SAP2000 can be used to determine response spectrum from a user-input time history of ground motion as follows:
- Define the time history function using "Define > Functions > Time History Menu" menu command.
- Define time history load case using "Define > Load Cases > Add New Load Case" menu command.
- Run the time history analysis.
- To determine response spectrum of the ground motion, select a fixed joint and use "Display > Show Response Curves" menu command to display the response spectrum for the selected joint:
