Harmonic Response of a Piping System Considering Pipe - Support Friction via HFT Method

The harmonic response of piping systems is in general estimated considering linear behavior, i.e. neglecting pipe-support dry friction, shocks between adjacent pipes or between pipe and supports, unidirectional supports, gaps, etc. Under this hypothesis, harmonic analysis is straight forward for a forcing frequency and not specially demanding in terms of computational cost. On the contrary, if any nonlinearity is taken into account, integration in time is required until the system achieves a steady-state solution, which demands dealing with initial conditions, intensive computation and long calculation times. In the particular case of support friction, vibration amplitudes calculated using the linear assumption may be well overestimated for some systems or conditions, thus misguiding designers and analysts, which traduces in excessive cost in system construction. In this work, the Hybrid Frequency-Time method (HFT) is used to calculate the steady state amplitudes of a piping system subjected to harmonic excitations and considering pipe-support friction. Comparisons between a full integration scheme and the proposed methodology are presented and discussed for a typical system. Results show that the HFT method is a valid practical option to estimate the harmonic response of a piping system when considering support friction.Copyright © 2011 by ASME