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Calculating VC for Lowboy clearance

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Message 1 of 13
mnorton
5147 Views, 12 Replies

Calculating VC for Lowboy clearance

I'm in search of a method/software to design a low vehicle clearance vertical curve.  The access road to my site crosses a levee and I need to bring in equipment on a 40' lowboy trailer with 8" clearance.  I've searched AASHTO, AREMA, ITE, DOTs, and various manufacturers to no avail.

 

Thanks,

Norton


Mike Norton - The Civil Guy
12 REPLIES 12
Message 2 of 13
witzel
in reply to: mnorton

Mike,

 

Let me know if you find anything.  

 

I searched long for anything on vertical curves and trucks.  We had a site with a steep driveway and we needed a way to find out if trucks would bottom out on the curve.

 

The only thing I ever found was cross slopes on shoulders for tipping.

 

Thanks,

Conan Witzel

Message 3 of 13
sboon
in reply to: witzel

Check AutoTurn Pro from Transoft Solutions for this. 

 

From the brochure:


Generate 3D swept path envelopes with vehicle height and ground clearances
to analyze designs in a three-dimensional space. Users also have the options to
display the 3D swept path of the vehicle body or body clearance.

http://c464509.r9.cf2.rackcdn.com/autoturnpro.pdf

Steve
Expert Elite Alumnus
Message 4 of 13
mnorton
in reply to: mnorton

Conan,

 

I think the Institute for Transportation Engineers (ITE) may help you. They have several publications pertaining to design for low clearance vehicles.

 

Mike


Mike Norton - The Civil Guy
Message 5 of 13
mnorton
in reply to: sboon

Steve,

 

Thanks for the brochure.  I requested their demo version and will post my results.

 

Norton


Mike Norton - The Civil Guy
Message 6 of 13
jmayo-EE
in reply to: mnorton

At a minimum with a design like this I would want a profile at the top of the vehicle so I could see the clearance in profile view.

 

If I had a corridor I would add a vertical link and marked point to the CL extending up to the top of vehicle. I would hide the vertical link in the subassembly code.

 

If I did not have a corridor I would copy the FG profile and move it up to the top of vehicle.

John Mayo

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Message 7 of 13
mnorton
in reply to: jmayo-EE

Thanks, John, but in this case I'm only interested in that the trailer undercarriage clears the top of the levee. 

 

I've performed a fairly exhaustive search at the state, federal, and local levels for applicable guidelines but no luck so far.  I also contacted a half dozen or so manufacturers thinking there might be industry guidelines but zero there too.

 

The literature on AutoTURN Pro software is promising but the program doesn't include lowboy trailers.  The Wisconsin DOT provides a lowboy trailer in AutoTURN format BUT THE DEMO VERSION WON'T IMPORT VEHICLES. Sorry, I was yelling and throwing things.

 

I actually calculated the clearance but my formula only accounts for two axles and the clearance - not the impact of the gooseneck pivot or the other three axles.

 

So... at the moment all I have for certain is a drawing of a tractor and lowboy trailer that looks really cool when I rotate it around my vertical curve.


Mike Norton - The Civil Guy
Message 8 of 13
jmayo-EE
in reply to: mnorton

Maybe AutoTrack can help where Autoturn did not.

 

http://www.savoycomputing.com/

 

I would still run a second profile but for the undercarriage to help identify problem areas as this is a quick estimation but it sounds like you will still need to manually draft the vehicle undercarriage line in the worse case position and manually place that along a profile. I would see if I could get a profile label to place a block of the undercarriage all along the profile. It will look ugly but you should be able to clearly see issues.

 

I would guess you have measurements on the tractor/trailer and or manufacturer's data to get the undercarriage line drafted.

John Mayo

EESignature

Message 9 of 13
Buzz12345
in reply to: jmayo-EE

We've use Autopath by CGS for this.  

 

It's great for looking at both horizontal swept paths and vertical curve / vertical grade break analysis.  It comes with a selection of vehicles.

 

However, you can also add your own customised ones (for both horizontal and vertical anlysis).  (We've loaded our own truck towing a boat on a boat trailer for analysing boat ramp design - the custom vehicles look awesome).

 

When you run the software you can select a profile and it'll sit your vehicle on the profile and then run it along along the profile (use a 1:1 vertical exagerration in your profile view style). You can freeze the vehicle at any point and leave an outline on the profile if you want.

 

Have a look at the website here:

 (http://usa.cgsplus.com/tabid/551/language/en/Default.aspx)

 

Looks like there's a free trial available.

 

 

Michael
AEC Collection - Civil3D 2023 & Infraworks 2023
www.foxsurvey.co.nz
Message 10 of 13
mnorton
in reply to: Buzz12345

Thanks, Michael. (I think.) Now I've got three programs to evaluate - AutoTURN, AutoTRACK, and AutoPATH!

 

John, I have a truck/trailer drawing to visually check for clearances but it only accounts for two axles and the bottom clearance.  I'm not sure how to model the gooseneck pivot and the other 3-5 axles or even if it's necessary. I may be way overthinking this but it's going to be tough to explain if I send a truck to the river and it gets stuck on the levee road I designed. Oh, well.  I've been thrown out of better bars than this.


Mike Norton - The Civil Guy
Message 11 of 13
jmayo-EE
in reply to: mnorton

We use Autotrack for sweep paths through projects but I have not used the vertical path routines. I have only had to estimate vertical clearance for a couple of jobs and I have done it with profiles. I would really try to get one of the software packages to help with this but in the event of that not happening...

 

"I'm not sure how to model the gooseneck pivot and the other 3-5 axles or even if it's necessary"

 

I would think the model would need to be pretty specific for the tractor trailer combos used. Different 5th wheels, different 5th wheel locations and heights, tractor trailer sizes and king pin locations should have an affect on this. A low boy will probably have a fully oscillationg 5th wheel to allow for more side to side deflection as well. I think these mount a bit higher. You should be able to measure the deflection on a fith wheel without a trailer attached. It may take a few people and be quite greasy but you should be able to see how the 5th wheel pins in all directions. Max deflection between tractor and trailer should come to light when you draft this up. You may see the front of trailer hit the tractor frame or the top/rear of the tractor frame hit the bottom of the trailer but the limits should be seen.

 

I would think the number of trailer axles is important to model since you could have a situation where one axle may support the entire trailer and the other two would be in the air. You would also want to monitor the rear trailer overhang and make sure that this does not hit the ground.

 

 

John Mayo

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Message 12 of 13
mnorton
in reply to: jmayo-EE

John (and anyone else still interested)

 

We purchased AutoTrack and with some invaluable help from Mike Hutt in their UK office I now have a process in place that we've used on several projects.  I also now use the swept path feature to analyse vehicle access to all of our sites.

 

The program balked at using my Civil 3D profile for the vertical clearance analysis and I haven't had the chance yet to troubleshoot the issue.  I can't say enough good about the support I've received from Savoy Computing Services and I'm sure a fix is simply a phone call away.

 

Meanwhile, AutoTrack refused to select the profile object, so I did what any red-blooded Texan would do, I exploded the profile and everything worked just fine.  Desperate times call for desperate measures.  I had a crew in the field ready to lay some road.

 

Thanks for your help, John.


Mike Norton - The Civil Guy
Message 13 of 13
jmayo-EE
in reply to: mnorton

No problem MIke. I am happy to help and I am glad you got through it all.

 

I also have nothing but nice things to say about the folks at Savoy. They have treated us well since 05.

 

Be well, 🙂

John Mayo

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