VIBRATION CHARACTERISTICS OF SELF-MONITORING BENDER ELEMENT IDENTIFIED BY MODAL ANALYSIS

Abstract

To reveal vibration characteristics of bender element and help improving accuracy of shear wave velocity measurement in bender element test, the author has measured the vibration of a self-monitering bender element with a laser displacement sensor. The test results have revealed that the self-monitoring element shows complicated motion derived from at least two bending deformations not only in the length direction but also in the width direction.

By applying the modal analysis, the measured motion has been fitted to a series approximation which can be described by superimposition of some dominant vibration modes with different predominant frequencies including the two bending motions in the length and width directions. The fitted motion has well reproduced the observed motion by employing at least the two dominant vibration modes. Consequently, it has been concluded that the vibration characteristics of bender element can sufficiently be formulated by estimating modal parameters for the two dominant vibration modes.