A numerical technique for simulating the dynamic stresses in piping systems with limited vibration measurements

A practical procedure is investigated for the determination of dynamic stresses in pipelines through the use of Finite Element Method (FEM) in dynamic analysis and field measurement vibrations at selected points. Numerical simulation of a dynamically loaded pipeline is used to establish the validity of the procedure. The analysis was carried out in the frequency domain with harmonic excitation of the selected pipeline structure. The results show that if the location(s) of the actual exciting force(s) or the translation and rotational "measured" displacements at the ends of a force free pipe segment are completely specified the stress picture resulting from the application of the procedure is exact. Alternatively, lack of coincidence between the vibration measurement points and the input force(s), or the use of only translational vibration inputs results in an approximate stress picture. The extent of the "error" in these cases is found to depend on the spectrum of the vibration frequency, the proximity between the vibration measurement points and the input forces, the density of these points and the type of vibratory-motions they measure.