Steel bridge elements may be exposed to aggressive conditions from ambient environment and human activities such as the spread of de-icing salt on roadways. In order to increase the service life of these members and reduce maintenance costs, two coating solutions - metallizing and galvanizing – have evolved as effective and widely used in providing a physical barrier and a sacrificial protection against corrosion. In some practical situations, secondary elements of steel bridge structures are galvanized and are connected to primary elements that are metallized in slip-critical joints. North American bridge design codes, such as the Canadian CSA-S6, the AISC specifications - 360 and the AASHTO LRFD, do not prescribe slip coefficient values for high strength bolted connections that are metallized on one connection surface and galvanized on the other. Bridge fabricators are then compelled to mask off connection faying surfaces before coating. This exercise increases the cost of and delays fabrication in the shop. In order to eliminate the need of masking off of these connection faying surfaces, it is important to characterize the slip resistance of high strength bolted connections having combined metallized-galvanized faying surfaces in light of prevailing bridge design codes. The slip resistance of these combined faying surfaces is determined in this research from both short-duration slip tests and long-term sustained tension creep tests.
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