Step-by-step guide to Oakland Bay Bridge repairs

[denrep]

As of today, it's still closed.


First off, I don't have anything to do with the bridge or its repair, just thought we might like to follow along.

From: http://www.kron.com/News/SpecialCove...6/Default.aspx





"Thursday on the KRON 4 Morning News, Caltrans spokesman Bart Ney got out some diagrams of the bridge and a Sharpie and walked KRON 4's Darya Folsom through the process the transit agency is going through in making repairs to the Bay Bridge. This is a step-by-step guide to the process with Ney's diagrams and in his own words."

From: http://baybridgeinfo.org/

[Sandy]

So basically they didn't replace that cracked I bar, they put in a couple of rods along side it to hold what it couldn't and their temp job popped off because they "tacked" it??

Is that what I'm reading there?

Or maybe those rods aren't 'temporary'.

[denrep]

Originally Posted by Sandy

So basically they didn't replace that cracked I bar, they put in a couple of rods along side it to hold what it couldn't and their temp job popped off because they "tacked" it??

Is that what I'm reading there?

It seems like the reinforcement tie-rods were installed without provision for movement of the nearby pinned links, and then the rods failed due to bending fatigue. Now it looks like the repair rods are being anchored with a radiused seat, to allow for movement.

Not open yet...

From: http://cbs5.com/local/bay.bridge.closure.2.1283450.html

. . ."Construction crews continued a third full day of emergency repairs on Friday, but had to stop work at one point while they waited for new steel plates to arrive. The additional materials were needed to strengthen the troubled span before final tests could be run on the fix." . . .


"The pieces that broke were part of major repairs done Labor Day weekend after state inspectors found a crack on a key structural beam. Those fixes failed due to vibrations caused by high winds.

Work was delayed Friday after new rods had been installed and engineers decided to use 2-inch thick steel plates to further strengthen the work, said Ed Puchi, spokesman for MCM Construction Inc., of Sacramento, the contractor doing the work.

"We're not sure how long it's going to take to make those modifications," Puchi said.

Once the custom-fitting of the steel plates was completed, Ney said workers would grind areas where steel is rubbing on steel so that those areas are smoother."

Good Luck

[Sandy]

"The pieces that broke were part of major repairs done Labor Day weekend after state inspectors found a crack on a key structural beam. Those fixes failed due to vibrations caused by high winds."

Of course getting off the topic of the fix and into the source of the failure problem, I'll have to argue their use of words.

They are trying deserately to direct the focus off of the repair design and on to mother nature by saying the failure was "due to high winds". That's like saying a patched tire failed because it was driven down the road. There have always been high winds on that bridge and will always be high winds on that bridge with many higher winds yet to come for years and years. I think the failure was due to a pizz poor fix (patch job).

[denrep]

Hmmm:

[duaneb55]

So I take it this is where the support member cracked and was repaired.


"Enhanced Welds" New term for doing it right?

[denrep]

Originally Posted by duaneb55

So I take it this is where the support member cracked and was repaired.

I don't know, but if it is, it sure looks serious.

Here's a closer view of the repair saddle:

[duaneb55]

Those are some serious pieces of steel. Look to be about 24oz to the pound. Must have been interesting to see them placed.

[Sandy]

Yeh the original defect was a crack one of those dog bones. They call them "eyebars". Anyway they find a crack in the dog bone, put up temporary re-inforcement, and the re-inforcement fell off.

[rlitman]

Originally Posted by duaneb55

So I take it this is where the support member cracked and was repaired.
Attachment 40936

"Enhanced Welds" New term for doing it right?

Nothing was repaired.

The eyebar is cracked, and that can be seen clearly in the picture.
A pair of saddles was positioned around the pins on each end of the cracked eyebar, and four rods connect the saddles together, relieving the tension on the eyebar.

The first fix, had the rods passing through tight fitting holes on a cross piece, which was just tacked to the saddle. The cross member was held in place by the tension of the rods. Movement of the rods caused wear in the tight fitting holes, which caused a rod to fail. Without the tension of the rods, one of the cross members fell with the tension rods onto the road surface, hitting a car and truck.

The new fix, involves having cross members with enlarged holes that do not contact the tension rods, and which are securely welded in place. Then, the tension rods will have nuts that fit a spherical socket, which allows for motion without significant wear, and other pieces have been added to dampen vibration.

[duaneb55]

So what we're looking at is intended to be a permanent repair?

