Bridges

Friction-type connections are widely used to connect steel members where slipping is not permitted under serviceability loads. The friction developed between the faying surfaces transfers the design shear forces at the serviceability limit states. The bolts act in tension and are not subject to shear.As a rule, faying surfaces are coated with inorganic zinc silicate coatings and a slip factor for these coatings is specified in AS 5100.6. For other applied coatings and surface conditions, AS 5100.6 specifies testing in accordance with AS 4100 Appendix J.Epoxy zinc rich primers are generally not used for friction-type connections. This testing program was prompted when an epoxy zinc rich primer was proposed for friction-type connection during the course of a contract. Epoxy zinc rich primers have some operational advantages over zinc silicate primers and a testing program to assess the suitability of a range of zinc rich coatings for faying surfaces was initiated. Nine different zinc rich coatings and bare metal samples were tested in accordance with AS 4100 Appendix J and the results are presented in this paper. The effects of variations in bolt quality and the measures taken to modify the testing parameters to suit the bolts used for the test samples are discussed. The effects of coating dry film thickness (DFT) on the friction coefficient are also discussed.