Cul de sac design in Civ3d 2011

[LukeT]

I am having some problems trying to get a cul-de-sac into a corridor model.

 

All the online tutorials I have seen for cul de sac models work from the outside in - ie design the outside curb edge of the road and get the assembly to target the lane toward the middle of the cul de sac. But when I use the intersection tool that works from the road centreline outward.

 

Is it possible to create a cul de sac from the centreline? Or do I have to build separate geometry to the rest of the alignments around the outside of the cul de sac?

 

eg. Say I am designing a road that passes through an intersection then ends at a cul de sac. The best method I see is to build the intersection using the centreline of the road and generate offset alignments from the intersection tool. then use those offset alignments as a base to make new geometry just for the cul de sac.

The problem I see with this method is twofold - manually having to build the geometry is time intensive, and if the original alignment needs to be repositioned then the cul de sac may need to be remodelled. Compare it to an intersection: if the alignments move the intersection automatically updates.

 

Is there a better way of doing this, a different workflow?

 

Any links to good online tutorials to go into more detail would be greatly appreciated.

 

Luke

[BIGAL]

Normally a cul de sac is designed around the bowl not from the centre if you want to persist you can draw a very small arc at the end of your centreline and then design by going around the arc radially out to the kerb but its offset will change which is why its generally easier to design back in to the centre.

[LukeT]

I was aware that a cul de sac is typically designed around the bowl to the centre and stated as much in initial post.

 

I want to use Civil 3d to build road layouts for small scale urban planning with an intent to export to 3ds Max Design for visualization. I dont need high level of road detail, just basics, but I need the geometry of roads/intersections/cul-de-sacs to easily update as new layouts are designed and I need geometry that doesnt have gaps as that could cause problems in visualization.

 

So is there a better way of integrating cul de sacs into a road network that is predominantly built from road centre lines rather than outside edge?

 

If the only options are to manually calculate the cul de sac outside geometry and project inwards, or alternatively do a small arc at the end of the centreline (leaving the issue of the gap formed inside the arc), then I see those as two poor options and not conducive to a good workflow.

 

If this is a limitation of the software that would be good to know so I can adapt, otherwise details on a better workflow would be appreciated.

[CyberAngel]

Caveat: I haven't designed many corridors, and only one cul de sac. As I understand it, the way Civil 3D is designed, you can't design a cul de sac from the inside. That seems to be your question. It doesn't make much sense, since most of the time you're centered on the centerline and going out to the curb--then you have to switch gears, center your design on the curb, and go inward to the center point. The idea seems to be that you can slope the curb however you need to--in other words, they're trying to solve the problem for every possible situation, however complex, and making it needlessly complex for the most basic situations.

[BIGAL]

Another way forgot for a moment you design your road based on one side say left kerb not centreline but this alignment goes around your cul de sac ie left kerb to cl to right kerb. You change your road template once you get to the TP of the bowl to be a kerb only. Add a 3d centre point for bowl and hey you have a full 3d model that can be changed. Works well for straight cul de sacs curved gets a bit more interesting.

 

Other way is two roads second road starts at TP of bowl but uses grades and levels based on road section this is a usefull way to grade up to the bowl centre level.

 

The add on we use recognises multiple alignments as one road so it can jump from c\l to bowl edge

create edit kerb return

create edit roundabout

create edit cul de sac

create edit knuckle