Note: for an important correction to this story, click here.
SAN FRANCISCO (AP) Officials in charge of building a new eastern span of the San Francisco-Oakland Bay Bridge repeatedly questioned the work and quality control of companies involved in making long seismic safety bolts that broke while being tightened.
In March, a third of the 96 bolts failed, and transportation officials said it could take months to find the cause and fix the problem, meaning the scheduled Labor Day opening of the new, $6.3 billion span could be in jeopardy.
Hundreds of pages of documents released to news media by the California Department of Transportation show its inspectors found structural integrity issues with some of the bolts several years ago, before they were installed.
The documents were unclear about whether issues flagged by Caltrans’ own inspectors in 2007 and 2008 were remedied before the bolts were delivered and installed. The inspectors noted that the bolts failed elongation tests for structural integrity and said they were concerned about the quality of work by a company that galvanized the bolts to prevent corrosion.
Inspectors said bolts made by Painesville, Ohio-based Dyson Corp. had failed to meet certain standards during testing on three occasions.
Andrew Gordon, a Caltrans spokesman, said the agency would not comment during an ongoing investigation into why the bolts failed. Dyson Corp. also has said it will not comment during the probe into the bolt failures.
The bridge’s main contractor, American Bridge Fluor, did not return a call seeking comment.
Metallurgists said the documents contained no clear explanation about why the bolts cracked, but they suggested the cause was likely a confluence of missteps during manufacture and installation.
Among the most likely problems Caltrans and experts have highlighted:
• Galvanizing such large bolts — 17 to 24 ft. (5 to 7.3 m) long — could increase the probability of internal micro-cracks, which wouldn’t necessarily be caught by standard construction industry testing.
• Mistakes in heat-treating, which was repeated due to inadequate paperwork, could have introduced micro-cracks near threads of the bolts.
• Hydrogen, which is known to make steel brittle and subject to breaking, could have infected the steel during manufacturing and been sealed into the bolts by the zinc coating applied during galvanizing.
• The bolts may have been accidentally tightened beyond the maximum allowable amount, causing them to snap.
“This is most likely a perfect storm situation,’’ said David Xu, a mechanical engineer and metallurgist at Berkeley Engineering and Research Inc. “A lot of these factors alone might not have caused this issue, but together most likely could have pushed it over the edge.’’
The threaded bolt and nut assemblies connect the bridge deck to columns and run through a giant shock absorber called a shear key. It’s a massive concrete and steel structure that helps control sway during an earthquake.
The problem bolts were made in a batch in 2008. Another batch from 2010 has been installed and Caltrans has reported no failures in those bolts.
In October 2008, Caltrans admonished Dyson after finding that a test sample of bolts did not meet elongation requirements, a measure of the bolts’ structural integrity.
“Non-compliance elongation is not something I would let pass,’’ Xu said, noting the testing showed one bolt was nearly 2 percent under the required amount.
“That’s a pretty big deal,’’ he said
While three sampled bolts were just under the required numbers, Caltrans noted that it was the third such instance with Dyson since 2007. The agency did not provide statistics on earlier instances.
Documents show Dyson’s fix was to request that Caltrans accept the non-compliant bolt tests “as is.’’ The documents did not include a reply from Caltrans to the request.
“What boggles my mind is that this was the third time this happened with Dyson, and we don’t have records for two previous failed tests,’’ Xu said. “What happened to those?’’
The records show Caltrans inspectors also identified other issues with Dyson and its subcontractors.
Art Galvanizing Works, which put the protective zinc coating on the bolts, was criticized by inspectors for using approximate time guidelines for bathing the bolts, which Xu said can affect the integrity of the galvanizing.
“The procedure appears to function purely by ’seat of the pants’ judgment by galvanizing operators,’’ wrote Venkatesh Iyer, a Caltrans structural materials specialist who inspected the site.
The inspector also found that Art Galvanizing comingled rods with adequate coating thickness with insufficiently coated rods.
“Art Galvanizing Works does not have necessary quality control,’’ Iyer said in the report.
Adrian Klein, the company’s owner, said she had been told by Dyson not to comment while the investigation was open.
Robert Ritchie, a metallurgist at Lawrence Berkeley National Laboratory, said he thinks a mixture of events contributed to the failure of the bolts. If galvanizing was not done properly, he said, some corrosion could have entered the bolts. And problems in double heat treatment could have created a higher strength steel than required, which would create more brittleness.
Ritchie said the construction industry is not required to conduct fracture tests on the bolt threads — an area which is thinner and more at risk of failure than the rest of the bolt.
The failed elongation tests that Caltrans highlighted in its documents would not have detected cracks within the threaded area, Ritchie said.
Ritchie said that if a tougher standard of testing were required, any fracturing within the bolts would have been discovered before installation.
Now, with many of the failed bolts located beneath a concrete cap, they cannot be easily replaced, making a fix more time-consuming and expensive.
A correction/revision to ’San Fransisco-Oakland Bay Bridge Bolt Problems Questioned Years Ago’ published in CEG’s June 15 Western edition, #12.
Detailed Report Concludes Oakland Bay Bridge Anchor Rods Manufactured by Dyson Corporation Were Not Defective
Based on the detailed 55-page testing and analysis report of the failed anchor rods from shear keys S-1 and S-2 performed jointly by leading industry experts, anchor rods manufactured by Dyson Corporation were determined not to be defective. The results indicate that hydrogen embrittlement was the cause of the recent anchor rod failures.
Salim Brahimi, a consultant of American Bridge Fluor (ABF); Rosme Aguilar, branch chief of the California Department of Transportation (Caltrans); and Conrad Christensen, a consultant of Caltrans, conducted the report, which was commissioned by Dyson.
Through this report and mutual internal investigations, it was concluded that the Dyson Corporation met its requirements on fulfilling this order to the specifications requested. The experts found that Dyson had no involvement in the application of the products and that it was the specifications that were ultimately at fault.
“When this issue on the Oakland bay bridge was first raised, we worked very closely with the contractors and final customer to understand the problems they were having,” said Brian Rawson, president/CEO of the Dyson Corporation. “Our director of engineering and quality engineers were involved from the outset and assisted with the analysis and conclusions of the issues that were raised.”
“Throughout this process, other customers, our supply chain and the media were requesting information with regards to this issue. Our position was to support our customer and work together to conclude the analysis and report. The Dyson Corporation is an ethical company and our values and customer relationships will not be compromised,” said Rawson.
A detailed analysis and report from some of the leading industry experts was carried out and is now available at www.dysoncorp.com.
For more than 125 years, The Dyson Corporation has supplied domestic fasteners, forgings and machined parts to America’s transportation infrastructure of bridges, railroads and waterways, the fossil fuel industries of mining and power generation, shipbuilding and nuclear power, and the OEM supply chain.
Beginning in 1884, as a specialty forge shop in Cleveland, founder Joseph Dyson started to produce small forgings for various industries. Responding to customer demand, Dyson soon developed the capability to manufacture larger fasteners and forgings, as well as fork arms for the material handling industry.
Today, forgings made at the Painesville, Ohio plant range in size from 1/2 to 10,000 lbs. (5,536 kg). Equipment includes a combination of hammers, mechanical and hydraulic presses, upsetters, benders, and state-of-the-art hot part formers with in-line heat-treating. In addition, the company’s extensive CNC turning and milling operations, and the considerable thread rolling, drilling and tapping capability; have helped Dyson develop into a premier critical fastener manufacturer. Working in product diameters from 3/4 to 8 inch, Dyson is producing fasteners to various specifications, including ASME, MIL, ANSI, and DIN, and servicing critical component markets, such as military product and nuclear power.
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