On the Analysis of Rotor-Bearing-Foundation Systems

  • Katia Lucchesi CavalcaEmail author
  • Eduardo Paiva Okabe
Conference paper
Part of the IUTAM Bookseries book series (IUTAMBOOK, volume 1011)


This work presents a methodology to analyse the influence of the foundation or supporting structure on the rotor-bearings system. A frequency response analysis of the complete system was accomplished by considering physical co-ordinates for the rotor-bearings system and principal co-ordinates for the foundation. The mathematical procedure applied a modal approach to the supporting structure, using modal parameters of generalised mass, damping ratio and natural frequency, which were calculated from the frequency response functions (FRF) of an actual structure. Convergence of the method was verified and the effect of the flexible foundation on the complete system response was analysed. A new formulation for the Mixed Co-ordinates method was presented to evaluate the influence of the supporting structure on the directional response of a rotor. An analysis of the directional frequency response function (dFRF) of the complete system was accomplished considering directional co-ordinates for the rotor-bearings system and principal co-ordinates for the foundation. These results were compared to the conventional FRF procedure.


Flexible structures Mixed co-ordinates Modal parameters Complex modal analysis 



The authors would like to thank FAPESP and CNPq for the financial support for this work, and LAMAR team for the technical support. The authors also would like to acknowledge the invaluable contribution of professors Hans Ingo Weber and Nicoló Bachschmid to their scientific education in the rotor dynamics field.


  1. 1.
    Weber, H.: Über das gemeinsame Schwingungsverhalten von Welle und Fundament bei Turbinenanlagen. VDI-Berichte 48, 55–62 (1961)Google Scholar
  2. 2.
    Gasch, R.: Vibration of large turbo-rotors in fluid-film bearings on an elastic foundation. J. Sound Vib. 47(1), 53–73 (1976)zbMATHCrossRefGoogle Scholar
  3. 3.
    Morton, P.G.: Measurement of the dynamic characteristics of a large sleeve bearing. J. Lubr. Technol. 93(1), 143–155 (1971)CrossRefGoogle Scholar
  4. 4.
    Nicholas, J.C., Barret, L.E.: The effect of support flexibility on critical speed prediction. ASLE Trans. 29(3), 329–338 (1986)Google Scholar
  5. 5.
    Vance, J.M., Murphy, B.T., Tripp, H.A.: Critical speeds of rotating machinery: computer predictions vs experimental measurements. Part I: The rotor-mass elastic model. ASME paper VIB85RD-142 1–8 (1985)Google Scholar
  6. 6.
    Gasch, R., Maurer, S., Sarfeld, W.: Soil influence on unbalance response and stability of a simple rotor-foundation system. J. Sound Vib. 93(4), 549–566 (1984)CrossRefGoogle Scholar
  7. 7.
    Bachschmid, N., Bernante, R., Frigeri, C.: Dynamic analysis of a 660 MW turbogenerator foundation. In: International Conference Rotordynamic Problems in Power Plants, International Federation for the Promotion of Mechanism and Machine Science, Rome, pp. 151–161 (1982)Google Scholar
  8. 8.
    Buckles, J.R., Rouch, K.E., Baker, J.R.: Modeling support effects – finite element and experimental modal methods. In: Proceedings of the International Gas Turbine and Aeroengine Congress & Exhibition, ASME, New York (1996)Google Scholar
  9. 9.
    Cavalca, K.L.: L’Interazione tra rotori e struttura portante: metodologie per la sua modelazione. Ph.D. Thesis (in italian), Dipartimento di Meccanica, Politecnico di Milano, p. 143 (1993)Google Scholar
  10. 10.
    Cavalcante, P.F., Cavalca, K.L.: A method to analyse the interaction between rotor-foundation systems. In: 16th International Modal Analysis Conference(IMAC98), Santa Barbara, USA (1998)Google Scholar
  11. 11.
    Feng, N., Hahn, E.J., Sestieri, A.: A combined finite element/transfer matrix approach for including foundation effects on the vibration behaviour of rotating machinery. In: Proceedings of Sixth International Conference on Vibrations in Rotating Machinery, Institution of Mechanical Engineers, Bath, pp. 529–534 (1992)Google Scholar
  12. 12.
    Krämer, E.: Dynamic of Rotor and Foundations. Springer-Verlag, Berlin, p. 383 (1993)Google Scholar
  13. 13.
    McConnell, K.G.: Vibration Testing Theory and Practice, 1st ed. John Wiley & Sons Inc., p. 605 (1995)Google Scholar
  14. 14.
    Edwards, S., Lees, A.W., Friswell, M.I.: Experimental identification of excitation and support parameters of a flexible rotor-bearings-foundation system from a single run down. J. Sound Vib. 232(5), 963–992 (2000)CrossRefGoogle Scholar
  15. 15.
    Bachschmid, N., Pennacchi, P., Vania, A., Gregori, L., Zanetta, G.A.: Unbalance identification in a large steam turbogenerator using model-based identification and modal foundation. In: Proceedings of Eighth International Conference on Vibrations in Rotating Machinery, Institution of Mechanical Engineers, Swansea, pp. 383–392 (2004)Google Scholar
  16. 16.
    Cavalca, K.L., Cavalcante, P.F., Okabe, E.P.: An investigation on the influence of the supporting structure on the dynamics of the rotor system. Mech. Syst. Signal Process. 19, 157–174 (2005)CrossRefGoogle Scholar
  17. 17.
    Weiming, L., Novak, M.: Dynamic behaviour of turbine-generator-foundation systems. Earthquake Eng. Struct. Dyn. 24(3), 339–360 (1996)Google Scholar
  18. 18.
    Lee, C.W.: Vibration Analysis of Rotors. Kluwer Academic Publishers, Dordrecht, p. 312 (1993)Google Scholar
  19. 19.
    Okabe, E.P.: Rotor-Structure Interaction: Theoretical-Experimental Model. Ph.D. Thesis (in portuguese), Campinas, Departament of Mechanical Project, Faculty of Mechanical Engineering – Unicamp, p. 177 (2007)Google Scholar

Copyright information

© Springer Science+Business Media B.V. 2011

Authors and Affiliations

  1. 1.Laboratory of Rotating Machinery, Faculty of Mechanical EngineeringUniversity of Campinas, UNICAMPCampinasBrazil

Personalised recommendations