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Unlocking design flexibility: BIM software and temporary works on HS2’s Colne Valley Viaduct

Screenshots of the Colne Valley temporary jetty built by Taziker, in Tekla Structures

With a tight programme schedule, the use of Tekla custom components proved essential on the construction of HS2’s Colne Valley Viaduct temporary works, enabling Taziker to navigate design changes and modifications timely and efficiently.

Stretching for over two miles (3.4km) between Hillingdon and the M25, the Colne Valley Viaduct forms a critical part of the HS2 network. Carrying the railway around 10 metres high above a series of lakes, the River Colne and Grand Union Canal, the viaduct will be the longest railway bridge of its kind in the UK once completed. The design of the structure was inspired by the flight of a stone skipping across water, with a series of elegant spans making up its construction.

The project is being led by HS2’s main works contractor Align JV – a team made up of Bouygues Travaux Publics, Sir Robert McAlpine and VolkerFitzpatrick.

Understandably the construction of the momentous structure has come up against various logistical and engineering challenges, not least the location and tricky terrain. One of those challenges was to construct 292 bored piles, required to support the piers and abutments of the bridge. In order to enable these works and provide safe access for plant equipment and materials operating over the lakes, a series of temporary steel jetties were required. Spanning over four lakes in the South Harefield region, this temporary causeway was detailed, fabricated and installed by Taziker.

Screenshot of the Colne Valley temporary jetty in Tekla Structures

Measuring at over 3,000 km in length, the temporary jetties were constructed from circa 3600 tonnes of steelwork. At each pier location, the jetty was further widened to include the whole working area, with modular decking sections removed as required for permanent piling and to construct cofferdams.

Speaking about the project, Jarrod Hulme, MD Structural Solutions at Taziker said: We were working with an already tight programme schedule, making it challenging to decide how to start the model knowing there would definitely be upcoming design changes. With time pressing on, and with such a large volume of steel needing to be secured by our procurement department, the team decided to opt for using a largely complex custom component with over 860 parameters.

This was also necessary as the viaduct follows a very gradual curve over a 3.4km distance, meaning it was near impossible to detail correctly using a ‘copy to another plane’ or ‘copy to another object’ approach.

Through our use of custom components, once the crossbeams had been put into the model across the top of all the pile caps, all that was required was selecting one crossbeam, then another and the custom component created in Tekla Structures would automatically fill the gap with the top deck and all the latticed steelwork. This method allowed for modifications to be made to every deck simultaneously and efficiently, whenever we were provided with a new design change, as all parameters were interconnected.

Once steel started to arrive on site, it was reported that our 12-metre decks were landing on pile caps to within a 2mm tolerance at every single location – a fantastic result and our team were incredibly proud that the method was so successful.

photograph of the Tazkier Colne Valley temporary jetty at the Colne Valley ViadcutAs well as using Trimble’s Tekla constructible modelling software at the detailing stage, Taziker also utilised the cloud-based Trimble Connect platform once the steel had reached fabrication, enabling greater communication and traceability throughout.

Jarrod explained: By using Trimble Connect, the 3D model was easily accessible to the fabrication team in the workshop. With access to this level of detail and data, they were able to easily keep track of the steelwork coming into the shop, a task that would have been incredibly challenging without the software due to the sheer volume of steel.

In total, Taziker produced over 240 general arrangement drawings, over 1200 assembly drawings and over 1700 fittings drawings for the fabrication and construction of the Colne Valley Viaduct temporary jetties.

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