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Executive Summary

The United States became a victim of terrorism on a grand scale when a powerful bomb exploded in the World Trade Center in New York City in February, 1993. This event, however, was only a precursor to the devastating attack against the Alfred P. Murrah Federal Building in Oklahoma City in April 1995. These events, and other lethal attacks elsewhere, have generated considerable concern over the ability of the United States to protect buildings and their occupants from the continued threat of bombings and other direct physical attacks. The issue of ensuring structural integrity from explosive blasts has been an active topic with the military and national security communities for years. Such concerns arose initially in response to bombing threats during World War II; however, they continued through the Cold War, and more recently these concerns have grown with the increase in terrorism worldwide. A large body of theoretical and empirical knowledge regarding explosions and their effects has been developed as a result of research and tests sponsored by U.S. government agencies, including the Defense Nuclear Agency and the uniformed services.

In response to a potential threat of terrorist bombing attacks against U.S. civilian structures, the Defense Nuclear Agency requested the National Research Council to examine whether design methodologies and construction techniques developed for the protection of military facilities could be beneficially applied to civilian architecture. The Committee on Feasibility of Applying Blast-Mitigating Technologies and Design Methodologies from Military Facilities to Civilian Buildings was established and charged with three tasks summarized as follows:

• review the existing knowledge on blast-effects mitigation technology,



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Page 1 Executive Summary The United States became a victim of terrorism on a grand scale when a powerful bomb exploded in the World Trade Center in New York City in February, 1993. This event, however, was only a precursor to the devastating attack against the Alfred P. Murrah Federal Building in Oklahoma City in April 1995. These events, and other lethal attacks elsewhere, have generated considerable concern over the ability of the United States to protect buildings and their occupants from the continued threat of bombings and other direct physical attacks. The issue of ensuring structural integrity from explosive blasts has been an active topic with the military and national security communities for years. Such concerns arose initially in response to bombing threats during World War II; however, they continued through the Cold War, and more recently these concerns have grown with the increase in terrorism worldwide. A large body of theoretical and empirical knowledge regarding explosions and their effects has been developed as a result of research and tests sponsored by U.S. government agencies, including the Defense Nuclear Agency and the uniformed services. In response to a potential threat of terrorist bombing attacks against U.S. civilian structures, the Defense Nuclear Agency requested the National Research Council to examine whether design methodologies and construction techniques developed for the protection of military facilities could be beneficially applied to civilian architecture. The Committee on Feasibility of Applying Blast-Mitigating Technologies and Design Methodologies from Military Facilities to Civilian Buildings was established and charged with three tasks summarized as follows: • review the existing knowledge on blast-effects mitigation technology,

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Page 2 • assess the applicability of this technology to civilian buildings and identify gaps in knowledge and needs for research and development, and • recommend courses of action to implement technology transfer. The committee was composed of recognized experts in architecture and architectural planning, structural engineering and blast-effects, computer modeling, terrorism, and commercial development. Most of the committee members have direct professional involvement with the planning and design of buildings with quantifiable risk (military facilities, embassies, etc.). In addition to the expertise of its members, the committee was assisted in its work by agencies, organizations, and individuals that provided information on current engineering and architectural practices. This study, jointly sponsored by the Defense Nuclear Agency and the U.S. Army Corps of Engineers, is aimed at determining the applicability of defense-related efforts to civilian architecture and the potential to transfer this technology in a timely and cost-effective manner. The study does not examine the vulnerability of structures to an attack using toxic substances (such as the Sarin gas attack in Tokyo in March 1995). The committee believes this is an appropriate time to restate what the Oklahoma City and World Trade Center attacks have made so abundantly clear: the United States is vulnerable to a continuing threat of terrorist bombing. The current awareness of this threat by both policy makers and the general public should facilitate acceptance of the desirability and timeliness of transfer and application of some military protective technologies to civilian architecture. This report presents the findings of the committee's work and its recommendations for future action. Findings 1. Attacks against civilian buildings pose an unquantifiable but real threat to the people of the United States. 2. Blast-hardening technologies and design principles developed for military purposes are generally relevant for civilian design practice. However, because the knowledge base is incomplete, they must be adapted and expanded to be more specifically applicable, accessible, and readily usable by the civilian architect-engineer community. 3. Blast-hardening technologies developed by the military apply, for the most part, to building structural systems and must be expanded to include critical life-safety building subsystems. 4. Nonstructural architectural and engineering approaches can improve the blast resistance and response of civilian buildings. 5. Post-attack rescue and recovery operations can benefit from good emergency management planning, including rapid availability of building systems and

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Page 3 structural drawings and use of computer-based modeling and decision support systems to assess the extent of blast damage to the building's structural frame. 6. Buildings designed to be more bomb resistant through the use of increased mass in the lower levels will also benefit from increased resistance to dynamic forces from natural hazards such as hurricanes, tornadoes, and earthquakes. 7. Barriers exist to the effective transfer of relevant military technology to the civilian sector. These barriers include lack of professional education, classification of military technology, lack of established technology transfer mechanisms, and cost and financial issues. Based on these findings, the committee developed a series of recommendations aimed at adapting and transferring technology already available from the military to civilian sectors. For those areas where knowledge gaps exist, the committee has suggested a program of applied research. Recommendations 1. Adapt selected technical manuals, threat assessment methodologies, and relevant computer programs developed for military applications and disseminate them to civilian building-design professionals as one component of an integrated threat deterrent and blast-effects mitigation strategy (Findings 1 and 2). 2. Conduct experimental and analytical studies on the blast resistance of structural subsystems representative of conventional civilian building design and construction practice (Finding 2). 3. Conduct research and testing of common building materials, assemblies, equipment, and associated designs applicable to blast-resistant design of critical nonstructural building subsystems (Finding 3). 4. Establish a government/academic partnership whose purpose is to inform and alert design professionals regarding the range of measures that can and need to be taken to protect buildings from terrorist activities and the collateral benefits of providing such protective measures. This partnership should also take the lead in facilitating the transfer of this technology by interaction with the appropriate government and professional bodies (Findings 4, 6, and 7). 5. Explore the use of computer-based modeling and decision support systems to assess the extent of blast damage to a building's structural frame as part of the post-attack rescue and recovery operations (Finding 5). 6. Analyze all new civilian federal buildings, and existing buildings where appropriate, to determine reasonable ways of incorporating blast-hardening and other blast-effects mitigating features, and to document consequent building construction costs and financial performance (Finding 7).