Advanced Superelevation Roadway Design Using Non-Center Axis of Rotations

Advanced Superelevation Roadway Design Using Non-Center Axis of Rotations

Advanced Superelevation Roadway Design Using Non-Center Axis of Rotations

Karen Dowling, Senior QA Analyst, Autodesk, Inc.

Class Code: CI4031

This class focuses on the enhanced superelevation functions now available in AutoCAD® Civil 3D®, specifically axis-of-rotation (AOR), which now enables you to attain superelevation optimally, depending on project location and conditions. Historically, this problem was solved through a set of rigid procedures and only solvable to typical sections constructed in a limited manner. The new AOR feature allows users to define cross-sectional components in a very flexible manner and allows the dynamic editing of the axis of rotation to quickly validate various alternatives.

Learning Objectives

At the end of this class, you will be able to:

·  Use the superelevation wizard to define roadway types and superelevation axis of rotation points

·  Create a roadway assembly using the new LaneSuperelevationAOR subassembly to define potential pivot points

·  Describe how a corridor using an assembly with potential pivot points will use the pivot locations defined in the alignment

·  Explain how you can change the axis of rotation point and the corridor will dynamically update to reflect the new location

About the Speaker

Karen came to Autodesk Product Support in 2000 after spending 18 years in the civil engineering industry. She moved into QA for AutoCAD® Civil 3D® in 2002, and has participated in the development of various features since the inception of Civil 3D including the 2012 Superelevation Axis of Rotation feature. Her current position is senior quality assurance analyst.

Email Address:

Session Overview:

Today we will walk through examples of constructing simple and complex roadway assemblies that allow the assignment of many different non-center axis of rotation points for superelevated sections. The new subassembly, LaneSuperelevaionAOR will be used to perform these design scenarios. We’ll talk about why Axis of Rotation is essentially a work flow, as opposed to a feature. Using the alignment, profile, pivot method, axis of rotation supported assembly; we’ll examine how the corridor digests all this data to rotate superelevation sections of the roadway at inside and outside edges of lanes/pavements. We’ll examine how median geometry is handled for divided roadway types, and we’ll watch the corridor dynamically update when new pivot methods are assigned. In addition the handout for this class includes 5 appendixes which provide bonus details on, which of the existing subassemblies support axis or rotation and how users can add superelevation axis of rotation support to custom subassemblies and much more.

Session Agenda:

1.  Review the Big Picture

2.  Review new Superelevation Wizard User Interface (UI)

3.  Take a look at the new LaneSuperelevationAOR subassembly

4.  Ex. 1- Create a corridor for simple roadways using Axis of Rotation Points

5.  Ex. 2 - Create a corridor for divided roadways. Control median geometry

6.  Ex. 3 – Review ‘Towards Crown’ SA parameter for divided roadway assemblies

7.  Ex. 4 – Real life example

1.  Key Prerequisites for Success

·  Alignment Layout & Design – final or approaching final layout

·  Roadway Design Defined

Is it a divided or undivided roadway

Is it crowned or planar section type

Number of lanes each side of baseline

What about the median – does it need to change when the section warps for SE

2.  Review New UI

Existing Alignment Superelevation Wizard - Assigning Pivot Method

Alignment Superelevation Wizard

Within the existing Alignment Superelevation Wizard, on the Roadway Types page, each roadway type now has controls for assigning Pivot Method. As each pivot method is selected, graphics will display to show where the point falls on the roadway section. The methods, “inside” and “outside” are relative to the direction of the curve. “Left” and “right” are relative to the direction of the alignment stationing. “Baseline” refers to the location of the alignment/profile, whereas, “centers” refers to crown points of individual barrels in divided roadways.

**Side note regarding calculated SE lane slopes. The lane slopes that are calculated by the parameters set in the superelevation wizard do not change as a result of the selection of a non-center/baseline pivot point. All superelevation lane slope calculations use the same formula as previously released versions of AutoCAD Civil 3D.

