FATIGUE ASSESSMENT OF BRIDGE STRUCTURES ACCORDING TO EUROCODES

Fatigue is one of the main causes of damage in many structures. The process of fatigue damage is rather complicated and the design of structures with reference to fatigue requires a good knowledge in several fields including structural analysis, material mechanics and modeling of loads and load effects on structures. Therefore standards and recommendations related to fatigue design and analysis are often needed to assist the structural engineer in his design work. This applies both to the design of new bridges and the analysis of the remaining service life of existing bridges. General rules for determining all effects on bridges are specified in EN 1990 and Appendix A2. Verification if there is no structural damage due to fatigue should be performed in accordance with the scheme of EN, include the scope of the Ultimate Limit Stage (ULS) verifications. For the reason, that fatigue failure does not occur as a result of the load of a fixed maximum value but as a result of repetition of imposing load on an average level of internal forces, the effect of fatigue depends strongly on the properties of construction materials – steel and concrete. Thus, the effect, in the form of fatigue may be quite different in the case of steel bridges, concrete bridges or even a composite steel-concrete bridges. Therefore, the rules for determining the fatigue load are not specified in the overall standard, but are moved to detailed design standards: EN 1992 to EN 1999. Because of the high complexity of the fatigue verification, in the work the general fatigue calculation rules are presented.

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