New method for nonlinear seismic analysis in time domain using frequency analysis with superposition of pulse waves

In seismic response analysis of soft ground, there are two analysis methods in time domain and frequency domain. The analysis method in frequency domain, represented by SHAKE, has been used for years in seismic design because of its convenience and being able to do the pull-back calculation of seismic wave and the waveform separation. It is also known that the nonlinearity of the soils in frequency domain cannot be reproduced accurately by equivalent linearization technique. Besides, the limitation of its application in finite deformation scheme is also well-known. It has been tried to solve this shortcoming of the equivalent linearization technique by changing the stiffness of the soil based on the maximum strain during the whole vibration time, the so-called the concept of the effective strain. Unfortunately the efforts did not bring a complete solution to the problem up till now. Therefore, in this paper, the method of breaking a seismic motion into a number of pulses, and using each of the pulses for the seismic response analysis of soft ground in frequency domain is proposed to deal with the nonlinear seismic behavior in time domain. As a verification of the new technique, the vertical array seismometry records and reproduction analysis of the revetment dynamic experiment were carried out and good agreement was confirmed.