Damage assessment in steel members under seismic loading

Eurocode-3 (CEN 1993), defines fatigue as "damage in a structural part, through gradual crack propagation caused by repeated stress fluctuations". Depending on a number of factors, these load excursions may be introduced either under stress or strain controlled conditions. Depending on the number of cycles sustainable to failure, and on their amplitude, we can distinguish failure for high or low cycle fatigue.