STRUCTURAL MODIFICATION PREDICTION USING INCOMPLETE MODAL DATA

摘要

In many situations where structural dynamics do not satisfy the requirement set by structural analyst, a structure has to be modified and its dynamic characteristics should be re-analyzed. In this paper, an effective method is developed to predict the changes of modal parameters due to the known structural modifications using complete or incomplete modal data of the unmodified structure. Two different iterative computational procedures have been devised for cases of moderate and large magnitudes of modification respectively. It is flexible in the sense that it can be used to calculate the changes of any individual natural frequency and mode shape of interest without the others being involved. To verify its practicability, the method has been applied to a 10DOF mass-spring system as well as a complicated truss structure. Numerical results show that the computational accuracy of the proposed algorithm is comparable to that of conventional eigensolution method(s) while its computational cost involved is much lower. Furthermore, it has also been found that the number of original modes available has little effect upon prediction accuracy as far as lower modes of the modified structure are concerned. Also, advantages, limitations and range of practical application of the proposed method have been discussed.