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Buildings
Rapid Evacuation Concepts Aired
(enr.com 12/13/01)
By Nadine M. Post and Peter Reina in London
Tall buildings are not dead. That was
the message from experts at a conference on the future of
the skyscraper in London last week. While the post mortem
triggered by the terrorist attack on the World Trade Center
continues, the debate heats up over how much more security,
if any, is needed to enhance high-rise survivability.
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| (Photo
courtesy of Canary Wharf Group PLC) |
In a keynote delivered to more than
400 conference attendees three months to the day after the
attack, Charles, Prince of Wales, said, "The destruction
of the World Trade Center is unlikely to mark the end of tall
buildings." An outspoken adversary of tall buildings,
he added, "It has now become more important than ever
to question how such buildings should be built. I suspect
that the price of meeting the new [safety] demands...will
place considerable strain on the rationale of the buildings
themselves."
Speculating that additional security
would add as much as 9% to the construction cost, "this
is quite a small burden to put on a building," said Paul
Morrell, senior partner of London-based real estate consultant
Davis Langdon & Everest, at the Dec. 9-11 conference.
Called Building for the 21st Century, it was organized by
the Council on Tall Buildings and Urban Habitat, Bethlehem,
Pa. "Other than at the margin, the [cost] effect of Sept.
11 will be very, very limited," he predicted.
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| GROWTH
Although Prince Charles questioned the rationale of tall
buildings, London's mayor says it may get 20 more over
the next 15 years. (Photo courtesy of Newscast) |
Underscoring the positive future of
tall buildings, London Mayor Ken Livingstone forecasted that
20 new high-rise buildings would be constructed in the British
capital over the next 15 years. One of his first moves after
he became mayor in May 2000 was to reverse a policy against
high-rise construction to accommodate the fast-paced growth
London was having on brownfield sites.Livingstone's view was
supported by architect Norman Foster, of Foster and Partners,
London. "The tall building in a finite planet with less
and less available space is a lifeline," he said.
Foster is among several design professionals
investigating the emergency response of buildings, in the
wake of the Sept. 11 attacks. A multidisciplinary team, assembled
by the firm, is testing ideas for emergency evacuation on
a conceptual 50-story building. Under review are skybridges
to adjacent buildings, rooftop helipads, additional stairwells
and other measures. The study, due for spring completion,
is also borrowing from evacuation procedures from offshore
oil rigs, aviation and other industries.
A full-scale trial on a 50-story London
building by Arup Ltd., London, proved that properly protected
elevators can "assist rapid evacuation," said Robert
Emmerson, chairman of the London-based consulting engineer.
Using the elevators nearly halved the escape time compared
to using stairs only. Arup also believes that building owners
and tenants should be informed of relative risks from different
sources (see chart).
Reconfiguring the core can provide cost-effective
refuge areas and a dedicated elevator and stairwell for emergency
egress without increasing core square footage, said Jeffrey
Heller, president of Heller Manus Architects, San Francisco.
The system bundles a service elevator for use by firefighters,
a lobby and a stairwell, in a pressurized shaft.
Hardened safety areas on each floor
near the core have been mandatory in Israel since the Gulf
War in 1991, said Eri Goshen of D. Eytan E. Goshen Architects
Ltd., Tel Aviv, designer of a 70-story tower in Tel Aviv that
is set to start construction next year.
Emmerson and others agreed that educating
owners and tenants about emergency systems in buildings should
go hand in hand with engineering. Toward that end, the council's
task force on the future of tall buildings, which convened
for the second time at the conference, voted to distill the
results of the official post-Sept. 11 building studies for
use by owners, tenants and occupants. The group's first meeting
was in Chicago on Oct. 15 (ENR 10/22 p. 12). The guidelines
for building safety will be presented at a conference in late
May.
"The council's mission is to bring
a Reader's Digest version of the technical papers to the public
and to get the message out that buildings are still safe,"
said Ron Klemencic, chairman of the council and president
of structural engineer Skilling Ward Magnusson Barkshire Inc.,
Seattle.
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