Sustainable steel and composite bridges through increased lifetime by fatigue treatment

To achieve sustainable long-living infrastructures such as steel and composite bridges, the improvement of the fatigue behavior is crucial. By using high frequency mechanical impact (HFMI) treatment of critical welds, the fatigue service life of welded structures can significantly be extended due to the introduction of compressive residual stresses. Particularly with the use of high-strength steels in combination with HFMI-treatment has become economic in terms of fa­tigue design, thus, leading to reduced use of material resources. Even for welding in existing structures, positive results have already been achieved with post-weld treatment. For this inno­vative method, the amount of lifetime benefit and the conditions for successful application in the view of quality assurance have sometimes become object of critical questions. In various re­search projects, these questions could successfully be answered. By means of numerical and experimental investigations, design approaches have been developed and evaluated for the ap­plication of those treatments in constructional bridge design. The paper summarizes the results of two research projects on the subject of HFMI-treatment with the focus on the use for steel and composite bridges. An insight on the improved fatigue design, the practical use, the benefits for the constructions and possible application fields is given.