On the Evaluation of Dynamic Stresses in Pipelines Using Limited Vibration Measurements and FEA in the Frequency Domain

A practical technique is investigated for the determination of dynamic stresses in pipelines through the use of Finite Element Method (FEM) and field measurement vibrations at selected points. Numerical simulation of a harmonically loaded pipeline structure is used to establish the validity of the technique in the frequency domain. The analysis is carried out for a fixed-hinged pipe model. The results show that lack of coincidence between the vibration measurement points (VMPs) and the exciting force, or the use of only translational vibration measurements (TVMs) produce an approximate stress picture. The extent of the “error” in these cases is found to depend on the density of the VMPs and the proximity between these points and the exciting force location. A safety-related risk assessment is applied to find the minimum distance between measuring points that is needed to meet design codes reliability specifications.Copyright © 1998 by ASME