Leading Experts Present Emerging Developments in Multi-Hazard Engineering at AEI-MCEER Symposium
Over 115 structural engineers, architects, faculty researchers, and students convened in New York City for the Symposium on Emerging Developments in Multi-Hazard Engineering. Held September 18, 2007 at the McGraw-Hill Auditorium, the event was jointly organized by the Architectural Engineering Institute (AEI) of ASCE and MCEER. It also received generous sponsorship from the Steel Institute of New York.
The symposium was co-chaired by Dr. Mohammed Ettouney, Principal at Weidlinger Associates, Inc. and Past President of AEI, and Dr. Michel Bruneau, Director of MCEER and Professor at the University at Buffalo.
It featured 13 presentations by nationally-recognized researchers and practitioners that highlighted recent advances in the emerging field of multi-hazards engineering. These included perspectives and solutions for protecting infrastructure from specific hazards, as well as the potential to adapt existing design measures for multi-hazard protection of the built environment. Opening presentations focused on an “AEI Strategy for Multi-Hazard Engineering” and “The Four Rs of Resilience in Multi-Hazard Engineering,” a concept developed through MCEER research. An expert panel explored “Identifying the Path(s) Forward for Multi-Hazard Engineering.”
Other topics included:
- Lessons from 9/11 and Hurricane Katrina
- Analyzing Infrastructure Vulnerabilities to Multiple Hazards
- Risk Assessment of Infrastructure in a Multi-Hazard Environment
- Critical Issues in Achieving a Resilient Transportation Infrastructure
- Application of Multi-Hazards Theory to Bridge Design, Analysis, and Monitoring
Some of the speakers provided a historical perspective on the issues of safety and reliability of infrastructure systems subjected to extreme events, from safety factors, to component and system reliability with respect to a single hazard, to the load combinations of the LRFD approach. Others provided theoretical background by presenting the fundamentals of a general risk assessment framework. Still others presented the application of this theory to concrete illustrative examples.
Defining Multi-Hazard Engineering
One of the most important outcomes of the symposium was the clarification of what is meant by multi-hazard engineering. Multi-hazard engineering is not about studying infrastructure systems under several hazards acting simultaneously. It is not about addressing individual hazards sequentially.
Multi-hazard engineering is about simultaneously addressing all hazards as a problem of optimization under constraints, the criterion being life-cycle cost.
The range of hazards considered includes natural hazards (e.g. earthquakes, floods, and windstorms), accidental hazards, and malevolent action. Concurrent hazard events and interdependent hazard events such as fire following an earthquake, flood following a hurricane, or tsunami following an earthquake are addressed as special cases of importance.
The motivation for such an approach is the need for a rational basis for decision-making which will make it possible to:
- identify which risks should be mitigated first;
- select the best mitigation options; and
- define priorities in a context of limited resources.
AEI and MCEER Strategies Lay Foundation for Multi-Hazard Engineering
The symposium opened with a presentation (pdf) by G. Edward Gibson, Jr., 2007 AEI President. Gibson championed AEI’s mission which promotes a multidisciplinary approach and excellence in practice, education, research of architectural engineering. He made note of AEI’s technical committees, two of which focus specifically on the recent hazards of 9/11 and Hurricane Katrina.
Amar Chaker, AEI Director, and Michel Bruneau, MCEER Director, followed with presentations that emphasized the strong interests that their organizations have in multi-hazard engineering. Both outlined their strategies in this growing area, and gave an overview of the topics to be covered, as well as the challenges to be addressed in presentations to follow.
Chaker spoke of multiple hazards in the context of natural events such as earthquakes and windstorms; accidental man-made hazards involving fire and technological mishaps; and intentional man-made hazards posed by terrorism. He outlined AEI’s multi-hazard objectives to design and build buildings to address all hazards throughout their lifecycle to: protect building occupants, protect the building by limiting damage, and increasingly protect the building’s function and maintain continuity of operations. Among recent events that stress a need for multi-hazard engineering, he cited Hurricane Katrina’s wind, storm surge, and flooding.
Chaker also discussed multiple challenges to multi-hazard engineering, including how addressing one hazard may make matters worse for mitigating another, evaluation of overall building reliability for multiple hazards, and how interdependencies among infrastructure affect reliability. Among AEI’s expectations for its multi-hazards engineering strategy, he emphasized the importance of laying a sound foundation for the updating of codes and standards.
