Bridge Detailing 2.0: Computational Modeling Methods Using Civil 3D, Revit, and Dynamo

  • Civil 3D offers the most relevant tools for ‘linear’ element and earthworks design. By using shared project data shortcuts to alignment and surface content, the bridge model geometry is linked to the alignment design and other multidisciplinary project content.
  • Revit outputs provide parametric object modeling, as well as schedule and 2D drawing content creation.

A Real-World Case Study

‘Bridge K’ is a 160-meter long cycleway bridge over the River Severn in the UK, comprising seven spans of lightweight steel deck construction with reinforced concrete approach ramps at either end. The main cable-stayed river span is 70 meters long, supported by 26-meter high dual steel masts with 5No. support cables on each side of the deck.

The Site

The chosen bridge site over the River Severn is well suited to a cycle bridge; topology is relatively flat and ground levels on either side of the river are similar, leading to a bridge long section with a very shallow longitudinal gradient and only one vertical change in direction. Whilst ground conditions are fair it is likely that piled foundations will be required.

The Workflow


CivilConnection is a Dynamo for Revit package that enables the exchange of information between Civil 3D, Dynamo, and Revit. You can download the open source package, along with reference documentation. Its features include:

  • The ability to work directly with an open instance of Civil 3D, pulling data into Dynamo in a live fashion for immediate updates
  • The ability to read corridor features including alignments, auto-corridor feature lines, and assembly shapes
  • Placement of Revit elements according to feature line information
  • Lofting of assembly shapes into smooth mass solids with no faceting/tessellation
  • Creation of AutoCAD entities
  • Sending commands to the Civil 3D command line and creation of command line scripts

Element Breakdown

Successful deployment of any automation methods requires a clear modeling strategy from the outset, and a clear understanding of how each structure element shall be produced and controlled in terms of position or dimensions. This article defines bridge elements in terms of three broad categories, and in our modeling method we’ll be tackling these as follows:

Modeling Method

The overall workflow can be summarized as follows:

Subassembly Composer


The composer comes included as an optional subcomponent of Civil 3D and is not available separately. If you don’t see it under the Civil 3D heading in your Start bar:

  • Go to Apps & Features in the Windows settings/Control Panel
  • Find the relevant installation of Civil 3D
  • ‘Modify’ the installation, and add the Composer when prompted

Step 1: Creating Parameters

Creating your parameters first will allow you to then apply these within the points configuration in the next step. Think carefully about what parameters you require and how you want your assembly to ‘flex’; careful consideration now may make for fast design changes later, as parameters can be changed in the Civil 3D environment once loaded. Let’s look at the primary deck cross section for Bridge K:

Step 2: Adding Points and Links

  • Points define the basic structure, and when coded, produce auto-corridor feature lines
  • Links connect points, and when coded, produce surfaces
  • Shapes are defined by a closed region of links, and may be extracted into solids

Step 3: Defining Variables

Adding variables to your subassembly flowchart is a way of parameterizing expressions, allowing them to be recalled and used quickly throughout the flowchart.



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Aashish Mathew George

Aashish Mathew George


Entrepreneuring | curious thinker | technology advisor | photographer at stories by AMG | CTO of paradigm IT |