In frictional pretensioned bolted joints, the same specification is employed for contact faces in one joint in principle. Meanwhile, usage of different contact faces including the easy-processing faces might often provide labor-saving and accelerated works. However, in present study, slip coefficient in bolted joints using faces processed by grinder depends on the roughness of contact faces.

In this study, bolted joints including painted face with inorganic zinc rich paint and face processed by grinder using friction sims were made. Friction sims usually are used in drive unit for increasing the friction. And 21 bolted joint specimens were used in bolt pretention relaxation test and slip test. Finally, based on the results, the suitable slip coefficient in design is discussed.