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5
Findings and Recommendations

Terrorism is a reality which the United States must recognize and confront. Events over the past two years demonstrate that the United States is vulnerable to terrorist bombing. An awareness and acceptance of this threat by policy makers, building owners, and the general public is necessary for the application of blast-effects mitigation technologies and design methodologies to be effective. Prior to the bombing of the Alfred P. Murrah Federal Building in Oklahoma City (which occurred as the committee was completing its work), blast hardening measures seemed unlikely to have wide appeal within the civilian building community because of the relatively low level of public awareness of, and sensitivity to, the potential vulnerability of buildings in the United States to terrorist bombing attacks. At this time, the committee cannot speculate whether public attitudes will change over the long term as a consequence of the Oklahoma City bombing, and no such assumptions are made in arriving at the committee's findings.

The specific findings reached by the committee regarding applicability of the technology and blast-effects mitigation potential for commercial buildings, future research requirements, and technology transfer opportunities have been presented throughout the report and are summarized below.

Findings

1. Attacks against civilian buildings pose an unquantifiable but real threat to the people of the United States.

The historical record suggests that bomb attacks against civilian buildings will continue as the terrorist's tactic of choice. The hitherto generally low



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Page 71 5 Findings and Recommendations Terrorism is a reality which the United States must recognize and confront. Events over the past two years demonstrate that the United States is vulnerable to terrorist bombing. An awareness and acceptance of this threat by policy makers, building owners, and the general public is necessary for the application of blast-effects mitigation technologies and design methodologies to be effective. Prior to the bombing of the Alfred P. Murrah Federal Building in Oklahoma City (which occurred as the committee was completing its work), blast hardening measures seemed unlikely to have wide appeal within the civilian building community because of the relatively low level of public awareness of, and sensitivity to, the potential vulnerability of buildings in the United States to terrorist bombing attacks. At this time, the committee cannot speculate whether public attitudes will change over the long term as a consequence of the Oklahoma City bombing, and no such assumptions are made in arriving at the committee's findings. The specific findings reached by the committee regarding applicability of the technology and blast-effects mitigation potential for commercial buildings, future research requirements, and technology transfer opportunities have been presented throughout the report and are summarized below. Findings 1. Attacks against civilian buildings pose an unquantifiable but real threat to the people of the United States. The historical record suggests that bomb attacks against civilian buildings will continue as the terrorist's tactic of choice. The hitherto generally low

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Page 72 level of awareness of, and sensitivity to, the potential vulnerability of buildings in the United States to terrorist bombing attacks may have changed dramatically as a consequence of the Oklahoma City bombing, but only time will tell. 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. The committee found that the techniques of analysis and design for blast resistance and structural response developed for military purposes have general relevance to civilian architecture. Much of the existing knowledge on hardening of structures to high explosives has been documented in military engineering design manuals, as have the principles of threat assessment, critical asset determination, architectural planning, and related decision processes. Similarly, the military has produced an array of powerful computer programs for the estimation of blast-effects and the resultant structural response. However, civilian architecture differs from its military counterpart by typically being lighter in construction, while at the same time more structurally complex. Therefore, transfer of these technologies to civilian practice will require both modification of the design manuals to account for the fundamental differences between structural types and selective application of the most promising computer programs to civilian design problems. It must be noted that the more sophisticated programs are generally difficult to use and require a level of expertise and scale of hardware generally not found in the commercial architect-engineer sector. Considerable skill in computer modeling is required to analyze the structure and evaluate the output. Without experienced engineering judgment, it is quite possible to obtain erroneous results. Successful implementation of these approaches will require testing and validation of typical civilian structural types over a range of hypothetical explosions. Work will also need to be done to broaden or recast the planning manuals and other literature to make them fully usable for civilian settings. 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. Protection of nonstructural systems in civilian buildings is vital to survival and rescue of occupants and can significantly accelerate recovery of a building to its intended function. The effects of fire and smoke are not included in

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Page 73 the current blast-effects mitigation manuals, but this subject is covered in publications of the National Institute of Standards and Technology (NIST) and the National Fire Protection Association (NFPA) and is the subject of continuing research. Little attention has been paid to blast resistance of critical life-safety building subsystems such as lighting, communications, and ventilation. 4. Nonstructural architectural and engineering approaches can improve the blast resistance and response of civilian buildings. Representative of these approaches, for example, are building siting, controlled parking beneath structures, strategically situating high-profile occupants in inconspicuous locations, interior space planning, etc. 5. Post-attack rescue and recovery operations can benefit from good emergency management planning, including rapid availability of building systems and 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. The experiences from the World Trade Center and the Alfred P. Murrah Federal Building demonstrated the perilous nature of rescue and that competent management of emergency services of many types can be vital to the rapid evacuation of occupants, securing medical treatment for the injured, and reducing panic. Particularly important is the need to know the condition of remaining structural elements and the availability of drawings to support this determination would greatly aid the safe access to and removal of victims. Where drawings have been produced on computer, the availability of pre-engineered computerized models of the building structure would permit real-time analysis of a damaged building to identify potential hazards and suggest effective means of reinforcement while rescue operations proceed. 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. Although the dynamics of explosions and natural phenomena differ in significant details, the increased strength provided by structural solutions to potential blast-effects will resist natural forces as well.

