REDUCED ORDER MODELLING OF ELASTOMERS USED FOR VIBRATION ISOLATION

Abstract eng:
Elastomer materials are employed as vibration isolators for a wide range of applications, for example vehicles, machines and buildings. In the present study, the transmission of low-frequency vibrations in multi-storey wood buildings is investigated, such buildings often involving layers of elastomers between structural components. In order to design buildings of adequate performance regarding noise and disturbing vibrations, it is desirable to have tools for predicting the effect of structural modifications. The long-term aim of the study presented here is to develop numerical models for such purposes, employing the finite element method. Modelling of vibration transmission in buildings results in very large numerical models and model order reduction is, therefore, required. A substructuring approach is adopted here, creating reduced models of complete buildings by partitioning them into substructures and assembling reduced models of these [1]. The computational efficiency of the reduced substructures increases with a decreasing number of degrees of freedom (dofs) at their interfaces. It is, therefore, beneficial to reduce the number of dofs at the interfaces between the substructures. The elastomers layers separating structural components in buildings can be regarded as coupling elements in the assembly of substructures. A methodology, consisting of two steps, for creating computationally efficient coupling elements representing the elastomers is presented here. The first step is to reduce the number of dofs at the interfaces of the elastomers. For this purpose, the accuracy of a number of methods for interface reduction, all based on the use of condensation nodes [2] which represent the motion of the interface surfaces, are compared. In the second step, the number of internal dofs of the elastomer models are reduced. Different methods for performing the reduction are compared with respect to the computational efficiency of the resulting coupling elements and to the work effort required of the practicing engineer for creating the elements.

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