Abstract
Simulation analysis is an effective method for assessing building safety after an earthquake. This kind of analysis is effective for evaluating foundations or piles, whose safety cannot be confirmed by a visual check.
During such analyses, the input motion should be set to reproduce observed waves at observed points. In these cases, the modal iterative error correction (MIEC) method can be used to set the input motion even if the analysis model exhibits a nonlinear behavior. However, how to choose the mode for correction is difficult. Using a selection method by a singular value calculated by singular value decomposition, the previous paper presented a case, where the convergence calculation did not stabilize, and led to a divergence.
This study proposes a new mode selection method to stabilize the convergence calculation. The outline and details of the method are described, and the results of the experiments performed to confirm the method precision are presented.
The findings of this study are as follows:
(1) This study proposed two mode selection methods. One is the method of selecting modes by “the norm ratio of the residual vector.” This method selects the modes until the main shape of the residual vector can be represented. The second method is the method using the “norm of incremental input vector,” in which modes are selected until the norm of incremental input vector reaches a threshold for avoiding excessive input increment.
(2) The proposed methods were applied to a sample problem to confirm their accuracy. As a result, both methods can stabilize the convergence calculation through the MIEC. However, from the viewpoint of avoiding the unnecessary high-frequency component in the identified input motion, the method using “the norm ratio of the residual vector” is superior to that using the “norm of incremental input vector.”
