Could bridge collapse be prevented ?

Hi traditional,

Do you really think the MN bridge would not have collapsed if we had not been involved in a war? Give me a break.

I understand a repair involving bolting steel plates over certain sections (joints?) had been proposed but was turned down because drilling the necessary bolt holes would have caused even more problems. I really don't know if a more rigorous inspection/recommendation would have saved the bridge or not but I don't think funds were diverted away from essential public projects to fund the military effort.

Congress is in an uproar now over the nation's bridge safety. They always do this you know. They did it after Katrina. They did it when gasoline prices spiked. The only reason they yell and scream is to look good for their constituents.

I can't answer your #1 & #2 but I couldn't resist commenting on #3.

Regards,

-John

I get your point aboput war funding but if you recall before 911 we had a budget surplus (some sort of balanced budget) after the Clinton years. After 911 so much money has been funneled into anti-terrorism as well as the mid east war that we no longer have a budget surplus. Quite the opposite.

Now IF we had an ongoing budget surplus I suspect there would be more money available for infrastructure repairs at both the state and federal levels. It is a big IF and a very political issue, but I'm inclined to believe this would be so or at least this volume of money would be available for some other work whether it be research or some other subsidy.

Interesting speculation. However, before the events of 9-11, the political discussion of restoring infrastructure was very faint. Indeed, it was fully drowned out by clamors for tax cuts.

You get what you vote for!

Any load combination, positioning, location, application, calculation, etc... ,I believe have been taken into consideration for the design of structures, especially bridges. That's my comment for #1.

Modern bridges are built with embeded sensors to measure strain on the bridge structure. This strain signal is transmitted to a monitoring station. This is a concept which I have read about, I am not a Civil Engineer, but I am an Electrical Engineer. Electrical Engineers have got very little or nothing to do with bridge construction but with introduction of embeded sensors, this will bring Electrical Engineers in the same boat with Civil or Structural Engineers when it comes to bridge safety. Any one out there using the technology of embeding sensors in the bridge, can you shed light on this subject?

Retro fitting sensors in bridges and inspections that do more than look at joints will help. We have better tools today than we ever had for this and after that I expect we will use them more. Before we rush to solve all the other problems we need to know what happened to this one one first. I expect it is something more than than we have seen so far. gc

There are many reasons why bridges collapse. They mostly fall into two major categories: (1) compromised maintenance, (2) unanticipated "features" of a new design concept.

The history channel has prepared an excellent non-technical review of the recent history of bridge collapses http://www.history.com/minisite.do?content_type=Minisite_Generic&content_type_id=55377&mini_id=1335

Regarding the second: It is hard to argue against new designs, but since much of the concept polish in engineering is based on lessons learned (from disasters), we should at the very least recognize that there is significant inherent risk coupled with every departure from the tried and true. New concepts are thoroughly investigated by a modeling, but the models only evaluate the problems which we can think of, and often they cheat by adding complexity (tweakable knobs) so that modelers can "tune" their models to compensate for things that they cannot resolve intellectually. This subject is treated at length in an excellent book: The Future of Everything: The Science of Prediction by David Orrell

As to the first: A call to action was issued following the collapse of the Silver Bridge over the Ohio River in 1967 citing to inattention that we pay to our infrastructure. This call has been repeated after each ensuing collapse and is soon forgotten. Politicians play to the whims of the voters, which they skillfully manipulate. Politicians readily decide to spend a trillion dollars on a ill advised war, but can never find funding for basic human needs (education, health care, infrastructure, etc.). It's not their fault: we (re)elect them and put up with their fanciful tirades.

The best argument against democracy is a five-minute conversation with the average voter - Winston Churchill

We are fighting foreign wars and neglecting our infrastructure to satisfy the whims of a president run amock, with his false pretenses to put us in this position against the wishes of the majority of Americans who are totally against this unwanted war where we are wasting American as well as Iraqui lives, just so much waste of lives and money!!!! This money could be used to improve the infrastructure in our country which is falling apart and for health care, education and various other projects wisely, but our "Commander in Chief" thinks otherwise, and he says, "he is the decider", so what can we do?

You sound just a teeny tiny bit like a democrat.

So you prefer to fight the terrorists on our own soil!!!???

I think it could have been prevented if there were cracks at the failure point. As a contract welder I am certain that the bridge could have been reinforced besides making the proper weld repairs under the A.W.S. D1.5 code

Hi jamesbg,

It'll be interesting to see what failure analysis turns up as to the cause of the collapse. If there were cracks, etc. why did past inspections not bring them to the forefront so that folks like you could have been brought in to resolve the problems?

