Parametric design delivers on Barkston Ash rail bridge

In preparation for the rail line’s electrification, the Transpennine Route Upgrade is underway, with the initiative designed to transform journeys across the North. Better connecting towns and cities between York, Leeds and Manchester, the initiative will enable more frequent, faster and heavier passenger and freight trains to run.

The Barkston Ash Rail Bridge, which carries the rail network over the A162 London Road in North Yorkshire, is one of many new bridges being constructed as part of the upgrade. In collaboration with Harrisons Engineering, who undertook the fabrication work, Double Check Digital Engineering detailed the U-Type rail bridge structure in strict accordance with Network Rail Standard Designs, ensuring compliance within the existing railway infrastructure.

This marked the second U-Type bridge detailed by Double Check Digital Engineering, with the first modelled conventionally using Tekla Structures. For the Barkston Ash bridge, the team chose to introduce parametric modelling techniques, taking advantage of the direct link between Tekla Structures and Grasshopper.

Parametric design

Speaking about the discovery of parametric design, Glyn Holland, Managing Director at Double Check Digital Engineering, said: “I’ve always had an open mind to new modelling tools and thinking ‘is there an easier way of doing this?’ I remember when the Grasshopper-Tekla Structures live link was first launched; I became really interested in the capabilities and advantages it offered, fuelled by a Trimble webinar I had attended. After investigating further and taking an eLearning course, I tried applying the learnings on a project at my previous company, to great success.

“Fast forward to starting Double Check Digital Engineering in 2022 and I knew it was a workflow and approach I wanted to continue to build upon. After hiring a second engineer, Canaan Thomas, who came from a coding background, this really advanced.”

By taking the Network Rail Standard design information and creating a bespoke script in Grasshopper, the team could apply basic parameters to the algorithm to resize and adjust the output design accordingly. The script was then automatically written out to Rhino 3D, which produced a wire framed model, before being imported to Tekla Structures. Here, attributes were applied, including grades, profiles, thicknesses and numbering information, providing a completed and accurate model for fabrication.

Streamlining the design process

Glyn continued: “The benefits of this workflow are numerous but perhaps the key one is time savings. We spent a month modelling the first U-Type bridge conventionally using Tekla Structures. While the initial development of the Grasshopper script took roughly the same time, running the script on future U-Type bridge projects will take only around twenty minutes, cutting the design process down to 0.05% of the time it would have taken conventionally!

"Running the script on future U-Type bridge projects will take only around twenty minutes, cutting the design process down to 0.05% of the time it would have taken conventionally!"

“Repeatability is really where Grasshopper shines, especially when dealing with standardised designs. By developing this script for the Barkston Ash bridge, we can easily change the position and heights of the bearing locations to suit any new and similar projects that fall under the same Network Rail standard drawing framework.

Looking ahead to the future

“Ultimately, our goal is to revolutionise BIM workflow methodologies by extending the script's capabilities to output to various discipline-specific software platforms, as well as build up a library of standard structures and scripts. A host of components within the rail sector, such as footbridges, staircases, wheelchair ramps and lift access, all follow standard design processes – perfect for parametric design. Likewise, the highways sector is a similar case, where parametric principles can be easily applied.

“If this was to be adopted across the industry, the advantages would be numerous. For example, we could create a script and send it to the structural engineer for analysis, before being written out to the fabrication software. With an authentic data-rich source, all models would be connected via a coded script and set parameters, resulting in a more coordinated output.”

The Barkson Ash rail bridge was installed in Summer 2024, taking just eight days to remove the old bridge, replace the deck with the new stronger metal structure using a 700-tonne crane and renew the railway tracks.

For more information, please visit: www.tekla.com/uk.