FE 15.0711/2023/FRB
"Sustainable fatigue design of road junctions according to Eurocode"
In Germany, the fatigue design of roadway transition structures is carried out according to the national rules in the TL/TP FÜ on the basis of the fatigue load model FLM1EJ according to the European directive ETAG 032 (and its subsequent EADs). The fatigue load models in ETAG 032 were developed based on the traffic load models in DIN EN 1991-2 to demonstrate the load-bearing capacity and serviceability of road joints using the Eurocode design concept or a test-based design. Nationally in TL/TP FU, the computational requirements of the resistor side are higher than the requirements in EAD 120113-00-0107. In addition, the test-based verification methods according to ETAG 032 do not meet the national requirements, as the current TL/TP FÜ (2021) requires three successful continuous tests per component or kit.
Although the road joints in lamellar design, which have been tested according to TL/TP FÜ (1992 and 2005), have proven to be fatigue resistant in practice, they are not able to provide mathematical proof of fatigue strength when using the fatigue load model FLM1EJ according to EAD 120109-00-0107 and the notch drop tables according to EN 1993-1-9. As a result, rule-tested FÜ must be significantly strengthened by reducing truss spacing and thus increasing the number of crossbeams including truss boxes. The higher number of truss boxes makes installation and connection to the supporting structure more difficult. In summary, the discrepancy between practical experience and mathematical proof increases the material consumption, the processing effort and thus also the construction costs and the maintenance effort.
According to TL/TP FÜ (2021), in order to prove a sufficient service life of the field-proven and economical FÜ when using the fatigue load model FLM1EJ, a large number of continuous tests require the test-based determination of Wöhler lines on all notch details with biaxial alternating bending stress. However, these are time-consuming and cost-intensive. Therefore, within the framework of the project, construction details typical of the road transition of a total of 3 lamellar road transitions, these related to the base material, a welded joint and a screw connection, are to be selected and investigated.
The aim of the project is to develop a scientific basis for a reliable and economical fatigue verification of road transition structures within the framework of the Eurocode design concept through experimental and theoretical investigations. In this context, selected typical design details of the lamellar construction are investigated, which have proven to be robust in practice, but can no longer be verified with the current European regulations with regard to the load model and test execution (swell tensile fatigue tests). The benefit lies in improving the verification of current regulations with regard to the sustainable, reliable and economical design of road junctions in order to reduce material consumption, processing effort, construction costs and maintenance costs.