The dynamic analysis of piping systems using pseudo-dynamic techniques

This paper describes an application of pseudo-dynamic techniques to the dyn amic analysis of piping structures. Essentially it consists in coupling a d irect time integration algorithm, such as the Newmark method, to an experim ental step. At each time step the integration algorithm generates a displac ement vector of the structure, which is prescribed for the test specimen. T his is mounted in a rigid test rig fitted with a set of displacement actuat ors and load cells at the level of the structure degrees of freedom. The lo ad cells allow the reading of the internal restoring force vector, which is fed back to the direct time integration algorithm in an actual time step. Further calculations for the velocity and acceleration vectors will define a new structure configuration by evaluating a new displacement vector refer red to the next time step. This procedure makes it possible to assess exper imentally a realistic stress distribution at sections of complex shape pipi ng parts. The method is a precise tool in dynamic analysis and, on being ca rried out in a quasi-static procedure, it operates with less expensive equi pment than is necessary in real dynamic test.