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# Vertical curve verification

## Vertical curve verification

### RE: Vertical curve verification

Your transporter requirement being 7.5/(50*12)= 1.25% does not match any number grade number in the elevation plan.

### RE: Vertical curve verification

If the concern is the transporter high-centering on a sharp vertical curve, then have no worry. That's a sag vertical curve, so you're only increasing the clearance underneath, between the axles. And it's a fairly gradual/long one at that for the algebraic grade difference, so should be navigable by almost any road-worthy vehicle.

#

### RE: Vertical curve verification

Uh, that doesn't look anything like a vertical curve, trivedi...

(OP)
Any thoughts?

### RE: Vertical curve verification

It's nearly impossible to interpret those figures without accompanying text.
But a 7.5" chord offset to road surface is pretty clear. This equates to a 50' long vertical curve for a 10% difference in algebraic grade. It has a "k" value of 50/10=5.
The design has k values of 130 and greater, so they are much more gradual.
The sharpest curve has a k value of 130. The offset is 4" over a 200' chord, so is much flatter than the 7.5"/50 criterion.

### RE: Vertical curve verification

(OP)
Thanks CarlB,
Per Chicopee, 7.5"/50x12= 1.25%, according to you grade difference 10%. Is this related? My transporter requirement for vertical curve is 7.5" over 50'.Thanks.

### RE: Vertical curve verification

(OP)
Cont.
Also for sag curve the grade difference will be of subtraction of two grades, right?

### RE: Vertical curve verification

Chicopee was guessing what the criteria was, stated that a change of 7.5" over 50' is 1.25%, a basic calculation of slope. But your criteria is for no more than 7.5" difference between a 50' long chord and the peak (or sag) on a vertical curve. Same result for a crest or sag, a 10% grade change results in a maximum 7.5" vertical difference between the chord and the curve. You'll have to study up on the definition of vertical curves to be certain.

(OP)
CarlB,

### RE: Vertical curve verification

I sort of mis-read the title. I was thinking that to verify a vertical curve for correct geometry, you would drive over it quickly with a weight on the seat next to you. A passenger will do. If the curve geometry is correct, the weight (passenger) will feel a constant vertical force throughout the curve, neither further rising or sinking into the seat, once the curve is entered. This is fun to test. Maybe not in your transporter, though.

(OP)
Thanks

### RE: Vertical curve verification

(OP)
Hey CarlB,
Sorry I am not civil engineer and I saw that vertical curve is function of parabolic curve. Is there a formula or method to calculate 7.5" in 50' has grade difference of 10% ?
Appreciate help.

(OP)
Thank you all.

### RE: Vertical curve verification

The 7% in figure 58.1 is the maximum longitudinal slope mentioned in 25A.

25C is the maximum rate of change in slope. (the instantaneous slope at any two locations 6.5 ft apart on a vertical curve must not be more than 1% different.)

(OP)
TerryScan,

### RE: Vertical curve verification

(OP)
TerryScan,
1. 7% in Fig. 58.1 is clear.
2. Note 25c, is applicable to Transition slope , that could be horizontal transition and kind of levelness requirement, Am I correct? For vertical curve it is grade change and note 25G will apply, right? So 25C also apply to vertical curve along with 25G?

(OP)
note 25f

### RE: Vertical curve verification

Road length is length whether it is vertical or horizontal.

Slope is vertical (it is NOT talking about a horizontal transition). But yes, this would appear tho apply whether it was a vertical curve or some other miscellaneous grade change (typically a vertical transition takes the form of some kind of vertical curve). The bottom line for 25C is that two points 6.2 feet apart along the road LENGTH should not be more than 1% different in slope.

25G is about longitudinal surface smoothness. It is NOT about slope transitions.

As to which item applies - "shall meet the following specifications, in any combination" (they all apply).

### RE: Vertical curve verification

trivedi: are we still talking just about the profile in your first post?

To take the 450' Vertical Curve as an example:

I computed the surface for a 50 ft. segment:
Station ____ Elev. _______ Slope ______ Description
605975.0 ___ 4393.71 ____ 2.4753% ____ (25 ft. before)
606000.0 ___ 4394.35 ____ 2.4753% ____ near PVI
606025.0 ___ 4395.01 ____ 2.7236% ____ (25 ft. after...for total of 50 ft.)

25A - yes less than 7%
25B - (no cross slope information provided
25C - slope transitions are less than 0.25% in 50 ft. (so they are certainly less than 1% in 6.2 ft)
25D - (information not provided)
25E - (information not provided)
25F - Fig 58:
calculate the slope of the chord from sta 605975-606025: (4395.01-4393.71)/50=2.6%
calculate the elevation of the chord @606000: 25*2.6%+4393.71= 4394.36
difference from surface elevation: 4394.36-4394.35=0.01 ft = 0.12" (less than 7.5"- OK)
(don't see units for 7.5 but you said it is inches)
25G - need to check with 10 ft. straight edge

### RE: Vertical curve verification

(OP)
TerrySan,
I really appreciate all information. I am not a civil guy and I am trying to verify somebody's design against requirement. Is there a software to calculate the slope or use formulas?
Thank you

### RE: Vertical curve verification

Regardless, you should familiarize yourself with the calculations (Google search or Civil texts).

### RE: Vertical curve verification

(OP)
My requirement 25C above is for slope transition. What is "( slope transition"? Where and how do I verify this requirement? It is at road intersecting each other or road changing direction or changing width. from two lanes to one?
Any help? Is it different than longitudinal slope?
Appreciate any help with terminology.
Thanks

### RE: Vertical curve verification

Slope transition would be rate of change in slope. I tried to answer that in May 2 posts above. What don't you understand?

### RE: Vertical curve verification

(OP)
Hi TerryScan,
Sorry for my ignorance. I am trying to test this requirement
The requirement Is: "slope transitions are not to exceed 1% in 6.2' in road length in the direction of transporter travel" .
I have longitudinal slope 7%, Transverse slope of 2 1/2%. Is this requirement applicable to these slopes transition in the direction of travel? I read in WDOT that this transition in plan view with road with crown meets bridge with no crown. I am trying to understand the example where this requirement applicable?
Sometime obvious thing to expert may not be easy for learner. Again sorry for my ignorance and appreciate your help.

### RE: Vertical curve verification

I would interpret the plain reading of the requirement to mean than when one wants to transition a longitudinal slope, it cannot exceed the tolerance stated (it does say "in the direction of facility transporter travel").

So, for the profile you provided in your first post, there is a grade change from 1.36% to 3.84% (more than 1% total). 25C says one must transition from the 1.36% to the 3.84% in such a way that the change is not more than 1% in a distance of 6.2 ft in the direction of travel. The vertical curve at Sta 66060+00.78 achieves this. I provided some this information in my May 2 post. One would need to do the vertical curve calculations to verify this yourself. I used Civil software and CAD to computes this. You would likely need to do the same or to hire someone that can do this for you.

### RE: Vertical curve verification

(OP)
Thank you TerryScan.

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