Wednesday, August 29, 2007
Background: As you may know, I used to work for a very large company. I used to think that the only value that I saw in it was technical: great labs, great library (online access from my desk to all the ACS, Elsevier, Wiley... polymer and chemistry journals you could imagine) and technically competent scientists. My wife also worked at this same company too. Both of us suffered through the endless training and talks on business stategy, benchmarking, personality profiles...all the stuff that is fodder for Dilbert.
I was layed off from said company, and my wife quit, picked up a real estate license and is ecstatic helping real people with going through a huge transition in their lives. She started talking with another realtor who had been a realtor his whole career (Call it 20 years). He has just had started his own brokerage, and was talking to my wife about some of the challenges and that's when the lights went off. This guy knows nothing about all the stuff that I had just complained about as being a waste. He was having to bring in consultants to help with strategies, personality profiles... and the broker thought this was all great... that he was at the cutting edge!
So maybe there was something at that earlier employer that I only now appreciate. Certainly my wife has a huge advantage over other career realtors, and that is apparent as she is already threatening the stability of the other established realtors, which was part of the motivation for that conversation with the broker - if you can't beat her, join her.
1) Removal of the bridge pieces is now going more rapidly since 1) all the bodies have been recovered, and 2) the NTSB has taken whatever samples they have deemed necessary.
2) It already known that the collapse was particularly "catastrophic" (i.e., the whole thing fell all at once) as it was built in a time period were a lack of redundancies in the design were common. Bridges prior to that period (sorry, I can't define the period exactly) and since that period all have redundancies so that if a part of the structure fails, the rest of the structure is strong enough to support the load.
3) The media's attention at this point is on the gusset plates which connect the girders together. MnDOT had looked into strengthening them earlier this year by adding additional rivets, but this was not done as concerns were raised that the additional holes would weaken the structure more than the rivets would help.
What I want to know: bridges are all rated on a scale of 0 - 120. This particular one had been most recently at 50, but bridges with far lower ratings are still standing. Obviously the rating is not deterministic, but rather statistical. So, what's the standard deviation for any bridges rating? Is it constant, or does it vary with the rating? How accurate is a rating given that they are based on visual inspection? How well do ratings correlate with reality?
Thursday, August 02, 2007
“There but for the grace of God go I.” I’ve driven that bridge countless times, as recently as 4 weeks ago coming back from a cross-town visit to a client. It is in the center of the
That more people weren’t killed is truly a miracle. A school bus with 60 kids fell; only 10 of them are in the hospital. The rest are at home with their parents.
This isn’t supposed to happen here. Not in
Identifying the full causes will take a long time. Just accessing the bridge now is difficult as it is now in a 60 foot deep ravine with steep walls on both sides. We have three metallurgists on staff here with plenty of grey hairs between them, and plenty of experience with failure analysis. None of them are in yet at this hour, but I’m anxious to prod them for insight.
More to follow...