Simple Model of Frequency-Dependent Impedance Functions in Soil-Structure Interaction Using Frequency-Independent Elements |
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Authors: | Masato Saitoh |
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Affiliation: | Associate Professor, Dept. of Civil and Environmental Engineering, Saitama Univ., 255 Simo-Okubo, Sakura-Ku, Saitama 338-8570, Saitama, Japan. E-mail: saity@mail.saitama-u.ac.jp
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Abstract: | This study presents a methodology to make a simple equivalent model of frequency-dependent impedance functions of soil-structure interactions using a frequency-independent spring and dashpot, together with a proposed element called “gyromass.” The gyromass is frequency independent and is defined as a unit system that generates a reaction force due to the relative acceleration of the nodes between which the gyromass is placed. It is found that a model consisting of a spring, dashpot, and gyromass may generate various types of frequency-dependent impedance characteristics. This study proposes two types of simple models that express typical frequency-independent impedance functions of soil-structure interactions by using the gyromass. The advantage of these models is that the frequency-dependent characteristics can easily be expressed by a small number of elements and degrees of freedom. Moreover, they can be applied directly to conventional time-history analyses, even beyond the elastic region of the structural members. An example in which a simple model is applied to the time-history analysis of a soil-pile-superstructure system with an inelastic structural member when subjected to an earthquake wave is illustrated. |
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Keywords: | Soil-structure interaction Elastic foundations Soil-pile interaction Dynamic analysis Embedded foundations Frequency |
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