MECHANICAL TESTING AND POST FRACTURE ANALYSIS OF ASTM A354 GRADE BD RODS IN THE SFOBB, 2018
Following the fracture of thirty-two ASTM A354 Grade BD rods located at Pier E2 of the new east span of the San Francisco–Oakland Bay Bridge a comprehensive testing program was performed on the remaining rods. The mechanical testing consisted of in-situ testing, laboratory specimen testing, and laboratory full-size testing. The in-situ testing included approximately 45,000 hardness measurements on 1,296 rods utilizing the Ultrasonic Contact Impedance (UCI) method. The laboratory specimen testing consisted of charpy impact testing, hardness testing, and spectro-chemical analysis of specimens removed from 78 rods in service. Furthermore, slow load tensile testing was performed on nineteen full-diameter rods of varying lengths. These nineteen rods underwent a comprehensive post fracture examination in order to characterize the material properties and behavior. This consisted of non-destructive testing, mechanical testing, chemical testing, microscopic analysis, and fracture analysis. The nondestructive testing consisted of wet fluorescent magnetic particle testing on the threaded portions of the rods. Chemical analysis and electrochemical potential testing were performed on the galvanized coating, in addition to spectrochemical analysis performed on the steel substrate. Microscopic analysis was performed on transverse and longitudinal sections of the rods in order to evaluate the microstructure of both the steel substrate and the zinc coating, the inclusion count and rating, and the grain size at varying locations. Finally, both transverse and longitudinal sections were examined utilizing a scanning electron microscope (SEM) to evaluate the failure morphology, initiation and propagation.
– M. Wahbeh, R. Boundouki, T. Langill, G. Thomas and K. Hoffman, “Mechanical Testing & Post Fracture Analysis of ASTM A354 Grade BD Rods in the SFOBB,” 2018.