Repair welding is a proven method for maintaining steel structures, such as bridges, by crack removaland re-welding cracks that have occurred. The damage is mainly caused by increasing traffic loads whichleads to movements at the crack flanks. In order to enable re-welding under the influence of these crackmovements, promising approaches for welding under cyclic loads have already been investigated by theauthors. Otherwise, bridge closures with detour routes and additional welding work would be the result.Previous welding tests in a large-scale test setup were based on idealized cyclic loads that simulated uniformload cycles of individual vehicles. In addition, in this study the influence of high-frequency vehicle axles wasinvestigated in welding tests by applying a frequency of 15 Hz to individual vehicle axles. In the weldingtests under high-frequency vehicle loads, standard-compliant weld seam qualities and fatigue strengths wereachieved.

Steel structures, such as bridges, must be continuously maintained. Due to increasing trac loads, design and execution shortcomings, many steel bridges are subject to various types of damage, such as cracks. The bridges must be maintained by crack removal and re-welding the cracks. During this work, the bridge is closed for trac in order to suppress the crack ank movement during welding. As a result, trac loads on other routes are higher, which increases further damage on detour routes and subsequently additional welding work and costs on theses structures. Therefore, the aim is to provide a method that allows welding work on steel structures under running trac, respectively under cyclic loads. First, measurements at a representative steel bridge were conducted to derive gap opening parameters of amplitude and frequency for welding tests under cyclic loads. In a test setup for reproducible and comparable welding tests, specimen were welded under cyclic loads. Deep grinding of the root layer allowed defect-free welding within the range of 0.1 mm amplitude at a frequency of 2 Hz loadings. For such welds, the weld quality and the fatigue strength was comparable to the standard requirements.