The saga of the Bay Bridge bolts continues as Caltrans announced September 24 that it has asked the Toll Bridge Program Oversight Committee (TBPOC) for approval to end its contract with American Bridge / Fluor, the joint venture that built many parts of the new San Francisco-Oakland Bay Bridge, including a series of questionable anchor bolts. Caltrans is also seeking to hold the contractor accountable for project delays and faulty work.
Last year, Caltrans inspectors found that the contractor had not properly sealed more than 400 high-strength steel rods imbedded in the tower’s foundation, failing to protect them against the elements. The threads of one rod stripped through its bolt and failed, prompting a thorough investigation of all the rods. Two of these rods were removed for testing, and the remaining rods underwent in-place earthquake-force tests. Testing concluded that the bolts could withstand a severe catastrophic earthquake.
Last month TBPOC and Caltrans gathered a team of bridge experts to study hundreds of the anchor rods to see if any action is needed to further protect the bolts from possible seawater corrosion. The goal of the panel was to determine the condition and strength of the tower anchor rods, many of which have been exposed to sea water, and to "design an environmentally friendly system to protect them from corrosion far into the future."
The tower base anchor rods are part of a seismic system designed to ensure that during a seismic event there is no uplift during a massive quake.
The expert panel analyzed the anchor rods and their exposure to water due to poor grouting. The experts are currently submitting a list of potential tests they deem of varying importance for protecting the rods and foundation.
Caltrans says its engineers will seek TBPOC’s approval of the recommendations put forth by the panel to fix or mitigate the contractor’s construction errors that potentially increased the risk of corrosion for these rods. The TBPOC may decide to order all, some, or none of the panel’s recommended tests.
“The Oversight Committee must balance the need for adequate testing to verify structural reliability against the risk of running unnecessary testing or devising a long-term maintenance program that is more expensive than necessary. Our goal is to devise a testing and maintenance plan that is adequate and simple,” said Chief Toll Bridge Engineer Brian Maroney in a recent press release.
Engineering analysis conducted last fall, indicates that the rods are not critical to the bridge’s performance and are a redundant system. Even if none of the rods were present, the bridge is expected to perform its lifeline function, weathering ground motions that only occur once every 1,500 years, says Caltrans officials.
Before Caltrans can conclude its contract with American Bridge / Fluor and begin final negotiations over damages and penalties, it must obtain permission from the TBPOC, the multi-agency body that oversees construction of the bridge.