[LMB] OT: Bridge collapse

alayne at twobikes.ottawa.on.ca alayne at twobikes.ottawa.on.ca
Thu Aug 9 05:20:27 BST 2007


Here in Canada, there was a nasty scandal when an overpass collapsed in 
Laval, PQ, last fall, killing a number of people. A passer-by had noticed 
it was dropping bits of concrete, alerted the police, and a government 
inspector came out and said it was OK for now. And less than an hour 
later, it collapsed on top of a bunch of cars.

There's been all sorts of interesting info coming out of the Quebec 
provincial inquiry over the last couple months. One of the scariest was 
comments from an expert saying that visual inspection is not enough to 
determine the health of a bridge/overpass -- you need to look inside 
(whether by cutting a hole or X-raying or whatever).

The particular overpass that collapsed was improperly built (not according 
to plans). It's not necessarily obvious if a few steel girders are 
missing or not in the right place. Could be other bridges like that, too.

I also wonder if some bridges are, in fact, carrying loads that exceed 
their design capacity, as more freight gets shifted to trucks.

In any case, it is unwise not to fix bridges and roads well before they 
might fail, in case something else unexpected occurs. (I mean -- would 
*you* expect a tornado in Brooklyn?)

Alayne

On Wed, 8 Aug 2007, Beth Mitcham wrote:

> I'm not a huge news reader, so I miss a lot of stuff, but the little I 
> saw said that the bridge had recently been examined, and was rated as 
> needing repairs soonish but not urgently. If that means that there is a 
> 1 in 100,000 chance of collapse (numbers I made up), then we'd expect a 
> bridge collapse every few years since apparently we have approaching 
> 100,000 bridges in the US at that level of decay.
> 
> But it doesn't seem that unreasonable to leave a bridge open in that 
> condition.  Is there more info out there that shows the bridge was more 
> dangerous than reported in the first days?  Do people here know about 
> the standards for bridge safety, and know if the bridge failed them?
> 
> Here in Seattle we are shutting down one of the highways for big 
> repairs, which probably could have been done last year, but there is no 
> question it is a real big deal to do it.

-- 
Alayne McGregor
alayne at twobikes.ottawa.on.ca

"He that would make his own liberty secure, must guard even his enemy from
opposition; for if he violates this duty he establishes a precedent that
will reach himself." --  Thomas Paine



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