Quibble: The Bay Bridge lost a singlepart of the roadway because two  
parts of it were on opposite side of a fault. it is entirelymade of  
steel at that end.

The "Cypress Structure" in Oakland was the one that collapsed on top  
of dozens of cars due to inadequate reinforcment.

Neither of them failed because of the ground giving way; it just  
shifted and the structures themselves failed.
The only thing that was faulty about the reinforcement was not enough  
of it, combined with aging concrete.

Seattle has a long double structure exactly on the same plan as the  
Cypress structure; it will go down given an equal shock one day!

Lou Judson  Intuitive Audio

On Mar 5, 2009, at 7:26 AM, Dave Lewis wrote:

  Likewise the internal mesh of rebar and reinforcement has proven  
faulty in some cases; we saw that in the failure of part of the San  
Francisco-Oakland Bay Bridge in 1989.