CONSTRUCTION AND TERRORISM
by Norman Glover
The architecture and engineering of our homes, offices, schools, and public buildings have made them more vulnerable to acts of terrorism than necessary for their intended uses. The design of the Oklahoma City federal building set close to the street with a ground-floor atrium, glass-covered face, and light structural system made the method of attack used particularly devastating. The World Trade Center was peculiarly vulnerable to attack due to a local law requiring extensive public parking within the structure. This allowed the easy placement of the bomb vehicle. However, the building`s heavy steel frame with many redundancies of design prevented the catastrophe of a collapse.
A great deal of knowledge is available on explosive damage and the blast resistance of structures. This information will undoubtedly be utilized in the design of future buildings to reduce the risk of terrorist acts. Much less information is available on how we build and use these buildings and how they may be designed or modified to reduce the risk of terrorist acts …. The elements of buildings that could be designed or modified to mitigate damage include the siting and orientation of buildings and their connection to each other; the use of open space; the construction of building facade elements, doors, and windows; the elevators; the heating, ventilating, and air-conditioning systems; the electrical systems; and the interrelation of these systems and the spaces and purposes they serve.
The Architectural Engineering Division of the American Society of Civil Engineers has formed a Task Committee to study the technical, economic, social, and environmental aspects of this problem and its opportunities. It is anticipated that among the results of this study will be the development of guidelines for the design and construction of buildings to mitigate the effects of urban terrorism. (1)
The best defense to a bomb is distance. Some hazards can be reduced, however. For example, a number of alternate glazing materials have the potential to control the hazards of shattered glass. The recent Justice Department Vulnerability Assessment of Federal Facilities included as its sole specific action recommendation under Construction and Renovations: “Install Mylar film on all exterior windows” (shatter protection) ….
Design alternatives available to mitigate the effects of terrorist attack include the following:
Site Design–Stand-Off Distance; street architecture to restrict and direct access and deflect blasts–planting and bollards; lighting; surveillance and security system.
Façade–attention to glazing size and geometry; special glazing–can bear loads up to 240-275 kPa (35-40 psi) but can cause other problems.
Protection of structural systems and design for redundancy, lateral loads, and load reversal.
Protection of air intakes with closed-circuit television, sensors, and dampers.
Redundant air intakes interconnected and pressurized to prevent infiltration.
Venting.
Buildings must be designed with a consideration of their attractiveness as a target. If European and particularly Northern Ireland experience is valid, as government facilities are hardened and become less attractive targets, terrorists will change to other tactics or to a sophisticated combination of several tactics, such as assassination and bombing, or select “softer” attractive targets such as restaurants, departments stores, hotels, and air terminals.
Note: The above are excerpts from (1) “Mitigation of Terrorist Violence by Multidisciplined Facilities Planning,” Journal of Architectural Engineering, Sept. 1995 and (2) a presentation made at the American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc. Conference on Total Building Design, Chicago, Illinois, Oct. 16, 1995.
NORMAN GLOVER is chairman of the American Society of Civil Engineers, Working Group on the Mitigation of the Effects of Terrorist Violence. He is a member of the executive committee of the Architectural Engineering Division of the Society and a Fellow of the Society, the Society of Military Engineers, and the British Institution of Structural Engineers. He has a degree in civil engineering from Columbia University, where he has been a member of the Advisory Council to the School of Engineering and Applied Science for 25 years. He has done postgraduate study at Columbia, Harvard, and the U.S. War College.
