Defining the Boundary Conditions Contd...
Next, the tops of the columns must be permitted to move only in a vertical direction so that superstructure loading may be applied.
To do this:
1. Alter the view of the structure in the main window so that the top of each column can be clearly identified.
2. Open the "Properties | boundary Conditions" dialog box and select the 'Attach' button.
3. Fix the translation in the X- and Y-directions and rotation about the Z-axis by clicking the relevant buttons.
4. Select the nodes at the tops of each column using the mouse.
5. Click the 'Apply' button. The nodes will change colour.