Add Custom Nested Family for Corridor

Why Build a Custom Nested Family?

AutoBRIDGE generates corridors by sweeping a nested adaptive family along an alignment. The nested family defines the bridge cross-section shape — deck slab, girders, voids, barriers. Building a custom one gives you complete control over the geometry, parameters, and subcategory assignments used across the entire corridor.

Family Manager Interface

Before diving into the build steps, it helps to understand the five zones of the Family Manager panel you will use in Phase 4:

Adaptive Family Creation

Start by creating a new Metric Generic Model Adaptive family. This is the cross-section container that AutoBRIDGE will sweep along the alignment. Alternatively, copy the existing template from the AutoBRIDGE install folder and modify it — much faster for most projects.

01

Create a Metric Generic Model Adaptive Family

Go to File → New → Family and select the Metric Generic Model Adaptive template. Open the new family editor.

Select the Metric Generic Model Adaptive template to start the nested family

02

Open Front View

Switch to the Front view in the Project Browser. This is where the cross-section geometry and adaptive point will be built.

Work in Front view to set up the section geometry and adaptive points

03

Add Asphalt Reference Plane & Parameter

Draw a reference plane at the asphalt depth offset and assign a dimension parameter (e.g. Asphalt_Thickness) to control it. This lets the asphalt layer thickness be varied per corridor span.

Reference plane with a dimensioned Instance parameter for asphalt thickness

04

Set Work Plane to Center (Front)

Before placing the adaptive point, go to Set Work Plane and pick Center (Front). This ensures the adaptive point is placed at the correct origin for rotation control.

Set work plane to Center (Front) before placing the adaptive point

05

Add the Intersection Adaptive Point

Place an adaptive point at the intersection of the vertical Center (Front) reference plane and a new horizontal reference plane. This intersection point is the rotation pivot for the cross-section.

Adaptive point placed at the intersection of vertical and horizontal reference planes

06

Associate Rotation to Superelevation Parameter

Select the adaptive point and set Show Reference Planes to Always. Then associate the rotation angle to the family parameter Superelevation. AutoBRIDGE will drive this parameter from the Civil 3D or corridor data during creation.

Rotation angle of the adaptive point associated with the Superelevation instance parameter

07

Set Work Plane to the Adaptive Point Surface

Use Set Work Plane → Pick a Plane and click the surface of the adaptive point. All subsequent geometry must be drawn on this plane to inherit the rotation correctly.

Work plane set to the adaptive point surface to ensure geometry rotates with the section

Geometry Creation & Rotation Test

Draw the cross-section reference lines and attach instance parameters for all key dimensions. Then test that the superelevation rotation works before adding the boundary splines.

08

Create Reference Lines & Dimension Parameters

Draw reference lines to define the section outline — for example a box girder shape. Add instance parameters for each key dimension: Right, Left, Depth, and any other corridor dimension required. Remember: no formulas, Instance only.

Reference lines with Instance parameters — Right, Left, Depth and section dimensions

⚠ Critical parameter rules:

• Every parameter must be Instance — not Type.
• The formula column must be completely empty for all parameters. No formulas of any kind.

These rules are non-negotiable. Violations will cause AutoBRIDGE to fail during corridor generation.

09

Test Superelevation Rotation

Enter a value in the Superelevation parameter and verify the entire section rotates correctly around the adaptive point. If an error appears, dimensions are constrained to non-rotating reference planes — remove the incorrect constraints and reapply them to the adaptive point's work plane.

Rotation error — dimensions incorrectly locked to a non-rotating reference plane

10

Rotation Success — All Geometry Rotates Correctly

When set up correctly, the entire cross-section rotates smoothly with the Superelevation parameter. Reset to 0 before continuing to the boundary phase.

Superelevation rotation working correctly — all geometry follows the adaptive point

Boundaries & Subcategories

Draw the outer (solid) and inner (void) boundary splines through the reference line endpoints, create named subcategories in Object Styles, then assign each subcategory to the correct boundary. AutoBRIDGE reads these subcategory assignments to determine which geometry is structural material and which is a void cut.