Michel Bruneau explained the 4 R’s approach to Resilience – Robustness, Redundancy, Resourcefulness and Rapidity – and outlined the challenges facing the emerging field of multi-hazard engineering. He also stressed the need to identify the path forward for multi-hazard engineering, in terms of implementation and public policy. He provided examples of how a systems-approach to engineering design can be used to consider, from the onset, the multiple and often contradicting demands of multiple hazards, to develop single solutions that can adequately and cost-efficiently satisfy all the ultimate performance objectives.
Risk Assessment, Transportation Infrastructure, Lifeline Interdependencies, 9/11, and Hurricane Katrina included among Presentation Topics
Presentations throughout the remainder of the program touched on a wide variety of topics within the context of multi-hazards engineering and its challenges. These included talks on aspects of risk assessment, transportation infrastructure, lifeline interdependencies, and lessons learned from the disasters of 9/11 and Hurricane Katrina, among others. The following summarize these remaining presentations.
Sreenivas Alampalli, Director, Bridge Evaluation Services Bureau, New York State Department of Transportation, discussed applications in the area of bridge management, and noted that hazards interact as they affect a bridge. He showed an example where retrofitting a bridge by placing rip-rap around its footings to protect it from scour might lead to higher costs in the future if retrofitting for seismic hazard is needed. In another example, the solution for the optimum location of sensors in a structural health monitoring application was found to be different when using a multi-hazard approach than when considering one single hazard.
Bruce Ellingwood, Professor at Georgia Tech, provided a theoretical foundation of the basic risk equation resulting from the theorem of total probability. Ellingwood showed how the conditional probability of the loss exceeding a specific value is obtained from the triple summation of (1.) products of the annual probability of the occurrence of the hazard, (2.) the conditional probability of the damage (limit) state given the occurrence of the hazard, and (3.) the conditional probability of the loss exceeding the specific value given the occurrence of the hazard and the damage state. This deconstruction of risk into its constituent parts highlighted the role of hazard modeling, fragility curves, and loss modeling in assessing risk. This in turn forms the basis for risk-informed decision making which allows a balanced allocation of limited resources to mitigate the consequences of low-probability high-consequence events arising from multiple hazards.
Mircea Grigoriu, Professor at Cornell University, advocated moving beyond the current hazard-specific method toward a broader approach that considers the collective impact of different hazards in risk analysis. He outlined the elements of probabilistic multi-hazard risk analysis and showed how the system failure probability can be evaluated under multiple hazards. He also showed the effect of hazard concurrence on system reliability under multiple hazards, and noted that it is essential to ensure that the strategies implemented to mitigate one hazard do not amplify the vulnerability to another hazard. He pointed out that optimal design with respect to cost and reliability requires considering all relevant actions simultaneously.
A rich set of examples illustrating the practical application of this theory was also presented. Grigoriu and his former doctoral student, Cagdas Kafali, Research Engineer, AIR Worldwide, discussed the case of a typical off-shore platform subjected to seismic hazard and hurricane hazard (wind and wave loads), showed how the seismic activity matrix, the hurricane activity matrix and the system fragility can be combined to evaluate the system failure probability at slight, moderate and extensive damage levels. This example also demonstrated how different hazard actions can be dominant at different reliability levels. Their other example was the MCEER West Coast demonstration hospital for which an optimal rehabilitation strategy was identified using the concept of fragility surfaces for structural and non-structural systems. This example showed that a realistic assessment of performance needs to account for the joint effect of different hazards.
Anne Kiremedjian, Professor at Stanford University and Chair of ASCE’s Council on Disaster Risk Management, presented on behalf of her former doctoral student Stephanie King, Director of Risk Analysis at Weidlinger Associates, Inc. Kiremedjian discussed the concepts of hazard occurrence modeling, vulnerability, and damage and loss modeling as key elements of a general framework for risk assessment of infrastructure systems in a multi-hazard environment. She also showed how event and fault tree analyses can help quantify risk, clearly identify the contributions of risk components, and test the sensitivity of the results to assumptions and simplifications entering in the fault tree model. Finally, she explained that while the problem becomes significantly more difficult when a variety of hazards must be addressed, there are significant advantages to including multi-hazard considerations in the mitigation of existing and new infrastructure systems.
