2 or 3 Centered Compound Curve with Spirals

[HermChwa]

Anybody (gurus) out there able to help me with designing horizontal road alignment consists of:

1. Two-centered Compound Curve with 3 Spirals, and
2. Three-centered Compound Curve with 4 Spirals.

Thank you.

HC

 

[vsiccclubchamp]

What kind of software are you running?. Microstation, InRoads?. Those would be your best bets

 

[HermChwa]

I'm writing a program in Visual Basic which will compute the coordinates and curve data (eg. spiral angle, Ts, tangent bearings etc) of any interval points along the centreline of the alignment, using given data such as coordinates of IPs, lengths of spiral and radius (or radii) of arc.

The combined curve spiral-arc-spiral is pretty straight forward. I've managed to complete the program on this type of curve.

When it comes to compound curves with L1-R1-L2-R2-L3 and the likes, I found these formulae:

(R2+p2)-(R1+p1)cos(I) + (R1-R2-p)cos(I2)
ts1 = ----------------------------------------
sin(I)


(R1+p1)-(R2+p2)cos(I) + (R1-R2-p)cos(I1)
ts2 = ----------------------------------------
sin(I)

But how do you find I1 or I2, which are the total deflection angle up to the PCC? What data should be given prior to any further calculations?

Happy New Year and thanks.

Herm