[59halfstep]

This link was posted on the AWS site yesterday.

http://www.sfgate.com/cgi-bin/object...0500771088.jpg

picture #2 shows the link with the crack.

[denrep]

"Bay Bridge To Remain Closed Monday"

From: http://www.nbcbayarea.com/news/local...-68382392.html

"The California Department of Transportation still has no official estimate for when the San Francisco-Oakland Bay Bridge will reopen, but it will not be open in time for the Monday morning commute.

The crews are having problems getting an exact alignment of a huge screw type cylinders into a series of metal plates or eyebars They can't get them to fit correctly so that there is no metal on metal contact."

That's easy enough to believe.

Do we have a bridge man on staff?
What's with the complex repair anyway?
Could it be this complicated to just change the eyebar out?
Or stack a repair plate on the cracked eye?

I have to admit that I wonder why a replacement eyebar wasn't on the burning table as soon as the original failure occurred. There must be blueprints, unless they burned 'em to stay warm in the toll-booth.

The eyebar looks like a simple piece, and the rods used in the patch don't seem to add up to the same crosssection as the broken link. I wonder why a plate patch wasn't used? I wish they'd put a dollar in the picture so we could get a feel for the size of things.

I'm no bridge engineer, but I can't imagine any other system that uses eyebars, such as a large press, or a large mechanical linkage, which would be repaired with a tie-rod patch rather than rebuilding or replacing the original part.

When the bridge is open, it rings the cash register for over $100,000.00 per day! I guess I don't understand how a replacement eyebar of the time-proven design wouldn't be justified at practically any cost. Who knows what unknowns the patch is imposing on the rest of the structure. Seems like there could be other weak eyebars; may as well face it and develop a system to change them out. Plus Alfred wants the old eyebar and repair saddle for the post-driver.

Good Luck

[DSW]

My guess is that it's hard to unload the tension from the eyebar in order to replace it. It was most likely installed prior to all the deck members and road surface. How does one easily lift a bridge, and where do you attach your lifting cables? My guess is that the steel being used for the repair is of greater tensile strength compared to the original member, so they can reduce the size. It does seam like a goofy F'd up way to do a repair however.


As far as a comment of a permanent repair, thats happening right next door from what I understand. They are in the process of building a new bridge at which time this one will be demolished / dismantled.

[duaneb55]

So one could conclude the repair was the less expensive option to just buy them time to finish the new bridge.

[denrep]

I really wonder why another plate couldn't be stacked on the eyebar?

[duaneb55]

Originally Posted by denrep

I really wonder why another plate couldn't be stacked on the eyebar?

Attachment 40984

Put your request in now and maybe you'll get a chance at it come demo time. Tell Alfred too and maybe he'll get a stab at one or two of those eyebars.

[Sandy]

Here's a pretty good link for those of you with an understanding of these things. I'm still stumbling through it. Probably won't get too good a grip on it tho. Looks like not all the eyebars are the same length.

Lotsa pics.

http://www.sci-experiments.com/Broke...kenBridge.html

[jsfab]

I really wonder why another plate couldn't be stacked on the eyebar?

Probably because it would've required welding to the thinnest part of the dogbone (the long part) , thus creating a new stress point for the next crack to start. I would also assume, they had to draw everything up a little, to reduce the extra weight now on the other structural members, or THOSE would break next.

[denrep]

Originally Posted by jsfab

Probably because it would've required welding to the thinnest part of the dogbone (the long part) , thus creating a new stress point for the next crack to start. . . .

Go all the way to the other eye?
I wonder how thick the "dogbone" is?

[jsfab]

That's a pretty good link, Sandy.

[jsfab]

Originally Posted by denrep

I wonder how thick the "dogbone" is?

Apparently, thick enough to last 73 years, but not 74 years.

[salem747]

Whew, I thought at first you were talking about the GG bridge, last time I seen it it had one of my engineering school's bugs hanging from it! But I did drive across the Oakland bridge a few times when I was working in Fresno...and they made me pay EVERY time!!!!!!!!!!!!!!!

[DSW]

It's truly amazing how over built these older bridges really are. Think about bridges like the Brooklyn Bridge, the Golden Gate Bridge and hundreds of others. There is no way they could have predicted the volume and weight of traffic these bridges carry today. Yet these bridges are still in use day after day with no restrictions in general. This bar cracked, and cracked severely, yet the bridge was still standing, in use and did not fail. It took a visual check to notice the problem.

[salem747]

Civil engineering projects usually have a design factor of safety of like 5 or 10. Aircraft? 1.2 to 1.5!!!