Paul Mlakar, U.S. Army Research and Development Center, drew the high-level lessons he learned from the investigations of the limited collapse of the Pentagon building following the September 11 terrorist attack and the failure of the flood protection system in the New Orleans area following Hurricane Katrina. In the case of the Pentagon, the existence of alternate load paths (i.e., redundancy), the continuity of the reinforcing steel, and the energy absorption capacity of the spirally reinforced columns provided resilience to the building and enabled it to sustain local damage while the structural system as a whole remained stable. In New Orleans, the hurricane protection system evolved incrementally, with little consideration given to the consequences of a loading in excess of the design event. Both cases illustrate the importance of considering the consequences of events in excess of the design condition. The lesson is that we should design against failure as well as for failure.
Michel Bruneau used the Richelieu Apartments (Pass Christian, Mississippi) to illustrate the need for improved mitigation in order to enhance resilience and break the “construction-reconstruction cycle” that typically follows disasters. Bruneau explained that the apartments, located along the U.S. Gulf Coast, were destroyed by high storm surge from Hurricane Camille in 1969. In 1995, a Winn Dixie supermarket was built in the very same location, only to be washed away by storm surge from Hurricane Katrina in 2005. He added that current land owners plan to continue the “cycle” by developing the parcel again once the Gulf Coast economy rebounds.
Bruneau also cited a National Institute of Building Sciences study that underscores the cost-effectiveness of mitigation, stating that every $1 of mitigation results in $4 in saved losses. He advocated the leveraging of extensive earthquake engineering knowledge and advancements to enhance resilience against a broader spectrum of hazards, noting that earthquake engineering research has provided practical solutions that could likely address challenges presented by other extreme events. A photo of two bridges almost identical in collapse, one in Japan by the 1964 Niigata earthquake and the other by Hurricane Katrina storm surge, likely could have been saved by employing the same simple earthquake protective measures. Bruneau closed with examples of MCEER research that seeks to expand several single-hazard solutions to satisfactorily address multiple hazards.
Vilas Mujumdar, Program Director and Cluster Leader, Earthquake Engineering Research Centers, Division of Education and Engineering Centers, National Science Foundation, discussed the need for a risk-consistent approach and stressed the importance of taking into consideration the interaction effects and the cascading nature of some hazards. He also noted the physical interdependence among utilities and between structural and non-structural components in a building, and the current inconsistencies in hazard risk acceptance and recognition for different hazards.
Rae Zimmerman, Professor of Planning and Public Administration at New York University and Director of the Institute for Civil Infrastructure Systems discussed the effects of extreme events on urban infrastructure and of interdependencies on the critical infrastructure systems.
Milagros Kennett, Architect/Project Manager, Risk Management Series, Mitigation Division, Building and Technology, FEMA/Department of Homeland Security, introduced the FEMA Risk Management Series of publications. She focused on FEMA 452 which initially addressed only terrorist attacks on buildings and related infrastructure but was recently expanded to address all hazards. The publication, which was available to the Symposium participants free of charge, describes in detail the five critical steps of a multi-hazard risk assessment: threat or hazard assessment; asset value assessment; vulnerability assessment; risk assessment; and mitigation options. FEMA 452 also provides practical guidance and tools for conducting a comprehensive multi-hazard risk assessment such as the risk assessment database and the vulnerability checklist.
Joe Englot, National Director of Infrastructure Security, HNTB Corporation, focused on critical issues in addressing resilient transportation infrastructure. He called for an expanded role for the engineer, including the pre-event development of post-event scenario for incident management. He identified gaps in current knowledge (e.g., progressive collapse for bridges) and codes (e.g., provisions in the bridge code for hydrocarbon fire, vehicular impact, terrorist attack and flood). He showed an example where the use of shielding and plating of critical connections would offer protection from blast effects and hydrocarbon fire.
Mohammed Ettouney’s presentation focused on the need to consider design for multiple hazards as an optimization problem. He presented matrices showing possible interaction among common hazards for bridges and for buildings. Examples of such interactions include the lateral stiffness capacity resulting from wind drift requirement which will affect seismic design, and the gravity load carrying capacity of a floor beam system which interacts with its vibration properties, as any change in the floor beam characteristics would affect both. Ettouney illustrated the inherent resiliency that may exist between hazards and the very real benefits of a multi-hazard approach using the example of the retrofit design for blast and seismic design of a 49-story steel braced frame building. A striking life cycle cost savings of 18% was achieved using a multi-hazard design strategy to satisfy the blast and seismic demands, instead of a blast retrofit design developed independently from seismic future demands. Ettouney also noted the need for language in codes to address multi-hazard design.
A lively panel discussion between three of the speakers and the attendees concluded the event and provided the elements of a roadmap to tap the potential of multi-hazard engineering.