PSI - Issue 57

Elena Sidorov et al. / Procedia Structural Integrity 57 (2024) 316–326 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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1. Introduction Travelling overhead crane installations belong to the material handling equipment that is commonly used in many buildings of the industrial infrastructure such as production halls and warehouses. Such crane installations as exemplified in Figure 1a can be subdivided in a machinery part (the crane itself denoted as ‘3’ ) and its supporting crane runway beams (‘2’) that are usually designed by civil engineers according to EN 1993-6 (2007). In case of light crane service, these beams frequently consist of a hot-rolled I section with flat material as crane rail (‘1’) that is welded to the top flange as shown in Figures 1b and c. This type of rail fastening is addressed by this paper.

Fig. 1. Supporting structure of a travelling overhead crane: (a) example of a crane installation; crane rail fastening through (b) continuous and (c) intermittent rail welds; (d) chain intermittent rail welds, (e) staggered intermittent rail welds. Explanation: 1 – crane rail, 2 – crane runway beam, 3 – overhead travelling crane, 4 – crane wheel There are two possible ways to produce the rail welds: continuous rail welds as shown in Figure 1b and intermittent rail welds as shown in Figure 1c. Continuous rail welds have to be preferred over intermittent ones in humid environments to avoid excessive corrosion in the contact region under the rail. Furthermore, the fatigue resistance of continuous rail welds is greater compared with that of intermittent rail welds due to the missing stop-starts. On the other hand, continuous rail welds are less efficient because of the greater amount of welding and the heat input that induces larger thermal deformations that usually require a post-weld straightening of the crane runway beams. Thus, intermittent rail welds are attractive from the viewpoint of fabrication. Chain intermittent rail welds as shown in Figure 1d and staggered intermittent rail welds as shown in Figure 1e are possible. Crane runway beams differ from other steel structures for buildings because they are repeatedly stressed by the wheel loads of the crane (denoted as ‘4’ in Figure 1a) . From that reason, crane runway beams have to be designed against fatigue. This especially applies for the highly stressed rail welds that are subject to normaland shear stresses due to the wheel load introduction (multiaxial fatigue). In general, the stress ranges of the transverse normalstress in the rail welds caused by the repeated wheel load introduction are decisive for the rail weld design. The nominalstress method acc. to EN 1993-1-9 (2005) is usually applied for the fatigue verification as shown in Figure 2. The transverse normal stress in the rail welds, that is referred to as ‘ nominal stress ’ in this paper, is controlled by the contact between the rail and the flange of the crane runway beam. The calculation of the nominal stress (action effect in Figure 2) from the wheel loads (load action in Figure 2) is quite complicated since the proportion of the wheel load that is carried by the rail welds depends on this contact. The rail-flange contact cannot be visually checked for continuous rail welds since it is hidden by the welds. Therefore, continuous rail welds usually require larger weld sizes in comparison with intermittent rail welds because the contact between rail and flange has to be neglected for fatigue design purposes. In contrast, the rail-flange contact can be checked between intermittent rail welds by means of a feeler gauge. Thus, this favourable contact can be taken