PSI - Issue 64

Julian Unglaub et al. / Procedia Structural Integrity 64 (2024) 918–924 Julian Unglaub / Structural Integrity Procedia 00 (2019) 000–000

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Fig. 4. Fatigue results related on 2 Mio. load cycles from free regression and geometry of the fatigue specimen, Begemann et al. (2024).

4. Towards a DT framework for welding under service conditions In addition to the investigated butt joint detail, there are a large number of difficult to access and geometrically complex connections in steel bridge engineering. Orthotropic deck slabs are a common construction detail. These parts consist of a large number of welded plates and steel profiles in the longitudinal and transverse directions. When repairing such welded details, special requirements must be observed under service conditions. The presented repair method of grinding out the hot-cracked root layer from the opposite side is not directly possible here. In addition, multi-axial crack opening modes may be present that require further measurement tests on such complex weld details. The monitoring system used can only observe mode I cracks. Multi-axial conditions cannot yet be determined with this system. However, as the investigations on butt joints show, determining the loading regime is critical for rehabilitation. It is therefore necessary to investigate whether there is a characteristic mode of measurement that can reduce the measurement system to a few degrees of freedom. In order to implement the paradigm of predictive maintenance in bridge engineering, it is necessary to capture the information in a DT. Up to now, the data for monitoring the gap opening, the geometry and the damage history has been available in a decentralized and fragmented manner. The documentation of the rehabilitation process in particular provides important information about the prediction of load-bearing capacity. The investigations contribute to an estimation of the fatigue life in the nominal stress concept. For a realistic prediction of the true fatigue life, however, additional research on close to application scenarios are necessary in order to develop a new suitable DT concept for repair and retrofitting in bridge engineering. 5. Conclusion Damage caused by fatigue loads necessitates maintenance work, usually in the form of welding, on many steel bridges in Germany. To carry out the welding work, the structure must currently be closed to prevent the crack opening movement of the propagated crack during welding. As part of the research project, a new method was developed that allows welding work to be performed on existing and new structures under service load and to achieve weld seam quality and fatigue strength in accordance with DIN EN 1993-1-9 (2010).