One of the biggest challenges facing designers of U.S. embassies and other federal facilities is the retrofit of existing buildings to meet tightened security standards. But officials say that for the design of newer buildings, tougher criteria have been in place for years. "We already had a heightened posture toward security," says Charles E. Williams, director and chief operating officer of the U.S. State Dept.'s Bureau of Overseas Building Operations, Washington, D.C.
GUARDED Design based on prior attacks. (Photo courtesy of NBBJ) |
For the U.S. General Services Administration, the 1995 attack on the Alfred P. Murrah Federal Building in Oklahoma City was the "defining moment," says Ed Feiner, chief architect at GSA, also in Washington. The Sept. 11 attacks on the World Trade Center and the Pentagon "accentuated the need to move forward with what we had already started."
In 1999, GSA shifted from prescriptive security guidelines to performance-based standards. For each existing or new facility, the agency develops a risk assessment, taking into account potential natural disasters, accidents and deliberate attacks, says Wade Belcher, GSA's manager of security design standards.
Changes have not been made to projects under way in response to Sept. 11. Those attacks "showed how airplanes can be used as weapons," says Rick Thomas, GSA project manager in Seattle for the 23-story, 615,000-sq-ft federal courthouse there. "The best way to deal with this kind of hazard is to enhance security within airplanes," he says.
The building, designed by local architect NBBJ, is slated for completion in 2004. Its security criteria, developed after studies of prior terrorist acts, include a structural system designed to help resist progressive collapsea much-discussed topic since the 1995 and 2001 attacks.
Jon D. Magnusson, chairman and CEO of the courthouse's structural engineer, Skilling Ward Magnusson Barkshire Inc., Seattle, says one strategy to resist vertical progressive collapse is to use strong horizontal ties that transfer loads from the damaged area to other members of the frame. Chances of horizontal progressive collapse are minimized by very strong vertical elements that act as stops, or actually weakening horizontal ties, he says.
Engineers agree, however, that in designing a frame to resist an attack, much depends on the type and power of the weapon, how and where it is delivered, the force of impact, whether there is ensuing fire and other factors difficult to predict in advance.
The retrofit of existing buildings to resist progressive collapse is even more tricky. For steel structures, moment rather than shear connections are the answer, say engineers. For concrete buildings, with connections embedded within the structure, the preferred method is wrapping columns with carbon fiber or steel jackets, says Robert Smilowitz, a principal at Weidlinger Associates Inc., New York City.
GSA's "biggest problem" is vulnerable existing stockand not just structurally. Quick fixes, such as barriers to keep vehicles at bay, create the appearance of a government under siege, says Feiner, and that is not acceptable in the long run.
Since Sept. 11, GSA has held design charettes in New York City, Boston, Chicago and other cities, to address perimeter security and develop short-term and long-term solutions for specific facilities. Security is in part an urban design problem, says Gary Haney, a design partner in the New York City office of Skidmore Owings & Merrill. He attended a charette for a courthouse in Alexandria, Va., which is a selected site for trials of accused terrorists.
Private landlords and developers could also feel the impact of this new scrutiny of existing buildings. Earlier this month, the GSA proposed that the federal Interagency Security Committee develop guidelines for space the federal government leases from the private sector. The GSA leases some 150 million sq ft across the country.
|COMPOUND Embassies outside cities are more out of harm's way. (Rendering courtesy of Hellmuth Obata & Kassabaum)|
In the 2003 budget, GSA is seeking $986 million for repairs and alterations, up from $869 million, and $400 million for security, up from about $300 million. The State Dept. is seeking $1.3 billion for embassy security, construction and maintenance, up 2%. Within that total, $609 million would go for capital projects, down 8% from 2002. Aid for improved perimeter and compound security would rise 7%, to $146 million.
Thirteen U.S. embassies are in design or construction. Two are replacement facilities for the embassies destroyed in Nairobi, Kenya, and Dar es Salaam, Tanzania, by bombings in August 1998. Both are slated for completion in early 2003.
Before year-end, contract awards are likely for embassies in Conakry, Guinea; Phnom Penh, Cambodia; Tashkent, Uzbekistan; Harare, Zimbabwe; Cape Town, South Africa; Yaoundé, Cameroon; and T'bilisi, Georgia. The OBO plans to use standard designs for small, medium and large buildings. The method should accelerate construction since "we won't have to go back to the drawing board each time," says Williams. Designs will be adapted to climate and site conditions.
An embassy for Berlin has been stalled since 1996, when the State Dept. selected a design team led by Moore Ruble Yudell Associates, Santa Monica. The site, on Pariser Platz near the Brandenburg Gate, would not allow for a 100-ft setback generally required since the 1983 U.S. embassy bombing in Beirut. In 1999, the Senate Appropriations Committee, citing security concerns, said the land should be sold. But the project "is still programmed on the site that was selected," says Williams. "We are working through all the design and host-nation related issues."
John Ruble says his firm is working on bollards and planter boxes, gates and a non-climbable fence that would protect the building from vehicle and pedestrian-delivered explosives, yet still be sensitive to the historic site. The embassy needs to project an image that is "strong but not hostile," he says.
The Berlin project is a special case. For most embassies, the State Dept. avoids setback problems by locating facilities on compounds outside of city centers. While such facilities are sometimes less accessible to users, four to 12 acres are easier to acquire outside downtowns, says Bill Stinger, senior principal in the Washington, D.C., office of architect-engineer Hellmuth Obata & Kassabaum, which is working on several embassy projects. The State Dept. must balance land requirements and accessibility with security, he adds.