Minn. Bridge Collapse

[C-Dog]

http://news.yahoo.com/s/ap/20080115/ap_on_...e_collapse_ntsb

 

[kevo_55]

^^ The media has been talking about the guesset plates since the weekend. :dunno:

Was there an info leak?

 

[Guest]

^^ The media has been talking about the guesset plates since the weekend. :dunno:

I don't know enough about bridge design (or really structural design for that matter) to know about those plates or what aspect of the design that they find faulty.

Any insight kevo?

JR

 

[brick_27]

^^ The media has been talking about the guesset plates since the weekend. :dunno:
Was there an info leak?

Meanwhile, Transportation Secretary Mary Peters is expected to issue an advisory later Tuesday urging states to check the gusset plates when modifications are made to a bridge — such as changes to the weight of the bridge or adding a guardrail, said a federal official with knowledge of the plans. The official spoke on condition of anonymity because Peters had not yet made the announcement.

Currently, such calculations are done for the entire bridge, but not down to the gusset plates, the official said.

Is it just me? Whenever an original design is modified, all structural components should be checked. How can a load carrying member be reevaluated, but no regard given to the connection?

 

[kevo_55]

I don't know enough about bridge design (or really structural design for that matter) to know about those plates or what aspect of the design that they find faulty.
Any insight kevo?

JR

My guess would be a combo if poor inspection and crappy material. I bet if you pull the mill certs the steel plate for the gusset plates would be something less not as flexable as A36.

 

[maryannette]

I've worked designing parts and products for manufacture most of my career. There always has to be a balance between cost and quality, but in manufacturing (mass production) there is a bigger payoff for cost savings because of the volume factor. Most mass-produced products can be tested to ensure the design integrity while keeping costs low. In bridge design, it seems that you would want to focus on design of high integrity and use a large SF because you only get one shot. You can't do any prototype testing to find weaknesses.

 

[C-Dog]

And now some congrssional commision is recommending a $0.40 gas tax increase to pay for our fail infrustructure. But the president says that it should be done by private investment.... sheeeesh

http://www.npr.org/templates/story/story.p...toryId=18103037

 

[Guest]

But the president says that it should be done by private investment.... sheeeesh

Would that be like Adopt-A-Highway??

JR

 

[maryannette]

Sounds more like an opportunity for buy out and charging tolls.

 

[Capt Worley PE]

^^^ DING-DING-DING!!!! We have a winner!

 

[kevo_55]

MN has no tolls. We have a license tab fee associated with our plates to "cover" tolls.

 

[ODB_PE]

Is it just me? Whenever an original design is modified, all structural components should be checked. How can a load carrying member be reevaluated, but no regard given to the connection?

Even if you do consider the connections, you can still get burned.

In my case I had checked a connection as drawn (fine) but the connection itself was obscured, hidden by roofing materials, etc. From all outward appearances everything was built as drawn and in good condition. Well, turns out some lead insert anchors were used where cast-in-place studs were called for. There is no way you would have known without fully demo-ing the structure that was being renovated. Yada yada yada there was a partial collapse. Of a roof. At a public building. Nobody was hurt, and luckily owner's rep saw that it was a contractor error- problem is, all contractors were long gone. (Building built in 1960s).

Fortunately owner had no desire for $$$ and paid to retrofit all the bad conditions. Provided me a very valuable lesson.

 

[kevo_55]

OK, I finally had a chance to watch the news tonight.

WTF? Somebody goofed and used 1/4" thick gussets where 1/2" thick were required??? A material spec error I could see, but this type of error is beyond comprehension!!

 

[C-Dog]

OK, I finally had a chance to watch the news tonight.
WTF? Somebody goofed and used 1/4" thick gussets where 1/2" thick were required??? A material spec error I could see, but this type of error is beyond comprehension!!

Was it the original designers or the ones who did the analysis to show that the bidge could hndle 4x the trafic loads? Or both?

 

[Guest]

Interesting read from NTSB website ...

NTSB Press Release

http://www.ntsb.gov/Pressrel/2008/080115.html

FHWA Interim Report

http://www.ntsb.gov/Recs/letters/2008/H08_...uacy_Report.pdf

NTSB Recommendation Letter

http://www.ntsb.gov/Recs/letters/2008/H08_1.pdf

JR

 

[kevo_55]

Last night on the news, I've heard that they (the TV station) got the thicknesses wrong. They had said that 1" thick plates were calculated and 1/2" thick plates were used in some areas.

Can anyone rely on the news these days?

As for the 4x traffic analysis, I'm not sure who did the calcs for what. All I know is that I'd like to find the engineering team who designed the bridge and punch them in the nads.

 

[C-Dog]

Wow! I know where to point my finger! Based on the new calculations, it looks like it failed via overload, but they did not show any of the fracture surfaces of the gussets to cement this. I assume they could not find them in the river?

 

[squishles10]

I assume they could not find them in the river?

:huh: ouch

 

[Capt Worley PE]

MN has no tolls yet. We have a license tab fee associated with our plates to "cover" tolls.

I fixed it for you.

 

[maryannette]

Thanks for the links, JR. Interesting.