Thursday, October 29, 2009

Bay Bridge to Remain Closed for Friday Morning Commute

The Bay Bridge is to remain closed for the Friday morning commute tomorrow, Caltrans have said in a press conference early this evening.

The bridge closed on Tuesday evening when two steel rods and a crossbar crashed onto the upper deck

of the bridge, striking cars but fortunately causing no serious injuries.

Dale Bonner, Secretary of California's Business, Transportation and Housing Agency, said it was possible the bridge would open later on Friday but it would depend on the repair work being finished and the right weather conditions to

produce a sufficient means of testing the new fittings.

The work is scheduled to finish by 10 am Friday, and then to need a minimum three-hour testing period by outside experts as well as the Caltrans - State of California • Department of Transportation - engineers who have designed the repair. The Federal Highway Administration and the Seismic Peer Review Board have been involved in the design stage and will be in the testing.

The accident was caused by vibration on the bridge that led to metal fatigue in one of a group of four eyebars from a total 1,680 eyebars. The bar came loose, bringing down the second bar and the crossbar with it. Caltrans say that high winds probably contributed.

Because of this, engineers will be waiting for windy conditions in which to test the bridge.

The eyebar had had a crack in it, which had been discovered incidentally during maintenance inspections on another part of the bridge over Labor Day Weekend. That crack had been repaired - it was the cause of delayed reopening of the bridge - and this accident was not related to the crack, said Mr Bonner.

The crack had not widened.

'We're not today anywhere near anything close to a catastrophic failure. What we are doing is moving quickly to nip a very small problem in the bud to keep a small problem small,' he said.

The repair involved replacing all four eyebars as a precaution, making sure the rods were 'centered' so unable to vibrate and cause metal fatigue, putting in additional high-strength steel rods and strengthening welds and bolts.

Journalists at the conference pressed him on several points. Why, asked one, had this happened when vibration was not new to the bridge?

'I don't want anyone to think that the structure itself (is at risk), (or that) there's been any change in the condition of the bridge,' he replied.

Another said commuters were worried that '5,000 tons of steel did fall down.' Some people would say that was catastrohic, the reporter added, and if the bridge couldn't withstand wind, how would it cope in an earthquake?

'I was confident then and confident now that the bridge itself is safe,' Mr Bonner replied. The problem with the design of the repair is that the Bay Bridge is a 73-year-old structure with an obsolete design. They had to have engineers 'go to the drawing board to make a design that will work.'

Journalists had been talking to critics of the design of the bridge. Were Caltrans listening to their critics and were they open to criticism?

Yes, said Mr Bonner, but they were 'not aware of anyone who has suggested a better design.'

Caltrans, said another reporter, were aware two weeks ago of movement with the eyebar fixture. Why had they not closed the bridge earlier?

'Hindsight is 20/20,' said Mr Bonner.

Will the repair pose a risk?

Mr Bonner admitted they could 'never be absolutely certain,' which is why from now on there will be continual inspections.

To repeated questions about the timing of the opening, Mr Bonner reiterated that experts will be given as much time as they needed to complete thorough stress testing.

The press coference was held in Oakland and after which journalists and TV crews were escorted onto the bridge by the CHP - California Highway Patrol - for examination, photos and filming.

A full viewing of the conference has been posted by KRON4:

For further updated info from Caltrans:

And for travel info from BART:

BART say they are not running trains overnight as they need the time to maintain their trains, especially with the extra workloads.

pics show the silent span over the bayside of San Francisco, and police officers guarding the on-ramps to the bridge.

No comments: