Nominal stresses in continuous and intermittent rail welds of crane runway beams

Abstract

Crane runway beams of hot-rolled I sections are frequently the supporting structures of top-running overhead bridge cranes. In case of light crane service, the crane rails are usually fastened to the top flange of the crane runway beams by fillet welds. A survey among steel construction companies revealed that continuous rail welds as well as intermittent rail welds are commonly used. The rail welds are subject to multiaxial fatigue since they are exposed to normal and shear stresses due to the local wheel load introduction and global bending. Currently, the design standards EN 1993-1-9 (2005) and EN 1993-6 (2007) neither provide an appropriate detail category nor a nominal stress formula for rail welds. The paper focuses on the calculation of the nominal stresses in rail welds as basis of the fatigue action effect within the nominal stress method. It describes the differences in the nominal stresses of continuous and intermittent rail welds because of the contact between rail and top flange that has to be assumed for intermittent rail welds. Based on work samples, the contact conditions of intermittent rail welds are characterized as ‚technical contact‘ (in contrast to ‚ideal contact‘) due to imperfections within the contact surfaces that are described in detail. A Finite Element model is presented that accounts for the ‚technical contact‘ between rail and flange. This model is analyzed in a parametric study to identify the decisive parameters on the nominal stresses in intermittent rail welds.