Quick Way to Build a Regular Structure

If a significant part of the model to be designed comprises a regular array of beams and columns, a special facility is provided to speed up the creation of all the necessary elements to define the fully connected structure. Even if the model is not completely regular in layout, it can be quicker to use this facility first and then to modify the design as necessary, rather than build up the design section-by-section.

The new model is stored in the hierarchy as described in Hierarchy.

1. From the main menu bar, check that automatic Profile allocation is On and Primary Node creation is Off, as in Automatic Profile and Primary Node Allocations (Storage areas and specifications need not be set yet.)

2. From the main menu bar select Create > Sections > Specials.

   The Section Creation window is displayed which lists all available methods:

   

3. To initiate the use of any available method select it from the Available Creations pane of the Section Creation window. For example, select Regular Structure, then click Dismiss.

   A Regular Structure window is displayed which gives you complete control of the whole design process. For the purposes of this user guide, this window is looked at in three distinct parts.

The areas labelled Column Data and Beam Data are used to set the storage areas, profile specifications and justification p-lines independently for the two types of section.

4. To enter each Storage area name, navigate to the Subframe and type CE.

   The name of the current element is automatically populated.

5. To enter the Profile specifications, click Profile to display the Section Specification window and pick the required specification and pline settings.

6. Click Dismiss to discard any information and close the Section Specification window when the settings are complete.

The Grid Origin area defines how the structure is to be positioned spatially.

The Datum setting defines the element, the reference axes determines the origin and orientation of the structure.

The Underside of Base-Plate sets the lowest point of the structure (underside of baseplate) relative to the datum axes. From this, you can define the elevations of the structural members relative to a plane which does not correspond to the base of the overall structure. In this case this is set to 1000, so that the bottoms of the columns are truncated at an elevation of 1000mm. (The effect of this is seen when the completed model is viewed.)

The XEast Spacings and YNorth Spacings lists specify the relative spacing between adjacent columns in the given directions. The Elevation list specifies the absolute elevations of the beams which represent the floor levels.

These settings creates 16 columns on a 4x4 rectangular grid, with a uniform inter-column spacing of 3000mm in the East direction and 5000mm in the North direction. The columns are 4000mm high, to accommodate two floors at elevations of 3000mm and 5000mm relative to the datum plane, but with the bottoms of the columns truncated so that they do not extend below the 1000mm elevation specified by the baseplate setting.

7. Select Trim sections to Plines, so that the beams have their lengths calculated to fit between the columns to which they are connected.

8. With view limits set for zone and view direction set to Iso 3, click Preview to display a ‘stick’ representation of the specified structure.

9. Check and, if necessary, correct the settings, then click Apply to create the structure.

   The sections first have the specified profiles applied to give them their 3D geometry, then they are trimmed to length and connected. The process involves a lot of calculation, and might therefore take a minute or two to complete; progress is shown in the status bar.

10. Click Dismiss to discard any information and close the Regular Structure window.

The structure can now modified by the removal of beams:

11. From the main menu select Delete > Identified and then pick the beams which are to be removed.

12. Press ESC and confirm the deletion, when prompted.

    You are left with some columns that do not have any beams connected to their upper ends. The height of these columns has to be reduced.

13. Rather than modify each one separately, select Utilities > Lists from the main menu.

    

14. If a list already exists select Remove > All to remove the list and select Remove > List to remove the list name.

15. Select Add > List to name the list, then use the Add > Identified option in the Lists/Collections window.

16. Add the columns into the list by picking them in the 3D graphical view. If a mistake is made, click the column again to deselect it, to exit, press Esc.

17. From the main menu bar select Position > Extend > By.

    

    You are prompted to ‘Identify Section’.

18. Pick any of the columns and then, when the Extend Section - Explicit window appears, select the new list as the item to be modified.

    Note: If a column is already selected you are not prompted to Identify Section.

    The Extend option list requires you to specify which end of the item is to be moved. You must adjust the upper end of each column, but is this its Start or its End? To check this, make any one of the columns the current element and select (from the main menu) Settings > Mark Section. The Start and End is tagged in the graphical view.

    

19. From the Extend drop-down list, select the point to extend from.

20. Select the Maintain Section’s Node Positions checkbox so that the positions of secondary nodes are not affected by the length adjustments (only really relevant if you move the Start positions).

21. Set the Extension by to a Distance to reduce the length of each item in the list.

22. Click Apply then click Dismiss to discard any information and close the Extend Section - Explicit window.

Note that the secondary nodes which were at the tops of the deleted columns are still present, even though they no longer serve any useful purpose.

To delete these:

23. Navigate to the Subframe.

24. Select Delete > Tidy Nodes from the main menu, which includes GENSEC element, JLDATU and FIXING elements (which are marked with aid graphics).

    A Tidy Nodes window is displayed populated with the redundant nodes that have been identified.

    

25. Select the Mark Nodes for Deletion checkbox to tag these nodes in the 3D graphical view, then click OK to delete them.