The problem, I think, is just plain old bureaucracy, not a lack of funding as has been suggested by others on this thread. It's a little bit like the movie Jaws where the mayor (bureaucracy) doesn't want to close the beaches (bridge) because it would disrupt the tourists (commuters) in spite of the police chief's (inspector's) insistence. The chief kept telling the mayor, we've got a dangerous situation here, but the mayor refused to realize the scope of it until it was too late.

Regards,

-John

John john

I agree with your points, sometimes practicality trumps money and bureaucracy could complicate a ham sandwich .

These are valid questions that help to explain a difficult situation.

and sheds light on an area I had not considered .

thanks for your input

I thought engineers were supposed to be logical?

1) There never was a budget surplus under Clinton. There was a budget surplus projection based on the 'bubble' created by the shut down of the military after the cold war ended (If it ever ended?) and the idiot driven internet bubble where profits matter. (A lesson for the economic majors and Harvard Business School graduates.)

2) Visual inspections are cheap but virtually useless in establishing a bridges condition. It didn't even catch the Mianus River bolt that was as loose as a goose form months before it collapsed.

3) The Minaus collapsed in 1983-No Iraq war!

4) The media went nuts and the statistics tossed around were virtually identical to those being tossed around this week.

5) Techniques using finite element stuctural analysis have been in use since the mid eighties. I worked with Dr. DeWolf at the University of Connecticut and we had them installed and working on multiple bridges over a five year period. They were ignored or rejected by DOT people in the late 80's and into the 90's (No Iraq war!) as too expensive to implement even though they could have been coupled with Acoustic Emmission technology to remotely to remotely provide early and accurate assessment of fatigue, scouring and other structural changes related to incipient failure to centralized maintenance offices.

6) There is not problem with money in Mn! They are building a new stadiums etc. with all there surplus wealth.

7) The problem lies not in the stars, but in ourselves!

Let's keep politics out of our engineering discussions. We should be smarter than that! Vibes!

True, people don't vote for the guy who closed the bridge, even if it did prevent them from being killed (they don't really know they would have died, so it is unrealized). Rather they vote for the guy who kept the bridge open, as long as they don't die. If he is lucky it last for another term and he retires and passes it on to the next guy, and kept the Cities/States budget down while passing new social special interest policies to save something.

Hmm this seems to be wandering off into a discussion about foreign policy. Please keep in mind that the infrastructure has been failing for decades, not two terms in office. Also bridges fall under the State transportation offices who receive federal funding. Obviously, the State of Minnesota felt that the traffic headaches and lost time for the voters would be worth the risk to health and safety for a little while. They gambled and lost. It does bring up the question about the investment we place in infrastructure since the 1960's, versus prior to 1960's. A good example here is the Oakland Bay Bridge Collapse. Note there was a much older bridge nearby that has weathered many more earthquakes. Good infrastructure is about investing money into qualified engineering. Design/build for older structures tended to be a real qualification process, not a design/build by the cheapest.

The CEQA/NEPA process, litigation, political pandering, special interests, and many other environmental programs have severely impaired the decision-makers perspective on priority. You can no longer decide to repair a bridge when it needs it. If you modify it, you may have to perform an entire EIS, because some influenza infected falcon may have nested there 10 years ago. You have to consider ways to mitigate perceived impacts on the poor, sound impacts, historical significance (maybe someone famous looked at that bridge in the 1960's), aesthetics, the guy who jogs across the bridge on sunday and owns a lawyer, etc.. The CEQA/NEPA process could take years to resolve with all the -ologist seeking billable hours. Under these types of processes the do nothing option is always viable, and i have not observed a portion that places adequate weight on risk to human life (actually i think risk to human life might be less important than risk to potential nesting habitat). The problem is that there are no special interest pressuring/paying politicians to maintain infrastructure, and protect the health and welfare of the public anymore (and they tend to perceive the general public as sheeple, and rightly so given short term memory)

I think you make a good point .Thanks

There are two threads on this same topic running simultaneously. Both seem to be shifting towards "it's the fault of the government" or some other and very little speculation on what really happened.

Having seen other "failures" in my time, both large and small, I would have to say that it's the human in us all.

Perhaps the bridge was designed for only, say, 10,000 cars or trucks per day. So, somebody comes up and says, "they usually design these things with a little extra so let's just increase the utilization just a bit." Before long, it's not just a bit anymore. I've seen this attitude in some companies, my present one included. Curiously, it's not the engineers who make this decision.

It's also possible that knowledge at that time the bridge was built was not as good as today. They built the Titanic, thinking that it was unsinkable. Unfortunately, the metallurgy in those days prevented engineers from seeing that the metal used in that ship was flawed. Might this have been a similar case?

Sadly, engineers are humans too. Taking shortcuts in design or costs, finding ways to do it quickly instead of surely, the list goes on.

