Increasing the accuracy of responses through improving equivalent linear analysis in comparison to using nonlinear analysis

摘要

The complex response method is easy to understand and the responses are not significantly influenced by one’s level of experience. However, this method makes extensive use of superposition and thus is only applicable to linear systems. Therefore, when observing nonlinear effects, the equivalent linear method is more traditionally used.Recent observations of extremely large earthquakes require engineers to consider the nonlinear effects on the ground materials. However, these huge nonlinear behaviors may not be appropriately analyzed using the equivalent linear method, as the accuracy of the responses in the high frequency region may be compromised.In this paper, the equivalent linear method in the frequency domain and the nonlinear analysis in the time domain have been compared. The applicability of the equivalent linear method in analyzing large strain levels has also been examined. The following improvements on the equivalent linear method to increase the accuracy on the responses in comparison to nonlinear analysis are suggested: 1) the use of strain dependent dynamic properties based on the least square method, 2) computation of stress by complex stiffness, 3) the use of effective strain coefficients as a function of input motions and 4) the introduction of the multi-equivalent linear method in order to improve the response at higher frequency regions.