take the edge off CIVIL 3D

Take the following:

• 2 independent strings
• 2 independent profiles
• 2 independent slope batters

and resolve the intersection of the batters, with the option to add a channel width, all in a dynamic corridor…

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the challenge..

Normally a ‘template based design’ works on cross sections which go from the inside out.
In Civil 3D language, we create an Assembly with an insertion point and add subassemblies to project outwards.

What we are after for this exercise is a more peculiar pancake. We want to project from the outside in with specific grades, resolve the intersection point and maybe put in a ditch.

We do this with a specific subassembly and a ..marked point

1. Set up the Marked Point

There is really only one trick to this (and one thing to watch out for afterwards).
The trick is to use a generic link to position the marked point.

• Corridors > Create Assembly - call it ‘2Batters’
• Add the Sub Assembly LinkWidthAndSlope from the generic links

The Width and Slope are arbitrary because the values will be controlled by an alignment and profile.
- Side: Right
- Width: 5m
- Slope: 2%
- Omit Link: YES
The sole purpose of this link is to position the Marked Point so we ‘freeze’ it by setting omit link to YES.

• Add the Marked Point

Pick a sensible name for the marked point as we will refer to it later when inserting the link2Slopes sub assembly. - I’ve picked ‘SeanT’ in this case.

2. Add the LinkSlopesBetwenPoints Subassembly

Its under Generic Links.

• Select the Assembly as the insertion Point.
• Type the Marked Point Name (SeanT in my case)
• Specify Slope1, Slope2 and Ditch Width (can be 0)
• Dont worry when the graphics look strange - its a conceptual representation.

3. Form the Corridor

• Create Corridor, Pick Alignment 1, Profile 1 and the new assembly ‘2Batters’
• Click Targets, Set the Alignment2 and Profile2 as the parameters. This positions the marked point on the correct string so the software can calculate the corridor.

• The green batters in the image below below are produced - the roads had already been calculated but we are using the same strings so if the road design changes, the green batters can updated by rebuilding the new corridor model.

One thing to watch out for…

Well, first of all, don’t forget to rename the subassemblies to sensible names. In this case, there are not many so its possible to get away without renaming but its a bad bad habit to get into.

More importantly, the order of subassemblies has to be correct. The software has to know about the Marked Point before it encounters the 2Slopes subassembly looking for the marked point. To control this, right click on the assembly, select properties, go to the construction tab, right click on the Marked Point components and select ‘move up’ if it isn’t already at the top.

What else?

Marked Points can be used for a few other cunning purposes. Check out LaneFromTaperedMedian subassembly for starters.
You can also use marked points to form surface models from strings without building ‘real’ corridors - more on this, and reference planes in general soon.

cheers,
SeanT