Oakland Bay Bridge officials consider the failure of 32 anchor rods in March due to hydrogen embrittlement to be “a closed matter.”
MTC Executive Director Steve Heminger has conceded that Caltrans failed to provide adequate specifications to the manufacturer or mandate specific tests that would have revealed whether the bolts, manufactured between June 4, 2008, and September 6, 2008, were susceptible to hydrogen embrittlement.
But rigorous testing continues on the roughly 2,300 bolts used in the $6.4 billion eastern span of the Oakland Bay Bridge, Heminger said at a May 29 meeting of the Bay Area Toll Authority in Oakland. FIN covered the meeting via an online audio feed.
Officials are trying to determine if the necessary retrofit to replace the failed bolts can be completed in time for a Labor Day opening of the eastern span. “It will be the facts about the bolts that will drive the decision,” Heminger stated.
So far the testing has produced promising data for the remaining Grade A-354 BD bolts. “The remaining bolts continue to perform as designed - no other observed problems or failures.” Heminger said bridge officials are concerned about high-tension bolts experiencing stress corrosion fractures. Currently several of the remaining bolts are undergoing what Heminger referred to as a “wet” test — an accelerated test being prepared to determine the longer term susceptibility of the material to stress corrosion.
Full-sized bolts will be soaked in a controlled concentrated salt solution while tensioned progressively over a number of days until failure. Data from this test will be used to determine the susceptibility of the material to stress over time and under various loads.
Caltrans Director Malcolm Dougherty said his agency is evaluating the remaining bolts for safety. “This will be a data-driven decision with safety as the controlling factor,” Dougherty explained. Officials are conducting three types of tests: field tests for hardness, specimen tests, and full-scale bolt testing. “We are testing the full audience of bolts to a multitude of tests,” he explained. “All data so far show a clear distinction between the failed 2008 bolts and all the subsequent bolts.”
Most of the testing should be completed by late June, giving officials the data they need to determine whether the bridge can open with the remaining bolts in place.