Federal Regulators Sign Off on New Bay Bridge Fix

11/03/2009

By JT Long

Caltrans delayed opening of the San Francisco-Oakland Bay Bridge until federal inspectors sign off on the second bridge repair in as many months. Traffic was allowed to cross the span at around 9 a.m. Monday morning.

The transportation corridor, which carries an estimated 280,000 cars per day, closed Tuesday evening after a steel bar cracked during a windy afternoon commute, dropping a 5,000-lb crossbeam and steel connectors into traffic, causing a non-injury accident and an enormous traffic jam.

The pieces that fell were part of an emergency fix by Sacramento-based bridge-builder C.C. Myers Inc. over Labor Day weekend after an inspection unrelated to the company’s installation of a new onramp revealed a crack in a steel structural eyebeam in the cantilevered eastern span. Caltrans worked with contractors fabricate a steel saddle brace to wrap around the cracked eyebar, redistributing tension away from the damaged area and linking it with tie rods to a lower saddle.

Crews worked for 70 hours straight to complete the fix before the Tuesday morning commute. The contractor was heralded for the quick work and Federal Highway Administration inspectors never checked the repairs.

Caltrans inspectors did continue to monitor the fix and a week-and-a-half before the Oct. 27 failure noted vibration on the support bars, but did not consider it an imminent problem, according to Dale Bonner, California secretary of Business, Transportation and Housing.

“I want to stress that while a cracked eyebar can lead to catastrophic failure, we are not anywhere near that,” he says.  He adds that the crack is not migrating. What failed was a piece of the brace.

To fix the repair, Caltrans worked with another bridge contractor, North Highlands, Calif.-based MCM Construction Inc., which is working on the Oakland touchdown portion of the new bridge and happened to be near the scene on Tuesday evening. Caltrans used an enhanced version of the Labor Day fix that focuses on limiting vibration, and therefore limiting the fatigue engineers believe caused the failure.

All four steel support rods were replaced. Damping devices were installed to keep bolts from moving. Additionally, welders gouged out the connecting welds and deepened them to structural welds.

MCM Construction also added straps to hold the four new tie bars to the eyebar. “Tying off the rods will ensure that if there is a failure, pieces won’t fall down,” says Caltrans spokesman Bart Ney.

Contractors custom ground any areas where steel could potentially rub against steel to avoid fatigue. Once the rods were back in place, tensioning took three hours and then the repair was tested by third-party inspectors. “We gave inspectors all the time they need to test the repairs,” says Bonner.

This time, the replacement pieces were fabricated in Sacramento and trucked to the site. In the previous fix, the saddle was dramatically flown in from Arizona and given a police escort from the airport.

Work was delayed during the week because of safety issues as high winds of 50 mph limited loads on equipment, says Ed Puchi, MCM Construction treasurer.

The result was a “temporary fix” intended to hold the 73-year-old bridge together until the replacement bridge is complete in 2013.

Bonner says engineers considered replacing the eyebar, but the process would take many months “and may not solve the problem.”

Between now and then, Caltrans plans to increase inspections from every two years to every three months. Additionally, Caltrans plans to close two lanes each Saturday for inspections.

Meanwhile, the damaged pieces from the Labor Day fix will go to a metallurgist for testing to determine the cause of the failure.

Dan Baker, project manager for C.C. Myers, which installed the original fix and is still working on portions of the new bridge project, says his company was not responsible for the failure because the design was approved by Caltrans.

Ney says the cost of the original fix was less than $2 million and came from emergency funds. He adds the current project would probably fall under the same funding mechanism with the same $3 million limit.

Ney says it was not likely that Caltrans would charge back C.C. Myers for the failure. “We are very happy with the performance of both contractors,” says Ney.