Fatigue hazards in welded plate crane runway girders - Locations, causes and calculations

Steel crane runway beams compared with other building structures are exposed to extremely complex load-stress conditions. It turns out, that significant from the point of view of the resistance of the crane runway beams is a cyclic nature of fluctuating loads, which leads to formation of numerous cracks and damages. This effect is especially characteristic for webs in plate I - cross sections of crane runway beams. The complex state of stresses is generated by overall bending that causes normal and shear stresses - σ x , τ xz , and by crane wheel eccentric load that produces respectively stresses - σ z , x , σ o , x , τ o , xz . Stress components produced by overall bending are determined as I kind stress, whereas the stress components from the crane wheel load are introduced as II kind stress. Such a combination of stresses lowers the fatigue strength of the web, which is ignored by many rules specified in standards. Limited fatigue strength is observable, among others, in crane rails splices. The results of numerical analyses obtained as II kind stresses in the web located directly beneath the crane rails splices that occur as: orthogonal contact, bevel contact and stepped bevel contact as well, confirmed the complexity of the issue. Following that, other factors, not being defined yet, but affecting the stress state of the both crane rail and crane runway beam are scheduled to be studied, as for instance, the eccentric load induced by crane trolley in mentioned above elements.