Bridge Collapse in MN 29

[bridgebuster]

Let’s hope that good will come from this tragedy: That the scores of “concerned” politicians will actually address the problems with this country’s infrastructure and not forget what happened after Election Day passes.

In the meantime, we should avoid public speculation on the collapse. As some one noted there is a lot of incorrect information in the news. Some ludicrous statements I’ve noted:

“State bridge engineer Dan Dorgan said the bearings could not have been repaired without jacking up the entire deck of the bridge. Because the bearings were not sliding, inspectors concluded the corrosion was not a major issue.” IF THE BEARINGS WERE NOT SLIDING THAT IS A PROBLEM!

"I would be stunned if this didn't have something to do with the construction project," said David Schulz, director of the Infrastructure Technology Institute at Northwestern University. "I think it's a major factor." STICK TO TEACHING!

“This bridge is unique because it was constructed with a single 458 ft steel arch to avoid putting piers in the water which would impede river navigation, according to the U.S. Dept. of Transportation. “ I GUESS THEIR DICTIONARY HAS A DIFFERENT DEFINITION OF UNIQUE.

 

[COEngineeer]

I am not a bridge expert. So do you think the support is suppose to be free to slide (slotted maybe?) or do you think it is bolted down? Maybe the pier moved when the bridge went down, not before.

Never, but never question engineer's judgement

 

[csd72]

unclesyd,

did they censor your forum?

This in an interesting link that is more related to the other forum:

http://news.yahoo.com/s/ap/20070803/ap_on_re_us/bridge_collapse_sensors

 

[unclesyd]

Yelp!

Here is another approach to the detection and monitoring of fatigue cracking on steel structures in real time. I would imagine that all such approaches to automating detection and monitoring of cracking will have tons of money dumped on them shortly.

http://www.matechcorp.com/index.html

 

[jike]

Wikepedia's description yesterday said that there were "geared wheels" to accomodate expansion. I cannot locate that decription today.

 

[SteelMover]

The problem with these technologies is LAWYERS. We actually tried to do this with stadiums, but we were cut off because there was too much liability involved. Your entire organization would be hung unless legislation was passed that barred the possibility of lawsuits against engineers as long as good faith (no bribes, gross negligence, etc.) was in place during the monitoring. I guess the only thing you can do is tell the DOT whats wrong and indentify nothing as "Safe" or "Acceptable". You all can imagine where the first fingers would point though.

Unfortunately politicians are almost all lawyers, who want to find blame in the engineering not the funding....

 

[COEngineeer]

so does the geared wheels have a stop on it? Can this geared wheel pull on the pier when it collaps? Can you also lift this gear up or is it restraint up?

Never, but never question engineer's judgement

 

[jike]

Normally, expansion bearings have keepers that limit the maximum movement allowed and I certainly would expect that to be in this case also.

During a collapse situation damage can occur to the pier, expansion bearing, and other elements that will obviously make it act differently then under normal conditions. The trick is to find out the chain of events from all the different broken, tilted and twisted pieces. Which happen first?

 

[bridgebuster]

Go to Page 2-3 (37 of 100) of the URS report (Volume 1 of 3), there are photos of the expansion bearings. You'll see what was referred to as "geared wheels". Essentially, it's a roller nest. I've seen some unusual bearings but I've never actually seen one quite like that.

jike is absolutely right, the chain of events needs to be established.

 

[unclesyd]

csd72,

I re-posted in thread765-194020

bridgebuster,

That style/type of bearing was quite common on Railroad Bridges in my area several years age.

 

[bridgebuster]

On the MATECH web site, the bridge on the left appears to be I-20 over the Mississippi River, in Vicksburg. I worked for the engineer who designed it. He used that design as the basis for the replacement of the original Silver Bridge in West Virginia.

WVDOH needed a set of plans quickly and when they learned that length and channel clearance of Vicksburg Bridge was more or less what they needed, he got the job.

 

[denoid]

To add to bridgebuster's list of ludicrous statements above, we have a local weatherman here in the Twin Cities who has been freely speculating on the collapse during his weather forecasts, because:
1. He must consider himself qualified because he took some science classes;
2. He said his wife is an Architect, who had to take some structural engineering classes in school (many years ago).

His (and her) theory is that the vibration of the train running below the bridge at the time is the main culprit, along with the rush hour traffic. Somehow, I don't think it was the first train to use those tracks during rush hour!

(I guess that makes me a Meteorologist, because I have a rain gauge and thermometer in my back yard).

