Modal Combination in Response Spectrum Analysis of Piping Systems

Abstract

Modal combination methods in the response spectrum analysis of piping systems have been investiaged. Two particular effects are identified, viz, (i) the residual rigid response, also known as the higher modes effect (HME); (ii) the correlation between the modal response and the rigid response. Gupta’s method accounts for both these effects. It is shown that Gupta’s method gives results which are much closer to the direct integration analysis results than are the results obtained from any other modal combination rules which ignore either one or both of the foregoing effects.