STRUCTURAL DYNAMICS AND FRACTURE CALCULATIONS OF THE BEHAVIOR OF A DN-425 TEST PIPING SYSTEM SUBJECTED TO TRANSIENT LOADING BY WATER-HAMMER

Within the scope of the German HDR safety programme, several tests wer e carried out to investigate transient pipe loading initiated by a sim ulated double-ended guillotine break event, and subsequent closure of a feedwater check valve (water hammer, blow-down). Numerical analyses by means of finite element programmes were performed in parallel to th e experiments. Using water hammer tests of a DN 425 piping system with predamaged components, the procedure of such analyses will be demonst rated. The results are presented, beginning with structural dynamic ca lculations of the undamaged piping; followed by coupling of structural dynamics and fracture mechanics computations with simple flaw element s (line spring); and finishing with costly three-dimensional fracture mechanics analyses. A good description of the real piping behaviour ca n be made by the numerical methods, even in the case of high plastific ation processes.