When an external force is applied to spot welded structures, the load assigned to each spot is not uniform. Moreover, the fatigue life of a welded spot can not be set deterministically and thus the life has to be evaluated from the statistical viewpoint.
In this study, the distribution pattern of load imposed to individual spots was first examined experimentally, and, then, fatigue tests to obtain the life distribution were performed by using a number of specimens in single-spot and multi-spots types. By combining the distribution characteristics of load imposed to respective spots and the fatigue life distribution of single-spot joint, theoretical derivation was attempted on the fatigue life distribution of multi-spots joint. Finally, a good agreement was accomplished between the theoretical and experimental fatigue life distributions of this type of welded joints.