3.  The Big Picture

There are 4 ingredients required to build a corridor whose superelevated sections rotate about non-center pivot points:

1. Have a defined horizontal alignment and vertical profile
2. Have selected a pivot method in the Superelevation Wizard
3. Have calculate superelevated lane slopes for all roadway lanes
4. Have created an assembly that supports superelevation and Axis of Rotation (AOR)

Axis of rotation is more than a feature. It is a workflow that incorporates the data from many features; alignment, profile, assemblies and the corridor object.

4.  Using the LaneSuperelevationAOR Subassembly

The new LaneSuperelevationAOR subassembly is found on the Lanes tab in the Tool Palette for civil subassemblies.

Civil Subassemblies Tool Palette

The new LaneSuperelevationAOR subassembly supports both superelevation and AOR pivot points. It is the only shipping subassembly that contains the parameter, “Potential Pivot” which allows for assigning non-center pivot locations on the roadway section.

LaneSuperelevationAOR subassembly

Using Existing Subassemblies with AOR

Many other shipping subassemblies have been modified so that they support non-center axis of rotation, meaning, if the subassembly is used in an assembly that also contains LaneSuperelevationAOR subassembly and a non-center pivot is assigned, the subassembly will work as expected. Here is an example of a subassembly that supports AOR.

ShoulderMultiLayer subassembly supports AOR

Here is an example of a subassembly that does not support AOR.

CrownedLane subassembly does not support AOR

Here is an example of a subassembly that conditionally supports AOR

Some subassemblies conditionally support AOR

For more information on AOR support for individual subassemblies, see Appendix ‘A’ in this document and, the Help for the individual subassemblies.

5.  Ex.1 Create and edit a corridor for a simple roadway section using AOR.

1.  Open ‘Begin Demo.dwg’

File Description: Begin Demo.dwg contains a horizontal alignment named “curve to the right” with a design speed of 40mph (see alignment properties). The layout profile is named, “proposed finish ground”. The layout profile was designed flat at elevation 100.00. This will make it easy to see the resulting elevation of the sections as the pivot point is applied and changed.

2.  In Prospector select alignment curve to the right, right click and select Edit Superelevation.

3.  Select Calculate Superelevation Now

4.  Select Undivided Crowned Roadway type. For Pivot Method, select Center Baseline and pick Next

5.  Accept defaults on the Lane page. This will calculate lane slopes for a total of 2 lanes, 1 each side of baseline, pick Next

6.  Accept the defaults on the Shoulder Control page and pick Next. This example does not need shoulders.

7.  Accept defaults on the Attainment page and select Finish

8.  The Superelevation Tabular Editor will open and display the calculated superelevation lane slopes.

**Side Note regarding Outside and Inside Lanes in tabular editor. The only instance where Inside Lanes will be calculated is if more than 1 lane on either side of the baseline is created. Only then will there be inside and outside lanes. Otherwise if only 1 lane either side is calculated, these are always outside lanes** See Appendix ‘B’ at the end of this document for more details.

9.  Construct the Assembly

Pick Create Assembly and notice the new Roadway Type parameter in the Create Assembly dialog.

The assembly has the ability to check to make sure that the user is creating an assembly whose section correctly represents various roadway types. If the user sets Divided Crowned as the roadway type and creates an assembly section that is Undivided Crowned, the assembly will warn the user that there is a discrepancy.

Set an incorrect roadway type, Divided Crowned, so that the warning system will be prompted. Steps to resolve will follow.

Select the assembly and open Tool Palettes

On the Lanes tab select the LaneSuperelevationAOR subassembly.

Set the following parameters and insert the subassembly on the right side of the assembly

LaneSuperelevationAOR subassembly parameters – right side insert

Proceed to insert the subassembly on the left side. Set the following parameters and insert the subassembly on the left side of the assembly

LaneSuperelevationAOR subassembly parameters – left side insert

The assembly is displaying new icons. There is a warning symbol on the assembly itself and there are flags as the end points of the LaneSuperelevationAOR subassemblies.

Warning Symbol – hovering over the warning symbol will display a tooltip that gives some information about what the warning is. This warning is indicating that no center points are found on the assembly. Recall that when we created this assembly, we set the incorrect roadway type, Divided Crowned. Because the Divided Crowned roadway type was set, the assembly is expecting to find crown points on either side of the baseline which is not present in this undivided assembly. To resolve the issue, select the assembly properties and change the roadway type to Undivided Crowned roadway type. See Appendix ‘C’ at the end of this document for a detailed list of warnings.

