Earthquake Calculation is made by Mode Summation Method in Time History, which is explained in TDY 4.8.3 and Annex 4B.3.
Location of GM Records for Mode Superposition Command
You can access the GM Records for Mode Superposition command under the Ribbon menu Analysis and Design tab Analysis heading .
Usage Steps
Click on the Analysis Settings icon.
In the analysis settings dialog , select Mode superposition method in time domain as the seismic forces calculation method.
Click the OK button to close the dialog.
Click the GM Records for Mode Superposition command.
Enter ground motion records for mode superposition method.
Click the OK button to close the dialog.
Do Analysis+Design (F9).
Seismic calculation will be made by Mode superposition method in time domain according to defined grounda motion records.