Fatigue cracking of welded railway bridges: A review

Steel railway bridges of all types comprise a large portion of the infrastructure inventory of several countries. Due to the ageing of these structures and increasing traffic loadings, structural fatigue increasingly became an important concern, leading to bridges deterioration. In this context, it is well-known that welded connections are among the weakest locations in steel bridges since they are prone to stress concentrations leading to the initiation of fatigue cracks. Although its importance, the study of the development history of welding technology applied to steel bridges is often overlooked in introductory texts about fatigue of metallic bridges. However, to understand the historical development of welding in steel bridges construction and its impact on fatigue design is fundamental, mainly because fatigue evaluation depends on the age of structures. The goal of this paper is to review the history of fatigue cracking of welded railway bridges, discussing the structural behaviour of welded bridges under dynamic traffic loads and the different causes of fatigue damage of welded connections. The presented case studies cover a period from the beginning of application of welding to steel bridges in the 1930s, revisiting well known cases of cracks documented in the literature due to their historic relevance and presenting also recent cases of the last decades due to new traffic conditions related to Heavy Traffic Loads (HAL) and High-Speed Trains. For this purpose, an in-depth literature review covering more than one-century history was carried out, providing a multidisciplinary analysis with insights into the welding history and practice and fatigue of welded joints, especially applied to steel railway bridges.