AutoCAD Civil 3D General Discussion

AutoCAD Civil 3D General Discussion

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jmayo
Posts: 2,798
Registered: ‎11-13-2006
Message 31 of 43 (486 Views)

Re: Grading Contours not true to slope values

02-19-2013 07:30 AM in reply to: Joe-Bouza

"Wow ! So now we need a projection grading that finds the first contour then turns to be perpendicular to it?"

 

Apparently those contours are also going to need some legal advice aas well. :smileysurprised:

 

If anyine in this office or a reveiewing agency complained about contours being spaced 9.7' to 10.7' when it should be ten feet I would first need to contain the laughter, next advise them that their scale may need to be calibrated (holding in the laughter once again) and then remind them that the contours are only accurate to 1/2 the interval so with +/- 1 foot, 9.7' and 10.7' are really 10 to 11 feet and I meet the grading criteria.

 

:smileyhappy:

John Mayo, PE
IDSP 2014
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Valued Mentor
fcernst
Posts: 1,094
Registered: ‎01-07-2011
Message 32 of 43 (478 Views)

Re: Grading Contours not true to slope values

02-19-2013 07:54 AM in reply to: jmayo

John you have to keep up with us now...  It's not a question about contour construction. The C3D contours are correct as constructed. That's been established. Grab some coffee.

 

It's a question of whether the designers are aware the projection slope used in the C3D routines does not necessarily determine the surface slope. The OP mentioned in Section we typically  show a 2:1 max and the intent is to not exceed that for surface slope per code, but in many cases the resultant surface slope is steeper than that.

 

Hailey had a question about slope labeling precision not contour construction. 

 

 

 

 

 

 

 

 

 

 

Fred Ernst, PE
C3D 2015
Ernst Engineering
www.ernstengineering.com
*Expert Elite*
jmayo
Posts: 2,798
Registered: ‎11-13-2006
Message 33 of 43 (474 Views)

Re: Grading Contours not true to slope values

02-19-2013 08:23 AM in reply to: fcernst

Oh Fred my laughter from this thread woke me. I understand exactly what is being discussed. I am just not sure if the issue is more funny than the indignation. :smileyhappy:

John Mayo, PE
IDSP 2014
Win 7 64, Xeon ES165@3.2Ghz,
64 GB RAM, Quadro K4000 (x2)
Valued Mentor
fcernst
Posts: 1,094
Registered: ‎01-07-2011
Message 34 of 43 (468 Views)

Re: Grading Contours not true to slope values

02-19-2013 08:38 AM in reply to: jmayo

??? Your post talks about contours not being accurate. 

 

The legal I'm talking about, is the expert demonstrating for the other side, that the design surface slope exceeds code.

Fred Ernst, PE
C3D 2015
Ernst Engineering
www.ernstengineering.com
*Expert Elite*
troma
Posts: 2,520
Registered: ‎05-21-2008
Message 35 of 43 (440 Views)

Re: Grading Contours not true to slope values

02-19-2013 12:22 PM in reply to: Joe-Bouza

Joe mentioned a grading 'finding the first contour and then turning perpendicular'.  Sounds awkward of course.

But in message 14 on this thread, Brian reminded us how to add vectors.  Kudos to Brian.

 

So, what is really needed (or at least wanted by some) is the ability of the grading slope to subtract vectors.

 

Let me put it to you this way:

Say, within the grading settings there was an option you could turn on and off, lets call it "Remove Parent Object Slope from Grading"

When turned on, this setting would subtract the vector of the slope of the parent feature line from the required slope of the grading; thus resulting in a true slope of what the user inputs.

 

Would you object to such an option?

Would you use it?  Why, or why not?


Credit where credit is due! Give kudos or accept as solution whenever you can.

*Expert Elite*
Jeff_M
Posts: 4,317
Registered: ‎07-22-2003
Message 36 of 43 (422 Views)

Re: Grading Contours not true to slope values

02-19-2013 12:39 PM in reply to: troma

Just for the sake of stirring the pot, this topic was covered quite well.....7 years ago.

http://forums.autodesk.com/t5/AutoCAD-Civil-3D/Create-slope-perp-to-contours/m-p/1849529#M34354

 

I had thought there was another, similar, thread that James Maeding had started, but I could not locate it.

Jeff_M, also a frequent Swamper
Valued Mentor
fcernst
Posts: 1,094
Registered: ‎01-07-2011
Message 37 of 43 (419 Views)

Re: Grading Contours not true to slope values

02-19-2013 12:43 PM in reply to: troma

No, because it would be utterly meaningless. This thread should have been over after Message #3:

 

Is your feature line sloped? Grading occurs perpendicular from the feature line and not from the contours.

Fred Ernst, PE
C3D 2015
Ernst Engineering
www.ernstengineering.com
Valued Mentor
fcernst
Posts: 1,094
Registered: ‎01-07-2011
Message 38 of 43 (408 Views)

Re: Grading Contours not true to slope values

02-19-2013 01:03 PM in reply to: Jeff_M

This doesn't really stir anything up. Engineers need to evaluate the surface gradient (normal to contours) for geotech slope stability and code items. Code items and design criteria based on free body diagrams of people and cars sliding around.

 

Code items such as ADA, handicap parking areas can not exceed 2% in any direction (resultant), in Colorado we can't have greater than 4% in any direction (resultant) in parking lots due to ice. 

 

Surveyors and contractors want offset staked. Engineers have to make sure everything is safe when things are offset staked.

 

What's to stir up?

Fred Ernst, PE
C3D 2015
Ernst Engineering
www.ernstengineering.com
*Expert Elite*
jmayo
Posts: 2,798
Registered: ‎11-13-2006
Message 39 of 43 (401 Views)

Re: Grading Contours not true to slope values

02-19-2013 01:14 PM in reply to: fcernst

I agree Fred and forgive me for being rude before. If the model exceeds the max slope I just back down the grading criteria from 1:2 to 1:1.9 and move on. If contours seem spaced to tight I'll do the same. I might even just through a txt string into a profile, section or plan calling out a max. slope ignoring the model or without modeling anything. We are constrution the information on the plans not the model.

 

 

 

John Mayo, PE
IDSP 2014
Win 7 64, Xeon ES165@3.2Ghz,
64 GB RAM, Quadro K4000 (x2)
*Expert Elite*
Neilw
Posts: 2,253
Registered: ‎09-04-2006
Message 40 of 43 (401 Views)

Re: Grading Contours not true to slope values

02-19-2013 01:16 PM in reply to: SDcivil

I say, slap a slope label on the plan view and add a disclaimer not to scale the drawing. Let the contractor take the liability. :smileywink:

Neil Wilson (a.k.a. neilw)
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