Chung Report Critical of Caltran’s Protocols, Data Interpretation and Conclusions re San Francisco-Oakland Bay Bridge SAS Span Integrity


A report titled Validity of Caltrans’ Environmental Hydrogen Embrittlement Test on Grade BD Anchor Rods in the SAS Span dated December 2, 2014 prepared by Yun Chung, Materials Engineer (Retired), purportedly for Steve Heminger, Chair, Toll Bridge Program Oversight Committee recently surfaced. Seven other professors, consultants and engineers purportedly reviewed the report and provided comments, including Robert G. Bea, Ph.D., Russell Kane, Ph.D., Harold J. Mantle, P.E., Charles J. McMahon, Jr., Sc.D., Cory Padfield, P.E., Patrick Pizzo, Ph.D., and Pierre R. Roberge, Ph.D., P.E. The Chung Report responds, in part, to Caltrans’ conclusion “that all the 2,210 HDG BD rods in the SAS are “safe” as installed from future EHE failures.” The San Francisco-Oakland Bay Bridge Self-Anchored Suspension Bridge Evaluation of the ASTM A354 Grade BD Rods was issued on September 30, 2014.

In part, the Chung Report concludes that “This review revealed that Caltrans’ EHE test protocols and data interpretation are both problematic and unscientific and that their conclusions as to the integrity of the [self-anchored suspension span (SAS)] could not be supported.” Section 8.0 of the Chung Report sets forth 12 conclusions and recommendations, including that “Caltrans’ conclusions and recommendations in their September 2014 report on the A354 BD Rod Evaluation are incorrect and will not resolve the concerns about possible hydrogen embrittlement (HE) failures of hot dip galvanized (HDG) Grade BD rods that are critical to the structural integrity of the self-anchored-suspension (SAS) span.” Among other things, the Chung Report recommends that Caltrans should “adopt the strategy of using HDG BD rods that are metallurgically not susceptible to EHE failures, for example those with peak hardness of 32 – 35 HRC maximum” and “identify HDG BD rods in the SAS that are susceptible to EHE failures and replace them with new HDG BD rods or equivalent rods not susceptible to EHE failures.” As for monitoring, the Chung Report recommends that Caltrans “concentrate on the tower base anchor rod performance because they are not replaceable and their failures would be critical to the SAS structural integrity…. It may take years but it is difficult to predict the timeframe of EHE failures. Caltrans should develop a risk analysis of the tower base anchor rod performance.”

Additional Source: The Sacramento Bee, Independent report calls Bay Bridge Tests ‘unscientific,’ ‘erroneous’ (Dec. 2, 2014).