11

Reset Rotation & Draw Boundary Splines

Set Superelevation back to 0. Draw a Model Spline through the outer boundary points (deck extents) and a separate spline through the inner boundary points (hollow void). Each closed loop becomes one subcategory.

Outside boundary (solid) and inside boundary (void) drawn as separate closed splines

12

Create Subcategories in Object Styles

Go to Manage → Object Styles → Generic Models. Click New to create two subcategories — one for the solid outline (e.g. Deck_Solid) and one for the void (e.g. Void_Box). The exact names will be shown in AutoBRIDGE's family selector.

Creating solid and void subcategories under Generic Models in Object Styles

13

Verify Both Subcategories Are Created

Confirm both subcategories appear in the Object Styles list before proceeding. The colour assigned here will be the colour used in AutoBRIDGE's 2D section preview.

Both subcategories confirmed in Object Styles — solid and void correctly listed

14

Assign Subcategories to Boundaries

Select the outer boundary spline → Properties → Subcategory → assign the Solid subcategory. Select the inner boundary spline → assign the Void subcategory. Save the family with a unique name.

Solid subcategory assigned to outer boundary; Void subcategory to inner boundary

Tip — Sub-nested families without rotation: You can load additional sub-nested families onto the rotated adaptive point without applying rotation to them. This allows more complex geometry to be controlled independently inside the corridor.

AutoBRIDGE Family Manager

Register the completed nested family in AutoBRIDGE's Family Manager. This makes it available as a cross-section option in all corridor creation methods.

15

Open AutoBRIDGE → Family Manager

Click the Family Manager button in the AutoBRIDGE ribbon tab. The interface opens with five zones: Nested Family Preview, Template Section, Nested Family List, Subcategory List, and the Current Template indicator.

Family Manager — five zones for managing templates, families, and subcategories

16

Create a New Template

In the Template Section, click New Template and enter a name that reflects the project or bridge type (e.g. BoxGirder_TwinCell_v1). Templates group nested families together for reuse across multiple corridors or projects.

Create and name a new template in the Family Manager Template Section

17

Set the Template as Current

Select the new template in the list and click Make Current. Only the current template is used during corridor creation — this step is essential before adding the nested family.

Template selected and set as current — it will now be used for corridor generation

18

Add the Nested Family

Click Add in the Nested Family List and browse to your saved nested family .rfa file. AutoBRIDGE reads the family, validates its parameters and subcategories, then displays a success message.

Nested family added successfully — AutoBRIDGE validates parameters and subcategories on import

19

Verify the Nested Family Appears in the List

Confirm the nested family name appears in the Nested Family List and the subcategories (solid and void) are shown in the Subcategory List. The 2D preview panel should display the cross-section outline colour-coded by subcategory.

Nested family visible in the list with subcategories correctly detected and previewed

Corridor Validation

Open any AutoBRIDGE corridor creation tool and confirm that the new template and nested family are correctly detected in the Family section. Then run a test corridor to validate the geometry end-to-end.

20

Confirm Family Appears in Corridor Creation

Open AutoBRIDGE → Corridor Creation (Civil 3D, 3D Polyline, or 3D Mass method). In the Family dropdown, confirm the current template name and your nested family are shown correctly.

🏗️

For full corridor creation steps, see: Corridor Creation Workflow →

Custom nested family correctly visible in the Corridor Creation family selector

21

Corridor Generated Successfully

Run the corridor and verify the output. The cross-section geometry, superelevation rotation, solid extrusions, and void cuts should all appear correctly along the full corridor length.

Corridor successfully generated — custom section with correct solid and void geometry

Reuse tip: Keep consistent parameter names and subcategory labels across all your nested families. Templates using the same naming convention can be swapped between projects without rebuilding any families.