Sustained and Fluctuating Loading on Bolted Joints

The design of high strength friction grip bolted joints in structural steelwork requires knowledge of short-term and long-term load-deformation behavior of the joints and the effect of anticorrosive coatings on the faying surfaces. Determination of the coefficient of friction is usually by short duration tensile tests on double-lap single-bolt joints. The paper analyzes the forms of the load-extension curves obtained and the effect of loading procedure and describes a test procedure used by the writers. Sustained and fluctuating load tests on chains of joints with faying surfaces coated with zinc silicate paint are then described. Creep slip of the joints was found to be negligible. This result is examined in comparison with other work purporting to show continuous creep slip under sustained load; the test procedure and method of analysis of results used in the other work are questioned.