Select the Points tab in the Spectrum Definition dialog box to define spectra coordinate points.
To define a new spectrum, enter the appropriate value amount in the X and Y fields. The default values have been selected in the Abscissa (X axis) and Ordinate (Y axis) fields on the Spectrum tab. Notice if the Logarithmic Scale option has not been turned on for the mentioned axes. Clicking Enter or Add enters the point of the given values to the spectrum definition.
A previously defined spectrum may be modified. Once an appropriate point on the list is selected, the point coordinates are displayed in the X and Y fields. Enter new coordinates and click Modify.
A previously defined spectrum may be removed from the spectrum definition. After an appropriate point on the list is selected, click Delete.
Click Open to open a spectrum definition prepared in a text file. This file is formatted in two columns in which the amounts of appropriate values are given (value of Abscissa X and ordinate Y). Remember the settings of these values on the Spectrum tab in the Abscissa (X axis) and Ordinate (Y axis) fields.
Click Sa(T) ← F(t) to open the Response Spectra Calculations dialog.