All
I am working on a spreadsheet to check designs. I am essentially looking to input vertical intersection points and curve lengths, after which the speradsheet will then output gradients, gradient lengths, and curve radii.
BRT is set to vertical curves as parabolic and annotated with equivalent radius R = 100K
My issue is, that the vertical radii I calculate is different that what BRT presents. My calc is R= 100*L/G where L is length of curve and G is the difference in gradient.
For two grades of G1=0.638% to G2=0.589% and L =30m I get R=61124.4898m
BRT gives R = 60653.170m
Now I am willing to give BRT the benefit of the doubt over a couple of m due to accuracy in the input compared to what the software holds, as well as the conversion from K to equivalent R, but this is a ~570m difference in the calcs.
Can anyone advise where this is going wrong?
Thanks
A
yes K = l/(g2 - g1). I can check using check integrity that the value is correct and annotation is correct (version 08.11.07.685 and 08.11.09.904)
R=61224.4898
Thanks for checking jpln
What worries me then is that the definition of the curve in the alignment I am checking is either
A) Not set to parabolic
B) Is set to parabolic but annotated in Vertical Profile or Profile Annotation as Radius as opposed to 100K
If you use the same alignment you used to check this for me, and change the vertical curve definition to Curve/Radius - what radius does check integrity return for you?
if I change parabolic to circular for the existing vertical alignment then radius reported is 61227.947
Hello,
I have the same question, for US units. We normally do not take radius equivalent to any accounts as all standards for US railroads go by R value of parabolic curve, regardless speed.
However, while working on one of HSR projects, I need to verify radius equivalent while having grade grades in and out, and vertical curve length. What is the formula for that?
Hi Alastair,
I believe this is due to the precision of the Grade used to calculate the Equivalent Radius.
For example:
For 2 Grades of G1 = 0.0.047% to G2=-0.059% and L=30m I get R = 28301.8867m
However BRT gives R = 28181.67m
On Closer inspection I found that the G1=0.047% is actually a Grade of 0.0470983% & G2=-0.059% is actually a Grade of -0.0593539% when I use a precision of 7 decimals in BRT.
On Calculation for L=30m using these values I get a value of R = 28181.663m which is same as the value that is generated by BRT.
Similarly when I use grades of exactly 0.047% & -0.059% in BRT it reports a radius of 28301.89m which is same as the one calculated using the formulae.
Hope this helps.
Regards
SP