Form: Analysis Cases, Analysis Case Tree
An analysis case defines how loads are to be applied to the structure, and how the structural response is to be calculated. An unlimited number of named analysis cases of any type can be defined in SAP2000. The analysis case(s) is selected when the model is analyzed.
Note: Load cases by themselves do not create any response (deflections, stresses, and so forth). An analysis case must be defined to apply the load.
Before defining analysis cases, define any load cases or functions that will be needed:
For seismic analysis, the ground-acceleration loads are already built-in and do not need to be defined. For all other loads, use the Define menu > Load Cases command to define the loads to be applied.
For response-spectrum analysis, use the Define menu > Response Spectrum Functions command to create the necessary input acceleration functions.
For time-history analysis, use the Define menu > Time History Functions command to input the time functions.
For moving-load analysis, use the various options available under the Define menu > Bridge Loads command to define traffic lanes, vehicle live loads, and classes of vehicle live loads.
Tip: Every time a new load case is defined, the program automatically creates a corresponding linear static analysis case of the same name that applies the load. For a new model, the program creates a default load case called DEAD, which applies the self weight of the structure. The corresponding linear static analysis case is also called DEAD.
Use the Define menu > Analysis Cases command to access the Analysis Cases form and add, modify, or delete cases. The form also displays when the Analysis Cases item is selected and the Define/Show Analysis Cases button is clicked on the Bridge Wizard. Use the following buttons on the form to achieve the desired action:
Add New Case button.
Click the Add New Case button to display the Analysis Case Data form.
Use the various options on the Analysis Case Data form to define the new analysis case.
Add Copy of Case button.
Highlight an existing analysis case in the Case Name/Case Type display areas.
Click the Add Copy of Case button to display the Analysis Case Data form and create a new analysis case based on the settings of the selected case.
Use the various options on the Analysis Case Data form to change the necessary options to define a new analysis case.
Modify/Show Case button.
Highlight an existing analysis case in the Case Name/Case Type display areas.
Click the Modify/Show Case button to display the Analysis Case Data form.
Use the various options on the Analysis Case Data form to make the necessary adjustments to the case definition.
Note: If you change the definition of an analysis case that has already been run, results for that case and any case that depends upon it will be deleted.
Delete Case button.
Highlight an existing analysis case in the Case Name/Case Type display areas.
Click the Delete Case button to delete the analysis case.
Move Case Up or Down in List Click on an existing analysis case to select it, then click the Up Arrow or Down Arrow button next to the case list to move the selected case upward or downward in the list. Rearranging the case list is primarily for viewing convenience. An analysis case may depend upon other analysis cases that are above or below it in the list. During analysis, the cases will be run in the order required by their dependencies. For example, a response-spectrum case may be listed before the modal analysis case upon which it depends. When the analysis is run, the program will automatically run the modal analysis case first to generate the modes needed by the response-spectrum case.
Show Analysis Case Tree button. Click this button to display the Analysis Case Tree form. As the name suggests, the form displays a tree of the analysis cases defined for the model. Use the Expand All or Collapse All buttons on the form to show all cases or limit the display of cases, respectively. With the analysis cases displayed, right click on an analysis case name to display the form needed to edit that analysis case. With the form displayed, click the F1 key on the keyboard to display context-sensitive Help for that form.
Note: The Show Analysis Case Tree button also appears on the Set Analysis Cases to Run form.