What Happened To the Bay Bridge?

farnsworth writes "Tony Alfrey has put together a fascinating page with some history, analysis, and possible explanations for what ultimately went wrong with the recent emergency repair of the San Francisco-Oakland Bay Bridge. The bridge has been closed for days and is not scheduled to open for days to come, hugely inconveniencing more than 250,000 people a day. His analysis touches on possibly poor welding, a possibly flawed temporary fix, and the absence of a long-term fix or adequate follow-up by Caltrans, the agency responsible for the bridge. Slashdot is a great engineering community; what other insights do you have on the bridge situation?"

Comments

Speaking as the owner, I'm furious

[Anonymous Coward]

Four years ago I bought that bridge along with a package of subprime mortgages to highly qualified homeowners.

And where did the retro-fit funds go?

[ttimes]

McSweeny's has a great article on this, broad reaching in its investigation of the many problems at hand. One thing that troubles me: I have seen many times in the California University and Transportation groups, failure to use earthquake retro-fit funds - they simply use them elsewhere. Its only when a problem like this arises that we learn they have not been used.

small

[anonieuweling]

The USA is small. Think bigger than just the 250k people. The whole infrastructure in the USA is lagging in maintenance, care, repairs and/or replacements. The USA needs trillions to fix this problem but other shenanigans of course have higher priorities. P

Re:small

[neoform]

The US spends $1.15 trillion a year on 'Defense', only bleeding heart liberals would want to waste any of that money on silly things like infrastructure.

Wrong audience

[Noose For A Neck]

Slashdot is a great engineering community; what other insights do you have on the bridge situation?

No, Slashdot is mostly made up of computer janitors; the greatest insight you'll get out of most of the posters here is, "hurrr durr, the bridge must've been running Windoze! LOL!", with maybe a little "omg the twin towers were collapsed by EXPLOSIVES!!!!"-style conspiracy theory and "THE GOVERNMENT IS BAD!!!" braindead libertarianism thrown in for color.

Re:Wrong audience

[demonlapin]

They did withstand airplane impact. What they did not withstand was hours of several-thousand-degree fire.

Caltrans Says

[tlord]

The engineering authority in charge of the bridge and repairs already gave their answer to this on the morning news (yesterday, I think):

They found the crack. They designed the "band-aid": the saddle, T-bar, rods, etc. They had it fabricated and installed.

In subsequent days, they went back up to look at how it was doing. They found that it was vibrating more than they thought it should: it wasn't as rigid as it was designed to be. They recognized that this would lead to fatigue and failure.

They began designing the improved "band-aid" and planned to install it sometime in coming weeks.

To their surprise, *perhaps* related to unusually high winds, the system failed sooner than they thought it could.

The completed their improved design and are now installing it. (And they are counting their blessings that nobody was killed: they got lucky, that way.)

-t

Closing the bridge makes it 100% safe

[Anonymous Coward]

If their goal was to improve the safety of the bridge, then they totally succeeded.

Welders are a scapegoat

[SethJohnson]

As a hobbyist welder, and someone who has worked with welders in an industrial setting, I strongly doubt that the welding is the culprit. "Faulty welding" doesn't happen on something of the scale of a bridge. If it's one welder working, maybe. But this bridge repair would have had dozens of welders working. No one person's welding could have broken a bridge. Sure, they were under a time crunch, but that doesn't result in shoddy welds. It means more welders are put on task. Those guys are trained and certified and their work is defined by specs that they follow and then is inspected by city or state engineers. If the welding is the problem, it means the original spec was faulty.

Seth

Re:Welders are a scapegoat

[Snowblindeye]

I strongly doubt that the welding is the culprit. "Faulty welding" doesn't happen on something of the scale of a bridge.

You're right on. If the author of the article would have watched any of the Caltrans news conferences, they would have answered some of his theories.

The weld that he claims failed was clearly described as only being tacked, not structurally welded. That weld wasn't supposed to hold the structure together, the tie rods were, which failed. One of the improvements they are making now is to replace the tacking with a structural weld, so that even if something broke, these pieces won't come apart. The other improvements center around reducing vibration, especially in the tie rods

Who wrote that article anyway? Some guy on the internet who looks at some pictures of the repair and thinks he knows what a bunch of engineers working on the problem didn't know?

What happened indeed

[hardihoot]

Perhaps if the state of California hadn't diverted transportation funds and had actually used the money to maintain its infrastructure (similar to New Orleans not using its allocated money to maintain the levee system) this probably would not have happened.

Raids of Public Transportation Funds

Ruling on a case started in 2007 by the California Transit Association, the California Appeals Court found that the gimmicks used to reroute public transit funding to other programs were not consistent with voters' intent for the funds to be spent on public transportation

nearly $2.5 billion was diverted away from transportation programs

Re:Lack of redundancy

[Graymalkin]

The Bay Bridge is not the only way from Oakland to San Francisco, there's the Richmond-San Rafael bridge to the North and San Mateo bridge to the south. There's also BART and various ferries and worst case scenario a trip through the South Bay and then up the peninsula. There's lots of ways into the city even if one of the bridges is out of service for some reason. The past two labor day weekends the Bay Bridge was shut down for repairs (the latest of which apparently caused the current problems).

The positioning of the Bay Bridge is limited by the layout of both San Francisco and Oakland. The Bay Bridge already spans one of the narrowest points between the cities and is bisected by Yerba Buena Island to reduce the effective length of the individual spans. There's nowhere else to really put another bridge in the area. There's no other spots with convenient freeway locations on both sides of the bay which would require whole new sections of freeways be build which means buying out a whole bunch of land that people already live on and a host of other problems. This construction would be in addition to building a whole new bridge.