Offset Controlled Superelevation
Eagle Point now supports offset controlled superelevation. Through the use of special PT codes, the superelevation limits of the typical section will hold their offsets through the typical section rotation due to super elevating. With this method the subsurfaces will remain parallel to the surface above it when the typical section is superelevated. This results in the outside slopes of the typical section being adjusted in order to maintain offsets of the typical section. This new superelevation method only applies to typical sections that have their subsurfaces extending out to the foreslopes.
New PT Codes have been added to the PT Code Library to account for the offset controlled superelevation. The new PT codes added are as follows:
-22 Offset controlled superelevation limit
-23 Offset controlled outside superelevation limit left
-24 Offset controlled inside superelevation limit left
-25 Offset controlled inside superelevation limit right
-26 Offset controlled outside superelevation limit right
The –22 offset controlled PT code is used on 2 lane roads and divided highways where you are not using special alignments to control the offsets. The other PT codes (-23, -24, -25 and –26) are used on 2 lane and divided highways where you want to control the offsets of the superelevation limits with special alignments. Keep in mind that the PT codes listed above are special PT codes and can only be used as specified above. If these codes are used for reasons other than controlling superelevation and superelevation is defined for the project, unexpected results may occur.
Here are some general rules to follow when using these PT codes on your typical section to control superelevation:
1) The subsurfaces must extend to the foreslope of the typical section.
2) You must have a PT code of 1 placed at the center of each set of lanes for divided highways.
3) On typical sections in CUT you must have a PT code of 3 at the toe of foreslope.
4) You cannot have shoulders defined outside the superelevation limits. Shoulders need to be superlevated using this superelevation method.
5) PT codes –23, -24, -25 and –26 cannot be used more than once on a typical section. PT codes –23 and –24 may only be applied to the left side of the typical section and PT codes –25 and –26 may only be applied to the right side of the typical section.
Figure 1 illustrates a 2 Lane typical section example. PT Code of -22 is used at the superelevation limits. Also note that the subsurfaces extend to the foreslopes.
Figure 1 - 2 Lane Typical Section Example
Figure 2 illustrates a divided highway typical section in a cut condition. PT Codes of -22 are placed at the superelevation limits. Since PT Code of -22 is used, the edge of pavements cannot be controlled with special alignments because there are two PT Codes of -22 on each side of the centerline. When you need to control the edge of pavement alignments, use PT Codes of -23, -24, -25 and -26 instead. Also Note that there is a PT Code of 3 placed at the toe of foreslope.
Figure 2 - Divided Highway Typical Section in Cut
Figure 3 illustrates a divided highway typical section in a fill condition. In this example, the superelevation control points are also controlled by special alignments. When controlling your typical section with special alignments, the PT Codes being controlled need to be unique. Therefore, in this case, -23, -24, -25 and -26 PT Codes are used instead of the -22 PT Code that was outlined in the previous example.
Figure 3 - Divided Highway Typical Section When Controlled
by Special Alignments
Figure 4 illustrates a divided highway that has been superelevated with offset control. In this figure, you will see that all of the subsurfaces are parallel to the top surface and extend out to the foreslopes. You will also notice that the slopes of the foreslope on each surface have changes to maintain the offset as drawn in the typical section.
Figure 4 - Divided Highway Superelevated with Offset
Control