Cross section design for roads

[Coolmo]

Cross sections for roads in Civil 3D are pretty cool but I'm having a hard time actually designing ON the cross section and then putting that information back into a proposed surface or corridor. By "having a hard time" I mean I can't seem to find how to do this at all. I understand how to create an alignment, existing ground profile, proposed ground profile with vertical curves, assemblies for the road, a corridor, and a surface from this corridor with tiebacks to existing. Once all that's done I can simply place that information into the cross section. My only problem with this method is that you have to completely DESIGN the surfaces and other "stuff" before you place it in the cross section which basically means the cross section is a representation of the design. In my opinion, that's completely backwards.. isn't it? Cross sections for roads are suppose to be design tools themselves.

I guess here's the question. Is there any way to draw linework (lines, polylines, etc) on each cross section for each station and then tell Cicil 3D to place those objects, with reference to the cross section, into the proposed surface?

[smcgypsea]

I completely agree! My engineers scream that that is their job, to decipher the default info we give them, and make 'tweak' recommendations. I'd like a way to make CAD read those tweaks! (Right now we are still using LDD. Engineers and change...)

[brian.hailey933139]

I would disagree with both you. The cross section is simply a result of the design, just as the contours are a result of the surface. In days gone by, engineers would "design" contours. What they were actually doing is designing the surface in their mind and then draw the contours based on that surface. The surface existed, just not on paper or in a computer.

The same goes for the cross section. You don't change the cross section, you change the model. Now, if you have ancient engineers that are stuck doing things the way "they've always been done", you can still accomodate them. You can edit each individual corridor section and that will automatically update the cross section. The commands for that are under Corridors->View/Edit Corridor Section.

[Harold Pei Jr]

I would disagree with both you. The cross section is simply a result of the design, just as the contours are a result of the surface. In days gone by, engineers would "design" contours. What they were actually doing is designing the surface in their mind and then draw the contours based on that surface. The surface existed, just not on paper or in a computer.

The same goes for the cross section. You don't change the cross section, you change the model. Now, if you have ancient engineers that are stuck doing things the way "they've always been done", you can still accomodate them. You can edit each individual corridor section and that will automatically update the cross section. The commands for that are under Corridors->View/Edit Corridor Section.

I would have to agree. I've never seen anyone model a road or anything else off of a cross section. They've always modeled the section after the surface.

Brian, you mention that they can change the corridor section, would that mean that the surface and corridor will change as well?

[brian.hailey933139]

Brian, you mention that they can change the corridor section, would that mean that the surface and corridor will change as well?
Absolutely, as long as you have it modeled correctly.

[Aquaserpent]

I would have to disagree with both of you; I have been doing civil design for over 25 years now and use plan, profile and cross section geometrics to insure my design is complete and connected. Having started in the computer world on Softdesk version 7.0, and have progressed with each version to today’s Civil 3D version. I still use all three planes to insure a complete and connected design. The rule is if it will not work in one of the planes it will not work in the real world either. This will require your contractor to have to fake it, or in essence completes the design for you. You can not have an element hanging in space; it has to be connected back to the existing and or another proposed element.

[Harold Pei Jr]

I would have to disagree with both of you; I have been doing civil design for over 25 years now and use plan, profile and cross section geometrics to insure my design is complete and connected. Having started in the computer world on Softdesk version 7.0, and have progressed with each version to today’s Civil 3D version. I still use all three planes to insure a complete and connected design. The rule is if it will not work in one of the planes it will not work in the real world either. This will require your contractor to have to fake it, or in essence completes the design for you. You can not have an element hanging in space; it has to be connected back to the existing and or another proposed element.

I understand that, and as you put it, I'll have to agree. It sounds like you use the tools given to you (cross sections, profiles, etc.) to check your work, and possibly plan what you're going to do next for your design.
From what I was getting from the OP, it sounded like he wanted to use just the cross sections as design tools. I may have misinterpreted what was originally asked, and if I did, then I apologize.
The way I've learned is was to do the design, and use profiles and cross sections to check your work. Cross sections before hand would be used to help plan your design.

[Aquaserpent]

Sorry, I must have misinterpreted what you meant in your response. I apologize for any inference that you were incorrect, in your assessment. But I will say that I do use cross sections to make adjustments to my terrain models.

[Harold Pei Jr]

I've never used my cross sections to change my terrain. Though, I didn't realize you could show that change in your surface until recently.
My preference is to use it as a checking tool. Especially on problem areas, it's saved me a few times already.
Though, after what Brian had said, I'll have to look into using the cross sections as a tool to use to design the surface, figure out how it determines where each section goes from point A to point B, etc.

[Coolmo]

In my opinion, to simply check your work with what the computer spits out instead of being able to directly manipulate what it spits out is reckless. Especially in road cross sections, there are too many variables depending on existing features to simply build a model and have it show you the results. We do a lot of road widenings and tacking on turn lanes to existing roads and there's NEVER a typical situation. Some examples are: checking to see whether or not ditches flow and the methods you need to make them flow correctly (different tie-back slopes). You can't just stick with a simple 3:1 slope or your shoulder slope may need to change depending on the existing cross slope of the road due to a particular rollover. Civil 3D is good but it can't tell me when and where I need to overlay an existing road or mill up the road to achieve a cross slope. Wedging the asphalt is a whole other thing.

With all of this in mind I find it easier to cut the existing road sections and design all of these factors into each section as they are needed, on a section by section basis. After I have this polyline drawn on each section (that represents the proposed grade) I simply wanted to grab each one for each section and have it update the surface some how.

[sinc]

Civil 3D is good but it can't tell me when and where I need to overlay an existing road or mill up the road to achieve a cross slope.

Have you tried the "Mill and overlay" subassemblies?

[Coolmo]

Have you tried the "Mill and overlay" subassemblies?

Do they work on a section by section basis? Or even a foot by foot basis depending on existing features and other criteria?

[maurice.cote]

I have been designing roads for 15 years and use Horizontal, Vertical and cross sections.
The cross section is a design in itself and is tied to the alignments. Original ground is modeled and cross sections cut on station, then the design cross section overlayed on top of that. Superelevation, road widenings, graded ditches are all applied to these cross-section templates.

I hope this helps the original poster ... I am rather confused by designing contours then cutting sections???