FURTHER DEVELOPMENT OF A STATIC SEISMIC ANALYSIS METHOD FOR PIPING SYSTEMS ... the load coefficient method

摘要

Currently the ASME Boiler and Pressure Vessel Code is considering a simplified Static Analysis Method for seismic design of piping systems for incorporation into Appendix N of Section HI, Division 1, of the Code. This proposed method, called the Load Coefficient Method, uses coefficients, ranging from .4 to 1.0, times the peak value of the in-structure response spectra with a static analysis technique to evaluate the response of piping systems to seismic events. The coefficient used is a function of the pipe support spacing hence the frequency response of the system and in general, the greater the support spacing the lower the frequency, the lower the spectral response, hence the lower the coefficient. The results of the Load Coefficient Method static analyses have been compared to analyses using the Response Spectrum Modal Analysis Method. Reaction loads were also evaluated with one important modification, a minimum support reaction load as a function of nominal pipe diameter has been established. This assures that lightly loaded supports regardless of the analytical method used will be loaded to realistic values and eliminate the potential for under designed supports. With respect to the accelerations applicable to inline components, a factor of 0.9 times the Square Root of Sum of Square of horizontal floor spectra peaks was determined to envelop the horizontal accelerations and a coefficient of 1.2 was shown to envelop the vertical accelerations. Presented in tins paper is the current form of the load coefficient method, a summarization of the results of the over 2700 benchmark analysis of piping system segments which form the basis for the acceptance of the method, and an explanation of the use of the method.