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Accessible ramp workflow?

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Message 1 of 6
deltacoolguy
1944 Views, 5 Replies

Accessible ramp workflow?

Would you be willing to share your workflow for designing handicap accessible ramps?  Can be in conjunction with a corridor, or stand-alone, or both.

 

We have tried a few feature lines, but that doesn't seem enough.  We have tried a feature line for everything, and that gave us a great result, but proved to be a boondoggle time-wise.  Seemed to take longer to design than build, and was a budget buster.

 

We could use a calculator and static labels... old school... but we'd prefer not to.

 

There has to be a happy medium someplace, and we are struggling to figure out where that happy medium is.

 

Any help or suggestions would be most appreciated.

 

We have C3D 2013, but will be moving up to 2015 within a few weeks.

 

 

Windows 10-64 Pro
8GB RAM (Home)
12GB RAM (Work)
AutoCAD Civil 3D 2019
5 REPLIES 5
Message 2 of 6
jeff_rivers
in reply to: deltacoolguy

We have been working through the process for a couple years now.  I have been meaning to start this discussion too, so thanks for initiating it, I would like to hear what others are doing.  

We have identified three design levels for ramp design difficulty & complexity.  

Case 1: If the flowline is 2% or less then a standard plan from our State DOT is sufficient - the Standard Plan shows the required ADA grades and contractors are familiar with the std. plans.  

Case 2:  The flowline is between 2% and 4%.  Design will be a little more difficult, a specific design plan or detail is required.  We have learned that too much information on the plan makes it too complex and challenging for contractors to understand.  Show the bare minimum grades the contractor will need to construct the ramp.  Do not show elevations.  

 

Case 3:  The flowline exceeds 4%.  The most challenging case, a unique design for the ramp is required, elements of it will likely be non-compliant with ADA.  Show all grades the contractor will need to construct the ramp, and note on the plans which grades will be non-compliant.  This will avoid confusion in the field (and sometimes contractors find ways to make ramps more compliant).  

For Case 3 ramps here's my design process.  I prefer using featurelines, and using sites and featureline heirarchy within sites to help control the complexity.  Colleagues prefer starting with sketches and hand-calculating the grades to get their preliminary design (note, 'hand-calculating' means they use excel for the heavy lifting, but to me they are doing it 'by hand' instead of using Civil 3D for this work).  

I start with an alignment and profile that follow the proposed flowline.  I make a profile view and include that in the plan set.  I make a proposed profile for the back-of-walk through the ramp so I can check grades, find out if I can apply the '15-foot rule' from PROWAG, and see what the ramps will look like.  

 

Then I start adding featurelines to define the shapes and the grades of the landings and the ramps.  

My featureline heirarchy uses three levels: highest is the flowline, I never want this to change once I've set it.  Next lower priority is the ramp featurelines.  Editing my flowline will alter the ramp FLs where they join the flowline, but no lower-heirarchy FLs can alter the ramp FLs.  Last are all the other FLs, the ped curbs, the back-of-walk, and so on.  Editing the ramp FLs will drive the pedcurb or back-of-walk FLs up or down as appropriate.   

 

If I am matching in to existing sidewalks I create FLs for the existing surveyed sidewalks, and these FLs have the same heirarchy as the flowline- I do not want these to ever accidentally change due to a clumsy edit.  I will warn you that often problems occur here because the surveyed EG just wasn't accurate enough, resulting in field fit problems.  

 

If I need to know what's happening beyond the back of the ramp I will make a quick grading object from the back-of-walk FL and get daylight lines from it to see if I will have any significant cut/fill issues.  I've used the FL offset tool to make the FLs for the pedcurb at the back of parallel or combo ramps.  I have this foggy memory of the offset tool not always working correctly.  I figured out the cause but at the moment can't recall what it was.  There's a situation where the offset tool doesn't make the new FL respect all the elevation points of the original FL.  

I have tried modeling every piece of complex ramps using oodles of featurelines but as you note the complexity soon far outstrips any advantage you get.   I use the fewest FLs needed and I tweak them around until I get to a point where I can tell if the ramp is compliant, and/or identify which parts will not be compliant for documentable reasons.  I make a FG surface and throw in grade labels where needed.  

 

We have decided to not show proposed elevations on our plans- contractors tell us they don't need them, and in fact once the curb-and-gutter is poured it is usually off from the designed flowline anywhere from a few hundredths to a tenth or so.  This means any proposed BOW elevation we would show will now also be off, causing confusion.  

 

Our ADA team has created a Priority List for ramp design which ranks the individual parts of a ramp in order of importance.  I.e. Flares are the least important component, so steepen the flare slope before changing any other parts.  Gutter slopes is next highest importance after flares, adjust the gutter slope before changing any following parts.  I can send you the list if you would like.  

Most complex project so far was an overlay that was ~2 miles long through eleven intersections, seven were signalized.  The project passed through a vertical curve with about a 15% grade.  We upgraded every curb ramp, there were over 80 ramps, and we added APS to the signals.  All I did for six months was design curb ramps and APS.

 

Now what are others doing?  


Jeffrey Rivers
Win 10 Pro 64-bit, Intel i9 3.7GHz, 64 GB
NVIDIA RTX A4000
C3D 2020 V13.2.89.0
Message 3 of 6
TomDiVittis
in reply to: jeff_rivers

My answer would be similar to Jeff's.....basically do what is necessary and no more.

 

A respected colleague of mine like to build a ramp surface, then paste that into final grade.  I do think that methodology (at least can) simplify the process.  Since the ramp configuration is a byproduct of the rest of the design, this seems to be a logical approach that isn't likely to screw up something else unintentionaly.


I would love to do them with corridors, but the extra sections required seems to make that not worth the effort.

Message 4 of 6
kcobabe
in reply to: deltacoolguy

It would seem this is a little to over thought of a process.

 

My process is simple.  I use a comdination of a calculator and the fetureline editing tools.  I can do anything from a complex ramp to you typical Green Book ADA ramps in a matter of minutes.  Main thing to remember is, unless you plan on going out there and surveying your gutter flow line or any matching flowline you will always be off.  This is were a good contractor comes into play.

 

A good contractor will always only want your PC, PI and PT elevations.  After that if you start plugging in to much information they will build it that way and you will be wrong.  However, if you give them a detail they will build it that way and make it fit ADA compliance.  On your detail you will want no more than what you would see in the Green Book or entity standards.  Typically this is just slopes and dimensions.

 

I have done this with sport complexes, residential, industial, DOD facilities, parks, etc...  and have yet to find an issue.  There's a reason when you go out to the field you will constantly hear "**** engineers." It's usually from to much information that makes them have to RFI or as-built the thing for you causing them undo work.


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Message 5 of 6
avaloncafe90
in reply to: deltacoolguy

Hi c
Could you please send me the priority list of ADA ramp design

Thanks
Message 6 of 6
TomDiVittis
in reply to: avaloncafe90

Priority list?

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