To define a time history type using spectral parameters, use the following procedure.

1. On the Loading ribbon tab, select the Time History > Forcing Function tool in the Dynamic Specifications group.
   
   The Add New: Time History Definitions dialog opens.
2. Type an Integration Time Step value in seconds.
3. (オプション) Select the Consider Missing Mass Mode option if necessary.
4. (オプション) Select the Save option to generate a file with time history data.
5. Select the Loading Type for your data:

   Acceleration

   または

   Force

   または

   Moment

6. Select the Spectrum option in the Function Options group.
7. Specify the time data:
   1. Enter the maximum time (in second) in the generated time history in the Tmax field.
   2. Enter the time step (in seconds) in the DeltaT field.
   3. Enter the time at the end of rising acceleration in the T1 field.
   4. Enter the time at the end of the steady acceleration in the T2 field.
   5. Enter the time at the end of the acceleration decay in the T3 field.
   注記: The value of T1 must be greater than zero. Further, T3 > T2 > T1 and Tmax must be greater than T3.
8. Enter the damping ratio in the Damp field.
9. Specify the options:
   1. (オプション) Type a Random Seed value. 一意の乱数生成"シード"として使用する正の整数（1～2,147,483,647の範囲）を入力します。シード値ごとに一意の時刻歴が生成されます。"前のシード値で生成された時刻歴とは異なる"が統計的に等価の時刻歴を生成する場合は、この値を変更します。
   2. Enter the No of digitized Freq. This is the number of equally spaced frequencies at which the input shock spectrum is re-digitized (by interpolation).
   3. Enter the No. of Iteration which will be used to perfect the computed time history.
10. Click Add.