Fatigue Strength of Coated Steel Structures in Seawater

摘要

Fatigue tests were carried out in synthetic sewater on H-type test specimens which simulate the longitudinal structure at the slots of transverse web of ballast tanks of ships. In order to clarify the effect of coating films in seawater, coated specimens with tar epoxy resin were tested under the frequency of cyclic loading of 0.17 Hz simulating the averaged speed of ocean waves. The fatigue lives in seawater decreased in comparison with those in air. In the present paper, the slight effectiveness of coating is considered with the relation to crack initiation behavior due to the high stress concentration and residual stress at the weld toe. Finally, for the design of coated structures in a ballast tank, a treatment idea for welded beads is suggested.