13 replies to this topic

[LastManAlive]

I started my Drafting course this year out with having a research report on why I thought the Minneapolis bridge colapsed. As a class, we had to create a powerpoint presentation as well with pictures doncumenting the above possible causes. Because of many reasons, we got the presentation extended and have to now include a chart, graph, or, in this case, a poll will work. So, I was hoping to get at least some of the more respected or known members as well as any that feel free to join the poll to vote on what they think is why the bridge collapsed most likely collapsed. In my paper I used a selection of many reasons that, when combined, may have been the lead to collapsing the bridge. I am asking to, obviously since its a poll, pick one reason why your think the bridge collapsed. This is purely opinion. Feel free to post your opinion in here to further explain your ideas on the incident. Those that post your ideas and whatnot, I might choose your post to print and view to my class. If I choose your post, I will PM with a release agreement just saying that I am not steeling your idea, but simply sharing it. Onto the info!



So, I put 5 (6 including the 'Other' option) options up that my class found to be what may have led the bridge to its plunge into the Mississippi. The first, though funny, it's very possible, pigeon dung, was said by many resources to cause rusting and corrosion on the steel members and screws and other structural features. Yes, I laughed too when first hearing this, but my opinion was changed. Let alone big dung being corrosive and powerful, pigeon dung can be highly corrisive after going through the heat of the Minneapolis summer sun. But even more so when it goes through a process of baking in the sun and mixing with water and other compounds found in the air and in rain, and makes electrolytic salt. Pigeon poo alone is corrosive, but in this form, it strips paint off a car if you don't hit a good rain shower soon.



The next reason was also one of those "Yeah right...it's like blaming a fart for the air smelling just to cover yourself up". Global warming is the term that many articles are choosing to use for it. I called it extreme climate change or extreme weather. Apparently, as said by Minneapolis citizens, the first of August was a hot day like the past week or two had been. My reasoning, before I read the article, was that heat made the expansion joints close thus not allowing the bridge to move like most bridges need in order to function properly. After reading the article, I was right. But not the movement part. The joints closed to the point that the structural members that take tension away from the bridge couldn't take any more and the same to those of compression. On top of that, the concrete above said members to form the roadway had surpassed its rating for compression as well. So its potential to buckling and crumbling beneath the rush hour traffic was very high. This was, personnally, my pick of why the bridge actually fell on top of the others that weakened it and 'helped' it fall in the meantime.



Third, lack of maintenance. This theory goes so deep that the current President of the United States is at fault to some people. That thought goes about the fact that funding for maintenance on bridges in the U.S. was limited (quite obviously) thus, maintenance was not possible. But the actual lack of maintenance broke down to missing bolts, rusted members, slipping plates, and even the mesh gaurds to keep the pigeons out not being replaced after being broken into and corroded. This was my second pick of reasons to build off of.



The forth is poor infrustructure. The idea behind this was that with disregard to the lack of maintenance and only focusing on the rust, that the bridge just fell because it was so weak. It basically goes back to the maintenance since rust and corrosion can be treated after a while and even the pigeon dung, but if only over time the bridge rusted and caused it to fall. I didn't touch on that too much.



The last, besides the 'other' option, was the type of bridge or whatever was just not the right choice. Again, I didn't touch too much on that because there wasn't many resources or information on that idea. But the idea was that the bridge was designed in the year it was for that ammount of traffic and modifications needs to be made to take on the heavier load of the growing population.



These are all theories and opinions. Nothing is for sure yet. So, I ask for your help in this to get a good poll going to why you think the bridge went down. And if you choose other, please say what you think. I would greatly love to share with my structural class other ideas. Your ideas will be credited in our presentation if we plan to use it. Thank you in advance.

[nerfsharpie6]

I chose poor infrastructure. I am by no means a structural engineer and am not qualified to be making statements based off of what I saw. I will tell you my theory how ever. Number one, the bridge being in use for how ever long it was up, began to developed stress cracks in the concrete. If it was reinforced with rebar then this shouldn't have been a problem. But with lack of funding they just built the pillars, layed the concrete and was done with it. Since concrete isn't flexible in its non-enforced form couldn't take the stress of x amount of cars hour after hour, day after day. Ounce the cracks formed rain water with corosive materials (pigeon poo) seaped into the cracks that formed a type of "road" to metal componets (screws, plates, etc) causing it to become weakened. Then the over all pressure of the cars comes into play again where the corroded parts failed, collapsing the bridge. I don't know if that makes sense or if you can understand it, but thats just my theory.

