OAKLAND -- Caltrans has released 15 volumes and hundreds of pages of inspection and test data on thousands of high-strength steel fasteners installed on the eastern replacement span of the Bay Bridge.
The documents are part of the ongoing probe into why 32 out of 96 very large high-strength anchor rods snapped on the span in March, and whether the remaining 2,210 fasteners made out of the same grade of steel are vulnerable, too.
The three agencies overseeing the $6.4 billion bridge construction project -- Caltrans, Bay Area Toll Authority and California Transportation Commission -- have commissioned extensive testing of all the steel.
In the meantime, Caltrans and the contractor, American Bridge/Fluor Joint Venture, are installing an external saddle and cable system designed to carry the loads in the seismic stabilizers where the bolts broke.
The bridge team has not yet said when the contractor and the retrofit fabricator, XKT Engineering, Inc. of Vallejo, will finish the repairs or if it can be done in time for the Labor Day opening.
The retrofit schedule and bolt testing and analysis will determine whether the bridge opens to traffic on Sept. 3 as scheduled. The bridge team will brief the authority on the construction status on July 10.
Metallurgists have already concluded that the broken bolts fell victim to a well-known embrittlement phenomenon where hydrogen atoms invade high-strength steel under heavy loads, causing them to fracture and break.
, The rods -- 3 inches in diameter and 17 to 24 feet long -- were part of a batch fabricated in 2008. They are embedded in seismic stabilizers called shear keys on the large pier east of the suspension bridge's main span tower.
Caltrans' first two volumes of bolt fabrication and test data released in April contained documentation on the 2008 rods as well as 192 bolts in adjacent shear keys and bearings that were manufactured in 2010.
The 15 new volumes Caltrans released midday Friday feature similar agency manufacturing site audits, inspectors' reports, certified material test results, shop drawings and a plethora of test results for the fasteners of varying sizes and purposes installed throughout the self-anchored suspension span.
With relatively few exceptions, the fasteners passed all the requisite tests. Although some of the steel would not have passed the new, lower hardness threshold the state set in April after the bridge bolts snapped.
The acceptable range at the time the bolts were ordered was 31-39 on the Rockwell hardness scale; the new maximum is 35. The harder the steel, the more susceptible it is to embrittlement and fracture.
Hardness results above 35 may not be significant, however. Less than half of the fasteners on the bridge are under loads metallurgists consider sufficient to trigger embrittlement.
A review of the nearly 8-inch-high stack of documents also showed:
The documents also offer a window into the day-to-day decisions on-site state inspectors made at the facilities of contractors that performed work such as fabricating, galvanizing, sandblasting, painting and machining.
In June 2009 at Dyson's Ohio facility, for example, nuts for hex bolts failed what is called a "go-no go gauge"an inspection tool used to check a workpiece against allowed tolerances, which in this case measured the threads to ensure that pieces fit together. But the inspector noted that the pieces assembled properly and recommended acceptance.
An inspector in April 2011, however, ordered the return of a Dyson shipment of 3½-inch spherical nuts and washers that had been shipped before Caltrans had finished its quality assurance testing and approved the products.
In other instances, inspectors held up shipment until missing paperwork was provided, ordered illegible identification stamps cleaned and directed that sharp edges on anchor rods be removed.
An inspector also ordered Monnig Industries, a Missouri steel galvanizing company, in July 2011 to stop using brake parts cleaner on the ends of galvanized threaded rods intended for use in the suspension span's anchorages.
A load of the same type of rods fell off a truck in Nevada, and a Caltrans inspector deemed 13 out of 55 damaged beyond repair. The others were fixed and the state later accepted them for use.