Journal of Bridge Engineering IMPROVED ASSESSMENT METHODS FOR STATIC AND FATIGUE RESISTANCE OF OLD METALLIC RAILWAY BRIDGES

13 A large number of the bridges in the European railway networks are metallic bridges. 14 The increasing volume of traffic and axle weight of trains mean that for many 15 structures the loads today are much higher than those envisaged when they were 16 designed. This paper presents a summary of the different recommendations and 17 advices proposed in “Guidelines for Load and Resistance Assessment of Existing 18 European Railway Bridges” of the European Union founded project “Sustainable 19 bridges” for assessing old metal railway bridges. The knowledge of the material 20 properties of existing metal bridges is essential for the resistance assessment and 21 the determination of the remaining lifetime of old metallic bridges. Furthermore, old 22 bridges require more exact and efficient assessment methods that call for a precise 23 description of the material. Among the problems met in metal bridges and material 24 properties estimation, fatigue is the most common cause of failure. To be able to 25 make accurate assessments of existing bridges, it is important to know the behaviour 26 of bridges exposed to fatigue, and how the old materials behave due to cyclic 27 exposure. The main question answered herein is how to make a safe estimation 28 concerning the remaining life in service. The possible traffic load on steel rail bridges 29 is usually limited by the fatigue resistance, but for certain situations the static 30 resistance has also to be checked. Most design rules for steel structures, for instance 31 those in Eurocode 3, are applicable also to riveted structures. However, some 32 information is missing on how to deal with the special case that elements are 33 intermittently connected in contrast welded structures that are connected 34 continuously. As the traditional methods for assessing the resistance of steel bridges 35 are based on elastic analysis, a method for utilizing a limited redistribution of bending 36 moments based on beam theory is proposed. 37