Bridging the gap from design to installation with Tekla Structures

Designed to offer visitors to Telford an impressive gateway into the town, the new Telford Central Footbridge project is an excellent example of a collaborative approach to construction, with Trimble’s Tekla Structures software playing an important part in the process.

The scheme, funded by a Department of Transport grant, involved the replacement of an existing footbridge that linked Telford Central train station to the town centre. The old footbridge, viewed by many as offering an unwelcoming view to visitors, did not meet modern design standards or disability requirements and was no longer cost-effective to maintain.

The new bridge spans across two dual carriageways, used by around 14 million vehicles a year, as well as a live railway, with four trains passing beneath it per hour. As a result, the working area for construction was very limited and careful coordination and planning were essential in order to ensure that minimum disruption was caused to the road and rail users during the installation on site.

As part of the delivery team (Nicoll Russell Studios/Jacobs/Balfour Beatty), SH Structures assisted with the design development before being tasked with manufacturing and installing the new footbridge. The company has relied on Tekla as its default software system for many years, as Tim Burton, Sales and Marketing Manager at SH Structures, explained:

Tekla Structures provides exactly what we need on complex engineering projects, such as this. We have used Tekla since 2000 and the software is now embedded within all our manufacturing, purchasing and site installation systems. It was used throughout every stage of the Telford Central project, from design to fabrication and installation.

Tekla Structures was used for all the modelling and detailing work required on the project, which, due to the nature of the work, was extensive. In addition to the primary steel structures, which included the two bridge spans, lift towers, approach ramps and stairs, SH Structures also provided all the architectural finishes. Using the Tekla model, they were able to model the tensile fabric roof covering, Glass Reinforced Plastic (GRP) soffits and all the glazing for the bridge and lift shafts.

Tim continued: The developing 3D model became the hub of everything we did on this project. It enabled us to fully develop the details of, not just the primary structure, but all the critical interfacing elements and finishes.

The software also has significant benefits as a collaborative tool. The ability to exchange 3D data between the various members of the professional team dramatically improved the efficiency of the design stage, enabling the quick resolution of any issues raised. The team were able to work remotely, reducing the need for design or coordination meetings, with clear financial benefits to all those involved.

However, Tekla Structures is not just limited to the design stage of a project, for the software can also ensure a smooth information and work-flow from detailing through to production. Tim said: Once we had the completed 3D model, we were then able to use the information it contained to produce all the fabrication and shop assembly drawings for the individual bridge components. The benefits of the constructible data being directly transferred from the model to the fabrication and assembly drawings are huge, minimising the possibility for error or subsequent delay both off and on-site.

When working on a project of this size, the final assembly and installation of the structure can often present just as many challenges as the initial design stage. Considering the location of the footbridge, the large number of components and architectural finishes, as well as the bridge itself, SH Structures had to invest a lot of time into the planning of the installation process. A trial-assembly took place in Yorkshire prior to transporting the fabricated sections to Telford, with Tekla Structures and the 3D model used extensively in the development of the on-site methodology.

In order to safely install the footbridge with minimum disruption to road and rail-users, the bridges were lifted into place during overnight rail and road closures. As a result, it was imperative that the installation was carried out efficiently and within the allotted time period, explained Tim Burton.

Prior to commencing an installation of this size and complexity, we must first produce a plan that meticulously details our whole assembly method, accompanied by lifting assessments and crane layouts, all of which we were aided by the Tekla model. The software enabled us to extract accurate weights of components and the centre of gravity of complex assemblies, including the bridge structure itself; all information that was crucial for optimising crane locations and ensuring an efficient and safe installation.

Due to the sheer size of the structure, the footbridge had to be split up into transportable sections and then re-assembled on-site, along with the installation of the various architectural fittings, continued Tim Burton.

As a result, various temporary works were required in order to assist with the assembly of the fabricated sections. Thanks to the software’s flexibility, being suitable for use on both permanent and temporary structures, SH Structures once again turned to Tekla Structures for assistance.

To carry out the assembly, shallow pad foundations and temporary steel support frames were constructed on-site, enabling the footbridge structure to be correctly aligned whilst being welded together, prior to being lifted into place. It was vital that these temporary works were modelled accurately using the existing data from the 3D model and fabrication drawings, as any errors could have resulted in costly re-work, delayed completion of the project or even damage to the structure itself.

It was also decided that the majority of the aesthetic finishes would be installed whilst the two bridges were sat on the temporary works, thus eliminating the need for work to be carried out above the road and railway.

The new Telford Central footbridge was successfully lifted into place in September 2018, with an official opening of the bridge due to take place in spring 2019.

Tim Burton concluded: Trimble’s Tekla Structures was invaluable on this project, assisting at every stage of the process, from the initial design right through to assembly and installation. The 3D model was at the centre of everything we did, with its accurate and constructible data easily transferable, helping create the fabrication drawings, installation methodology, crane layouts and temporary works details. The project brought with it many challenges but undoubtedly Tekla helped us overcome them, allowing for a smooth and efficient delivery of this complex scope of work.

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Images courtesy of: Nicoll Russell Studios (main images no.2) and Balfour Beatty.