Generic Links

Generic links are subassemblies used in a corridor model to meet specific needs where a pavement structure is typically not required.  They can often be used to model in areas grading objects are of no value.  For example:  In some cases creating grading objects to model a complex pond may yield undesirable results.  In these areas, generic links can be a viable alternative although one would typically find them used in roadway construction.

Think about this:  You’re modeling a complex object, or a complex site.  You’ve tried to work with grading objects all day, but you’re crashing.  But based upon yesterday’s post, the software is simply trying to building triangles, and you’ve introduced something… well… unusual.  It would be nearly impossible to trouble-shoot every place one could possibly send the software into a mathematical tailspin, so you may as well plan for it – plan for the worst, hope for the best.  Software builds triangles, in order to manipulate triangles we create breaklines.  Corridors create feature lines, feature lines can be extracted from corridors, and with a right click they become breaklines.  So if you find yourself in a complex grading situation, get back to basics.  Grading objects not working out for you so much?  Try building a corridor with generic links.  The pond below crunches all day – curve, reverse curve, compound curve, into a reverse curve, all tangent to one another and the object closes.  If the object is too small, you’ll hit a tight spot in the small curves and if you’re not careful, you’ll spin your wheels for hours trying to figure out what’s wrong.

I created the pond above with generic links.  Doesn’t that mean I had to create an alignment and profile the pond?  Yup.  Is there anything wrong with that?  Nope.

I’ve had one common question in the past, and it’s related directly to the pond:  Why can’t I add curves to a terrain model?  When I grade around a curb and gutter, can’t I use a polyline with a curve in it?  Nope.  Why not?

Triangles aren’t round.

Scott McEachron
www.121pcs.net

Civil 3D Tutorials*
Register Today to access to our comprehensive library of Civil 3D Tutorials for as low as $20.

*Access to the Library is a free service to our clients.