A comparison of fillet weld strength and U.S. Navy design specifications for non-combatant ships and the economic implications

Abstract

There is a great interest in the strength of fillet welds because the welding operation accounts for about 30% of the labor cost in planning and constructing ship hulls. One way to reduce welding cost is to reduce the required weld size. Background information is obtained by reviewing the major experimental and theoretical work in the areas of static strength, fatigue strength , and shear strength of fillet welds. In order to appreciate the conditions in the real world, design considerations, fabrication considerations, and corrosion considerations are discussed. Typical joints from existing U.S. Navy ships are employed to obtain detailed geometry and local loading information to be used as input for a computer model which was developed at Massachusetts Institute of Technology which uses the finite element method for determining the static strength for fillet welds. In one particular joint a reduction of 30% in the required weld size is justified. A future system for analyzing fillet weld strength is proposed and explained by the use of an example, The economics of intermittent and continuous welds are examined, and the economic impact that a reduction in the required fillet weld size would have on ship construction cost is estimated.