This subassembly is used to overlay a four-lane crowned corridor over gutters (between flow lines) on each side, holding to required slope and breakover ranges. This subassembly differs from OverlayBrokenBackBetweenEdges because it overlays existing gutters to a known profile on the curb face, rather than overlaying between known flange points.
To use this subassembly, you should have separate alignments defining the left and right curb face points. Elevations at these points could come from surfaces or profiles. Furthermore, if the component defining the edges (for example, curb and gutter) is also a rehab component, then they could be passed in as marked points, thus transferring offset and elevation information.
The attachment point is (near) the crown point of the subassembly. Since the subassembly places lanes on either side of the crown, this attachment point is typically at the assembly baseline point. While in layout mode this point coincides with crown point, in the corridor state the finished grade profile point (or baseline marker point) may not be same as crown point, since crown point offset and elevation are computed by input data such as left and right (Curb face) offset values.
Note: All dimensions are in meters or feet unless otherwise noted. All slopes are in run-over-rise form (for example, 4 : 1) unless indicated as a percent slope with a “%” sign.
If target parameters are provided, the parameters above (namely default offsets and marked points) will be ignored as applicable.
This section lists the parameters in this subassembly that can be mapped to one or more target objects, such as a surface, alignment, or profile object in a drawing. For more information, see in the AutoCAD Civil 3D User’s Guide Help.
This subassembly uses an iterative pocess to develop acceptable slopes of the inside and outside links. The initial slopes are set as described below. Each time the slope of one link is adjusted, resulting changes in the adjacent links may put them out of design tolerances. If a solution is not obtained within 10 iterations, a message is displayed and the process is aborted.
From the attachment point, the left edge of the pavement point is located based on: (a) the location of the alignment through "Left Gutter Point" target parameters, (b) if this is not provided, then it is based on the assigned marked point (to Left Gutter Point), or (c) if both of these are not provided, it is based on the default (Left Gutter Offset) offset value.
Similarly, the elevation for this point is computed based on: (a) Left Gutter profile target parameter, (b) if this is not provided, then it determines the surface elevation from "EGTopSurf" Logical assignment, or (c) if these two are not provided, then the assigned marked point determines the elevation. An error messageresults if none of these two conditions are met and the corridor fails to build.
From the attachment point, the right edge of the pavement point is located based on: (a) the location of the alignment through "Right Gutter Point" target parameter, (b) if this is not provided, it is based on the assigned marked point (to Right Gutter Point), or (c) if both of these are not provided, then it is based on the default (Right Gutter Offset) offset value.
Similarly, the elevation for this point is computed based on: (a) Right Gutter profile target parameter, (b) if this is not provided, then it determines the surface elevation from "EGTopSurf" Logical assignment, or (c) if these two are not provided, then the marked point determines the elevation. An error message results if none of these two conditions are met and the corridor fails to build.
Quarter Points and Crown Point Offsets
The distance between left and right flange points is divided by four to get the two quarter points and the crown point. These points elevations are computed by adding the minimum overlay depth to the existing ground at these offsets.
Inside and Outside Pavement Slopes
The resulting overlay links from the previous steps are checked for being within the slope tolerances for the outside and inside lanes. If the slopes are within the tolerance, then the case is a simple overlay as show in the following diagram.
If the overlay links are too steep, or if the Maximum Breakover is exceeded at the centerline, or the Min Crown Deflection is not obtained, some or all links are flattened to their maximum slopes. Milling surfaces are inserted to hold the minimum overlay depths at the quarter points and centerline.
If overlay links are too shallow, the depth of overlay is increased to achieve the minimum slopes. If this results in too much breakover, further adjustments and milling may occur. The following diagram illustrates the overlay with milling case.
A positive slope may be allowed on one inside link if the other inside link has a negative slope, as shown below.
In layout mode, this subassembly inserts two lanes at either side of the attachment point. The firts two edge points will be located based on left/right offsets. These left and right point elevations are calculated, in layout mode, by subtracting crown height from the ordinate of attachment point. Then the "Crown Point" is located halfway between these two points. However, since the programatic defaults are the same for both left and right, by default, the crown point matches the attachment point. Lane slopes in layout mode are equal to the "Min % Outside/Inside Slope" value. Thickness of pavement is equal to Minimum Overlay depth.
The following table lists the point, link, and shape codes for this subassembly that have codes assigned to them. Point, link, or shape codes for this subassembly that do not have codes assigned are not included in this table.
