October 29th, 2009

alan's flowers

The Bay Bridge -

As those who live in the Bay area know, especially if they have been in a car, the bay bridge is unexpectedly closed in both directions, which means that traffic in many places is very slow. Agitation leads to accidents, and so, from what I hear, there was near gridlock going into or out of SF from Marin last night. We were wisely viewing the movie Amelia which is showing close to home, so were unaware of the problems, though we enjoyed the movie and a near empty theater.

The problem is that a piece on the Bay Bridge that was repaired seven weeks ago broke because we had gusts of wind of 30 mph. Now, my experience is that gusts of 30 mph are not unusual in the Bay area, especially where the bridge is located.

I check out the highest recorded winds on Wikipedia and get this:

The highest surface wind speed ever officially recorded is 372 km/h (231 mph) at the Mount Washington (New Hampshire) Observatory in the US on 12 April 1934, using a heated wire anemometer. The anemometer was later tested by the US National Weather Bureau and confirmed to be accurate.

The highest surface wind speed ever officially recorded in Asia was recorded in Afghanistan on 14 August, 2008
: 328 km/h (204 mph) in Ab-Paran, Ghowr.

Windspeeds within certain atmospheric phenomena (such as tornados
) may greatly exceed these values but have never been accurately measured. The figure of 509 km/h (316 mph) during the F5 tornado in Moore, Oklahoma is often quoted as the highest surface wind speed but was measured 30 m (9 feet) above ground.


I know we can't build for the greatest hazard, such as winds of 231 mph or 204 mph, but surely the Bay Bridge needs to be able to withstand winds of let's say 90 mph, though looking at this website, that may be a conservative number to target. I see that on December 12, 1995, there was a peak Bay area wind of 103 mph. October 13th of this year, the peak wind was 77 mph. Perhaps that is what weakened this piece on the bridge, but what are we thinking of if we are building a bridge in the windy land of SF that is frightened of wind?

Check it out:

http://ggweather.com/basi.htm

I think we need to look at why this "little piece" was rubbing back and forth. Seven weeks is not a long time for something that was certified to be well-done and complete to fall apart. The fact that no one was killed is astonishing, if not, miraculous. Is there something bigger going on, some movement elsewhere that has not been calculated? And so again we put a band-aid on the bridge and maybe this one will hold, but I wonder who is looking at the whole picture, the whole bridge, and not one little piece.