Dynamic soil-structure interaction problems are a major part of the seismic analysis and evaluation of the long-span bridges. The accurate modeling of major bridges with multiple spans for seismic analysis requires that the whole bridge and its foundations be modeled, usually using finite element method. This is specially so when nonlinear behavior is present in both the superstructure and the substructure. However, finite element methods for bridges having multiple spans crossing extended area are difficult to be implemented because of the enormous amount of computations. As a result, simplified models have been proposed for modeling of the foundations of the long span bridges. The effectiveness of conventional Winkler-type foundation models become questionable for the case of a large number of closely spaced piles, which often form the foundations of long-span bridges. A new approach for developing a discrete parameter models using genetic algorithms is introduced in this paper. This method gives the simplified Winkler-type foundation models with finite-element-method-like accuracy regardless the complexity of the problem. Simple preliminary results are presented. It is shown that the Winkler model constructed from genetic algorithms gives satisfactory result for seismic analysis. Due to the flexibility of the method, the model can be modified and even more simplified without severe loss of accuracy for any given purpose.
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