[LordoftheRing434]

I honestly believe that there was more than just one reason at hand. I chose repairs because the construction they had going was indeed really stressful to the structure on the bridge. It was normally a 4-lane freeway, which they narrowed to 2 lanes on one side of the bridge. That left a poor weight distribution on the bridge, and with metropolitan rush-hour traffic... something was bound to happen.

Secondly, there was a train running underneath the bridge at that time. My dad had a hunch about the oscillation of soundwaves generated by the train, and how they could have played a role in the bridge's collapse. Maybe an engineering major can help me out in explaining this, as my focus is on psychology and not civil engineering.

Thirdly, it was a hot day. The heat could have added further stress on the steel joints of the bridge.

Now that I'm back at school, the gravity of the situation has sunk even deeper. Going across campus, I can see the barges and the twisted steel that has been hauled onto the bank. It's eerie to look at and imagine just what went down. My girlfriend was distantly related to the last victim to be recovered as well, so that was a topic we didn't bring up at her family reunion. It isn't exactly a personal touch so much, but it just made me appreciate the scope of what happened there.

That sounds like an engaging research report. It's better when teachers/professors make their lessons applicable to real life.

~Rings

[theschief]

As you say, there wasn't just one cause. Bridges don't just collapse, and so perhaps the best answer would be: bad luck.

Many different problems built up and eventually caused the collapse, but these problems (e.g. pigeons) were not unique to the 35W bridge. As was pointed out in the days following the collapse many other (The Star Tribune said over 30....) bridges in Minnesota were in worse condition then 35W when it collapsed. So its likely that the straw that broke the camel's back in this case was something unique to 35W, perhaps the train line, perhaps a structural flaw. ("gusset plates"?)

I put Lack of Maintenance because in the end, MinDoT is responsible. The failure of leadership in the department (especially from the Lieutenant Gov) and the failure to keep bridge maintenance up to date could have solved some of the problems that contributed to the disaster. In fact, all previous damage by pigeons, weather, or whatever else could have been repaired if maintenance had been kept up. This leads from a lack of money in the department as well. Certain people have made good arguements that if the state government was less interested in slashing taxes and building new roads as opposed to fixing old ones, things may have not turned out as they did.

Edited by theschief, 12 September 2007 - 04:22 PM.

[six-five-two]

Didn't really read your long post, but it probably was both poorly designed, pigeon... droppings collected on the bridge (not a big factor), and the bridge was worn down over time.

[anders]

It was the communists.

No seriously I have no idea but it was probably a combination of different factors. A similar thing happend in Sweden really long time ago but i can't remember why.

[Recruit]

I pick options A,B,C and E

[b00m13]

This will sound low-brow, but I'm just going to say "shit happens".
There are hundreds of thousands of bridges in the world (many of which you wouldn't think of as bridges).
They take abuse everyday, day and night, non stop. When it's not from automobiles, it's from tremors, or the weather, etc. Imagine those play ground jungle-gym bridges you see at the park everywhere. Sure, it looks sturdy, but put 1 too many kids on it and the chains will bend!

Although I said that, I still picked "Other"

and since I'm required to explain,...
I chose the last option to be open minded (to the paranoid).

Sure, it could be a perfectly logical explanation like poor maintenance, or the weather, or old age...

but what if it wasn't?

What if it was a conspiracy covered up by the government?

Perhaps Jack Bower failed, and terrorist did manage to take down another giant structure, the Feds would have to keep it "hush-hush" or else they would get in so much trouble to letting something that serious happen again.

Or perhaps it was the government's own doings. Maybe it was a plan to make tax payers willingly pay a 'lil extra to have all the bridges in the nation inspected and kept in tip-top shape. All the while, have all the fundings get sent to fueling the war for oil?

Sure it might sound crazy, but as I said before, I chose to think "outside" the box.

Edited by b00m13, 14 September 2007 - 08:52 PM.

[keef]

Poor infastructure definatlly.
That and poor matienence.

B00M13-
If you think the feds would do that and have innocent peoples' lives lost, then Democracy is no better than Communism, and something is wrong.

Is America trying to show the rest of the world that accidents happen here too?
Or was it to complete a deal?