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Page 74 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. The committee has found that there are several serious barriers to technology transfer from the military to the civilian sector. The first major barrier is education. The current academic and professional training of architects and engineers does not adequately prepare the design professions, either technically or philosophically, to incorporate blast-hardening principles in civilian structures. Thus a strong educational commitment is required by university schools of architecture, construction, and engineering, as well as by professional engineering societies, if the potential for technology transfer is to be realized. Another barrier is that much of the military technology is classified, and these security classifications will have to be removed before the technology can be transferred. Traditionally, the process of declassifying government testing programs and research results has been slow. The third barrier is the lack of established mechanisms to transfer applicable technologies and techniques for structural hardening and blast-effects mitigation from the military to the civilian sectors. Near-term agents offering the best opportunity for technology transfer are federal and state governments and professional engineering societies. It is essential to involve the country's university schools of architecture, construction, and engineering if this technology is to be accepted by the design professions. Design guidelines from professional organizations and government will probably be the first vehicles incorporating counter-terrorism design principles. In the long term, the three Model Building Codes in the United States, the Standard Building Code, the Uniform Building Code, and the BOCA National Building Code, may reflect or incorporate certain blast-mitigating measures that are also applicable to other more common hazards, such as fire, smoke, wind, and seismic conditions. The final major barrier to the application of these technologies is the negative impact of blast-hardening technology on financial performance. The additional construction costs created by the use of this technology, whether in the design stage of a new building or in retrofitting an existing building, may be a major barrier to adopting blast-hardening principles and procedures in the private sector. Thus the cost and other financial issues related to providing structural hardening and blast-effects mitigation treatment of a

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Page 75 prototypical commercial office structure may not be supportable on an economic basis at this time. It is generally agreed (and supported by the design manuals cited in this report) that thoughtful architectural planning and proper engineering design can accomplish significant improvement in building performance for minimal additional cost. The accuracy of this assertion will need to be demonstrated on a case-by-case, project-by-project basis. However, for those commercial buildings, and certain government buildings, whose financial performance is not the sole or primary decision factor, the application of available technologies and physical security measures should be considered on a case-by-case basis. While retrofitting existing buildings with hardened and reinforced construction is more costly and disruptive than incorporating these features in the original design of a new building, many of the planning and other blast-effects mitigation techniques can be applied to existing as well as new construction. Where the threat potential is sufficiently high, and where economic first-cost is not the primary driver, military design and construction principles can be beneficially applied. Based on these findings, the committee developed a series of recommendations aimed at adapting and transferring the already available technology from the military to the civilian sectors. For those areas where knowledge gaps exist, the committee suggests a program of applied research to address those areas. Recommendations 1. Adapt selected technical manuals, threat assessment methodologies, and 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). The most attractive candidates for technology transfer are the design principles, guidelines, and methodologies incorporated in the following: • Structures to Resist the Effects of Accidental Explosions Manual, 1990, Army TM 5-1300, Navy NAVFAC P-397, AFR 88-22, Departments of the Army, the Navy, and the Air Force (approved for public release; distribution is unlimited). • Security Engineering Manual, 1993, TM 5-853 (currently restricted to official use only). • Design and Analysis of Hardened Structures to Conventional Weapons Effects Manual, 1995 (DAHS CWE) • Threat Analysis and Vulnerability Assessment, developed by the U.S.

