ABSTRACT
The limit state of the webs of steel plate girders subjected to many times repeated loading is considerably affected by the cumulative damage process generated in the web “breathing” under the repeated loading. This process brings about the initiation and propagation of fatigue cracks in the “breathing” plate elements, with them substantially influencing the failure mechanism of the girders and their fatigue limit state. The paper reports about the main conclusions of a new stage of an extensive experimental investigation into the problem witch has been under way at the Institute of Theoretical and Applied Mechanics in Prague for several years now and describes the main aspects and factors that influence the “breathing” phenomenon. Based on the results obtained by the authors, the paper also examines several approaches to the definition of the fatigue limit state of thin walled steel girders under the action of repeated loads, and puts forward a recommendation as to how the results obtained and the conclusions drawn can be taken into account in the fatigue analysis of steel bridges and similar structures.
