• Reduced mass
  • Kinetic energy of the distributed mass of the analyzed structure is compared with that of the corresponding reduced mass having the same displacement as the point of the structure to which the reduction is done.
  • Point to which the reduction is done is usually the point of maximal deflection
  • Equality relation for kinetic energies:

where v is the speed of a structure mass element dm

v₀ is the speed at the point of the reduction

• Reduced mass:
  If we suppose the harmonic movement, with the displacements u and u₀, corresponding to the speeds v and v₀

• Reduced compliance
  • Based on the static deformation by the load F in the point of reduction
  • If this force gives rise to the deflection u₀, the reduced compliance is given by:

• Alternative approach
  Supposing that we know one of two reduced elements and the resonant frequency

• Possible differences can be explained by the fact that the first approach is based on the static solution of system behaviour
  whereas the second approach is based on the dynamical behaviour