The purpose of this study is to verify the applicability of damage indexes relating to strains calculated in nonlinear FE analysis. The experiment and the numerical analysis of reinforced concrete (RC) simple beam were conducted to clarify the influence of loading speed on their fatigue lives. The fatigue lives obtained in both experiments and FE analysis were generally decrease when loading speed increased. Furthermore, the full scale railroad viaduct was modeled by FE analysis. Fatigue life on the full scale model was decreased with increase of loading speed, even though resonances were observed in some cases. On the basis of FE analyses,fatigue damages were estimated by damage indexes, those are; the second invariant of deviation strain √????′2 and consumed strain energy ????????. The progress of damage was captured by indexes, however fatigue livesdetermined by indexes were not consistent with those calculated from conventional methods.