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Page 76 Army Corps of Engineers, and Balanced Survivability Assessments developed by the Defense Nuclear Agency. A unique opportunity exists for the Defense Nuclear Agency to influence ongoing development of an electronic hypertext version of the Joint Services DAHS CWE manual. This effort is intended to convert the manual to an interactive computer program complete with text, graphs, tables, equations, and stand-alone computer codes. Distribution of this product is intended to be on CD-ROM for both DOS-(WINDOWS) and Unix-based platforms. This is precisely the type of engineering design aid that should be tailored to the needs of the civilian building-design community and widely disseminated. However, before these manuals can be fully adapted for use by the civilian sector, a program of applied research (as described in Recommendations 2 and 3), directed at the critical structural and nonstructural subsystems, components, and materials normally found in civilian buildings, will need to be undertaken. 2. Conduct experimental and analytical studies on the blast resistance of structural subsystems representative of conventional civilian building design and construction practice (Finding 2). A base of knowledge regarding the performance of structural subsystems will be required to extend and adapt existing blast-resistant design principles, guidelines, and computer programs to the needs of civilian design professionals. This knowledge base will also serve to validate first-principle computer programs, extend the applicability of semi-empirical programs, and provide a basis for evaluating the conservatism in the explosive loading and structural resistance incorporated in current military design manuals and computer design programs. A very strong experimental and analytic capability already exists in this country and abroad that could facilitate future research and development in the area of blast-effects mitigation. This includes various test sites throughout the United States, from indoor laboratories for small-scale component testing to very large ranges for field testing of full-scale structures. The United Kingdom has a facility for full-scale testing of structures indoors and has expressed an interest in working with the Defense Nuclear Agency and other U.S. research agencies involved in blast-effects mitigation activities. Cooperative efforts also should be sought with foreign governments actively engaged in bomb-resistant civilian building design with whom the United

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Page 77 States already has relevant data exchange agreements (e.g., United Kingdom, Israel, Norway). Such test facilities are usually well equipped with both high-quality instrumentation and trained technical support staff. Although in the past, U.S. facilities have been operated primarily in support of defense activities, arrangements could be made to enable the civilian sector to gain access to selected testing sites. In particular, the committee notes that several federal agencies, including Defense Nuclear Agency and U.S. Army Corps of Engineers, Waterway Experiment Station, have the intellectual and programmatic infrastructure in place to carry on a program of research and development of new blast-effects mitigation knowledge and to assist other agencies and industry in the beneficial application of this knowledge. 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). The following specific areas of investigation are recommended: i. Behavior of common non-load-bearing assemblies under various blast intensities to determine whether their design can be enhanced to reduce production of damaging fragmentation and vulnerability to fragmentation loading. For example, research could be conducted on developing interior partition assemblies, such as metal stud and drywall that could be bonded together for less fragmentation following an explosion. ii. Survival of ducts, conduit, and other distribution sources. Investigate whether certain materials and assemblies offer improved survival potential and whether design techniques employed in military construction (including shock isolation) can be cost-effectively applied to civilian building design and construction. A study of protective designs might be developed for plumbing distribution piping and for investigating new materials that could be used, including protective jackets. The study could explore whether increased ductility of the piping or joints is beneficial. iii. Protection of equipment and machinery. Blast-hardened walls are not always feasible to protect equipment or maintain air locks to prevent smoke propagation in tall buildings. A study is needed to determine the survival potential of commonly used building systems and equipment under various blast conditions. These include generators, chillers, switchgear, pumps, motors, etc. Designs for housings that could offer

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Page 78 improved protection to equipment should be investigated, including lightweight shields or assemblies that could protect machinery, or maintain an air lock, even after partial failure. For example, a generator might be able to survive the explosion if a shield could minimize debris and fire from reaching the generator and its controls. A wall system might buckle, but hold together well enough to maintain an air lock. In this connection, it would be useful to prepare a summary of known information from the military and related efforts. Equipment resistance arising from studies under the SAFEGUARD missile defense program, including vulnerability shock data for equipment and lifelines, nuclear power plant design and construction, and other specialized industrial projects are examples that could be used for civilian applications. iv. Research is needed to find ways of making elevator cabs and shafts less susceptible to smoke infiltration. 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). This partnership is not envisioned as a single organization, but rather as an institutional network to foster cooperation between the public and private sectors and academia and industry to establish appropriate technology transfer mechanisms; such a network can also be used as a vehicle to introduce departments in architecture, engineering, and construction schools to the protective technology and procedures currently available and under development. 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). The immediate objectives of post-attack rescue and recovery will be influenced by an engineering assessment of the building's safety and the requirements for safe and rapid removal of debris and temporary shoring of specific structural elements. This assessment could be improved substantially if validated computer-based modeling and decision support systems are made available as an immediate and practical aid for the assessment process. In turn, this will require the availability of building plans and all relevant structural design data, as well as the ability to rapidly model the post-attack status of

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Page 79 the damaged building structure. The analytical capability for such assessment exists, but needs to be adapted and made available for post-attack operations. 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). These analyses will contribute to a broader appreciation of how blast-hardening planning and design can mitigate the effects of terrorist bombings, provide a database on architectural design solutions applicable to the commercial sector, and will assist in the formal education of design professionals. Until such time as this capability develops in the civilian architect and engineer community, several federal agencies, including Defense Nuclear Agency and the U.S. Army Corps of Engineers, Waterway Experiment Station (and their contractors), currently possess technical resources and expertise to assist in the analysis of existing and proposed civilian buildings to determine the need for (and cost of) blast-effects mitigating measures.

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