Bridge collapse in Minneapolis

[00Rocket28]

My dad is a towbat captain that works the Upper Mississippi River, which is St. Louis on up North. I talked to him tonight, he's up there right now working. He said he's a little ways from it but was headed that way when it occurred. His friend had just gone under that bridge and through the lock less than an hr before the collapse. He said they've been working on this bridge for a couple of years.

[KY Thorobred]

The lengthy area of collapse might be explained by a phenomenon called "aereolastic flutter".

 

Any engineers in the house?

 

Here's some basic info on this "flutter" effect:

 

Flutter is a self-starting vibration that occurs when a lifting surface bends under aerodynamic load. Once the load reduces, the deflection also reduces, restoring the original shape, which restores the original load and starts the cycle again. In extreme cases the elasticity of the structure means that when the load is reduced the structure springs back so far that it overshoots and causes a new aerodynamic load in the opposite direction to the original. Even changing the mass distribution of an aircraft or the stiffness of one component can induce flutter in an apparently unrelated aerodynamic component.

 

At its mildest this can appear as a "buzz" in the aircraft structure, but at its most violent it can develop uncontrollably with great speed and cause serious damage to or the destruction of the aircraft.

 

Flutter can also occur on structures other than aircraft. One famous example of flutter phenomena is the Tacoma Narrows Bridge.

 

Thats interesting, but I would think that if this were the case, that the bridge next to the I35W would have damage as well. I honestly believe it is going to be the combo of the age of the bridge as well as the jackhammering that was going on. Obviously I wasn't there but this seems to be the idea of the eye witnesses.

[Italian Stallion]

Imagine how terrifying that would be to see or experience.

 

Any word on an official cause?

[True blue (and gold)]

I have been away from communication the past 6 hours. This is awful. Prayers to everyone involved.

[Ms Liberty]

Horifying.....I have a fear of bridges.

 

I do too.

[Ms Liberty]

Was working outside and then came in to watch a movie, just turned on Fox news about 15 min. ago. This is awful.

[Ms Liberty]

Prayers go out for all involved and for the rescue workers that are working the scene. Divers are in the water now and are expected to be in the water overnight. 6 confirmed dead, much more expected -per:Mayor of Minneapollis. As many as 50 cars were on the bridge at time of collapse.It was told that the work going on at the bridge was not structural in nature. This is just terrible, very tragic. May God bless everyone involved (Victims, Emergency workers, Police, Doctors, Hospital workers ........all involved) and the famlies of these people.

 

Was also reported that there were no signs that this tragedy had to do with terroism.

Don't they always say this SOON to soon.

[Ms Liberty]

When we turned on the tv they said 7 dead, now just then they said 14.

[saint4]

When we turned on the tv they said 7 dead, now just then they said 14.

 

 

Horrible stuff. I saw it when they said 7, but they had said previous that the exact amount was not yet determined. Very sad.

[sportsfan41]

This is just horrible to hear about. My thoughts and prayers go out to all of those families. I just truly can't imagine, I like many others, don't much care for bridges, and absolutely HATE getting stuck in traffic on one.

[NHS BIG DADDY]

Everytime I cross a bridge I always think about the possibility of it collapsing. My favorite part of crossing the bridge is when I make it over to the other side ok. The less time Im on them the better.

[PurpleHaze]

We are watching it right now....how horrible. They are stopping for the night on rescue efforts. They said that there are at least 7 dead right now. It was said that the death toll is assumed to go way up in the morning when the resume the search in the morning.

 

God be with everyone.

[sportsfan41]

I kinda wonder how strong the current is and how many weeks they may find others that are "missing", just looking at some of the footage, and it looked like a strong current from what I could tell.

 

I know that Texas has been dumped with rain this summer, this could've been alot worse had alot of that rain made it to the upper midwest.

[Ms Liberty]

News this morning still staying at 7 dead , sorry for the wrong report. Looks terrible in the morning light.

[Son of Bear]

In regards to the Tacoma Narrows Bridge failure, it was induced by transient winds (or extreme lateral loads) that were overlooked by designers. That bridge was a suspension bridge, unlike the one that failed yesterday in Minnesota (truss bridge). Lateral loading such as winds, earthquakes, and stream flow should all be ruled out as a cause for the Minnesota bridge collapse IMO.

 

The SE on CNN last night made some good points on a possible failure mode. He said a localized failure probably led to the global failure of the structure. In other words: A corroded element, such as a truss chord or diagonal that was rusted may have been subject to an overstress (possibly taking the load of an above semi-truck at rest on the deck). When this member failed, it put a greater load on the next member causing it to fail and so on.....take into account this all happened extremely fast. Structural steel from the 1960's would be more brittle than what is used today as well.