Is it realistic to install sub structures under weakened bridges to provide a "crutch " to prevent failure until permanent repairs or replacement .

Yes. Two railway viaducts come to mind where an arch that was weak has been supported by a new cast concrete arch located beneath it. As a repair it is economic in comparison whith wholesale renewal, and can be carried out with the service still operational on the line above it. Reducing the line from double to single track is also attractive, so as to prevent the weight of two trains bearing upon the structure simultaneously.

Blisworth Tunnel, the ninth-longest canal tunnel in the world, was also repaired by the technique of casting a concrete arch beneath the failing brickwork.

Thanks for addressing that issue ; so substructures are a viable answer .

Maybe that might be implemented in some fashion to reinforce existing structures .

I remember the Romans built wooden supports then installed arches and finally removed those supports.

I wondered if a modern blown in version might be viable. .

The Blisworth Tunnel repair was done by using the http://en.wikipedia.org/wiki/Shotcrete method.

I remember the Romans built wooden supports then installed arches and finally removed those supports.

They did indeed. So did Stephenson. And Brunel, and Telford, and a few dozen others. This is the standard way of creating an arch and the timber structure is called "centreing".

Do you think centering could be applied to older structures utilizing a balloon that could be injected with high density foam or other light weight material to achieve a temporary stabilization

An assessment of the strength of various materials might indicate that non-porous shotcrete has an advantage: a porous material is always open to the possibility of water accumulating within the matrix and freezing, the associated expansion of which would rupture it over time.

There is always a compromise to be achieved between strength, flexibility and cost.

I have to agree with Vulcan in post 16.

The bridge was built fourty years ago and not designed for the traffic that had been traveling across it daily for who knows how long.

Consider the population of that city forty years ago when you might have have 5-100 vehicles on it.

Flash forward to today and look at the bumper to bumber traffic that would be still traveling acrossed it had it not colapsed. That would be 3 to 50 times or more weight than it may have been ititially designed to support in daily traffic.

Now consider this. How many bridges in your area have been around that long and are still in service. Do you drive on them just because they are more convenient.

Also take note that when doing road repairs when a new surface is laid that they do not do this to bridges. This is because it adds so much tonnage to the bridge that is gets it too close to the load limit.

That being said, how much difference is there between overloading a bridge with motor vehicles and blacktop?

Also I believe, if I am not mistaken, it is not the Federal Governments responsibility to maintain these bridges. It is the State and local Governments responsibility.

Just my 2 cents....OK mawbe that was a quarters worth.

I'm surprised that I haven't seen any reference to corrosion! Whenever I travel in the northeast (they may think of themselves as the northern midwest), I always notice a lot of rust, probably aggravated by all the salt they use in the winter. In one article on this bridge I read that back in the '90s a report mentioned something about joints that were no longer flexible, or something like that. It would not surprise me at all if they were to find the true cause was corrosion.

Some of the rail bridges in the UK were built over 100 years ago by the private sector at a profit. They now have traffic on them that is several hundred times the running load in those days and probably beyond expectectation, they are still there. Designing to a cost is projected over time, probably not 40 years in this case so politicos need to plan for redundency and put something in the pot for replacement not just as needed repairs, which often do not get done. But this is a never ending stupidity that will happen again and again.

Hmm if age and design load consideration at the time of design were a factor, why hasn't the George Washington Bridge or the Golden Gate collapsed. I know the traffic is much heavier in San Francisco now than it was in the 1930's.

Simple.

The Golden Gate and GW bridges were designed to support at leats 5 time what was deemed necessary and constructed to be able to "Suit the needs of the future"

Both can be acredited to engineers being on the ball. Also both have been reconditioned to account for the additional traffic that is currently being sent across them and for future traffic conditions.

You're assuming that all bridges built back then were overdesigned by a small amount. It is typical that engineering designs are built to withstand 2x the expected load or natural stress (storms, earthquakes, etc).

The really good engineers designed for even more than that. The long standing bridges, dams, bridges were probably designed to last practically forever. Something like designing it to stand up to a Force 20 storm when only Force 5 has been experienced in that area.

I don't know how much traffic was designed into the Golden Gate Bridge but since it's been standing for so long, I'd have to guess that it's been overdesigned by a lot. Plus the fact that it has been receiving regular maintenance and repairs.

the point that is of interest to me is regarding the ancients. Now mind you that many of these structures have fallen. But a truly remarkable number stand in some level of entactness at least at footing or embankment.

These engineers built a structure(s) which had the inherent properties needed to be strong. They stand because of design. Period.

Oh yeah, and the absence of serious earthquakes.

