The Bay Area Toll Authority voted this week to pay an engineering firm $1 million to develop designs that would address problematic eyebars on the Bay Bridge that shut down the bridge last year, the authority’s deputy executive director said today.
The toll authority oversight committee met Wednesday and voted to amend a contract with engineering firm T.Y. Lin to pay the company $1 million to develop a series of dampers that would attach to eyebars along the eastern span of the bridge, according to Deputy Executive Director Andrew Fremier.
During Labor Day weekend 2009, crews spotted a cracked eyebar and made an emergency fix, but on Oct. 27, high winds shook loose the temporary repair, sending a steel crossbar and two tie rods crashing onto the upper deck. Several cars were damaged.
The cracked eyebar was believed to be due to high winds that caused vibrations on the bridge. Fremier said recent inspections of other eyebars on the eastern span have led to the discovery of “indications,” small nicks that could be precursors to cracks.
He said crews have repaired the indications by grinding them out, and the dampers that are being designed “are just a bit of added insurance that eliminates that vibration.”
He pointed out that a similar operation was done on London’s Millennium Bridge, which shook when it first opened due to foot traffic. Dampers were eventually added that helped eliminate the vibrations on the bridge.
The contract with T.Y. Lin also calls for designs for a device that could quickly replace an eyebar if it were to crack like last year, as well as regular inspections of the bridge every three months, Fremier said.
He said plans are also being developed to put acoustic monitors on the bridge in the near future to gauge the types of stresses that are being put on the eyebars.
“The real concern is seismic, but the bridge is showing us it’s getting to the end of its useful life and showing signs of fatigue in some places,” he said.
The new eastern span of the bridge, which is designed to survive a major earthquake, is scheduled to replace the existing bridge in 2013.