PSI - Issue 75

Jeroen Van Wittenberghe et al. / Procedia Structural Integrity 75 (2025) 111–119 Jeroen VAN WITTENBERGHE and Vitor ADRIANO / Structural Integrity Procedia (2025)

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Boundary conditions are assigned as depicted in Figure 2. As previously described by the authors in [2] the SHM method utilizes measurements from optical fibre sensors (type FBG) measuring strain as well as operational SCADA data. The complexity of the crane and correspondingly of the digital twin model as well, is much higher for the Crane AM. For example, the Crane-OCAS only contains about 30 welds (with a total weld length of about 100 m), while the digital twin model of the primary bridge structure of the casting crane is tracking the fatigue life of 1298 welds (total weld length in excess of 1 km). For both cranes a large set of load cases is run covering all fatigue loading conditions of the crane.

Figure 2: FEA models and boundary conditions of Crane-OCAS (left) and Crane-AM (right).

2.2. Fatigue damage calculations The FEA simulation results are post-processed for fatigue analysis of the welds. First, the weld locations are defined Figure 3-a). Then, weld properties are assigned to each weld. This includes the assignment of FAT classes based on EN 13001 [4] and weld geometry. In addition, the stresses are reoriented in the weld directions and the following stress components are extracted following EN 13001: normal stress longitudinal to the weld axis ( ), normal stress perpendicular to the weld throat ( ⊥ ) and shear stress (in plane of the weld throat) parallel to the axis of the weld . These stress components are extracted at a pre-defined distance to avoid capturing local stress concentration effects, which are already translated into the FAT class of the weld detail. Since FEA is used to calculate weld stresses, care must be taken when combining them with the fatigue Notch Classes from EN13001. For every simulated load case, the results are post-processed using the reasoning described above. The stress components ( , ⊥ , ) obtained at each assessment point (for each simulation) are used to calibrate a Reduced Order Model (ROM). The ROM outputs the stress state at any weld assessment point in the crane structure for a given load case eliminating the need to perform further FEA simulations, which are computationally more expensive.

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Figure 3: a) Welds (in red) in the LK120N main structure. b) Geometry of the weld is defined.

During service, the crane structure is subjected to load cycles, which induce fatigue damage. A damage estimation is calculated using the integrated digital twin approach which links the reduced order models with the time series of the measured signals (strain measurements and SCADA data is described in [2]). For each assessment point of the welds the ROM calculates a stress time history for the three stress components ( , ⊥ , ). The cyclic stress ranges