Pivot Flags – The default value for LaneSuperelevationAOR is to use pivot points (see image above captioned, “LaneSuperelevationAOR subassembly”). With Potential Pivot toggled on, when the assembly is inserted into the assembly, the assembly will display potential pivot flags. Any one of these flagged points could be used as a pivot point. Which point the corridor will ultimately select will be determined once the corridor is defined and the alignment tells the corridor which point method in the superelevation wizard was selected. Remember that at this moment, the assembly is independent. It has no connection at this time with the alignment so it will display all potential points of rotation.

Now that all the ingredients are ready to go; alignment is defined, the AOR point selected, lane slopes calculated and assembly created, the final step is to build the corridor which will bring all this data together.

10.  Create simple corridor

Select the alignment, ‘curve to the right’, the profile ‘proposed finished ground’ and the assembly just constructed.

11.  View the results in the Section Editor by selecting the Corridor in Prospector, right click and pick Section View Editor.

Currently the pivot method is set to Center. To observe the roadway section rotation about the center point of the road, scroll through the sections. See that the center point is the anchor and the lanes rotate about it (see center elevation 100.00 is maintained).

Roadway pivoting about Center

12.  Edit Pivot Point – To change the pivot point; go to ‘curve to the right’ alignment, right click and select Edit Superelevation.

The Curve Manager will display.

Note that you do not have to go back into the Superelevation Wizard to change the pivot point.

**Side Note recalculating superelevation data via the wizard will cause any manually edited values in the curve manager or the tabular editor to be lost**

In the Curve Manager scroll down to the superelevation criteria node and find the Pivot Method Property. Change the Pivot Method value to Left Inside

Change Pivot Method in Curve Manager

As Left Side is selected, notice what happens to the Corridor object in Prospector – it will go out of date. Rebuild the corridor and re-view the sections in Section Editor to examine the results of a Left Side pivot. To observe the roadway section rotation about the left side point of the road, scroll through the sections. See that the left side point is the anchor and the lanes rotate from it (see left side elevation 99.80 is maintained).

Roadway pivoting about Left Side

13. Controlling the location of the pivot flags on the assembly

Add another LaneSuperelevationAOR subassembly to each side of the assembly and see that the pivot flags that were at the end points of each subassembly move to the outside end of the newly added lane.

Pivot flags locations with multiple AOR lane subassemblies

The rule for potential pivot flags is, the assembly will find crown points, and find the nearest and furthest potential points either side of marked crowned points. Points in between will be ignored.

You can control the placement of a pivot flag at an intermediate point by changing the value of Potential Pivot on the outside lane subassembly to NO.

Change Potential Pivot to NO removes flags

End of Ex.1. To examine the results of the previous steps, open “End of Dem 1 – Simple Undivided Roadway.dwg’

6.  Ex.2 Create assemblies for divided highways

Non center pivot locations for divided highways have an additional consideration: medians. How should the median behave in superelevated sections?

·  Is the intention is to have each barrel rotate independently,

Each barrel rotates independently – median distorts

·  Is the intention to have the entire roadway rotate about a single pivot point

Entire section rotates about a single pivot point – median shape maintained

The behavior of the median between the barrels will be determined by which you choose.

In this example we will examine how pivoting on non-center points works in conjunction with divided highways and its effect on median geometry between the barrels.

1.  Open “End of Dem 1 – Simple Undivided Roadway.dwg’

2.  Create an Assembly – assign Divided Roadway type to the assembly

3.  This assembly is going to be created so that the lanes subassemblies are inserted at the crown points of each barrel. This is important to note and we will discuss it further in Ex.3.

4.  Select the assembly and open Tool Palette, on the Generic tab select LinkSlopeAndOffset subassembly

5.  First attach LinkSlopeAndOffset subassembly to the right with the following parameters: Offset from Baseline = 20 and Slope = 0%

6.  Next attach LinkSlopeAndOffset subassembly to the left with the following parameters: Offset from Baseline = -20 and Slope = 0%

7.  On the Lanes tab select LaneSuperelevationAOR subassembly