Analysis of results of modal influence on fatigue damage 5.1. Maximum fatigue damageThe comparison of modal contributions to the maximum fatigue damage, determined by using the procedure outlined in the previous section, corresponding to the straight track condition is shown in Fig. 18. It should be noted that the ordinate is expressed in terms of logarithmic damage, where the maximum possible damage is unity, representing failure. Therefore, the shorter bars indicate greater fatigue damage. In addition, in Fig. 18, ‘all’ represents the contributions by all 10 vibration modes. It is clear that the 2nd vibration mode has the greatest contribution to the total damage, followed by the 8th mode under the straight track conditions, while the 3rd mode has the least contribution. A similar trend can be observed under the curved track conditions, as can be seen in Fig. 19. A detailed comparison, based on 95% survivability between the two conditions, is given in Fig. 20.In the straight track condition, the contributions to the total damage of mode 2 and mode 5 as well as mode 8 are more significant than those of the others. Mode 2 or the ‘mid-beam vertical bending’ mode is the most dangerous mode, as shown in Fig. 19. The frequency of mode 2 is equal to 79.84 Hz, which is close to the maximum response of acceleration. Fig. 8, shows that the load in the actual track condition directly affects this mode. It also shows that the modal displacement response of mode 2 is larger than the others in Fig. 14. Those factors commonly cause mode 2 to become the most dangerous mode, and the same can be assumed to modes