Think ya' used enough dynamite there Butch?

Mike T., Swampeast MO

Sept. 9, 2004 6:53 a.m. Old Mississippi River bridge, Cape Girardeau, MO.

Demolition team gets more than they bargained for. Planned demolition of one span section brings down entire bridge and part of one main pier.

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Yellow horizontal line shows the span that was <I>supposed</I> to come down. Red arrows point to spans that were to be brought down in two additional demolitions. Arrow on right points to a "mirror" section of the only one that was supposed to be demolished.

Note green arrows. Pier on right used to be the same height as that on the left. This was not supposed to happen.

UTTERLY COOL TO WATCH!!!

Main channel for barge traffic is in the middle of the big cracked section. No barges moving through here for a while...

Other photo is full size and unmodified.

Boilerpro_3

They were just doing alittle fishing....

DYNAMITE STYLE!

Boilerpro

Constantin

Odd.. Redundancy Failed

I can see why the center span failed... it's not really designed to stand having one of its piers erased from under it. However, the span to the far left should have been left standing. To me, that points to either bad design or implementation.

Either way, they're going to have one hell of a time removing that mess. Nothing scares demo experts more than "wounded" buildings (i.e. where their charges didn't do the trick the first time) because the unpredictable nature of them - they can collapse at any moment. Exposed steel like this is probably easier to gauge, but I'm glad it's not my job.

As for Dynamite Dan, I imagine he's now got a number of really good friends at the US Army Corps of Engineers.

Mike T., Swampeast MO

That pier wasn't supposed to be affected. Floating crane was already on site and they've already fished out quite a bit of the steel in the properly destroyed section.

Bridge built 1922-24 I believe.

Photo shows closeup of failed pier section. About 40' of it fell intact into the river. Sorry for poor exposure--my digital camera doesn't have the exposure adjustments like my good old SLR and the pier was in deep shadow.

Sides of the piers are slightly tapering cylinders connected by a thinner rectangular web. You can barely make out the slight shearing on this side of the cylinders (most prominent on left). For the life of me, I can't see any steel reinforcement in there. You could always see the pour lines and it almost looked as if it just toppled over at one of the lines. Happened quickly, we had to be far away, and there was a lot of smoke in the air so it was hard to see just what happened. Will likely be on national news (CBS, ABC, CNN, FOX most likely) so watch for it.

Constantin: Have you checked your e-mail? Sent you another spreadsheet. Need your physical mailing address to send the disk.

Mike T., Swampeast MO

24 Hours

Local news says they have 24 hours to clear a navigation channel without "serious consequences".

Mike T., Swampeast MO

Video Link

Bridge Demolition

Their server seems swamped right now, but it will probably work later.

Weezbo

Eased....from under it...:) terse yet comprehensive:)))

ALH_3

Continuity

As a civil engineer that's pretty cool to watch. After watching the videos I'd say the reason the left center span fell was because once the span on the right was demolished the moment in the remaining span increased.

With the continuous bridge the maximum moment was (9/128)wL^2, at 3/8 of the span from the center pier. Once the continuity was removed the maximum moment moved to the center of the remaining span and had a value of (1/8)wL^2. This means the moment was 1.78 times the intended value, plus it was at a different point in the span than was originally intended. The cross-section was deeper near the center pier. This may or may not have been enough to cause the collapse.

They didnt really show it happen on the videos but the third span looks like it broke to the left of the pier when the other one bent. Unintended results can be the most interesting. Thanks for posting the links.

-Andrew

Mike T., Swampeast MO

Update

Was wrong about the channel. The main navigation channel is under the intentional portion. The blocked area is an alternate used mainly during high water.

Paul Bock_2

NOVA

There is an excellent public television documentary about the construction of the stayed cable bridge in the background of the photo.

the new bridge didn't go in all that easily either. It's part of the NOVA series on construction, and is well worth the time to watch it.

paul

Gordy

Bridge

I have been doing bridge construction for 22 years. Constantin is right on with his assumptions. Main super structure was not designed to be dropped 40',causing domino effect to the rest of superstructure. Variable in this demo was the rebar or lack of. I have torn down bridges from that era and earlier. Some had rebar, very little, some did not. Old plans may not have existed to do research on.Back then they depended on the mass of concrete to carry the load. Ahh torch and swing, torch and swing. I would definetly get it down in the river first. Demolition, building in reverse is not as easy as it looks sometimes.

There is a cool documentry by Nova on the Clark Bridge in Alton IL. Another cable stay bridge. The Bridge business is a tough one. Always fighting mother nature,deadlines,design flaws and the traffic.