Welding under service conditions in compliance with standard requirements for weld seam quality and fatigue resistance, IGF-Nr. 20678 N
Steel structures, such as bridges, are subject to high loads due to increasing traffic. Built in the 1960s, they were designed for much lower loads than they have to carry today. Due to these increasing loads, many bridges are subject to various types of damage, such as cracks. The structure must be maintained by crack removal and re-welding the cracks. While this work is being carried out, the structure nowadays must be closed for traffic in order to suppress the relative movement of the removed crack during welding. As a result, traffic is forced to be diverted to other routes, which, in turn, are overloaded.
The aim of the project is to provide a method to carry out welding work on steel structures under service conditions and to achieve weld seam qualities and fatigue strength in accordance with the regulations. For this purpose, the crack opening amplitude and frequency under different traffic situations on a bridge is recorded by a measuring system developed by the Institute of Steel Structures and the recorded movement is then simulated in a test rig. The welded joints produced in the test stand under load are metallographically examined by the Institute of Joining and Welding and evaluated with regard to their weld seam quality. Subsequently, the fatigue strength of the joints produced under load is characterized in fatigue tests.
From the welds in the test rig a better understanding of the relationship between frequency and amplitude of the crack opening and the achievable weld quality is expected. At the end of the project, the results will be used to derive recommendations for the determination of local seam flank movements under service conditions and for the repair welding of fatigue-damaged steel structures. The determined fatigue strengths will be integrated into existing regulations and will thus be available to a wide range of users in the future.