Vibration of linear structures having internal material damping is considered. Energy supplied to such structures by external dynamic loads and mechanical energy flow inside these structures are investigated. The paper aims at presenting and discussing relations which are useful when studying energy transmission through mechanical systems. Special attention is paid to the case of stationary harmonic vibration, but general stationary vibration is also discussed. Continuity equations for the active and reactive mechanical intensities are derived for a solid continuum model. Limits for the active and reactive power supplied to a structure in terms of structural and loading properties are also established. Numerical examples with discrete, continuous and discretized structures demonstrate the results obtained.

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