Position Coordinates Menu

The ‘Modify Geometry> Position Coordinates’ sub menu provides a collection of geometry editing functions which all operate by repositioning the co-ordinates of the analytical node points. When then co-ordinate of a node point is changed, all analytical members which connect to that node point are also changed in geometry. This in turn will change geometry of the physical members.

Caution! – care must be taken when using these tools to manipulate geometry, since a change in nodal ordinates might affect the straightness of a physical member or integrity of a curved member. Where a physical member is no longer straight, it is automatically split into separate straight physical members.

Position on Straight Line

This function enables you to position a selected set of existing nodes on a straight line between a start node and end node.

Various options and methods are available to control the nature in which the node move to the straight line. Taking the example below, nodes 2 and 3 could move to any point on the line between nodes 1 and 4 to form a straight line.

The options allow this to be controlled as follows,

Equal Spacing – Node 2 and 4 are moved to form an equal spacing between 1 and 4

Retain X or Y or Z Co-ordinate – Depending on the axis of the intended straight line in relation to the original node positions, the node may only move in one of the three global axes to reach its position on the straight line. In the example above nodes 2 and 3 could have the retain X co-ordinate option to only move the nodes in the Z axis (blue arrows) to the straight line, or they could have the retain Z co-ordinate to only move in the X axis (green arrows) to the straight line. In this case the retain Y will have no effect since the line is on XZ plane.

Note that for certain geometries, some of these options may not produce a desirable result, for example if the straight line is in the X axis and the node to move is offset from the line in Z axis, then to retain the Z co-ordinate would not permit the node to move to a point on the straight line.

Perpendicular to Line – Nodes 2 and 3 will move in the direction perpendicular (orange arrows) to the straight line.

Retain adjoining member alignment – If say node 3 had an adjoining member whose projection intersected with the straight line, then the node would move in the axis of this member (dark green arrow) to the straight line.

Keep Physical Members Straight – If the node at the end of physical member moves and affects the alignment of this member, then other intermediate nodes in the physical member may be automatically adjusted to ensure the physical member remain straight and therefore intact as one physical member. Where this is not possible, the physical member will be split up in to separate straight physical members.

To position nodes on a straight line

1.Click on the ‘Nodes to Change’ to ensure you are in the nodal select mode

2.Graphically select the nodes to move onto the straight line. This can optionally include the start and end node of the straight line

3.Enter a ‘Start Node’ and ‘End Node’ in the inputs. These can either be manually entered, or by firstly clicking on the ‘Start Node’/’End Node’ button and graphically picking the node. Once the start node is graphically selected, the program automatically moves to the ‘End Node’ input. If no start and node and end node is entered, the program uses the largest and smallest node numbers of the selected nodes in step 2.

Note, the selected nodes need not be internal to the start/end node straight line. In the example given nodes 2 and 4 could be moved to the straight line between 1 and 3, or nodes 1 and 2 could be moved to the straight line between 3 and 4.

4.Review the move settings as described above.

5.You can optionally click on the ‘Preview Changes’ check button at the bottom of window, to enter the preview mode. This shows the changes to made in preview mode.

6.To action the change, click on ‘Apply’ button at the bottom of the window.

Tip - You may find it useful to annotate the node numbers and perhaps nodal co-ordinate values on the frame graphics during the use of this function. In cases where graphical changes in co-ordinates may be imperceptible, the annotated co-ordinate value may confirm that the appropriate change has taken place. This can be done using the ‘Nodes and Coordinates’ panel on the top tool bar.

Angle/Slope (XY Plane) check box - Alternatively to positioning selected nodes on a straight line between two nodes, they can be placed at a defined angle or slope ratio. This function only operates in the XY plane. Using this function

1.Click on the ‘Nodes to Change’ to ensure you are in the nodal select mode

2.Graphically select the nodes to position on the XY plane line.

3.Enter a ‘Start Node’. This can either be manually entered, or by firstly lick on the ‘Start Node’ button and graphically picking the node. This defines the start point on the XY plane slope line.

4.Choose the ‘Slope from XZ plane’ option, to then define the slope ration as a ‘1 in’ value. Eg, if you enter 4, this is an XY slope line of 1 in 4, i.e. a rise in Y of 1m for every X value of 4m. OR

5.Choose the Angle from XZ (degrees) option, to then define and angle from then horizontal plane

6.You can optionally click on the ‘Preview Changes’ check button at the bottom of window, to enter the preview mode. This shows the changes to made in preview mode.

7.To action the change, click on ‘Apply’ button at the bottom of the window.

Position on a Circle

This function enables you to position a selected set of existing nodes on a complete of part circle, defined by the circle global plane, centre point on that plane, radius, start angle on circle and finally angle increment between the selected nodes on the circle.

The selected nodes are positioned on the circle in order of the node numbers from smallest to largest. The original position of the node does not influence its new position on the circle.

To position nodes on a circle

1.Click on the ‘Nodes to Change’ to ensure you are in the nodal select mode

2.Graphically select the nodes to reposition on the circle.

3.Choose the global plane for the circle from the ‘About’, i.e. XY, YZ or XZ.

4.Enter the ‘Start Angle’ in degrees, measured anti-clockwise from the horizontal axis of the plane chosen.

5.Enter the ‘Increment’ angle in degree, which will the angle spacing between the nodes on the circle in a +ve angle anticlockwise direction. Enter a -ve angle for a clockwise direction.

6.Enter a ‘Radius’ in meters

7.Enter the pair of ‘Centre’ co-ordinate values on the plane of the circle. These can be entered manually, or by click on ‘Centre at…’ then picking a node to set the first co-ordinate, then clicking again on a node (likely the same point) to see the second plane co-ordinate.

8.The ‘Reverse X, Y and/or Z’ check boxes will invert (multiply by -1) the co-ordinate of the selected nodes in the select axes.

9.You can optionally click on the ‘Preview Changes’ check button at the bottom of window, to enter the preview mode. This shows the changes to made in preview mode.

10.To action the change, click on ‘Apply’ button at the bottom of the window.

Position on an Arch

This function enables you to position a selected set of existing nodes on an arch, defined by start and end nodes, an arch height (camber), and a rotation angle for plane of the arch from the vertical axis.

To position nodes on an arch

1.Click on the ‘Nodes to Change’ to ensure you are in the nodal select mode

2.Graphically select the nodes to reposition on the arch.

4.Enter a ‘Rotation’ in degrees. This determines the plane of the arch, with a zero or unspecified value being the vertical plane.

5.Enter a height of the arch in the ‘Camber (m)’ in meters

6.Choose between

a)‘Equal spacing’ to space the selected nodes evenly over the arch

b)‘Retain local value’ to shift the nodes to the arch perpendicular to the arch base line from their original position

7.You can optionally click on the ‘Preview Changes’ check button at the bottom of window, to enter the preview mode. This shows the changes to made in preview mode.

8.To action the change, click on ‘Apply’ button at the bottom of the window.