Finite element analysis of ground borne vibrations in sensitive buildings using inputs from free field measurements T.N. Tuan Chik 1 , J.M.W. Brownjohn 2 , M. Petkovski 3 1,2,3 University of Sheffield, Department of Civil and Structural Engineering Sir Frederick Mappin Building, Mappin Street, Sheffield, S1 3JD, United Kingdom Email: [email protected], [email protected], [email protected] Abstract The development in modern fabs manufacturing of micro-electronics components like chip processors and laboratories fully equipped with high resolution devices requires very low level of vibration due to small allowable tolerances of the size of the equipment. As a result, the generated vibration level at the site is critical for estimating and providing suitable conditions for vibration sensitive facilities. For this purpose, ground borne vibration levels at specified locations are considered as input for the simulation analysis which is used in assessing the response of the structure in time domain and also in one third octave band frequency domain. This paper investigates the transmission of the amplitude of ground borne vibrations generated by external sources, into low rise structures housing sensitive facilities. Finite element analyses of the structure are used to predict the dynamic response of the structure, which is then compared with the free field measurements (input). The results of FE analyses are checked against the generic vibration criteria guidelines for vibration sensitive equipment. The results show that prediction based on dynamic response analysis can be used for selecting and designing an effective foundation system. The effect of the foundation system will provide guidelines for designing new vibration sensitive facilities. 1 Introduction The modern laboratories producing integrated circuits consisting of smaller, more tightly packaged and high-tech elements require greater precision and stability in micro-electronics manufacturing and evaluation equipment. There is a need for a better understanding of the effects of environmental low level vibrations on this type of equipment, in order to enable microelectronics facility designers to provide a suitable condition without costly overdesign of the structure. Manufacturers provide vibration specification for some, but not all sensitive equipment. With a few exceptions, the information provided is incomplete. In these cases further analyses have to be carried out to ensure that the equipment follows the existing guidelines. In this paper, the state of the art of low level ground borne vibration with a focus on vibration criteria for sensitive facilities and dynamic response of the buildings is assessed. Ground borne vibration induced by external sources such as moving traffic like trucks, trams, trains etc. can produce unacceptable vibration to humans and especially to buildings which accommodate very sensitive equipment [1]. The vibrations propagate through the ground and into buildings often causing vibrations at the resonant frequencies of various components of the building, such as floors and walls. Predicting the transmission of ground borne vibration waves to a structure is one of the problems that need to be taken into account when designing the building. The potential sites for advanced technology buildings are limited by varying degrees of ground borne vibrations from a variety of potential sources [2]. The vibration sensitive equipment has been investigated by Gordon [3] and his colleagues since 1980s, for various vibration sources, including ground borne vibration. There are several significant research contributions with theoretical and experimental studies related to vibration sensitive equipment. Gendreau et al. [4] investigated a desirable vibration environment at a site may be degraded by ground borne 759
Finite element analysis of ground borne vibrations in sensitive buildings using inputs from free field measurements
Jun 04, 2023
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