On Mon, 19 Jun 2000, Jan Steinman wrote:
> I might have slipped a decimal here or there, but I'd also be
> surprised if the bridge weight limit didn't have a hefty contingency
> factor. I also tried to err conservatively in the other assumptions.
I think perhaps you did, because before that you wrote:
<10 tonnes>
> That's 10 million grams, or 10 million cubic centimeters of water.
> The weight density of snow varies all over the place, but let's call
> it 1/10th that of water to keep the numbers round -- 100 million
> cubic centimeters of snow, or 1,000 cubic meters.
100 million cc = 100 cubic meters (there are one million of them to a
cubic meter, which is why 1 cubic meter of water weighs exactly a
tonne).
<100 m^2 bridge area>
> So a big nor'easter blows in and dumps 10 meters of snow on the
> bridge, and it fails! This has gotta happen, what, every ice age or
> so? Heck, let's even assume that it's especially dense snow -- as
> dense as water, in fact -- and get rid of our factor-of-ten fudge for
> snow. You'd still have to flood that bridge with an entire meter of
> water for it to fail!
It would only have to be 1m of snow or 10cm of water, which might
conceivably happen, esp if the bridge had sides.
However, I suspect that you're right about the main reason for covering
being to protect against rot, though.
--
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