Gas prices by me have stayed leveled and non-fluctuating a month before it happened.
Are we just making deals with the Mid-east to end the war? Or are we just trying to hide something in our Government?

So many questions and everything, but the real answer is- Why?

Why go through all the trouble of all the above for little benefit?
Its just not worth it.

So thats why I choose "Poor Infrastucture".

The bridge inspectors in NYC don't do their jobs right and throughly, so why not other places?

Edited by keef, 14 September 2007 - 09:06 PM.

[nerfsharpie6]

This will sound low-brow, but I'm just going to say "shit happens".
There are hundreds of thousands of bridges in the world (many of which you wouldn't think of as bridges).
They take abuse everyday, day and night, non stop. When it's not from automobiles, it's from tremors, or the weather, etc. Imagine those play ground jungle-gym bridges you see at the park everywhere. Sure, it looks sturdy, but put 1 too many kids on it and the chains will bend!

Although I said that, I still picked "Other"

and since I'm required to explain,...
I chose the last option to be open minded (to the paranoid).

Sure, it could be a perfectly logical explanation like poor maintenance, or the weather, or old age...

but what if it wasn't?

What if it was a conspiracy covered up by the government?

Perhaps Jack Bower failed, and terrorist did manage to take down another giant structure, the Feds would have to keep it "hush-hush" or else they would get in so much trouble to letting something that serious happen again.

Or perhaps it was the government's own doings. Maybe it was a plan to make tax payers willingly pay a 'lil extra to have all the bridges in the nation inspected and kept in tip-top shape. All the while, have all the fundings get sent to fueling the war for oil?

Sure it might sound crazy, but as I said before, I chose to think "outside" the box.

Ya know that actually makes a little sense. I know I sound crazy saying but goddamn it actually makes sense. Except maybe Jack Bauer he kicks ass and would never let terrorists win.

[shadowkid33]

Secondly, there was a train running underneath the bridge at that time. My dad had a hunch about the oscillation of soundwaves generated by the train, and how they could have played a role in the bridge's collapse.

This is an interesting idea, but a seemingly unlikely one. Now, don't get me wrong, I'm no expert either, but in order for the soundwaves themselves to damage the bridge, they'd have to be one of two things. The first is they'd have to be amazingly loud. I'm talking hundreds, if not thousands of decibels. The second is the frequency of the sound waves could be the natural frequency of the bridge itself. It's similar to the breaking of a glass by hitting the right note with your voice. I'm sure that scenario is just as unlikely as the first one though.

But I must say, I thought that was a very interesting idea you threw out there.

Poor infastructure definatlly.
That and poor matienence.

That's my answer too.

[Flaming Hilt]

I chose weather but personally I believe it was a combination of reasons. As many people have been saying, bridges don't just collapse.

The train idea is certainly an interesting one. I wouldn't agree so much with the sound waves part of things, but chances are with the unequal weight distribution that some part of the bridge was on the edge of it's capacity, and the vibrations and stress caused by the train pushed it over.

Another thing to consider is the type of bridge. I know you mentioned this but I mean it differently. Obviously when you build bridges you have Suspension, Compression, Arch, and your simple span bridge. I consider 35W a span bridge but I think by technicality it's an Arch.
Anyways, the point is there are two means to support any kind of bridge: Independent support bridges and variable support bridges. Variable support is the safer of the two, it just means that if one part of the bridge breaks the load that part was carrying will be distributed evenly throughout the rest of the parts and the bridge will not collapse. Independent means that the weight is held only one way, and if those parts break then you're screwed.

I suppose this falls under infrastructure...

Anyways, 35W was an independent support. It was made to be strong, but if you got pigeon crap, a lot of heat, vibrations from a train, the lane reductions putting all the weight on one spot, and etcetera, that strength can fail pretty easily.

[shadowkid33]

What if it was a conspiracy covered up by the government?

Perhaps Jack Bower failed, and terrorist did manage to take down another giant structure, the Feds would have to keep it "hush-hush" or else they would get in so much trouble to letting something that serious happen again.

This interested me, but I think if it was truly another terrorist attack, they'd would be bragging so much about it we'd know by now.

A good 'outside the box' thought though.

[Recruit]

Not if the terrorist were all silenced before they could brag.


I am just kidding, Ok folks.

Edited by Recruit, 22 September 2007 - 04:55 AM.