Modal effective parameters in structural dynamics
Keywords:
dynamic structural analysis, vibration mode, modal response, parameter identificationAbstract
Modal superposition techniques are generally used to analyse low frequency dynamic responses of complex structures. Within this context, modal effective parameters allow us to characterize in a comprehensive and intrinsic manner the eigenmodes, and to compute frequency response functions while controlling truncation effects. The general formulation is first given, introducing the effective jlexibilities, masses and transmissibilities. These parameters provide a physical understanding of the dynamic phenomena; they also respect summation rules related to particular static properties so that truncation effects can be estimated in terms of residuals. Finally, they can be directly used for many purposes : selection of important modes, comparison of modal bases, elaboration of equivalent models, and computation of responses of any type.
Downloads
References
[BAM 71] BAMFORD R.M., WADA B.K., GARBA J.A., <
normal modes», Technical memorandum 33-380, Jet Propulsion Laboratory, Feb. 1971.
[CRA 81] CRAIG R.R. Jr., << Structural Dynamics - An Introduction to Computer Methods »,
Wiley, New York, 1981.
[GIR 85] GIRARD A., << Reponse des structures a un environnement basse frequence »,
N.TCNES 115, March 1985.
[GIR 86] GIRARD A., IMBERT J.F., << Parametres modaux effectifs et effets de troncature en
dynamique des structures >>, Colloque Structures des vehicules spatiaux, Toulouse,
December 1985, ESA SP-238, Aprill986, pp 81-86.
[GIR 87] GIRARD A., IMBERT J.F., << Modal Effective Parameters and Truncation Effects in
Structural Dynamics >>, Proceedings of the 5th International Modal Analysis Conference,
London, April 1987.
[GIR 91] GIRARD A.,<< Modal Effective Mass Models in Structural Dynamics»,
Proceedings of the 9th International Modal Analysis Conference, Florence, April 1991.
MB 78a] IMBERT J.F., MAMODE A., << La masse effective, un concept important pour Ia
caracterisation des structures avec excitation a Ia base », Mecanique, Materiaux,
Electricite, July 1978.
Structures », World Congress on Finite Element Methods, Bornemouth, October 1978.
[ITS 97] << PROTO-Dynamique User's Guide», INTESPACE, January 1997.
[MAC 71] MACNEAL R.H., << A Hybrid Method of Component Mode Synthesis »,
Computers and Structures, Vol. I, 1971, pp. 581-601.
[MSC 95] << MSC/NASTRAN Version 68 Reference Manual >>, MacNeal-Schwendler
Corporation, 1995.
[MOR 79] MORAND H.J.P., << Regles de sommation en mechanique vibratoire- Application
aux problemes d'interaction fluide-structure », Congres Choc et Vibration, Lyon 1979.
[NEU 64] NEUBERT V. H.,<< Lumping of Mass in Calculating Vibration Response», Journal
of the Engineering Mechanics Division, Proceedings of the American Society of Civil
Engineers, Vol. 90, No. EM!, February, 1964.
[PLU 54] PLUNKETT R., <
Proceedings, 2nd Nat/. Congress of Applied Mechanics, ASME, 1954, pp. 121-126.
[RUB 75] RuBIN S., << Improved Component-Mode Representation for Structural Dynamic
Analysis >>, AIAA Journal, Vol. 13, 1975, pp 995-1006.
[WAD 72] W ADA B.K., BAMFORD R.M., GAYMAN W.H., << Equivalent Spring-mass - a
Physical Interpretation>>, The Shock and Vibration Bull. W 42, Pt. 5, 1972, pp. 215-225.
[WIL 45] WILLIAMS D.,<< Dynamic Loads in Aeroplanes Under Given Impulsive Loads with
Particular Reference to Landing and Gust Loads on a Large Flying Boat >>, Great Britain
RAE Reports SME 3309 and 3316, 1945.
