PSI - Issue 64

Urs Meier et al. / Procedia Structural Integrity 64 (2024) 29–39 Meier/Winistörfer / Structural Integrity Procedia 00 (2019) 000 – 000

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Dr. Andreas Winistörfer, as the CEO of Carbo-Link, the manufacturer of the carbon hangers, to obtain approval in individual cases from the Stuttgart Civil Engineering Office and the inspector, Prof. Ulrike Kuhlmann, with the client SSB AG's approval. Fatigue tests conducted by Empa with 11.3 million load cycles, equivalent to over 100 years of use, have demonstrated the suitability of CFRP as hangers. Fig. 7 proves that not any change happened in the loading behavior due to the fatigue experiment. The Stuttgart light rail bridge, world's first bridge fully relying on carbon hangers, Meier, Winistörfer and Haspel (2021) is in operation since 2021.

Fig. 6. One of the 72 CFRP hangers of the Stuttgart light train bridge.

Fig. 7. Extension/Load-Diagram for Hanger B for loading and unloading before and after 11.3 million fatigue cycles.

Figure 8. Easy application of the lightweight CFRP hangers with one hand in less than two minutes at Stuttgart light rail bridge.

In autumn 2023, the German National Railways completed the second bridge of its kind featuring all carbon hangers for the Oder River crossing. The main span of the bridge measures 130 meters, located 85 km east of Berlin. As part of this project, the German National Railways commissioned a study to compare the sustainability of CFRP hangers with steel hangers. The results were quite surprising. When considering the cradle-to-gate stages, which assess the environmental footprint of a product from raw material extraction to factory exit, the CO 2 footprint of steel hangers was three times higher than that of CFRP, with energy consumption 2.5 times higher than that of CFRP. Details of the calculation can be found in Meier, Winistörfer and Haspel (2021). These excellent results are specific to this application. Typical general values are given in the next section. Particularly notable was the ease of hanger installation in the bridges due to their lightweight nature, taking no more than five minutes in most cases (Figure 8). The German Federal Ministry of Transport and Digital Infrastructure commissioned a comprehensive study on the subject of "Reinforcing older concrete and pre-stressed concrete bridges", Schnellenbach et al. (2016). The study showed that 52% of the upgrades of bridges with external post-tensioning have so far been carried out using steel tendons. Externally bonded CFRP laminates were used in 12%, near-surface mounted CFRP strips in 3% and post tensioned CFRP laminates in 1%. The remaining 32% of the retrofits were carried out using conventional methods such as externally bonded steel sheets and dowelled concrete.