Ultimate load analysis of prestressed concrete reactor pressure vessels considering a general material law

A method of analysis is presented, by which progressive fracture processes in axisymmetric prestressed concrete pressure vessels during increasing internal pressure can be evaluated by means of a continuum calculation considering a general material law. Formulations used in the analysis concerning material behaviour are derived on one hand from appropriate results of testing small concrete specimens, and are on the other hand gained by parametric studies in order to solve questions still existing by recalculating fracture tests on concrete bodies with more complex state of stress. In a synoptical way it is pointed out how consideration of material behaviour is induced into the numerical computation. For analysing stresses and strains the so-called dynamic relaxation method is employed. Using the ultimate load calculation procedure thus developed, overload tests on concrete models of vessels or vessel components are recalculated. The progressive failure events during increasing internal pressure are shown. Measurements and observations in course of the tests are compared with computational results. The agreement between the experimental and computational results is satisfying on the whole. Thus, it is demonstrated that ultimate load design for prestressed concrete reactor pressure vessels can be carried out by calculations only, if a comprehensive formulation of the various processes in the material before and beyond failure is incorporated