By CAROLYNE ZINKO
San Francisco Chronicle
May 26, 2007
Suicides -- more than 1,250 since the bridge opened in 1937 -- concern bridge officials, but so does the possibility that changes to the suspension structure could affect how it behaves in the wind, causing it to become unstable or even collapse. Aesthetics are another sticking point at the major tourist attraction and the world's No. 1 suicide magnet.
In the eighth attempt to build a suicide barrier in the bridge's history, wind-tunnel tests by DMJM Harris of Oakland, Calif., and West Wind Lab of Marina, Calif., showed that it is possible to add to the existing railing, replace the railing or build a net that juts out from the deck.
All options would require devices to reduce wind stress on the bridge. None of the options would interfere with a planned movable median barrier designed to prevent head-on collisions.
"You can think of a cross section of the bridge as an airplane wing, and if you change the flap, you change how it responds to wind," said Denis Mulligan, chief engineer for the Golden Gate Bridge, Highway and Transportation District.
At a meeting Thursday, members of the district's Building and Operating Committee saw more than a dozen renderings of possibilities. No action was taken, and none is expected by the full bridge board until spring 2008.
The meeting turned into a Physics 101 class of sorts, as Mulligan explained wind dynamics and the so-called solid ratio -- the percentage of the railing that is solid, such as metal slats -- compared with the open space between the slats.
The bridge can swing safely 27 feet in either direction, up 10 feet and down 6 feet in response to temperature changes (which cause steel to expand and contract) and the weight of traffic on the road.
Any addition to the existing 4-foot-high railing could be no more than 14 feet tall and would require "winglets," curved pieces of glass similar to the top of a bus shelter, at the top of a new railing to create lift and reduce wind forces on the bridge. Lift is necessary to prevent the bridge from twisting in its most vulnerable spot -- between the two towers -- and collapsing.
If the existing railing were removed, a new railing would allow more flexibility in design options, including a railing made of glass panels, akin to tall vertical blinds, Mulligan said. Winglets could be placed above the railing or could be hidden below.
A third option, netting, would require replacing the existing railings with a similar-looking but more aerodynamic railing and would require "fairings," or tubular spoilers, along the outside of the bridge. They would streamline air as it moves across the railing and deck of the bridge.
In response to a question about the views, committee member Dick Grosboll was told that small gaps or window-like spots could be included in the design to allow visitors to snap panoramic photos.
The report was the first phase of a $2 million study paid for with regional transportation funds. The second phase will begin June 14. It will focus on federal and state environmental studies that evaluate how the barriers might affect the environment and how the effects could be minimized. That draft environmental impact report is to be completed in the fall.
A final environmental impact report will be released in spring 2008, when the full bridge board will decide whether, and how, to proceed.
To date this year, 17 people have jumped to their deaths, and 40 others were prevented from jumping off the bridge, said Mary Currie, a district spokeswoman. A 37-year-old man jumped to his death from the bridge on Saturday.
Barrier boosters, including Dr. Mel Blaustein of the Psychiatric Foundation of Northern California, called the report promising. At the meeting, he unveiled an orange commemorative ribbon pin that supporters are distributing though www.pfnc.org to raise awareness of the cause.
Distributed to subscribers for publication by
Scripps Howard News Service, http://www.scrippsnews.com
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