In Autodesk Civil 3D, junction structures have built-in resize behaviors that control how far you can move the rim, connected pipes, and sump up and down.
For example, if you move the top-most pipe invert up, raising its elevation to the point where it reaches the top of the structure (rim), the rim moves up automatically. This is to ensure that the pipe remains connected to the structure below the vertical pipe clearance area. The resize behavior allows the junction structure to maintain the frame height, cone height, and honor the vertical pipe clearance area, at the top of the structure, with no pipes connecting in to that part of the structure.
If you try to move a connected pipe into the structure’s vertical pipe clearance area, you will notice in your drawing that the top of the structure (rim) automatically moves up.
This is just one example of the resize behavior that is built in to junction structures. Other resize behaviors control how far you can move the junction structure’s rim or sump up and down.
Before editing junction structures, make sure you understand the following about the resize behavior:
- Elevation changes to the junction structure’s rim, connected pipes, or sump, could occur when the structure is grip edited, or when the referenced surface changes, or when pipe elevations are changed.
- The resize behavior of junction structures is independent of the behavior supplied by part rules. However, part rules can be configured so that they affect the structure resize behavior.
- Note that the resize behaviors explained here apply only to junction structures. They do not apply to inlet/outlet structures or null structure types.
- To verify that a structure is categorized as a junction structure, check that the Part_Type property is set to Struct_Junction. This is displayed on the Part Properties tab of the Structure Properties dialog box, in the Part Data section.
Moving Junction Structures That Are Connected To Pipes
This section describes the structure resize behavior that is invoked in the following situations:
- moving the top of a junction structure (rim) up or down
- moving a pipe that is connected to a junction structure up or down
- moving the bottom of a junction structure (sump) up or down
These changes to elevation in the junction structure’s rim, connected pipes, or sump, could occur because the structure is grip edited, or because the referenced surface is edited, or because a connected pipe elevation is moved. Any of these types of edits may result in elevation changes to parts of the structure.
Moving the Rim
When a junction structure’s rim (top of structure) is moved up, the rim simply moves to the new elevation. Connected pipes, and sump elevations, remain unchanged.
If you try to move a junction structure’s rim down, to an elevation where it violates the vertical pipe clearance area, you will not be able do so. The rim must always be located above the vertical pipe clearance area.
Moving Connected Pipes
When a pipe that is connected to a junction structure is moved up, to the point where it violates the vertical pipe clearance, the top (rim) of the structure automatically moves up so that the pipe does not touch the vertical pipe clearance area. In this case, the structure’s rim elevation changes (moves up).
If you move the pipe up, but not to the point where it touches the vertical pipe clearance area, then the pipe is moved up, but the rest of the structure remains where it is. In this case, the structure’s rim elevation remains unchanged.
Understanding the Control Sump By Property
When you are moving a connected pipe down, there is a part property associated with the junction structure that affects the structure resize behavior in this situation. That property is the Control Sump By property, and it can be set to Depth or Elevation. When this property is set to Depth, the sump depth is controlled by the depth, based on the lowest pipe invert. When this property is set to Elevation, the sump depth is controlled by the elevation value of the sump. The resize behavior is different depending on how this property is set on the structure.
When a connected pipe is moved down, to a point where the pipe moves below the connected structure’s sump elevation, and the Control Sump By property is set to Depth, since the sump elevation is set to be controlled by the depth, then the sump elevation will be moved down, to a new elevation. This new sump elevation will be the depth of the lowest pipe invert, minus the sump depth value.
If a connected pipe is moved down, to a point where the pipe moves below the connected structure’s sump elevation, but the Control Sump By property is set to Elevation, then the sump will automatically move down, to an elevation equal to the lowest pipe elevation. This sets the sump depth to zero.
Moving the Sump
Using the sump depth grip, you can move a junction structure’s sump up to the point where it meets the lowest connected pipe. You will be prohibited, however, from moving the sump up past the point where it touches the lowest connected pipe.
When you move a junction structure’s sump down, the sump will simply move to the new elevation, and not affect any connected pipes, or the structure’s rim. This behavior is the same whether the sump is controlled by depth or by elevation.
Moving Junction Structures That Are Not Connected Pipes
When there are no pipes connected to a junction structure, the rim and vertical pipe clearance take precedence over the sump.
Moving the Rim
When you move the structure’s rim up, and the Control Sump By property is set to Depth, the sump moves up the same distance as the rim.
When you move the structure’s rim up, and the Control Sump By property is set to Elevation, the sump moves up the same distance as the rim.
When you move the structure’s rim down, the sump does not move. You can move the rim down, but only to a location just above the sump. The rim must always be above the sump.
The following sections describe the resize behaviors on junction structures that have no connected pipes.
Moving the Sump
When you move the structure’s sump up, and the Control Sump By property is set to Depth, the new sump elevation can be below, at, or above the vertical pipe clearance area. This does not affect the rim elevation, and it sets the sump depth to zero.
When you move the structure’s sump up, and the Control Sump By property is set to Elevation, the sump can only move up as far as the bottom of the vertical pipe clearance area.
When you move the structure’s sump down, the sump is moved to its new location (new sump depth), but the rim elevation does not change.