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The total base shear value does not correspond to the sum of modal base shear values
Linear calculation protocol of a seismic load case
The user expects, that the total base shear forces is the sum of the values for each mode in the table, i.e.
which are not the values provided in the output table.
The total base shear forces Fx and Fy at the bottom of the summary table of seismic load cases in the linear calculation protocol show the modal superposition value of the modal components, not the sum.
In the presented example, SRSS superposition is used. The correct calculation is
The same applies for the moments Mx and My.
For more information about modal superposition techniques, see the related theoretical background.