Analysis Case Data - Buckling Form

Access the Analysis Case Data - Buckling form as follows:

Click the Define menu > Analysis Cases command to display the Analysis Cases form.
Click the Add New Case button, or highlight a previously defined analysis case and click the Add Copy of Case or the Modify/Show Case button, to display the Analysis Case Data form.
Select Buckling from the Analysis Case Type drop-down list to display the Analysis Case Data - Buckling form.

The Analysis Case Data - Buckling form is used to view and change the definition of a buckling analysis case. A buckling analysis is always linear.

Stiffness to Use. Choose to solve for the buckling modes using the stiffness of the unstressed structure, or at the end of a nonlinear static or nonlinear direct-integration time-history analysis case. See Stiffness to Use for more information. If you are uncertain which option to use, choose the Zero Initial Conditions - Unstressed State option.
Load Applied. Buckling modes are always calculated with respect to a set of applied loads. Different buckling modes will result from different sets of loads. The loads from one or more load cases or built-in acceleration loads may be applied.

Important: All loads specified will be added and applied in combination. Only a single response will be calculated. Create different analysis cases to obtain separate responses to separate loads.

Load Type. Choose to apply a load case or a built-in acceleration load.
Load Name. Choose the load case name, or the global direction of ground acceleration, depending on the type of load. See Applying Acceleration Loads for more information.
Scale Factor. Enter a scale factor that multiplies the load before adding it to other loads applied. The buckling factor computed during buckling analysis will be with respect to the magnitude of the applied loads. For example, if you scale all the applied loads by a factor of ten, the buckling factor will be ten times smaller than if you had scaled the loads by a factor of one.

Add button. To add a load to the set of applied loads, enter the load type, load name, and scale factor at the top of the table, then click the Add button.
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 scale factor at the top of the table, then click the Modify button.
Delete. To remove a load from the set of applied loads, click on the load in the table to select it, then click the Delete button.

Number of Buckling Modes. Enter the number of buckling modes to be computed. We recommend that you compute three or more modes, since the buckling factor for the first few modes may not be very different.
Eigenvalue Convergence Tolerance. Calculation of buckling modes is an iterative process. Enter a relative tolerance to be used to determine when the eigenvalue (buckling factor) has converged. The default value is usually adequate.