# Civil AM NCEES Problem # 113 / Green Book



## RJs (Sep 26, 2010)

I am not understanding why this problem can not be solved by finding Elevation of PVC and then using equation to find elevation on any point on the cureve (i.e. Elevx = R/2 x^2 + G1x + Elev BVC? When I use this equation I get different answer than NCEES solution. Can someone explain? Can I use L/2 to get the stat of PVC?

Is the vertical curve in the question is a unsymmetric curve (how to determine symmetric or unsymmetric based upon the given info in the Question)

Also is Green Book required for AM Transpo. I am not been able to understand how to use Green Book Charts to solve the questions.


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## boo (Sep 27, 2010)

RJs said:


> I am not understanding why this problem can not be solved by finding Elevation of PVC and then using equation to find elevation on any point on the cureve (i.e. Elevx = R/2 x^2 + G1x + Elev BVC? When I use this equation I get different answer than NCEES solution. Can someone explain? Can I use L/2 to get the stat of PVC?Is the vertical curve in the question is a unsymmetric curve (how to determine symmetric or unsymmetric based upon the given info in the Question)
> 
> Also is Green Book required for AM Transpo. I am not been able to understand how to use Green Book Charts to solve the questions.



can you please write the question?


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## pmblair (Oct 1, 2010)

RJs said:


> I am not understanding why this problem can not be solved by finding Elevation of PVC and then using equation to find elevation on any point on the cureve (i.e. Elevx = R/2 x^2 + G1x + Elev BVC? When I use this equation I get different answer than NCEES solution. Can someone explain? Can I use L/2 to get the stat of PVC?Is the vertical curve in the question is a unsymmetric curve (how to determine symmetric or unsymmetric based upon the given info in the Question)
> 
> Also is Green Book required for AM Transpo. I am not been able to understand how to use Green Book Charts to solve the questions.


Yah that problem had me going too.

You have to take the PVI to The PVC then use the 3.0% to go down the 4.5stations from the PVC on the 3% line and then you add the offset using the 4.5stations.


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## Ambrug20 (Oct 4, 2010)

RJs said:


> I am not understanding why this problem can not be solved by finding Elevation of PVC and then using equation to find elevation on any point on the cureve (i.e. Elevx = R/2 x^2 + G1x + Elev BVC? When I use this equation I get different answer than NCEES solution. Can someone explain? Can I use L/2 to get the stat of PVC?Is the vertical curve in the question is a unsymmetric curve (how to determine symmetric or unsymmetric based upon the given info in the Question)
> 
> Also is Green Book required for AM Transpo. I am not been able to understand how to use Green Book Charts to solve the questions.


i am not a big expert in this, but study a lot to answer. When use the formula suggested by you, the curv elvation is getting low than tangent elev.(remember, its a sag curve). It ring the bell that we need to do something different. The formulas given in this problem solution are explain how to calculate sag curve turning point. These problems are all tricky and we have to careful analyse the data.

If you don't know how to use Green Book, don't buzer, you'll waste time.

Its a lot of data in this book and you realy need toknow how to use it.

I can't say for sure that you don't need it. From my undestending on the morning portion would be horizontal curve design only. Good luck


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## gnat (Oct 24, 2010)

Boo,

Check your work again. I used the BVC method you have described to solve this problem and got 19'.

BVC elev 357.06, x=4.5 sta, 73+00 elev 346.93, clearance 19'.


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## CaltransPEHopeful (Oct 24, 2010)

The NCEES solution is valid, but over complicated. To solve this simply use the parabolic form for vertical curves: y = (R/2)x^2 + g1x + y0 where x is the horizontal distance from BVC in stations, R is the rate of change in grade, g1 is the grade entering the curve, y0 is the elevation of the BVC, and y is the elevation ON the curve at x. Take this elevation and subtract it from elevation at bottom of bridge structure to get clearance. Try it out...hope it works for you.

Oh yeah...R is defined as (g2 - g1)/L

L = length of curve (also in stations)


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