12.9.1 Modal Response Spectrum Analysis

Seismic load determination is made automatically according to the selected Modal response spectrum analysis method.

In the Modal Response spectrum analysis, mode shapes are taken as basis in the distribution of the total earthquake force. This method is to evaluate the equations that give the behavior of multi-degree of freedom systems separately for each mode shape. Unlike the equivalent lateral force method, in determining the total earthquake strength, the number of vibration modes depends on the mass participation ratio and many modes affect the behavior.

Calculation methods can be selected from the Analysis settings - general settings tab.