In large vessels, the thickness of deck plating has increased significantly during the last decade. Hence, it is not possible to ignore the effect of plate thickness on fatigue strength for these structures. To complement existing data and to establish the effect of plate thickness on fatigue strength, constant amplitude fatigue tests were carried out under tensile and bending loads for base material and butt welded specimens of various thicknesses made from high-tensile EH40 steel. Based on the fatigue test results and available literature, the thickness exponent was derived.
"Container ships are increasing in size all the time, with the 10,000 TEU barrier finally having been broken. Nearly half of the container ship order book is comprised of ships with a capacity of greater than 6,000 TEU. With containerships of this size the owner and the builder will be particularly focussed on the reliability and performance of the hull structure over the course of the vessel's transpacific trading life• - these are quotations from the article "Towards the ultra-large container ship" published in Lloyd's Register technical news magazine "Horizons", March 2005 issue. Increase in container ship capacity inevitably leads to increase in size and thicknesses of hull structures. Hence it is not possible to ignore effect of plate thickness on fatigue strength of deck structures such as deck (hatch) opening corners. To estimate fatigue life of these structures, fatigue resistance data (S-N curves) for base material and butt welded specimens of various thicknesses are required. The effect of plate thickness on fatigue strength has been studied by a number of investigators who have primarily considered T and cruciform non-load-carrying joints. However experimental data for base material and butt welded specimens are very scarce. To complement existing data constant amplitude fatigue tests were carried out under tensile and bending loads.
