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Re: AP: Wash. State bridge collapses into Skagit River; sends vehicles, people into water

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Hassan -

Thank you for the interesting and thorough explanation. I realize your 
response is general in nature and I certainly understand the reason the 
Washington bridge failed is due to the fault of the truck driver, but I 
invite you to look at the pictures of the bridge that failed even in areas 
that did not yield. Also, the condition reports of 6 out of 9 etc bothers 
me. Maybe we should have the rating system displayed on the bridge like 
restaurants so that we as informed commuters can chose our route not only 
on convenience but risk as well.

T. William (Bill) Allen, S.E.
ALLEN DESIGNS
Consulting Structural Engineers
San Juan Capistrano, CA 92675
V (949) 248-8588/ F (949) 209-2509
-----Original Message-----
From: Abolhassan Astaneh [mailto:astaneh(--nospam--at)ce.berkeley.edu]
Sent: Friday, May 24, 2013 04:24 PM
To: seaint-seaosc(--nospam--at)mail-list.com
Subject: Re: [SEAINT-SEAOSC] AP: Wash. State bridge collapses into Skagit 
River; sends vehicles, people into water

Allen,The primer being under the final surface paint maintains its 
elasticity, but the final paint being exposed to whether and especially to 
sun becomes brittle over the years. When this bridge collapsed , it hit the 
 water surface , which has a very high stiffness and is like a rock at the 
instant of impact, the members bent and created large strains in the steel 
as well as the primer and the final paint. The final paint being brittle 
got fractured and flaked out and dropped. The primer being flexible 
stretched with the steel and remained on it.This is like testing a specimen 
 in the lab. We whitewash the specimen and when the base steel yields , the 
 white wash does not yield and fractures and flakes out. That is the way we 
 realize what parts have yielded.I have used this notion of surface paint 
flaking out of areas of steel that yield so often during my investigation 
of post earthquake damage or failure investigation of collapsed structures. 
 It is a great tool (by default). It is like all bridges are whitewashed 
and ready to be tested when an earthquake hits and then we go in and see 
which part of our specimen (i.e. the actual bridge!) has yielded.As an 
example of how valuable such observation can be , when i was investigating 
the damage due to the 1994 Northridge earthquake to steel buildings and 
bridges, in case of steel bridges, almost in all cases I realized that the 
damage is not due to cyclic behavior. It was like someone has hit the 
structure with

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