Gore Area Grading

[onsionsi1]

Hi There,

I would like to ask about grading for gore area between main road and Semi Directional Ramp.

For Main Road i have a profile and superelevation.

For Semi Directional Ramp i have just known superelevation and i would like to make a grading for the connection between the Main Road and Semi Directional Ramp ( For Gore Area ).

As you know i have to respect the elevation for the connection between Main Road and Semi Directional Ramp ( Broken Bake line elevation as shown in attached file ).

By traditional ways it takes many days (trial and error). 

So, is there any way with Civil 3D Subassembly or other way to solve this issue in less time.

I'm very appreciate for your advice.

Thank you.

[sboon]

Yes this is possible. I use this method often for exit ramps and intersection turn slots.  I'll try to post more details and pictures in the morning.

[Joe-Bouza]

At the risk of sounding ignorant, and oversimplifying your situation; doesn't the gore grade itself between the main road corridor and the exit ramp corridor"? Or by marked point on the assemblies?

[onsionsi1]

I will very appriciate for your help.

Thank you.

[sboon · Accepted solution]

Sorry - it took longer to get back to this than I intended.

The basic idea to do this is to start from a baseline at the edge of the lane (the blue line) and immediately use a generic link to move the assembly left.  In the corridor targeting you will attach this link horizontally and vertically to a feature line extracted from the edge of the main road (at the magenta line).

The second step is to attach a right side lane to that point, which will also use targeting to stretch horizontally back to the lane edge - the same alignment that you started from.  You will want to make sure that the lane sub is set to use the appropriate superelevation parameters from the lane edge baseline.  In my example I manually created superelevation stations and filled in values for the Outside Right lane.

The thing to keep in mind is that a corridor baseline must have an alignment and a profile to build from, but in this case the profile is irrelevant - the assembly doesn't really use it.  I then added top surfaces to both corridors so that I could check the slopes, and cut a top surface profile at the lane edge so that I could see it.

Once the gore was finished I decided to add an assembly to continue the exit ramp beyond the gore.  I created one with a left lane attached, and made sure that the left side superelevation parameters of the alignment matched the right side values that I entered earlier.  This allows the lane to continue the slope transition through the curve.  Since the ramp lane now needed a design profile I used the top surface profile to start from and continued the design from there.  I then added the new corridor region and changed the corridor baseline to use the new profile.

I use this variations on this method for curb returns, entry and exit ramps or other situations where the design elevation should be specified by lane cross slope.

[sboon]

Joe ,

The problem is that it's very difficult to draw a design profile along the edge of the gore which can produce the desired cross slopes throughout the transition from the main road to the ramp.  The asphalt is rolling from one slope to another and widening at the same time.  The profile you need isn't a straight line, and doesn't usually fit a normal vertical curve either.

[Joe-Bouza]

Thanks Steve, I think I understand the complexities, but I'm having trouble following your description. The Blue line I see, is in the center of the main road and I do not see a magenta line.

The main road is the known , right? And the exit lane right edge is the unknown, correct? So could an alignment and profile be extracted from the main road to use for the exit ramp with an offset assembly targeting the the right edge baseline alignment?

Not trying to be ASA, only want to better understand the grading. I wish I can get your file but our FW prevents me from downloading

[sboon]

Sorry Joe - I should have specified that the lines I am referencing are from the image attached to the original post.

[Joe-Bouza]

LOL

now your explaination reads perfectly

[onsionsi1]

Thank you very much for your help and i'm very appreciated for that.

I will try to do your method soon

Thank you again.

[Anonymous]

Hello,

Sounds like a good method to do this. Which profile do you use for your new baseline though? 

How I modeled this in the past is as follows:

I create a "dummy" corridor to get my say: 2% cross fall from the main road.  Then I create a finsihed grade surface, and then a profile from surface and use this for my ramp profile for the gore area.

My ramp assembly at the gore area  has a left lane attached with superelevation assigned targeting to the inside edge of the gore area using a horizontal target polyline. Then I attach another lane subassembly  to the left (I ussually call this subassembly "GORE AREA") that targets a feature line extracted fron the main corridor edge of pavement, and use it for horizontal and vertical target.  This lane subassembly transitions the grades within the gore area between the two roads with different supers.

Past the gore area I use a separate design profile for the ramp ensuring is tying properly to my surface profile.

Hope this also give you some ideas for modeling.

Francisco

[onsionsi1]

I face some difficulties about how to create feature line elevation from top surface of main road and other thing i tried several time to let link offset and elevation to attach with the feature line but it didn't success.

As you can see in the attached the top surface is at lower left line and the yellow line is link offset attached to existing survey

So, what is the problem with me.

For your advice

Thank you.

[sboon]

You should be able to extract a feature line from the lane edge of the main road while maintaining a dynamic link to that corridor.  That will become your target for the other corridor.  One thing to remember is that a corridor cannot target to one of it's own featurelines.  You have to use a second corridor for the gore and ramp for this method to work.

[sboon]

---

Sounds like a good method to do this. Which profile do you use for your new baseline though?

You can use any surface profile.  The point of this method is that the corridor never actually uses it, except as a starting point for the link which moves the ramp lane over to the edge of the main roadway.

I create a "dummy" corridor to get my say: 2% cross fall from the main road.  Then I create a finsihed grade surface, and then a profile from surface and use this for my ramp profile for the gore area.

My ramp assembly at the gore area  has a left lane attached with superelevation assigned targeting to the inside edge of the gore area using a horizontal target polyline. Then I attach another lane subassembly  to the left (I ussually call this subassembly "GORE AREA") that targets a feature line extracted fron the main corridor edge of pavement, and use it for horizontal and vertical target.  This lane subassembly transitions the grades within the gore area between the two roads with different supers.

If I understand this method then you have two grade breaks - one at the outside edge of the main road and another at the inside edge of the ramp lane, with the grades "floating" in the space between them.  I'm pretty sure that you could achieve the same result using my method if you assign superelevation slopes to both the inside and outside lanes, and then have the inside lane controlling the gore.

---

[onsionsi1]

I'm very thankful and very appreciate for your effort.

Just i have final question.  My two surfaces ( Main Road & exit Ramp ) didn't match excactly and there is a difference for about 2 cm and you can see my query highlighted in the attached files.

So, do you know why?!!!  

Thank you again.

[sboon · Accepted solution]

It's hard to tell for sure but I would guess that the featureline extracted from the main road is interpolating the elevations at points where the ramp ties in.  Try increasing the frequency of the corridor sections in this area and see if that helps.

[onsionsi1]

Dear Mr.Steve,

For more clarification, you will see in the attached file Corridor view Editor.jpg (highlighted area) it's going right and two surfaces was matching each other but in the other attached file you will see that the two surfaces didn't match excactly (highlighted within two circles)and the difference is about 2 cm.

I will be very appreciate if you can find the solution for my problem.

Thank you.

[onsionsi1]

Yeah it is work with me.

Thank you very much and i'm very appreciate.

[Anonymous]

@sboon 

Hello, I am trying to follow the solution that you have provided and I am having issue with my assembly link. I have attached a "Link offset and Elevation Subassembly" from the C3D generic tool palette. I have assigned the subassembly  to target the broken back line (I created a feature line for this). It worked for the offset, but the elevation of the point uses the default value of 0m instead of the elevation of the feature line. I checked the profile of the feature line and it seems fine. Can you please help me with this issue?

Thank you!

[sboon]

Look down a little lower in the Target Mapping dialog that you posted.  There is a separate section for elevation targets.  You need to target the same featureline again.

Steve
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