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seismic safety bolts

JHOLLAND1

JHOLLAND1

Titanium
Joined
Oct 8, 2005
Location
western washington state
the new Oakland San Francisco Bay bridge has additional complicating
wrinkle--failure of about one third of seismic anchor bolts--ranging in length
from 9 to 24 feet--each 3 inches in diameter and all embedded in concrete



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jh
 

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I live in earthquake country...earthquake central actually. In '96, the plates shifted off of Eureka (Petrolia, CA) and raised the seabed 4 feet! That's a lot of stuff to push around. I am quite skeptical that any bolt, regardless of where it's made will withstand Mother (nature) when she decides to kick ass and take names. All this engineering is done to placate the populous into believing we (man) are in charge and things are going to be OK!:eek:

Stuart
 
Ahh...the old Hydrogen embritlement.... Busted Bolts... and a less than designed strength...

In the old old days, I spent some time using a huge testing machine to pull bolts apart to failure...
the break point never looked anything like that shown....seems to me that every failure started with the bolt streatching and getting smaller at some point and eventually stretching like pulling chewing gum,,,thinner and thinner and then a rifle shot that you knew was comming but it still skeered the hell outa you... and the parting line NEVER looked like that photo...

So....... SanFran people... enjoy the ride over your less than spec bridge... while it stands...
ummm...do you think the toll taker will give you a discount??
 
slnielsen said:
Wonder if it's another example of buying to cheap?
Why didn't someone test them before pouring the concrete?
Click to expand...

At least from the photos it appears that these are accessible from below (which is why they are nine feet long) so can be changed. My Dad had the dubious honor of setting some huge anchor bolts that were sleeved down about 36" to a steel plate encapsulated in the pour 6" too low. The bolts were to anchor the tension members of a cantilever system that held the roof of a huge hanger over a really wide door opening, and were set in a 16' concrete cube, which was connected by the rebar to a 20' x 20' x 4' footing. Since this was a tension anchor, they couldn't just chop the bolts out and replace; as I recall, they ended up cutting six inches off the perimeter walls of the building, and lowering the floor a like amount to match the grade of the bolts.

Dennis

Dennis
 
Part of the information said that they were set in the concrete (way down in the hole) with almost all of the rods exposed for several years. The hole filled with water logically, and if there any microscopic cracks the water would penetrate over time.
Luckily, I don't use that bridge and will continue to avoid it in the future.

Lee (the saw guy)
 
oldster said:
.....all of the rods exposed for several years. The hole filled with water logically, and if there any microscopic cracks the water would penetrate over time. Lee (the saw guy)
Click to expand...

C'mon, now......The dam thing ain't been standing long enough for the things to rust yet..... where do you come up with that crap?
 
Looks to me like they are sleeved through the pour. Note in the third pic their are nuts on the bottom of the haunch, so they are meant to be removable. If they were poured in, there would be nuts under an internal plate encapsulated in the concrete, and they would never be able to be changed. That would be bad, because they will deteriorate over the years.

In the forth pic, I don't think we are looking at the break, but rather a cut end. The purpose of the pic seems to be to wow us with their size (ho hum) rather than let us try to study the nature of the fracture.

Dennis
 
The one problem with overseas contracts is that there is less integrity. I was in a shop when the site engineer, a German, didn't like the look of some guardrail pipe. He sent a sample out for testing and it failed yet all the mill certifications from China were supplied and showed the pipe as passing quality control. My boss was dancing on that one but was able to pass it up the chain to the steel supplier.
I talked to one welding inspector who checked out the welders and they passed the plate test. He tested something like ten welders. when he came back to China next month and saw how much work had been done. It was obvious others had been brought in once he was gone.
Trying to get qualified welders one contractor looked at India and found some. He thought he was being smart testing them in India before doing the paperwork. When the welders arrived in Edmonton they did not match up to the photos taken when they tested out. Obviously the work visa had been sold to the highest bidder. This is not saying that there are not top hands that are also Asian only that the culture is naturally corrupt.
We are just a bunch of round eyes that are so easily taken.
 
What are typical sources of hydrogen embrittlement other than welding (none obvious) and electroplating? Given the environment, I'd expect hot dipped galvanizing rather than any sort of electroplating. Just curious if there are other sources of embrittlement, such as perhaps their forging process? And, if there are other sources, is the embrittlement not reversible via baking the parts within a short time after completing the process that causes embrittlement?
 
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