Recent Advances in Assessment and Mitigation of Multiple Hazards

The special collection on Recent Advances in Assessment and Mitigation of Multiple Hazards is available in the ASCE Library (http://ascelibrary.org/page/jsendh/assessment_mitigation_multiple_hazards).

Recent events, such as the 2011 Tohoku earthquake and Hurricane Sandy in 2012, have highlighted the potentially catastrophic effects that multiple hazards can have on structural and infrastructure systems. As a result, the engineering community has recognized that proper evaluation, modeling, and assessment of the effects of multiple concurrent, cascading, or non-concurrent hazards (e.g., earthquakes and tsunamis, earthquakes and fires, hurricane wind and storm surge, wind and earthquake, earthquake and scour, earthquake and blast, fire and explosion) are fundamental to ensure the desired performance of engineered structural and infrastructure systems. Thus, the development of appropriate methodologies to evaluate and design structural and infrastructure systems able to withstand the effects of multiple hazards has become a very active field of research in recent years. To mitigate the detrimental effects of multiple hazards, new alternative and transformative approaches are needed for modeling the interaction among different hazards, analyzing the response of affected structural and infrastructure systems, assessing the associated risks, and designing individual components, structures, and entire infrastructure systems. This Special Collection contains one forum paper, one technical note, and 14 technical papers. It aims to provide an overview of the state-of-the-art and highlight some of the recent advancements in the fields of assessment, design, and mitigation of multiple hazards for structural and infrastructure systems.

The Special Collection opens with the forum paper by Zaghi et al. (2016), which introduces the concept of multihazard design in contrast with the traditional design approaches for multiple independent or noninteracting hazards. This paper proposes a new classification of multihazard effects from the point of view of structural engineering applications. It also acknowledges the limitations of current single-hazard design code approaches, highlights recent advances in multihazard assessment and design, identifies existing engineering knowledge gaps, and proposes future research directions that may lead to establish multihazard design as an essential tool for hazard mitigation.

Two papers in the collection focus on the hazard analysis of multiple interacting hazards. Mudd et al. (2017) develop a new tropical cyclone rainfall model using rainfall observations. This rainfall model is coupled with state-of-the-art probabilistic tropical cyclone models and future projected climate change scenarios to provide a joint probabilistic characterization of tropical cyclone hazards under current conditions and predict their variation under different climate change scenarios. The joint model is used to assess the potential future climate change impacts on the distribution of maximum rain rate and rainfall totals, and to investigate the climatological effects on the relationship between rainfall accumulation and maximum wind speed occurrence for the northeast U.S. coastline. Wang et al. (2017) propose a new approach for modeling the temporal correlation in hurricane frequency. They also derive closed-form expressions for the mean and variance of the cumulative hurricane damage when considering the effects of nonstationarity and correlation in hurricane occurrence. This model is applied to the hurricane damage assessment of residential buildings in Miami-Dade County, Florida. It is observed that the hurricane nonstationarity produced by climate change effects tends to increase the mean hurricane damage, whereas the temporal correlation tends to increase the hurricane damage variance.

General frameworks for risk and lifecycle cost assessment are presented in four papers. Baradaranshoraka et al. (2017) propose a methodology to assess multihazard vulnerability within the Florida Public Hurricane Loss Model and properly assign damage causation among the different interacting hazards during a hurricane event. Unnikrishnan and Barbato (2017) investigate the effects of multihazard interactions on the performance of low-rise wood-frame residential buildings subject to hurricane hazard by using the Performance-Based Hurricane Engineering framework (Barbato et al. 2013). Unnikrishnan and Barbato (2017) also examine the use of different hazard-modeling techniques and vulnerability analysis approaches, and propose a consistent terminology to classify different hazard-modeling techniques. Mahmoud and Cheng (2017) propose a probabilistic framework for assessing design alternatives for steel buildings based on their lifecycle cost when considering both seismic and wind hazards. The intensities are specified based on probability of exceedance according to code standards. Their results highlight the importance of adopting lifecycle cost as a performance measure in the design of new structural systems subject to multiple hazards. Salman and Li (2017) present a framework for risk assessment of electric power systems subject to independent nonconcurrent seismic and hurricane wind hazards. This framework considers both probabilistic and scenario-based hazard analysis that can be applied in predisaster preparation, multihazard mitigation, and postdisaster response planning.

Four papers investigate the response/fragility/reliability of specific structural systems subject to multiple hazards. Yang et al. (2017) use incremental dynamic analysis to evaluate the capacity curve of a tower and a tower-line system within an electric power system under spatiotemporally varying wind or earthquake loads. A comparison with simpler nonlinear static pushover analysis results highlights the importance of considering realistic spatial correlation for wind hazard and of record-to-record variability in seismic hazard. Gidaris et al. (2017) comprehensively review the state of the art of fragility and restoration models for typical highway bridge classes, which can be used in multihazard risk and resilience analyses of regional portfolios or transportation networks in the United States. This paper also presents an overview of key knowledge gaps in the literature. Taylor et al. (2017) investigate the behavior of long-span bridges with porous safety fences that are obstructed by snow or ice accretion during extreme wind conditions. A methodology based on wind tunnel test results is proposed to assess the probability of failure attributable to flutter under concurring extreme wind and extreme snow/ice events. The results suggest that the primary concern for these effects is the aerodynamic stability of the bridges rather than the increases in wind loading. Marasco et al. (2017) develop a new methodology to assess the total damage of structural elements caused by cascading hazards and apply it to hospital buildings. The paper explicitly considers earthquakes producing a blast, followed by fire. The proposed multihazard approach can be used for improving the structural safety, reducing the lifecycle cost, and enhancing the resilience of hospital buildings.

The behavior of structural components under actions from multiple hazards are investigated in two papers. Cao et al. (2016) experimentally study the performance of a semiactive damping device, referred to as modified friction device, under nonsimultaneous multihazard loads. They also develop a numerical model of the device considering wind, blast, and seismic loads, and compare the modified friction device’s performance with passive viscous and friction dampers. Bao et al. (2017) use high temperature measurements using a Brillouin scattering-based fiber-optic sensor for thermomechanical analysis of simply supported steel beams subjected to combined thermal and mechanical loading. This analysis is used to compare the structural behavior prediction based on different design standards.

The last three papers present new perspectives on and tools for multihazard mitigation and assessment. English et al. (2017) describe the components of amphibious construction as an innovative retrofit flood mitigation and climate change adaptation strategy. This paper also reviews the benefits of amphibious retrofit compared with permanent static elevation (PSE), and quantifies the wind vulnerability of PSE homes as a result of the increased wind loads corresponding to this type of retrofit. Sutley et al. (2017) propose a new two-stage approach to assess the effects of natural disasters by considering both physical (i.e., of structures and infrastructure systems) and social vulnerability (i.e., a community’s socioeconomic and demographic factors). This approach is applied to the case of seismic hazard, and it shows that the projected impacts of a disaster are particularly severe for the most socially vulnerable communities. Finally, Chowdhury et al. (2017) provide an overview of the design and development of the Wall-of-Wind (WOW) research facility at Florida International University, which is one of the experimental facilities under the National Science Foundation natural hazards engineering research infrastructure (NHERI) program. This paper illustrates the WOW capabilities to assess the impacts of hurricane wind, rain, and debris on civil infrastructure, and it explains the advantages and limitations of this facility.