Risk-Based Wind Loss and Mitigation for Residential Wood Framed Construction

As a result of increasing windstorm losses in the United States over the past 50 years, a variety of residential wind hazard mitigation methods have been suggested. Mitigation undoubtedly reduces windstorm losses; however, the expected economic risk reduction of mitigation practices over the life of the building depends on the building characteristics (i.e., capacity) and the intensity and occurrence of wind speeds (i.e., demand). Effective decision making requires estimation of potential future losses based on many variables. Many models, primarily mechanics-based simulation models, have been developed to predict building damage from wind events; however; fewer models of economic loss have been developed, although economic losses are more easily quantified over a spatial domain and have the potential for more effective widespread use. Additionally, many existing models consider damage and loss as a function of basic wind speed in open terrain and few address the variation in loss due to changes in surface roughness, although surface roughness is a critical component in surface wind speed. In spite of advancements in damage and loss modeling, the limitations of existing publications (e.g., geographically limited in scope, limited to specific building types, limited to specific events, limited to open terrain) prevent generalization and application of the results on a nationwide basis to support development of a mitigation decision-making framework. To address these limitations, this research presents a methodology to calculate tabular expected annual loss (EAL) results for 160 variations of one-story, single-family homes at each ASCE 7-10 wind contour through Monte Carlo simulation of local annual maximum wind speeds convolved with Hazus-MH economic loss functions for open terrain and non-open terrain. The results are integrated into a decision-making framework designed to provide customized consumer-level guidance to assist the mitigation decision-making process based on location, terrain, years of interest, and building configuration. The results provide practical results in an easy-to-use format to facilitate consumer-level mitigation decision making

Optimization of Sustainability and Flood Hazard Resilience for Home Designs

AbstractLife-cycle analysis is a beneficial tool that can be utilized to quantify the performance of buildings within the context of environmental impact metrics (e.g. carbon footprint). While typical life-cycle analysis incorporates regular building maintenance, structural repairs made as a result of natural hazard damages are largely ignored. This study presents an environmental impact design optimization model that can be used to compare multiple coastal, single-family residential (SFR) building designs subjected to coastal flood hazards based on environmental impact factors. For each design, the model measures the environment impact (i.e. embodied energy and carbon footprint) of initial construction plus flood-induced repairs. Repairs are quantified using a probability-based methodology and life-cycle analysis is used to measure environmental impacts. Design options can then be compared and optimal designs that meet performance-based resilience and sustainable design objectives can be selected. A case study is presented for an SFR building located in coastal St. Petersburg, Florida, USA, and demonstrates that up to a 64% reduction in embodied energy and carbon footprint can be achieved over a 50 year building life through more resilient component configurations and materials and by increasing first floor elevations

Generalized Cost-Effectiveness of Residential Wind Mitigation Strategies for Wood-Frame, Single Family House in the USA

Wind is one of the deadliest and most expensive hazards in the United States. Wind hazards cause significant damage to buildings and economic losses to homeowners. Economic losses average approximately $3.8 billion annually from hurricane winds and are not decreasing, even despite enhanced construction practices to reduce wind damage. Thus, the effectiveness of mitigation strategies should be evaluated in order to lower the cost incurred by this hazard. Several studies have suggested building code improvements to mitigate the wind hazard, this additional comprehensive research provides selecting economically beneficial mitigation strategies to consider in building code revisions. In a step toward addressing this need, the current study was conducted to determine the cost effectiveness of mitigation strategies for new and retrofit construction of a wood-framed, single-family, residential building case study. Net benefit, defined as the difference between the life-cycle wind loss before and after implementation of the mitigation strategy, was calculated for 15 wind mitigation strategies and their combinations, with new and retrofit construction costs ranging between$1,200 to $12,000 and a decision-making time horizon ranging between 5 and 30 years. Payback periods, defined as the number of years to recover the investment, were calculated for each mitigation strategy. Results were summarized by cost effectiveness for all ASCE 7 wind speed contour intervals. The results of this study serve as a starting point for further refinement of the economic justification needed to properly evaluate potential building code changes

Improved building-specific flood risk assessment and implications of depth-damage function selection

Average annual loss (AAL) is traditionally used as the basis of assessing flood risk and evaluating risk mitigation measures. This research presents an improved implementation to estimate building-specific AAL, with the flood hazard of a building represented by the Gumbel extreme value distribution. AAL is then calculated by integrating the area under the overall loss-exceedance probability curve using trapezoidal Riemann sums. This implementation is compared with existing AAL estimations from flood risk assessment. A sensitivity analysis is conducted to examine the variability in AAL results based on depth-damage function (DDF) choice. To demonstrate the methodology, a one-story single-family residence is selected to assess the financial benefits of freeboard (i.e., increasing lowest floor elevations). Results show that 1 ft. of freeboard results in annual flood risk reduction of over $1,000, while 4 ft of freeboard results in annual flood risk reduction of nearly$2,000. The sensitivity result suggests that the DDF selection is critical, as a large proportion of flood loss is counted below the top of the first floor. The findings of this paper will enhance DDF selection, improve flood loss estimates, encourage homeowners and communities to invest in flood mitigation, and provide government decision-makers with improved information when considering building code changes

Flood damage and shutdown times for industrial process facilities: a vulnerability assessment process framework

Much of the U.S. petrochemical infrastructure is heavily concentrated along the western coast of the Gulf of Mexico within the impact zone of major tropical cyclone events. Flood impacts of recent tropical disturbances have been exacerbated by an overall lack of recognition of the vulnerabilities to process systems from water intrusion, as well as insufficient disaster mitigation planning. Vulnerability assessment methods currently call for the aggregation of qualitative data to survey the susceptibility of industrial systems to floodwater damage. A means to quantify these consequences is less often employed, resulting in a poor translation of the threat of flood hazards to a crucial element of the economy. This paper reviews flood damage assessment for industrial facilities and presents a component-level conceptual methodology to assess the consequences of flood events. To more effectively communicate loss potential from flood events, the proposed methodology utilizes synthetic estimation to calculate repair requirements, shutdown time, and direct cost