Force Measurement in Vibration Testing - Applications to Modal Identification

Abstract

The paper first concentrates on the fundamentals of the vibration behaviour of a structure under base excitation. The equitations for the structural accelerations and the dynamic forces at the interface are presented and discussed. The principles of modal identification for structures under base excitation including the determination of the effective and modal masses are explained. Then the practical measurement of the interface forces, consisting of the resultant six-degree-of-freedom components, is described and the utilised force measurement devices are presented. The application of the modal identification method is demonstrated on a laboratory test structure as well as on a more complex structure. Examples for typical measurement data and the extracted modal parameters are shown.