TPC allows you to insert vertical curves into any traverse. The elevations of the traverse points that fall between the BC (Beginning of Curve) and EC (Ending of Curve) are automatically updated according to their respective vertical curves.
When you work with vertical curves, you would like to:
The Vertical Curve View displays the vertical curve data associated with a traverse. You can enter VPI's (Vertical Points of Intersection), grades, stations, etc.
To access the Vertical Curve View, open a traverse and choose Windows | Vertical Curve View.
If your traverse (alignment) already has grade breaks in it, TPC can automatically identify the grade breaks and insert vertical curves with the appropriate lengths. This is typical of road design where you have identified the vertical tangents and are ready to refine the alignment with vertical curves.
TPC will insert the VPIs into the Vertical Curve Screen and compute all of the curve values. It will not update the traverse. You can choose to update the traverse based on the vertical curve values after you have had a chance to review and/or edit them.
If you don’t specify any Change/Len combinations, the VPIs will still be identified, but no curve data will be inserted - you will need to enter the data for each curve manually.
You can enter your own vertical curve information. If the traverse already has some vertical alignment, it will be overwritten (updated) by the information you enter here when you compute vertical curves. You can even update the elevations of the points on the tangents between the vertical curves.
You can insert and delete VPIs or go back and change any of the values.
The VPIs are stored with the traverse data. If you save this survey, you can come back and review or edit your vertical curve information any time.
Once you have confirmed that the VPIs are where you want and the curve lengths meet the specifications of the project, you are ready to compute the elevations inside the vertical curves.
One of the important rules of computing vertical curves is that only existing traverse points are adjusted. If an existing point lies within a vertical curve, its elevation will be adjusted based on its location (stationing) in the curve. If the traverse does not have any points between the BC and EC, no points will be added.
At times, you will want to update the tangent (constant grade) points, proportioning their elevations based on their distance from the previous EC and the next BC. In effect, this causes the entire vertical alignment of the traverse to be controlled by the VPIs in the Vertical Curve Screen.
You can update a single vertical curve or selected curves.
If you use the Update Tangents options, the points on the tangents will be adjusted based on the vertical curve computations and grades.
If you update VPIs manually based on the grade breaks in the current traverse, L1 and L2 are assumed to be equal. You can, however, enter different values for L1 and L2.
If the values for L1 and L2 are different, the high or low point of the curve is still computed at the VPI station, but the BC and EC are computed at their respective distances (stations) from the VPI.
Vertical curves are viewed along with the profile for the traverse or alignment.