RAM Concept ’s Complete Harmonic SRSS Superposition analysis is based upon a classical mode superposition method, also referred to as modal analysis. In this approach individual (uncoupled) modal equations are solved to determine the individual modal responses which are then superimposed to obtain the total response. This approach results in a complete time history for the total response and calculates accelerations and velocities. This analysis is performed for each harmonic individually to facilitate combination of the response factors. Since a complete time history for each harmonic results is known the results can be combined using direct algebraic summation. This method can be computationally time consuming.

This analysis requires a duration and time interval to be used in the calculations. The recommendation is to select a duration that will include a minimum of approximately 30 cycles of excitation, and a time interval that is at least 10 times shorter than the shortest harmonic excitation period. For most problems with normal footstep frequencies, a 20 second duration with a 0.01 second time interval will provide good results.