OAKLAND -- More Bay Bridge anchor rods could snap in coming years unless Caltrans identifies and replaces the bolts with less vulnerable steel, a retired Bechtel materials engineer has concluded.

In an unsolicited analysis submitted to Bay Area transportation leaders Monday, metallurgist Yun Chung said "inadequate" Caltrans' specifications and inattention or ignorance led to the installation of 288 high-strength steel rods -- including the 32 that broke in early March -- that were, or may become, brittle.

Chung's 32-page analysis attracted immediate attention from the Metropolitan Transportation Commission and Caltrans.

Failed bolts have been found in Pier E2, the pier on on the east-side of the Bay Bridge’s single-anchored suspension span that ties down the road bed
Failed bolts have been found in Pier E2, the pier on on the east-side of the Bay Bridge's single-anchored suspension span that ties down the road bed as it transitions to the conventional skyway. These photos are dated Nov 2, 2012. (Karl Mondon/Staff)

"Yun Chung is an expert in his field and we have spoken with him about our investigation into the broken rods, and we will be speaking with him again," said Bay Bridge spokesman Andrew Gordon. "But it is too early to say how his conclusions will line up with other experts who are working on this investigation."

In an email to Chung, Caltrans Toll Bridge Program manager Tony Anziano called the 32-page analysis "thoughtful" and the two are scheduled to meet Monday morning to discuss Chung's findings.

Chung, who specialized in high-strength steel analysis for the nuclear power industry, is recommending the state test the surface hardnesses of all the bolts, replace all suspect rods where possible and institute a new testing requirement for high-strength steel used on public works projects in the future.

Chung believes that Caltrans may have installed rods that are harder on the surface than the threshold set by Caltrans. That can make them more susceptible to failure, which can occur when unprotected steel is exposed to the elements and hydrogen invades the material, making it more brittle.

"It is very apparent that no one was paying attention to the possibility of hydrogen embrittlement when the rods were in service," said Chung, who retired 20 years ago and lives in the East Bay. "Instead, they were focused on hydrogen in the production process. From what I see in the documents, Dyson (the manufacturer) gave Caltrans what it asked for. Caltrans fell on its face."

Inspired by what Chung described as Caltrans' unsatisfactory responses to regional leaders' questions about why the bolts failed, he delivered the report to Metropolitan Transportation Commission Chairwoman Amy Worth on Monday.

"I'm not an engineer, but Mr. Chung's analysis seems consistent with the understanding that is emerging about the nature of the problem and the solution," Worth said. "The other concern he highlighted is that it is possible to have the bolts lay dormant and fail later in an earthquake. These issues are why we need a comprehensive solution."

The commission and Caltrans, which co-manage the $6.4 billion construction of the replacement eastern span, are evaluating opinions from a broad range of experts.

At least one metallurgist does not believe Chung's prescription goes far enough.

When asked to review the analysis, retired University of Pennsylvania Department of Materials Science and Engineering Chairman and Professor Emeritus Charles McMahon Jr. said surface hardness testing would be insufficient.

Like Chung, McMahon believes a different grade of steel should have been used.

The grade of steel used on the bridge was much "too hard for this application," McMahon wrote. "It would probably have to be a specially made high-purity steel, and it would not be inexpensive."

Caltrans is scheduled to brief the commission Wednesday morning for a third time on the status of its broken bolt probe and a possible fix.

In early March, 32 out of 96 high-strength steel anchor rods -- 3 inches in diameter and 17 to 24 feet long -- broke at the bottom of their casings a week after contractors tightened down the nuts.

An additional 192 anchor rods installed in adjacent seismic shear keys and bearings in 2010 had not failed as of Caltrans' status report two weeks ago.

The bolts clamp the shear keys and bearings to the top of the bridge columns and the bottom of the bridge deck on the pier just east of the main span tower. They help control movement during an earthquake but they are not necessary for the bridge's day-to-day structural integrity.

Chung's analysis attempts to answer a key question: Why didn't quality testing alert Caltrans to the problem?

The bolts were manufactured in two batches in 2008 and 2010 by Ohio-based Dyson Corp. and Monnig Industries in Missouri, and passed Caltrans and industry specified tests conducted by independent laboratories.

The rods also passed Caltrans' quality assurance testing with one exception: Two of the seven samples fell slightly short in one category. But the state never tested the rods' surfaces, which Chung theorizes are harder than the hardness threshold set by Caltrans. Harder surfaces make the bolts more susceptible to embrittlement than what the specified tests indicated, Chung said.

Hydrogen embrittlement requires three simultaneous conditions, he explained: susceptible material, sufficient hydrogen and stress or load.

High-strength steel is prone to embrittlement due to its crystalline structure, which allows hydrogen atoms to infiltrate and weaken its bonds. Galvanizing further hardens the steel and exacerbates the problem.

Ample hydrogen could have found its way into the rods while they sat for five years in their casings on the bridge exposed to corrosive condensate, Chung wrote.

When contractors tightened the nuts on the large bolts in early March and applied stress, Chung said hydrogen predictably went to work on the steel and left a third unable to withstand the load within the first week.

Contact Lisa Vorderbrueggen at 925-945-4773, lvorderbrueggen@bayareanewsgroup.com, politicswithlisav.blogspot.com or Twitter.com/lvorderbrueggen.

bay bridge bolt update
Listen via live web audio streaming at www.mtc.ca.gov/meetings/schedule/.starting at 9:30 a.m. on Wednesday when Caltrans delivers a status report on the broken anchor rods on the new Bay Bridge to the Bay Area Toll Authority.