Vertical drop in roadway 1

[trivedi123]

How do I provide transition between two roads with elevation difference of 5'. My transporter
can accommodate 7.5" drop in 50' length. Roads intersect at 90 degree and I don't have enough horizontal distance available for vertical curve to accommodate 5' drop.
Is there any way method to accomplish this ?
I will appreciate help.
Thanks
CR

 

[milanov]

CR,

Can you provide a sketch showing the scenario you are describing?

 

[trivedi123]

Hi Milanov,
The top elevation of main road is 0'-0". The road perpendicular is at EL' -5'-0". Transition length is 200'.


[URL unfurl="true"]https://res.cloudinary.com/engineering-com/raw/upload/v1537817396/tips/Road_yiczry.xlsx[/url]EL. 0'-0"


EL -5'-0"


200'

t]

 

[BridgeSmith]

I'm not seeing the problem with making the transition. You'll likely want vertical curves in and out of the elevation transition. The length of the curves will depend on the design speed of the roadway. If your grading equipment is not able to make the profile, then you'll need to use something else.

 

[BridgeSmith]

25' level at the intersection, followed by 50' vertical curve to a 4% grade for 125' to another 50' vertical curve back to level, seems like it would work fairly well. The distance from the profile of the curve to the chord for those curves is only 3", so if the equipment has a range of +/- 7.5" in 50', it should work, right?

 

[trivedi123]

HotRod10
I am also a structural engineer like yourself but you know lot more about road than I do.
I am trying to understand the road profile for last 25'.I will appreciate help to see the final road profile looks like with 7.5' in 50' restraint I have.
Thank you.

 

[BridgeSmith]

I don't really know that much about road design, just what I see in bridge design from the guys who do the road design. Most of the road profile layout is done for them by the Geopak extension to the Microstation CADD program. I think there is a similar extension to AutoCad. Anyway, I've attached an Excel file with the vertical curve calculations using the inputs for the profile I proposed. Input cells are shaded. Stations are in feet (101+00 - 100+00 = 100 feet). I hope that helps with visualizing the profile.

As far as the limits of the equipment, you'll need input from someone more familiar with its operation and limitations to know whether it will work for you, although I'd be somewhat surprised if it would not.

 

[BridgeSmith]

Fyi, as you look at the vertical curve info, you'll see a value (0.25') labeled "M.O.", which is the middle ordinate, the distance from the curve to the chord (the straight line between the ends of the curve). That should represent the maximum adjustment required from level for the blade of a road grader with a 50' wheelbase to be able to grade the proposed curve.

Edit: Didn't mean to repost the attachment, but I don't know how to get rid of it. Help anyone?

 

[trivedi123]

Thank you. HOTROD10.
Appreciate your help.