This study is concerned with a reliability analysis of a nuclear concrete containment structure under earthquake loadings. A failure model of a ring-shaped element for the concrete containment wall is developed. It is derived from the biaxial and 3-dimensional fracture criteria for concrete material. The harmonic stress distribution along the circumferential direction on a containment wall under horizontal earthquake loadings is also considered. The present failure model may be able to consider the effects of the initial stresses explicitly. 3-node axisymmetric shell elements are used for modeling the structure. The validity of the present failure model is investigated by checking the simple bounds of the expected outcrossing rate of the failure condition for a ring-shaped containment wall. Time history analysis is also carried out for checking the validity of the stress simplification made on the midsurface of a containment wall. From the numerical analysis, it has been found that the present failure model is reasonable and simple for the use of safety assessments of concrete containment structure under earthquake loadings.
