Fatigue is a phenomenon that is rarely encountered by structural engineers, especially those who work exclusively in the realm of building structures. It only occurs when an element of a structure is subjected to cyclical loading over a sustained period. Hence this being a factor in the design of bridge elements, especially those that are exposed to vehicular traffic, as that is a form of cyclical loading.
This Technical Guidance Note defines what fatigue is and how its effects can be countered. Detailed analysis of fatigue is not covered as it is a complex procedure beyond the scope of a Level 1 Guidance Note.