Application of finite element method for reference channel selection in ambient vibration analysis

Conventional modal testing on large structures is difficult to conduct in most cases due to a lack of suitable mean to excite the structure, or measure the applied forces. Operational modal testing is an alternative to determine the dynamic characteristics of such structures. One of the problems in conducting Operational Modal Analysis (OMA) on large structures is that it is not possible to measure all responses at all points on the structure. This is due to the limitation of the number of available accelerometers or the number of input analyzer channels and as a result the structure is required to be tested in several times. Consequently, multiple reference points are required to correlate between the different tests on the structure. In this paper a method is proposed for the selection of optimum reference points which is based on the maximum displacement for all the modes in the range. The method has been compared with the conventional correlation method showing its accuracy. The numerical investigation also shows that the resistance to noise for the proposed method is more than that of correlation method. The feasibility of method is demonstrated by numerical study on a clamped-clamped beam. Also, the capability of method has been demonstrated by experimental results of a long free-free beam.

Keywords:

Reference channel , Ambient vibration analysis , SSI-COV/Ref method , Best Reference Points (BRP) method