parabolic superelevation transition

[roberttx]

Hi,

I am looking for a civil engineering software that can calculate parabolic superelevation transition on horizontal curves. Any suggestion?

Thanks,
Roberttx.

 

[Leongoring]

I am unaware of any such software. Is there any specific problem you have that necessitates the use of software?

 

[roberttx]

Hi, Leongoring:

I had this ramp bridge project submitted by a consultant in which a circular curve was combined with a vertical curve, and the ramp was widening also. Originally, the consultant had a linear transition for the vertical curve, then switched to parabolic transition. I learned the theory but it's almost impossible to calculate by hand.

Any ideas?

Thank you.

 

[MPENN]

The mix of horizontal and vertical curves is not unusual. Vertical curves are typically parabolic. I am unsure of your meaning of a "linear transition for the vertical curve."

 

[roberttx]

Hi, Mpenn:

I am sorry. I said it wrong. I was trying to say parabolic transition from regular superelevation to full super of the horizontal alignment. It all occurs within the deck.

Thank you.

 

[MPENN]

Within the change (runout and runoff) from your normal section to the superelevated section does the POAG have an associated vertical curve?

 

[roberttx]

Yes, that's correct.

 

[MPENN]

1. calculate the runoff length by applying your design parmeters to the current green book.

2. calculate length of runoff before the horizontal PC (or after PT)

3. calulate runout length - product of runoff length and the ratio of normal cross slope to e-max

4. you are now able to determine the starting station for application of the change from normal section (back to the green book) - this is not affected by the POAG being on a tangent or vertical curve

5. if you are calcing the superE over a uniform width of pavement (uniform distance between the POAG and edge of pavement or shoulder or other break point) or a diverging point - use the rate of slope change given by the sum of the absolute value of the difference normal cross slope rate and e-max and the uniform width and the sum of the runoff length and runout length - for a given station within the total transition length, the cross slope rate will be the sum of the normal cross slope and the product of the rate of slope change and distance from starting station determined in No. 4.

6. add the product of the given station cross slope rate calculated in No.5 and the width over which the cross slope is carried to the station elevation at the POAG - voila you have the elevation of the rotated section of pavement at a distance from the POAG

7. you have added a linear change to a parabolic change and they would be similar except for the small fact that any transition that is within the horizontal curve is radial and is at an actual lesser rate - this condition is usually ignored

8. I hope this somewhat confused presentation is without errors and provids you with guidance, this is from memory only, no benefit from my books