wei sun BTH-AMT-EX--2008/D-07--SE, pp. 60. TEK/avd. för maskinteknik, 2008.
In this paper an outline is given of output only modal analysis, some of the known technologies are briefly introduced.
Due to the unknown input force of the output only modal analysis, the mode scaling factor can not be estimated, only the un-scaled mode shape can be obtained from Frequency Response Functions. This paper introduces one simple method of adding masses on the structure. The natural frequency shift caused by the structure mass change is used to get the scaling factor and scaled mode shapes.
The simple method is illustrated on a computer simulation of one four-degree-freedom lumped system and also on an output only measurement on a short bridge in the Blekinge Institute of Technology.