Form: Generalized Displacements, Generalized Displacements Definition
A generalized displacement is a named displacement measure that is user defined. It is simply a linear combination of displacement degrees of freedom from one or more joints. For example, a defined generalized displacement named "DRIFTX" could be the difference of the UX displacements at two joints on different stories of a building. Another defined generalized displacement named AVGRZ could be the sum of three rotations about the Z axis, each scaled by 1/3.
Generalized displacements are primarily used for output purposes, except that a generalized displacement also can be used to monitor a displacement-controlled nonlinear static analysis.
Use the Define menu > Generalized Displacements command to access the Generalized Displacements form.
Use the buttons on the form to complete the appropriate action:
Add New Gen Displ button. Click the Add New Gen Displ button to access the Generalized Displacements Definition form.
Generalized Displacement Name edit box. Use the default or type in a new name in the edit box.
Type. Choose the type of displacement to be defined:
Translational option: The generalized displacement scales (with change of units) as lengths. Coefficients of contributing joint translations are unitless. Coefficients of contributing joint rotations scale as length.
Rotational option: The generalized displacement is unitless (radians). Coefficients of joint translations scale as inverse lengths. Coefficients of joint rotations are unitless.
Scale Factors. Note that joints are identified by their unique names in the model.
Add button. Click the Add button to begin specifying the coefficients for any joint translational and/or rotational components that contribute to the definition of the generalized displacement.
Delete button. Select the row of data to be deleted and click the Delete button.
Quick Add Selected Joints button. This button is enabled if the model is unlocked and a joint(s) is selected before the Define menu > Generalized Displacement command is used. When this button is clicked, the form is updated with the selected joints listed in the display area. If any of the selected joints already exists in the general displacement definition, those joints are skipped when the Quick Add Selected Joints button is clicked (i.e., the same joint is not included multiple times); a message displays indicating how many joints were skipped.
Modify/Show Gen Displ button
Select the named generalized displacement to be modified in the Generalized Displs list on the Generalized Displacements form.
Click the Modify/Show Gen Displ button to access the Generalized Displacements Definition form.
Make the necessary changes on the Generalized Displacements Definition form and click the OK button to close the form. Note the explanation of the Quick Add Selected Joints button in the preceding button procedure.
Delete Gen Displ button
Select the named generalized displacement to be deleted in the Generalized Displs list on the Generalized Displacements form.
Click the Delete Gen Displ button.
After running an analysis, use the Display menu > Show Tables command to display the Choose Tables form; click Analysis > Results > Displacement > Point Displacements - Generalized and then click the OK button to view the generalized displacements assigned to each joint in tabular form. Alternatively, the Model Explorer can be used in a similar fashion to display the data table: click Analysis > Results > Displacement > Point Displacements - Generalized.
With a deformed shape displayed, view the displacement components for a single joint by right clicking on a joint. The selected joint is highlighted and values are displayed in a floating Joint Displacements window. Clicking on any other joint updates the display. Clicking anywhere except on a joint closes the Joint Displacements window.
See Also