Abstract: Based on the characteristic period of the seismic influence coefficient curve, a new method to calculate Rayleigh damping is put forward that taking 1/5Tg and 1/Tg as the two target frequencies respectively. Time domain results based on the method put forward by Annie and the new method in this paper, and together with the frequency domain results based on equivalent linear method are compared by three single homogeneous soils with different thicknesses and a multilayered soil under three different ground motions. The results show that: the errors of the ground peak acceleration of the two forms of Rayleigh damping are within 10%; and the ground acceleration response spectra are consistent, but the method in this paper is not sensitive to soil thickness and input ground motions, that is, the error dispersions are small with different soil thicknesses and input ground motions. What’s more, the method in this paper is simpler and more convenient in application. For the method in this paper, the Rayleigh damping values can be determined by the characteristic period obtained from local site category, without the need of solving natural frequencies of soil.

Key words: seismic influence coefficient curve, characteristic period, Rayleigh damping, target frequency, soil seismic response