Math wizards question

[RobertEVs]

How would you determine "X" and "Y" when you have a 1% slope or anything except 0%? 0 would be easy to determine.

 

[fcernst]

Jeff’s diagram shows the issue with Civil 3D where profiles, surfaces and corridors are not offset orthogonally to the profile….or a surface is not offset planar normal to the surface plane. The vertical offsets in Civil 3D are not relative to the object plane orientation.. just simply absolutely vertical. 

Joe and I interpret the original diagram as 90 degree angles with the triangle height always perpendicular to the base .. no matter the base absolute rotation. 

[Joe-Bouza]

I see the effect that @RobertEVs  and @Jeff_M  are computing. but this raises another question. if the flow line slope is 2% then the upstream length become 9.1-feet and down stream become 5.9-feet which looks wrong, 

[CahaLF7RX]

Hello again,

Depending on what your standard curb height is.

For most projects I have worked on (for 33+ years) the standard has been 6-inches.

if the road vertical slope in not 0.0% (which is not practical for drainage), the ramp lengths will be different lengths (using the 1:12 max slope) or can be different slopes and the same length.  depends on who is sealing the drawing.

good luck,

nonbeard13

[fcernst]

This discussion has digressed and permutated from the original diagram for isolating and computing x for completing the small triangles at a relative 7.5% within the small triangles workspace domain .. to an absolute 7.5% constraint now for civil grading work. There were no parameter caveats stating this in the original diagram. For example, it originally to appeared to be  a simple trick question.. that now the OP doesn’t realize he subsequently posited. 

[Joe-Bouza]

I agree with you. I was only show the it impractical to use the flow line as a basis

[teerawat.pSCHYQ]

my understand that slope 7.5% are related with that 1%, and you talking about design profile for something. this is my idea about this,  if you create like a profile, and then add labeling for the tangent slope length, then you can get the correct slope length like this.  

[Joe-Bouza]

I agree with you. I was only showing that it is impractical to use the flow line as a basis