A 2.5D finite element - boundary element model for vibration isolating screens

Vibrations in the built environment are generated by a variety of sources, such as industrial machinery and road and rail traffic. These vibrations may cause malfunctioning of sensitive equipment and nuisance to people. Different measures can be taken to prevent vibration issues. Common measures include a stiffer structural design and the use of base isolation at either the vibration source or receiver side. In an existing situation, such vibration countermeasures are often impracticable and a vertical vibration isolating screen, placed between the vibration source and the building, offers a good alternative. A vibration isolating screen is composed of a very stiff or soft material, so that the waves that impinge on the screen are reflected back to the vibration source. As vibration isolating screens are very expensive, a numerical model is a useful design tool. The use of a classical three-dimensional finite element model requires a large part of the soil to be modelled in order tomitigate wave reflections on the model edges that contaminate the results. Consequently, the number of degrees of freedom becomes prohibitively large. A two-dimensional model, with a smaller number of degrees of freedom, is unrealistic as the wave scattering has a three-dimensional character. A 2.5D model is therefore applied, where a Fourier transform of the longitudinal coordinate allows to represent the three-dimensional wave field on a two-dimensional mesh. The screen is modelled by 2.5D finite elements and the soil by 2.5D boundary elements. The methodology is applied to assess the efficiency of an existing vibration isolating screen near a tramway on a site in Haren (Brussels). The site is fully documented: the soil properties have been determined experimentally and the influence of the vibration isolating screen has been measured for various vibration sources. These tests allow for a validation of the numerical model. © 2008 by the Katholieke Universiteit Leuven Department of Mechanical Engineering All rights reserved.

ISBN:978-90-73802-86-5

Publication year:2008

BOF-keylabel:yes

IOF-keylabel:yes

Authors from:Higher Education

Accessibility:Open