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Access the Analysis Case Data - Nonlinear Direct Integration History form as follows:
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The Analysis Case Data - Nonlinear Direct Integration History form is used to view and change the definition of an nonlinear direct-integration time-history analysis case. A direct-integration time-history analysis solves equations for the entire structure at each time step, as compared with a modal time-history analysis that uses the method of mode superposition.
Load Applied options. Loads may be applied from one or more load cases or built-in acceleration loads, each scaled by the same or different time functions. All specified loads will be added and applied in combination.
Load Type drop-down list. Choose whether the load to be applied is a load case or a built-in acceleration load.
Load Name drop-down list. Choose the load case name, or the direction of ground acceleration, depending on the type of load. For acceleration loads, choose direction U1, U2, or U3. See Applying Acceleration Loads for more information.
Function drop-down list. Select the name of a previously defined time-history function that specifies the magnitude of the load as a function of time.
Scale Factor edit box. Enter a scale factor that multiplies the load before adding it to other loads applied. For acceleration loads, the scale factor has units of acceleration, and should be consistent with the length units currently in use. For load cases, the scale factor is unitless.
Show Advanced Load Parameters check box. Check this box to reveal the following additional columns in the applied-loads table.
Time Factor edit box. Use this parameter to specify a positive factor that multiplies the time scale of the time-history function. The default value is one, which does not change the function. This should normally be used for ground-motion records. However, modifying the time scale can be useful, for example, to change the period of sinusoidal loads, or to increase or decrease the time to apply ramp or pulse loads.
Arrival Time edit box. The arrival time specifies when the time function starts during the analysis. A positive value delays the start of the function. If the arrival time is negative, that portion of the function occurring before the analysis begins is ignored.
Coordinate System drop-down list. Specify a coordinate system in which the acceleration directions are measured. See Applying Acceleration Loads for more information.
Angle edit box. Specify an angle by which U1 and U2 are rotated from UX and UY in the specified coordinate system. See Applying Acceleration Loads for more information.
Add button. To add a load to the set of applied loads, enter the load type, load name, and other parameters at the top of the table, then click Add.
Modify button. To modify a load in the set of applied loads, click on the load in the table to select it, make any changes to the load type, load name, and other parameters at the top of the table, then click Modify.
Delete button. To remove a load from the set of applied loads, click on the load in the table to select it, then click Delete.
Number of Output Time Steps and Output Time Step Size edit boxes. The total time of the analysis is the number of output time steps multiplied by the output time-step size. Results will only be saved at time zero and the subsequent output time steps, although the analysis will compute intermediate results at every time step of every applied-load time-history function.
Damping. This display box shows the type of damping being applied. Click the Modify/Show button to specify the Damping to use for the analysis.
Time Integration Parameters. This display box shows the analysis method to be applied for performing direct-integration time-history analysis. Click the Modify/Show button to specify the Time Integration Parameters to use for the analysis.
Nonlinear Parameters. This display box indicates if the nonlinear parameters are the Defaults or are User Defined. Click the Modify/Show button to define the Nonlinear Parameters to use for the analysis.
See Also