Properties of Anchor Rods Removed from San Francisco-Oakland Bay Bridge

In March 2013, the construction contractor for the new self-anchored suspension bridge between San Francisco and Oakland, California, tensioned the threaded rods between the bearings/shear keys and the concrete pier cap. Within days of completion, it was discovered that one-third of the rods for the two shear keys on Pier E2 had fractured. An investigation began to determine the root cause for the fractures. The work reported herein was in support of that investigation at the request of the Federal Highway Administration California Division office. It includes data on the mechanical, chemical, and microstructural properties of two samples removed from Pier E2. The testing showed a variation in material properties between the surface and core of the rods. It was concluded that improper heat treatment of the rods caused this variation. In addition, the tensile and hardness properties could have been judged to be in nonconformance depending on interpretation of the ASTM standards. It is recommended that the ASTM A354 and/or F606 standards be revised to provide more guidance on sampling for tensile and hardness properties for large-diameter products as well as guidance on impact toughness.