Crane runways – Fatigue evaluation of crane rail welds using local concepts

The introduction of the wheel loads into a crane runway with a hot rolled I-section and a block rail fastened by longitudinal fillet welds forms a multiaxial fatigue problem. At the point of wheel load application the top region of the runway girder is subjected to a stress field comprising local stress components induced by the concentrated load, i.e. local transverse pressure and local shear stress in addition to the direct and shear stress components due to global bending. The superposition of all aforementioned stress components (and stress ranges, resp.) during each single crane pass results in a so-called non-proportional cyclic stressing of the rail welds with alternating principal stress direction. Due to the variation of the principal stress direction the conventional fatigue evaluation procedures appear not to be reliable. To approach the complex issue two crane runway girders were tested under proportional multiaxial loading, i.e. under flexural bending and stationary wheel load, both simultaneously pulsating. The paper presents the fatigue evaluation of these tests using different local concepts.