دانلود رایگان مقاله روش جدید برای تعدیل حرکات زمین با تبدیل موجک و بهینه سازی بدنه کولیدی پیشرفته

Abstract

In this paper a simple and robust approach is presented for spectral matching of ground motions utilizing the wavelet transform and an improved metaheuristic optimization technique. For this purpose, wavelet transform is used to decompose the original ground motions to several levels, where each level covers a special range of frequency, and then each level is multiplied by a variable. Subsequently, the enhanced colliding bodies optimization technique is employed to calculate the variables such that the error between the response and target spectra is minimized. The application of the proposed method is illustrated through modifying 12 sets of ground motions. The results achieved by this method demonstrate its capability in solving the problem. The outcomes of the enhanced colliding bodies optimization (ECBO) are compared to those of the standard colliding bodies optimization (CBO) to illustrate the importance of the enhancement of the algorithm.

7. Concluding remarks In the present study, a new method is proposed for modifi- cation/reconstruction of ground motions utilizing a metaheuristic algorithm and wavelet transformation. From the results obtained, the following conclusions can be derived: (i) The accelerograms are modified in time and frequency domain using the wavelet transformation such that the response spectrums get closer to the target spectrum. (ii) A common method for solving spectral matching problem is iterative wavelet-based approach and this procedure has some disadvantages.However,intheproposedmethod,thisproblem is formulated as a constrained optimization problem leading to some improvements such as: modification of a set of ground motion and handling the manual requirements. (iii) The Eurocod-8 is utilized for spectra matching requirements and definition of target spectra. In the proposed method, the penalty function is employed to satisfy the corresponding requirements. (iv) The problem is non-convex and has some local optima because of using the overlapping frequency domain in wavelet transformation having some constraints. Hence the selection of an efficient optimization algorithm is an important issue for handling this problem. (v) An improved version of the recently developed metaheuristic algorithm called enhanced colliding bodies optimization is used to reduce the error between the response and target spectra. A comparative study of ECBO and CBO algorithms on modifying four sets of accelerograms clearly indicate that the response modified spectrums obtained by ECBO are closer to the target spectrum than those obtained by the CBO. (vi) It should be noted that the purpose of this paper has been the introduction of a new method for spectra matching of accelerograms. This goal can also be achieved by considering different target spectrums, manual requirements, optimization algorithms and transformation functions such as wavelet packet and S transform.