Move Part of the Structure and Maintain Correct Geometry

For the purposes of this user guide, this section shows how to move columns and beams to increase the overall length of a structure. Horizontal beams and any bracing member connected to the moved columns have to be extended and, in the case of the bracing member, realigned to maintain the correct configuration.

The objective is to demonstrate the dominant joint concept (as described in Dominant Versus Subordinate Joints) and to show how easy it is to restore geometry between sections which has been disrupted by the movement of parts of a structure independently.

An example of the results from this procedure are shown below, where the thick black sections are moved explicitly and the broken lines indicate the new final configuration:

In order to make the bracing member realign itself to maintain the specified bracing gap, the joint to which it is connected must be dominant. To make sure of this, the joints at both ends of all bracing sections must be dominant (as would be normal practice).

In this section you are shown how to make dominant the joints at both ends of each of the four beams between the columns to be moved (for example: the beams shown shaded in the diagram).

1. From the main menu bar select Connect > Joint Dominant.

   Each joint is identified by picking the section end to which it is connected.

2. When prompted, pick both ends of each bracing member created in Add and Modify Simple Bracing (six picks) and the ends of all relevant beams (eight picks), then press Esc.

   Note: In normal practice, only the joints at the ends of the bracing members would be made dominant.

   For further information on joint connectivity, refer to Connectivity.

3. Use the Utilities > Lists facility from the main menu bar to create a new list.

4. Select the Add > List option.

5. In the description box insert the list name.

6. Click OK to name the list.

7. Select the Add > Identified option.

   At the bottom left of the screen you are prompted to ‘Identify Element or -Escape-’.

8. Click the columns to be moved (shown black in the diagram) which highlights them in red.

9. Press Esc and the highlighted columns are added to the list.

   

10. From the main menu bar select Position > Relatively (BY).

    The Position By window is displayed to allow an item to be moved by a given distance in a given direction.

    

    

11. From the Current Llist drop-down, select from the options available to set the item to be moved to the list which contains the columns (Current List).

12. Enter the required movement in the Offset text boxes, for example 200 mm XEast.

13. Click Apply, the columns are moved as shown in the figure below, or click Dismiss to discard any information and close the Position By window (for further information on positioning relatively refer to To Position Elements.

    

At first sight, this appears to be a rather disastrous result. However, as long all of the connectivity rules are set correctly, particularly the joint dominance settings, the problem can be easily rectified by the reconnection of all of the sections which should be connected to the columns.

14. From the main menu bar select Connect > Trim to Section > all attached.

15. When prompted, pick each of the four columns in turn, then press Esc to restore the correct geometry.

Note: The Trim to Section differs from the Trim to Pline option, which was used before, in that Trim to Section maintains the pline connectivity that exists, and so retains any previously defined trimming, whereas Trim to Pline resets the connectivity to an explicit or rule-defined pline.

For further information on connectivity, refer to Connectivity.