 

[COEngineeer]

denoid.. maybe the frequency of the vibration of the train plus the frequency of the jack hammer matches the frequence of the bridge!

Good news, they reduced the number of missing people from 30 to 8. 5 people are dead so far. I hope there are not a lot of people walking under the bridge when it happens.

Never, but never question engineer's judgement

 

[unclesyd]

In the video of the collapse it shows a lady in a rapid exit screen left, barefoot. She must have been very close to the bridge when it started to fall.

 

[denoid]

"maybe the frequency of the vibration of the train plus the frequency of the jack hammer matches the frequence of the bridge!"

Maybe, but I'd rather hear it from someone other than the TV weather geek.

 

[NS4U]

My thesis is in train-induced vibrations (in buildings mind you)... but if this guy is serious keep in mind that even the train vibrations would need to travel through the soil, up the peirs/abutments, through the bearings pads (which will act as isolators or very high dampers) then into the bridge.

The magnitude of vibrations would be so small that resonance caused by the train is highly unlikely to bring the bridge down.

I think this guy watched one to many tacoma narrows specials

 

[denoid]

I guess my main point is, as bridgebuster put it nicely: "we should avoid public speculation on the collapse. As some one noted there is a lot of incorrect information in the news." The media is obviously looking for scapegoats to blame right now.

Having an obviously unqualified media person (weatherman) give theories just doesn't help anything. I'm a building structural engineer (as opposed to a bridge structural), and I wouldn't dream of giving any speculations to be aired in public right now, because I just don't feel qualified enough in that area. I'd rather hear what the true experts with experience in bridge design and/or collapses have to say.

The only good to come out of this right now is that it maybe brings some attention to a possibly dangerous condition in other bridges around the country. At least they will be looked at and re-evaluated. The politicians sure seem to be congregating in Minneapolis this week. They know, after Katrina, that how they respond might just have an effect at the polls in the very near future.

 

[bimr]

unclesyd, that was a good observation on the woman in the video although she is not barefoot. She was only about 100-120 feet away from the bridge.

The thing is, during her entire 15 seconds of fame, it looks like she never stopped talking on the cell phone during the entire collapse of the bridge. Amazing concentration!

 

[strguy11]

Denoid -

Your statement about the Guy's wife being an Architect got me thinking. Has anyone ever seen the intro for Building it Bigger on the Discovery Channel?? The host claims to know alot about engineering because he went to Architecture school. What a joke!!!

We need to let the engineers on the ground do the investigation and keep the speculation to a minimim as the drive-by media types will run with antyhing that they can use to make someone look like a scapegoat.

Hopefully what will come out of this is an is an increased knowledge, and a greater awareness of the poor state our infrastructure is in. I can believe the numbers being stated of how many bridges in the country are deficient, however, the media does not understand what alot of this data means, which is dangerous. ASCE has been publishing for years the condition of the infrastructure and a believe that our bridges normally get C's and D's.

 

[concretemasonry]

I am in complete agreement with the opinion that many “news reporters” are far beyond their expertise or knowledge. I guess they have to fill air time and have a hard time shifting from “entertainment reporters (ala Paris Hilton antics)” to real hard factual news reporters where they should seeks facts and professional opinions. – One female network personality was describing the “concrete” bridge and how difficult it will be to get the cars and debris out of the very, very deep water (actually, the barge channel is only 9’ deep as I recall).

I felt the response by officials (NTSB, MNDOT, etc.) to collect all historic information, photos and videos, interviews and recovering the debris to determine the real cause was a very positive step. It could be very valuable to the engineering profession.

It sounds like it will be a big project to visually reconstruct the bridge and examine the salvaged components. Despite the current, the odds on collecting all the major components are quite good. The river bottom is quite hard and is native limestone in many places; the depth is not that great (9’ barge channel) and the flow (in terms of volume) is not as great as you would expect. Just downstream there is an area where some debris that was flushed away will collect. – Maybe they will reconstruct it just like an airplane forensics project.

They are currently putting GPS equipment on all of the pertinent points of the structures to determine the present location before anything is moved.

After they get the physical components, they will then have an opportunity to look at the failure points (probably multiple sequenced failures) and then look at the possible causes including the unbalanced loads, vibration, effects of any repair efforts and “terrorism” without the “benefit”(?) of the newscasters and limit the investigation to the engineering facts.

This will hopefully be documentation to put teeth into the move to conduct engineering evaluation of all infrastructures for once.

Dick