The direct identification of structural spatial properties

Lee, Hun Gon (1990) The direct identification of structural spatial properties. University of Southampton, Doctoral Thesis.

Record type: Thesis (Doctoral)

Abstract

The dynamic behaviour of many engineering structures can be predicted using a wide range of analytical and numerical methods such as the finite element techniques. However, there remains the need to be able to characterise the vibrational behaviour of the structures directly from experimental observations. The experimental model possesses information relating to the true spatial properties. An experimental model based upon spatial properties could provide a more useful form for comparison with the finite element idealisation than that based upon the modal properties. A number of important contributions in the identification of structural spatial properties have been made since 1970. There are two general forms of approach that have been adopted for the identification of structural spatial properties from experimental test data: calculation from modal model and transformation from frequency response data. Most techniques for the identification of spatial properties involve the transformation of the experimentally determined modal models using the orthogonality relationships. The direct identification method of spatial properties from measured frequency response functions is a possible alternative and offers significant advantages compared with the methods based upon modal data. This thesis describes a method for the direct identification of structural spatial properties from experimental observations and the investigation of some possible applications for the resultant models. The development of a direct identification technique has involved both computer simulations and practical experiments on beam and plate structures. It has been shown that reduction techniques can be employed to define a higher order form spatial model which can be used to enhance predicted results. Models have been compared directly with finite element idealisation. They have also been used to predict the effects of structural modification and to identify specific regions of structures within which there are modelling errors in mass, stiffness or damping properties.

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