Form Joint Assignment - Springs
Assigning a spring to a joint object is only meaningful if structural objects are connected to the joint object. Otherwise the spring will support air, so to speak; that is, it will not support anything. Either the joint object must be connected directly to a structural object or it must be on top of a floor-type shell object that ETABS can automatically mesh.
Important Note: It is possible to assign negative spring stiffness to a joint object as long as the total stiffness at the joint still remains positive (or zero). If some negative spring stiffness is assigned to a joint object, do it with great care because it can cause trouble. Negative spring stiffness at a joint during the analysis causes a structure to be unstable and thus ETABS terminates the analysis and provides an error message that there is an instability. ETABS does not check for negative spring stiffness before running the analysis.
Assign joint springs that are oriented in the global axes directions to joint objects as follows:
Select the joint object(s) to which a previously defined spring property is to be assigned. Both translational and rotational springs can be assigned to a joint object.
Click the Assign menu > Joint > Springs command to access the Joint Assignment -Springs form.
Select a spring property from the display list and click the Apply button to make the assignment. Any previously assigned spring properties will be replaced by this assignment.
To remove all assignments, select the joint object(s), highlight the None option, and click the Apply button.
Note that clicking the Modify/Show Definitions button will display the Point Spring Properties form, which can be used to define a new spring property.
When the Apply button is used, the Joint Assignment - Springs form will remain open until the Close button is clicked. This allows selection of another joint object(s), to which a different assignments can be made.
If only one assignment is being made to only one set of selected objects, the OK button can be used to both apply the assignment and close the form.
See also