Spectrum analysis with quadratic participation for seismic design of light secondary system

Response spectrum method based on the square root sum of the squares (SRSS) modal superposition technique is widely used in seismic design. Also, this method has recently been expanded by Wu et al. (1978 ), Leimbach et al. (1979 ) and Lin et al. (1980 ) to be capable of treating the multiple support response spectra input. The SRSS technique is justifiable by the statistical theory for earthquake motions which have smooth response spectra over a wide range of frequencies. However, it can cause significant errors in the response prediction of the light secondary or appended system such as the piping system in a reactor building. This drawback is brought about mostly by the improper application of SRSS rule to the modal superposition without regard to the predominant characteristic of the floor response spectra input.