On the extension of global vibration modes with Ritz-vectors needed for local effects

Karim Sherif, Wolfgang Witteveen, Hans Irschik, Helmut Holl, Karl Mayrhofer

Research output: Chapter in Book/Report/Conference proceedingsConference contributionpeer-review

5 Citations (Scopus)


In Ritz-vector based model reduction techniques, the problem-oriented combination of different kind of Ritz-vectors may significantly influence the quality of the reduction base. It is common to combine global vibration modes with Ritz-vectors, which are necessary to characterize local effects. Even if the global vibration modes and the local Ritz-vectors may be separately orthogonal with respect to the mass and stiffness matrix, the combined reduced system is usually not decoupled. By using common decoupling strategies the separation of the two mode groups is lost. In this contribution, we will present a transformation procedure in order to obtain a combined and decoupled mode base, which is still separable into global vibration modes and Ritz-vectors due to local effects. Due to the clear separation of the two kinds of modes it is possible to give a frequency limit for the relevance of the inertia effects of the second mode group. In case the inertia effects of the second mode group may be neglected, the dimension of the differential equation of motion can be reduced once more again. At our theoretical considerations, an example is presented for the sake of illustration.

Original languageEnglish
Title of host publicationLinking Models and Experiments - Proceedings of the 29th IMAC, a Conference on Structural Dynamics, 2011
Number of pages10
ISBN (Print)9781441993045
Publication statusPublished - 2011
EventIMAX XXIX - Jacksonville, Florida, United States
Duration: 31 Jan 20113 Feb 2011

Publication series

NameConference Proceedings of the Society for Experimental Mechanics Series
ISSN (Print)2191-5644
ISSN (Electronic)2191-5652


ConferenceIMAX XXIX
Country/TerritoryUnited States
CityJacksonville, Florida


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