Holy CRAP! Bad bridge collapse in Minneapolis

HOW does that happen?!

Many engineers think that the failure of US highway infrastructure could be a huge national disaster over the coming decades. Here are a couple of major contributing factors:

1) Much highway infrastructure including many bridges were built prior to 1960 during the huge US national highway expansion boom. So they are just plain getting old.

2) The federal gov't and most state gov'ts do not invest nearly enough in structural inspection of bridges. Potholes in the bridge deck are obvious without the need for detailed inspection but incipient failure points in the substructure are not. I am somewhat familiar with the level of resources that New Mexico dedicates to this issue and let's just say you don't want to know how little it is.

To piggyback on ScottoNM's post. 

Bridges may have been built before the maximum weight of a tractor trailer was upped to 80,000 lbs or were designed and built so long ago they have met and exceeded their "lifetime load limit" (how many tractor trailers pass over it over the life of the bridge).  Could also be due to a few bad bolts/rivets.

There was a section of bridge in Milwaukee that dropped a few feet (not a total collapse) due to either bad bolts or the wrong bolts used (don't recall which).

Perhaps over the years of the elements and those lovely winters and the salts used, some of the steel managed to rust, fatigue and give way.  Dunno.

So, the HOW could be a lot of things.  Man builds stuff and we should expect that over time, nature along with use will weaken that which we build. 

Haven't not read the story yet or watched the news.

I agree.  It is sad when anyone dies,  but 400 feet of highway dropping 50-60feet into water during rush hour and we should be talking 100s of deaths.  

Quite a few of us have left messages saying we are ok, but a few more haven't chimed in yet.

http://www.beginnertriathlete.com/discussion/forums/thread-view.asp?tid=85740&posts=21#M911098

(edited to add link)

Thanks to all for your thoughts and concern.