GENERATION OF SIMULATED EARTHQUAKE MOTIONS CONSIDERING ACTUAL EARTHQUAKE ENVELOPE AND MULTI TARGET RESPONSE SPECTRUMS

Abstract

 Simulated earthquake motions whose response spectra correspond to the multi-target response spectra are often used to design earthquake-resistant nuclear power plant facilities. Therefore, it is advantageous to utilize simulated ground motions with an envelope curve of actual earthquake ground motions while designing these facilities. These motions can be generated by several methods. However, these methods cannot maintain the envelope curve of the simulated earthquake motions. A method to generate simulated earthquake motions that satisfies both the multi-target response spectrum and the envelope requirements does not exist.

 

 This paper proposed a novel method for generation of simulated earthquake motions by considering an actual earthquake envelope curve and multi target response spectra. This method is equivalent to the modal iterative error-correction method that is effective for solving inverse problems with significant discontinuities. Therefore, this paper proposed an improvement of this method for envelope curve and spectrum fitting.

 

 The findings of this study are as follows:

 (1) A novel method for generation of simulated earthquake motions that considers actual earthquake envelope curve and multi-target response spectra was developed. In this method, the input vector was changed from the amplitude spectrum to the acceleration vector of input motion. In addition, the targets were both the spectra and the envelope curve. Subsequently, the acceleration vector of input motion was changed (while maintaining a constant envelope curve) by using the modal iterative error-correction method to fit the target spectra and target envelope curve.

 

 (2) The proposed method was applied to sample problems to verify its accuracy. The results indicated that the simulated seismic motion accurately represented the envelope curve of the actual earthquake. Additionally, two acceleration response spectra were also created.

 

 (3) However, depending on the setting of the envelope curve, there was no suitable simulated ground motion. In such a case, it is effective to make a simulated earthquake motion by relaxing the restriction of the envelope curve, which is realized by increasing the time width of the envelope curve.