PDA

View Full Version : 2011 Building Surface For Layout



jamesdmstronach282214
2011-07-26, 04:29 PM
Hello All,

I'm new to the community and had it reccomended by a fellow drafter/GET. Hopefully you can offer some help or direction.

I am working with C3D 2011 & have been for a few years now however most of my experience has been producing simple 2D legal plans. I've recently taken a new job with a general contractor who uses GPS guided machines and have started encountering headaches when building Tin files. My experience in the past with Tins has been limited almost exclusively to building models of existing ground from surveyed data and I have little to no experience with "reconstructing" surfaces from a provided design.

In specific what I'd like to know is how best to go about building a tin model to represent sub/finished grades for basic civil works (building excavations, parking lots, landscape features) from an existing set of plans. I've used my existing skill set and combined that with the available tutorials within ACAD as well as my google-fu but am often coming up blank.

Is there a good resource for this kind of surface building you can think of or direct me to? I've created a short list below of the few major problems I find myself running into:


What is the best way to create a planar surface (like a parking lot) when I have spot elevations and design contours or % slopes available? I find I always end up with bumps and irregularities.
What's the best way to describe a curb? I've tried using various types of breaklines but never seem to get the clearly defined curb line I'd like to see.
What are good mid-ordinate, supplementing, and weeding factors to use for features like parking lots/concrete work? How about for contour lines defining landscape elements?


Any help you can all provide is greatly appreciated. Even a "hey look over here" would be of great assistance. If anyone feels particularly beneficient I could even provide more specific examples of what I'm trying to build/represent.

Thanks in advance, you seem to have a great community here.

sinc
2011-08-01, 04:22 PM
I usually use Feature Lines. You can also use Corridors, which are a bit more involved to setup, but might work better in some cases. Most of the time, I use Feature Lines, and use the Elevation Editor to match the spot elevations in the plans. Then build the surface from only the Feature Lines (without adding FG contours). If everything is done right, your result should essentially match the FG contours (unless the Engineer created them by hand, in which case the FG contours are sometimes wrong, or unless the Engineer failed to give you adequate spot elevations, in which case you may have to come up with additional spot elevations based on percent slopes and/or FG contours).
In most cases, Feature Lines work the best. If you really want to see a well-defined curb in your 3D model, you have to make sure to model all breaks in the curb, e.g. FL + Top Front of Curb + Top Back of Curb. For construction calcs, however, the Top Front of Curb is usually extraneous.
I typically use 0.1' as midordinate distance. Some people like a smaller M.O., but for most construction, 0.1' works well without increasing the number of triangles in your TIN by too much.


Also, keep in mind that you can use the Stepped Offset command on Feature Lines. So if you want a well-defined curb line, you can create either your FL or TBC from the spot elevations, then offset that Feature Line to get the other parts of the curb.

jamesdmstronach282214
2011-08-02, 12:34 AM
Thanks! I just was noodling around with the feature lines today and thought that might be the solution. I'll give it a try as well as trying to exclude the contours and using the spot elevations only.

k0379179k
2011-09-07, 11:37 AM
Hi,
I have manged to create existing surface and creat new /proposed surface by right click on surface ( propspector tab) and new surface , then select from defiinition / contours .The proposed is created but what i need is to creat pathways with no slope , and slope pathway ,so do i create another surface by same way or use grading to create that but i have a non rectangular patway.

Many thanks in advance.

mjfarrell
2011-09-14, 11:09 PM
feature lines and or gradings should work well for your pathways.
for feature lines...you could draw the path outline...for one side
convert to feature line, and have it cet elevations from the design surface...
edit as required by adding or removing elevation points, and slopes...
then use a stepped offset to get to the other side...using your path width as the offset with O as the difference change in elevation.