LOS ANGELES Gerdau Long Steel North America says that the steel it produced to create anchor rods for the San Francisco-Oakland Bay Bridge that have since failed met the specifications "it was ordered to."
A spokesman for San Franciscos Metropolitan Transportation Commission (MTC) said last week that U.S. subsidiaries of Brazilian steelmaker Gerdau SA produced the steel that was turned into rod for the bridges new east span.
The metallurgical condition of the 2008 anchor rods was "less than ideal," with a "higher-than-normal susceptibility" to hydrogen embrittlement, Malcolm Dougherty, director of the California Department of Transportation (Caltrans), said during a meeting of Californias Toll Bridge Program Oversight Committee. The same description was used in a Caltrans analysis of the rods.
In March, 32 out of 96 galvanized ASTM A354 grade DB rods manufactured in 2008 by Dyson Corp., a Painesville, Ohio-based fastener systems fabricator, broke when they were tightened to connect seismic safety devices called shear keys (amm.com, April 1). Gerdau Long Steels St. Paul, Minn., facility produced the steel used to make the rods, the MTC spokesman told AMM.
A second batch of 192 rods produced in 2010 and put into service hasnt shown the same problems, according to initial indications (amm.com, May 17), but they are now being tested for integrity. The steel for those rods was produced by Monroe, Mich.-based Gerdau Special Steel North America.
A decision on whether to replace the 2010 rods is expected at the May 29 meeting of the Bay Area Toll Authority.
Dyson has maintained that the metallurgical report on the 2008 rods, which were supplied to project contractors American Bridge Co., Coraopolis, Pa., and Fluor Corp., Irving, Texas, "exonerates" the fabricator because it determined the rods met the requirements of ASTM A354 grade DB.
A spokeswoman for Tampa, Fla.-based Gerdau Long Steel North America, who said the company takes great care to produce steel to the "most demanding standards," confirmed it produced the steel used for both the 2008 and 2010 anchor rods, but said in a statement it "met the specifications it was ordered to."
Gerdau said it was "looking into this matter," but noted that "there are many possible root causes, given the various steps associated with the fabrication and placement of steel products, and these root causes are being investigated by multiple parties."
The metallurgical analysis found that the principal source of internal hydrogen in the steel was "likely the freeing of trapped residual hydrogen by the upquenching effect of hot-dip galvanizing." The MTC spokesman later said the galvanizing was performed by Monnig Industries Inc., Glasgow, Mo.
Monnig vice president Jason Monnig declined to comment.
Dougherty said during an oversight committee meeting that Caltrans currently doesnt allow the use of A354 rods that are galvanized on "standard" bridge applications. But Brian Moroney, Caltrans chief bridge engineer, later said that its not uncommon for a bridge to contain several "deviations" from these standards.