In-Plane Fatigue Strength of Plates with Laminar Discontinuities

Although laminar discontinuities in steel are of concern primarily in applications where through thickness tension loads are applied to the plate (or shape), information was desired on the effects of repeated loadings on plates loaded parallel with the discontinuity. An example of such an application would be the flange of a girder (or rolled beam) of a bridge, which has a subsurface discontinuity that extends across part of the flange width and runs parallel to the flange surface for some length before terminating in sound material or in a welded flange splice. It was questioned whether the end of the discontinuity would propagate under repeated loadings. Consequently, a series of fatigue tests were conducted on strap-type specimens with and without a midplane discontinuity. Two types of specimens, both with as-received mill surfaces, were tested: (1) an unwelded specimen and (2) a specimen with a transverse groove-welded joint. Specimens of both types, both with and without laminar discontinuities, were tested. All specimens were machined from the web of a rejected ASTM A572 Grade 50 steel beam. This paper presents the results of the fatigue tests. The work is part of Project 164, sponsored by the American Iron and Steel Institute through the Engineering Subcommittee of the Committee of Structural Steel and Steel Plate Producers.