Rational Basis for Increased Fillet Weld Strength

The fillet weld strength increase occurs because of sensitivity to the direction of loading. At a loading perpendicular to the longitudinal axis of the weld, the weld has been shown to be on the order of 50 percent stronger than the lower bound for parallel loading. A full range of strength variation exists for intermediate force angles of 0-90 degrees. In the past, this effect had been conservatively and conveniently ignored for design but has now been recognized. While the detailed experimental justification reported in the literature is convincing by itself, the objective of this paper is to also demonstrate this increased strength with a simple rational model derived from first principles.