Introduction

In this chapter we will detail the various tools in place to help you modify the geometry of existing structures. This primarily deals with the geometry of ‘line’ type structural elements, e.g. beams, columns, bracing members, however, some of the tools can also be used to modify the position of grid lines and alter the geometry/position of Finite Element Surfaces. For clarity the following terms are used in this chapter.

Member – a structural line type element, e.g. beam, column, bracing, raking column.

•Analytical Member -  An analytical member is the line between two node points. Several analytical members may form one physical member.

•Physical Member – A physical member is formed from one or more analytical members that form a straight line, whose geometry is the start and end point of the physical member position. For example, in the case of a primary beam supporting one secondary beam, the primary beam will have two analytical members due to the connected node of the secondary beam. The physical member will be formed from the two analytical members. Physical members are used when applying section property definitions, member loading, geometric changes, and also for design purposes. Analytical members and physical members are therefore inextricably linked to each other. Physical members can either by straight or curved (pure arc), but not cranked.

Member Ends – the end of a physical member. This is not the same as a node, as a node is common to all analytical members ends that connect to it.

Node – A point at which analytical members join. An analytical member always has a node at either end.

FE Surface – A structural finite element surface. These surfaces are planar in geometry and their geometric shapes are defined by selected members to form their outer and inner boundaries. Hence if you change the geometry of a member which is used to define the boundary of an FE Surface, then the geometry of the FE Surface boundary is also changed.

Grid Line – A grid line is non-structural reference line in the horizontal plane (XZ plane) of the structure, whose geometry and placement can be independent of or attached to the structural geometry.

Graphical Entity Selection Techniques

While using many of Modify Geometry functions, graphical selection of entities such as members, FE surfaces and grid lines are required. Selection within the frame graphics window can either be done by

single select   - single left click on entity, or

window select - left click, hold down, move to draw window- and release to complete selection

In both select modes, the items that are about to be selected are highlighted in a preview select colour as described below. This confirms to you the selection that you are about to make.

To graphically select Members

The preview select colour is beige.

Single select    - Single click on/near member to add/remove from selection.

Window select - Window multiple members to add/remove from selection. Members are selected in window mode when their centre is included in the selection window.

The selected members will be highlighted in red.

To graphically select Member Ends

The preview select colour is cyan.

Single select - Single click near member end to add/remove from selection.

Window select - Window multiple members ends to add/remove from selection. Member ends are selected in window mode when the member end within a small tolerance (approx. 15 pixels) is included in the selection window.

The selected member end will be highlighted in a red dot a short distance from the end of the member.

To graphically select Nodes

Single select - Single click on/near node to add/remove from selection.

Window select - Window multiple node to add/remove from selection. A node is point and is therefore included in the selection if it is inside the window.

The selected node will be highlighted in a red dot.

To graphically select FE Surfaces

The preview select colour is yellow.

Single select -  move mouse pointer inside FE surface and close to one of the boundary edges until the yellow preview select colour is shown. Click to add/remove from selection.

Window select - when any of the edges of an FE surface are included in the window, the FE surface is added/removed from the selection.

The selected FE surfaces boundary members will be highlighted in red.

To select Grid Lines

The preview select colour is cyan.

Single select -  move mouse pointer close to the grid line until the cyan preview select colour is shown. Click to add/remove from selection.

Window select - when any of part of the grid line is included in the window selection, the grid line is added/removed from the selection.

The selected grid lines will be highlighted in blue.

By default, the selection operates on an add/remove basis, i.e. if a currently selected item is already in the selection, then it will be removed from the selection. In any of these selection modes hold down the

Ctrl key to exclusively add items to the selection (no items will be removed)

Ctrl + Shift keys to exclusively remove items from the selection (no items will be added)

The Modify Geometry Menu

From the top menu bar, the Modify Geometry menu contains a range of functions to allow you to quickly and easily modify the geometry of your structure.

Following any change using these functions, the Undo or Redo buttons in the Actions panel in the top tool bar can be used to undo or redo the changes made.