It just seems to me that there is a lesson in that point somewhere.

shrugged shoulders,

CR3

Le Pont Neuf (the new bridge) was completed in 1632, in Toulouse France. It continues to carry four lanes of heavy traffic (including trucks and buses) today.

It is a stone bridge, based on arch construction http://www.bonjourlafrance.net/france-city/toulouse-france/images/pont-neuf-toulouse.jpg

They don't build them like they used to!

You mean the Regean smaller government is not working? They are not protecting the people and watching out to make sure that life's are not put in danger because the states are bankrupt trying to support the federal mandates while the federal government cuts taxes and allows overbilling and fraud to abound overseas.

Everyone else in the USA is getting trickled down on .

People forget WE THE PEOPLE with our taxes built the greatest infustructure in the world. Then they started whinning let someone esle maintain it. We corporations who use the infustrucer the most with the heaviest loads should pay little if any towards maintance. Let us write all the fuel taxes we pay for roads off on our federal taxes. Shoot let us write of the fuel, parking and food whe we go for a business lunch too.

I know we can take the money to rebuild bridges out of the Illeagal Alien legal funds and the illegal alien housing funds and the illegal alien education funds.

In working in seismically active areas, structural Eng's will place to graduated rules opposite one another. One on each side of a joint or structural point inside a building (Intel has 'em all over the place) and mark where the lines met - a vernier gage.

This seems like a very practical and effective means to monitor the movement on bridge structures as well, but I have never seen one. Granted, iI am not really looking for them either. Perhaps they are hidden.

CR3

Generally, structures are built on a risk basis. The anticipated loads (be they full loading or assymetrical loading or dynamic loading) are given on a very rough basis but using all current knowledge to the best of our ability. This includes future use. Load factors are applied, mostly for the stress design criteria, which try to take into account variances in our load assumptions.

The design is then produced, after much mulling over and too many meetings, which is checked against various design criteria such as stress, displacements, fatigue, corrosion etc. Material factors are used depending on the type of material and its provenance.

The structure is manufactured and erected with the skill and checks that most contractors are capable of.

Maintenance of the structure is passed onto the client. A description of the maintenance required for the structure should be passed to the client by the design team and the contractor.

Short cuts should not be taken; everyone should have instilled in them the necessary responsibility that the building and maintenance of a structure requires.

This is a short desription of how the bridge collapsed. Most likely many of the above points contributed in a small way. The blame for the collapse is inevitably shared.

However, the shock that the collapse of a structure produces on the general public is concommitant with the fact that this rarely happens. The number of deaths and injuries resulting from structural collapses is very small. This does not mean that we should be lax in our jobs, on the contrary, we learn from each failure collectively.

It was a terrible tragedy that should have been avoided and the people that have been affected deserve recourse.

Where I live, they normally shut down the roads especially during bridge & overpass expansion/repair construction. It hasn't affected the career of the polititian. His past record and reputation (district boundries/constituents) allow him to make the difficult decision. They normally perform the (structurally) critical scope during the shutdown on weekends. The closures are made very public so people adjust their routes to accomodate the inconvienince. The risk assesment is based more on the critical action activities and provided completion schedule. The SME's opinion outweigh the complaints of the shoppers trying to get to the mall on the weekend. (Translate: Still a working man's town)

Try to avoid driving on bridges, overpasses and roads that are under construction/repair, even if your politician will let you. I can promise you it wasn't the construction forman's idea to keep it open.

Hi Guest,

You said "The closures are made very public so people adjust their routes to accomodate the inconvienince".

How about this idea (and I think the politicians would love it too). Whenever a bridge/overpass is being inspected, repaired, etc. large signs should be posted informing commuters and travelers that:

"THIS BRIDGE IS BEING INSPECTED OR REPAIRED FOR YOUR SAFETY! PLEASE BE PATIENT. YOUR DOT CARES AND WE ARE MAKING EVERY EFFORT TO INSURE THAT TRAGEDIES LIKE THE MINEAPOLIS BRIDGE COLLAPSE NEVER HAPPEN AGAIN. THANK YOU FOR YOUR PATIENCE AND UNDERSTANDING".

Who knows, it might even alleviate a little road rage.

-John

Now there a solution. Eye catching too!

LOL, think back to the last time you were stuck in traffic and passed a DOT work crew doing maintenance with the signs they usually post months before hand informing everyone of the impending maintenance. How many of you responding with some relief that they were repairing your transportation system rather than responding with some anger over the delay, which you had ample notification about. Now imaghine that you actually have some knowledge of what DOT is doing there, how the vast majority of people feel who do not have a clue and just think anything DOT does is a waste of tax money that could be spent on promoting some industry in the statte, a tax break, more police, more teachers, etc..

I know, I know. But you gotta start somewhere don't you?