Harmonic load

There is no need to carry out a special dynamic calculation for a weakly damped structure. The method of expansion into eigenmodes can be used to determine the final amplitude of deformation line as a linear combination of the eigenmodes (the phase shift between individual eigenmodes can be ignored for weak damping). This type of calculation only requires the definition of logarithmic decrement, frequency of excitation impulse in Hz and amplitude of nodal impulses (see Defining the harmonic load case).

The results may than be reviewed the same way as results of a standard static calculation (see also Evaluating the results for harmonic load).

If the phase shift between individual eigenmodes cannot be ignored due to stronger damping, the problem must be solved as a response to a general dynamic load.