This steel jetty will act as a temporary causeway for the upcoming HS2 project, Colne Valley Viaduct.
The temporary Jetty spans over four lakes in the South Harefield region and will enable plant and material access to the middle of the lakes where cofferdams will be used to pile into the lake bed for the columns of the viaduct. This infrastructure project is one of the largest in the UK and once completed will also be one of the longest viaducts in the country. At pier locations, the jetty will be widened to include the whole working area, with decking sections removed as required for permanent piling and to construct cofferdams. 292 bored cast-in-place piles will be required to support the piers and abutments. These will be up to 55 m in depth, with a diameter of 1.5 m to 1.8 m.
Clever use of custom components
To begin with we were working with an already tight programme schedule and an incomplete design, making it challenging to decide how to start the model knowing there will be definite upcoming changes to the design. With time pressing on, and with such a large volume of steel needing to be secured by the procurement department, the team decided to opt for using a largely complex custom component with 860+ parameters. This was also necessary as the viaduct follows a very gradual curve over a 3 km distance, so was near impossible to get right using a copy to another plane or copy to another object approach.
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 would fill the gap with the top deck and all the latticed steelwork. This method allowed for modifications to be made to every deck simultaneously within the custom component editor, whenever we were provided with a new design change.
Once steel started to arrive on site and it was reported that 12 meter decks were landing on pile caps to within 2 mm of desired location at every single location, the team were incredibly proud that the method was so successful. A section of the jetty, also known as 'Jetty D', had to follow an exaggerated curve which meant the custom component had to be abandoned for these five decks as it was too extreme to use. We ended up having to do it manually, and this was the only exception within the project.
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Important points or benefits:
- The temporary jetty is over 3 km in length with circa 3600 t of steelwork issued for fabrication.
- 240+ GA drawings, 1200+ assembly drawings and 1700+ fittings drawings.
- Taziker not only acted as a fabricator but installed the steelwork too.
- NC data was exported to steel profilers, who used a drill line to cut all the holes in the steelwork, so it came into the fabrication workshop pre-drilled. NC data was also used to get the plates all profiled before they came into the workshop.
- The model was accessible to the fabrication team in the workshop on Trimble Connect, where they could properly keep track of the steelwork coming into the shop, a task that would have been challenging without it, due to the volume.
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