Slip resistance of metalized–galvanized faying surfaces in steel bridge construction

• Slip-critical connections with metalized-galvanized (M-G) faying surfaces characterized.
• Extensive tests program in tension and compression designed.
• Effect of different connection variables on the slip resistance investigated.
• M-G faying surfaces developed greater slip resistance than the typical galvanized finish.
• Results significant for steel bridge fabrication in North America.

The slip resistance of high strength bolted connections depends on the surface condition of the connected parts, also known as the faying surfaces. Metalizing and galvanizing are two commonly used corrosion protection solutions in steel bridge construction, providing physical barrier as well as sacrificial protection. Practical situations exist where galvanized secondary structural components are joined to primary elements that are metalized in a slip-critical connection. Contemporary bridge design standards, such as the Canadian Highway Bridge Design Code, CAN/CSA S6-06, and the American Institute of Steel Construction (AISC) specifications, ANSI-AISC 360-2010, however do not specify slip coefficient for slip-resistant connections with one faying surface metalized and the other face galvanized. Steel bridge fabricators are therefore compelled to mask off all connection faying surfaces before metalizing. This exercise is time-consuming, labor-intensive, and costly. In this investigation, the resistance of slip-critical joints having metalized–galvanized faying surfaces is characterized in view of the current North American design standards. The mean slip coefficient, determined from short-duration tension and compression test regimes, revealed slip resistance greater than the typical faying surface with roughened hot-dip galvanized finish, and in the majority of cases, greater than the typical uncoated blast-cleaned faying surfaces.