve the hurricane performance, several feasible modifications are suggested, including installing hurricane straps at both the truss-to-wall and the purlin-to-truss connections, as well as improving the panel-fastener interface. In the construction of new roofs, this study found that using reduced spacing between roof members, hip roofs instead of gable roofs, and higher roof slopes leads to improved performance. These recommendations can make houses built through informal construction processes safer and more resilient to hurricanes as a form of climate adaptation.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. Spatial Distribution of Rock Disturbance in Assessment of Roof Stability in Flat-Ceiling Cavities

   https://doi.org/10.1007/s00603-023-03295-2  

   Park, Dowon; Michalowski, Radoslaw L (June 2023, Rock Mechanics and Rock Engineering)

   Three-dimensional stability of roofs in deep flat-ceiling cavities is analyzed. The stability number, factor of safety, and required supporting stress are used as measures of roof stability. Despite the simplicity of the flat roof geometry, the three-dimensional stability analysis presents some complexities owed to the shape of the failure surface geometry in the collapse mechanism. The failure mode assumes a rock block moving downward into the cavity, and the study aims to recognize the most critical shape of the failing block. Three specific block shapes are described in some detail, but more have been analyzed. Blocks defined by a special case of a 4th order conical surface (quartic) on a rectangular base, and a 2nd order elliptic surface (quadric) are found to be the most critical in the stability analysis. The kinematic approach of limit analysis was used, with the rock strength governed by the Hoek-Brown failure criterion. The parametric form of the Hoek-Brown function was employed. Interestingly, an absence of diagonal symmetries in the most critical failure mechanisms was observed in roof collapse of square-ceiling cavities. Computational results in terms of dimensionless measures of stability are presented in charts and tables. 

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3. Bayesian Multimodal Models for Risk Analyses of Low-Probability High-Consequence Events

   Vanli, O Arda (January 2024, Multimodal and Tensor Data Analytics for Industrial Systems Improvement. Springer Optimization and Its Applications)

   Gaw, N; Pardalos, PM; Gahrooei, MR (Ed.)

   This paper reviews a set of Bayesian model updating methodologies for quantification of uncertainty in multi-modal models for estimating failure probabilities in rare hazard events. Specifically, a two-stage Bayesian regression model is proposed to fuse an analytical capacity model with experimentally observed capacity data to predict failure probability of residential building roof systems under severe wind loading. The ultimate goals are to construct fragility models accounting for uncertainties due to model inadequacy (epistemic uncertainty) and lack of experimental data (aleatory uncertainty) in estimating failure (exceedance) probabilities and number of damaged buildings in building portfolios. The proposed approach is illustrated on a case study involving a sample residential building portfolio under scenario hurricanes to compare the exceedance probability and aggregate expected loss to determine the most cost-effective wind mitigation options. 

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4. Hazard Resistance-Based Spatiotemporal Risk Analysis for Distribution Network Outages During Hurricanes

   https://doi.org/10.1109/TPWRS.2024.3469168  

   Xu, Luo; Lin, Ning; Xi, Dazhi; Feng, Kairui; Poor, H Vincent (September 2024, IEEE Transactions on Power Systems)

   In recent decades, blackouts have shown an increasing prevalence of power outages due to extreme weather events such as hurricanes. Precisely assessing the spatiotemporal outages in distribution networks, the most vulnerable part of power systems, is critical to enhancing power system resilience. The Sequential Monte Carlo (SMC) simulation method is widely used for spatiotemporal risk analysis of power systems during extreme weather hazards. However, it is found here that the SMC method can lead to large errors as it repeatedly samples the failure probability from the time-invariant fragility functions of system components in time-series analysis, particularly overestimating damages under evolving hazards with high-frequency sampling. To address this issue, a novel hazard resistance-based spatiotemporal risk analysis (HRSRA) method is proposed. This method converts the failure probability of a component into a hazard resistance and uses it as a time-invariant value in time-series analysis. The proposed HRSRA provides an adaptive framework for incorporating high-spatiotemporal-resolution meteorology models into power outage simulations. By leveraging the geographic information system data of the power system and a physics-based hurricane wind field model, the superiority of the proposed method is validated using real-world time-series power outage data from Puerto Rico, including data collected during Hurricane Fiona in 2022. 

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5. Informally-Constructed houses under Typhoon:Building Capacity for Safer Post-disaster Shelter: Leveraging Local Understanding and Advanced Engineering Assessments

   https://doi.org/10.17603/ds2-d9g9-2d62  

   Venable, Casie; Liel, Abbie; Kijewski-Correa, Tracy; Javernick-Will, Amy (January 2024, Designsafe-CI)

   Although organizations build housing in resource-limited contexts after typhoons and other disasters that is intended to be safer than what existed previously, the performance of these houses in future typhoons—and the factors influencing performance—are unknown. This study develops a component-level, performance-based wind engineering assessment framework and evaluates the wind performance of twelve semi-engineered post-disaster housing designs, representing thousands of houses that were constructed in the Philippines after Typhoon Yolanda. We found that roof panel loss likely occurs first for most designs, at wind speeds equivalent to a category 2 hurricane/signal 3 typhoon. Roof shape determines whether this loss is caused by failure at the panel-fastener interface or purlin-to-truss connection. However, houses with wooden frames and woven bamboo walls may also experience catastrophic racking failures at wind speeds equivalent to signal 2 or 3 typhoons, a situation exacerbated by strengthening the roof. Results also show that wind performance varied with roof shape, component spacing, panel thickness, eave length and connection between purlin and truss. Organizations can use these results to improve housing performance, taking specific care to increase wall capacity. This framework can be expanded to assess housing performance in other resource-limited contexts.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. 

   more » « less