AN ASSESSMENT OF SOME OF THE DIFFERENT METHODS FOR ESTIMATING DAMPING FROM FULL-SCALE TESTING

The paper examines some of the different methods for obtaining damping from full-scale measurements on structures such as tall buildings. In particular it examines the practicalities and accuracy of the various methods. Full-scale measurements can be divided into forced or ambient categories. The paper outlines the considerations necessary when estimating damping from forced vibration tests, gives examples, and assesses the accuracy that is likely to be achieved. The paper then examines the problems of estimating damping from full-scale measurements of the response of structures to wind loading and other random processes. These estimates are statistically based and are generally less accurate than those from forced vibration testing. The problems encountered in obtaining data which is both stationary (a prerequisite for most random data methods) and sufficiently long that accurate characteristics can be calculated from it, are examined. The concept of selective ensemble averaging, which helps to overcome some of the stationarity problems, is explained.