LOS ANGELES Three companies that supplied or processed steel anchor rods for a new replacement span on the earthquake-damaged San Francisco-Oakland Bay Bridge have been cleared of responsibility for a structural failure.
A spokesman for San Franciscos Metropolitan Transportation Commission (MTC) said a report by Californias Toll Bridge Program Oversight Committee determined that none of the three suppliersPainesville, Ohio-based Dyson Corp., manufacturer of the rods, or bolts; Tampa, Fla.-based Gerdau Long Steel North America, which produced the steel; and Glasgow, Mo.-based galvanizer Monnig Industries Inc.was to blame for the rod failures.
"The report found that none of those firms are responsible for the hydrogen embrittlement," that caused the failure, the spokesman said.
The study determined that responsibility is shared by the California Department of Transportation, two design companies and the contractor on the self-anchored suspension segment of the new span, a joint venture between Coraopolis, Pa.-based American Bridge Co. and Long Beach, Calif.-based Fluor Enterprises Inc., which the spokesman said will share the estimated $20 million cost of a permanent retrofit for the steel saddle and cable system.
In March, 32 of 96 galvanized ASTM A354 grade BD rods, or bolts, manufactured in 2008 broke when they were tightened to connect shear keys, or seismic safety devices, on the new span (amm.com, April 1).
Nearly 24 years after its predecessor was damaged in the October 1989 Loma Prieta earthquake, the new eastern span of the Bay Bridge opened to traffic Sept. 2. The self-anchored span, initially estimated to cost $1.4 billion and take four years to build, instead cost $6.4 billion and took 11 years.
Most of the steel suppliers had already denied culpability. Dyson claimed in May that an earlier analysis for the state that determined that the rods complied with the basic mechanical and chemical requirements of ASTM A354 grade BD exonerated the fabricator of fastener systems (amm.com, May 17). Gerdau said the steel "met the specifications" to which it was ordered (amm.com, May 22). Monnig, which galvanized the rods, declined comment.
Meanwhile, a second batch of A354 grade BD 96 rod produced in 2010 arent susceptible to hydrogen embrittlement similar to the rods produced in 2008, the MTC spokesman said. The suppliers of the 2010 rod were the same as the 2008 rod with the exception of Monroe, Mich.-based Gerdau Special Steel North America, an affiliate of Gerdau Long Steel, which produced the steel.
"Clearly there are some very large metallurgical differences between the 2008 and 2010 rods," said the MTC spokesman, who noted that testing has been ongoing on the 2010 material, with "everything passing without a problem."
Vallejo, Calif.-based XKT Engineering Inc. and Birmingham, Ala.-based Steward Engineering Inc. are performing the permanent retrofit, the MTC spokesman said.