Cul De Sac Design.... Logic check.

[Robert Howell]

Good Day all.

I know how to design a bulb when it a standard crown. I just end my region at the beginning of the curb returns and from there I add a new baseline that transitions back to the road alignment and profile.

Here is my question.

For a bulb that is not crowned but has a crossfall of 4% (E to W) and climbing at 6% (S to E).

Under this situation if find creating a curb profile to be a little more complex. What I did was to use a typical transition assembly that had a 4% crossfall on it. I had this assembly transition beyond my proposed curb return alignment and then created a detached surface of the top of the bulb.

Now that the detached surface is created I created a profile of the finished top surface of the bulb using the curb return alignment. This basically "plotted" the elevation data of the curb return.

After that I added a design profile along the curb return ground profile and used this to attach my assembly to it. This assembly projects outward from the bul unlike the first example in which the assembly projected inward to create the paved travel way.

My question is. Does this method make sense and is there any other easier way to do it.

Thanks in advance

Robert Howell (LandMan)

[Robert Howell]

Fix to post: ..... and climbing at 6% (S to N.)

Sorry about that. The faster I type the more mistakes I tend to make.

[T_Bernhard]

Personally, I've only had to do two cul-de-sacs - both had a single crossfall. Because of circumstances, I did each a different way.

The first I did basically as you describe, except that I stopped the CL baseline at the start of the bulb and ran the entire bulb of the EOB/LOK alignment, kerb and daylights on the left, LaneToCrown on the right with a target to the CL elevation. It took some fiddling to make it right, but the result was good (the final design is almost identical to what they constructed - call the media!). I found that while the profile "trace" for the EOB was a good start, the biggest help in getting the design right was the dynamic contours, which helped me identify where in plan the high point was and where had to be raised/lowered.

The second was a bit different, both in design parameters and modelling technique, but in that instance it was the kerbs that were the critical factor, so having designed the kerbs to a minimum, I ran the centreline through, checked how it targeted and adjusted it from there. Again, the contours were a big help in visualising what I was getting rather than what I thought I was getting. I came back and plugged an asymmetrical island in the middle of that one too - looked good.

I don't know how that helps you, but I hope it assists you some.

Trevor

[Anonymous]

Hi Robert,

You can download a fully functional time limited trial version of Advanced
Road Design intersection from:

http://www.civil3dtools.com/

Treat the program as a teaching tool for cul-de-sac design. Just use the
tutorial drawing and try experimenting with the various design parameters
and observing the effect of changes to the design on the contours of the
design.

For me, the effectively instantaneous feedback from what I was doing when
adjusting various aspects of the design increased my understanding of the
vertical design of cul-de-sacs by an order of magnitude.

The specific situation you describe is easily treated by the program simply
by telling it to end the crown at the start of the cul-de-sac and adjusting
the kerb profile of the cul-de-sac.

Alternatively you can adjust the approach design cross falls and carry the
design centreline right through the cul-de-sac to achieve the same result.



--

Laurie Comerford
CADApps
www.cadapps.com.au
www.civil3Dtools.com

wrote in message news:5458994@discussion.autodesk.com...
Good Day all.

I know how to design a bulb when it a standard crown. I just end my region
at the beginning of the curb returns and from there I add a new baseline
that transitions back to the road alignment and profile.

Here is my question.

For a bulb that is not crowned but has a crossfall of 4% (E to W) and
climbing at 6% (S to E).

Under this situation if find creating a curb profile to be a little more
complex. What I did was to use a typical transition assembly that had a 4%
crossfall on it. I had this assembly transition beyond my proposed curb
return alignment and then created a detached surface of the top of the bulb.

Now that the detached surface is created I created a profile of the finished
top surface of the bulb using the curb return alignment. This basically
"plotted" the elevation data of the curb return.

After that I added a design profile along the curb return ground profile and
used this to attach my assembly to it. This assembly projects outward from
the bul unlike the first example in which the assembly projected inward to
create the paved travel way.

My question is. Does this method make sense and is there any other easier
way to do it.

Thanks in advance

Robert Howell (LandMan)

[mmccall]

I wonder if some creative use of the superelevation features would help in the modelling of cul-de-sacs like these.

... just and idea as I've never tried it.

[T_Bernhard]

You could possibly use SE successfully. But to my mind, you'd need an offset alignment (and thus a profile) anyway because of getting the kerbing to model correctly (perpendicular to the centre of the bowl). I used SE to give me the "trace" profile, but beyond that I can't see any advantage myself. But I've been wrong before.

Trevor