Significant Reduction of Errors in Cast-in-Place Concrete Structures
Valued at over £20 billion, Hinkley Point C is the first UK nuclear power station to be constructed in over a generation. Here we take a closer look at what role BIM and digital coordination played in creating its concrete structures with zero room for adaptations and rework.
Atkins was appointed as a Main Civils Detailed Designer and responsible for undertaking, assuring, and delivering the designs in 3D. As well as having a key role to play in helping trial and select the digital tools and processes at the very start of the project, alongside BYLOR and other major parties, Atkins delivered around 60% of Hinkley Point C’s reinforced concrete scope. Their work primarily focused on the construction of the nuclear plant’s Conventional Island, including 33 buildings and 10 km of underground tunnels.
Speaking about the project, Steven Burton, Associate Director – HPC Innovation and Digital Lead at Atkins, said:
Working in a safety-critical industry such as nuclear, it’s essential that you have an accurate, coordinated and as-built constructible model before you reach the site and begin construction. Essentially our models achieve an as-built like status, before the concrete is poured. For example, when it came to the reinforcement and embeds on Hinkley Point C, we were not allowed to post-fix fixings (such as those used to secure plant equipment); it all had to be cast-in-place. This meant that we were designing to incredibly tight tolerances, with zero room for adaptations or rework once the concrete pour had begun.
Given the scale of Hinkley Point C, we were dealing with incredibly dense reinforcement – densities that were three or four times that which you would see on a typical residential development. This drove the decision for us to carry out all the rebar modelling in 3D, rather than 2D, helping us to meet the demands of the site and deliver the nuclear quality required. Our involvement on this project first began back in 2014, when using BIM for rebar detailing wasn’t the norm. 3D modelling software for rebar detailing really was very much in its infancy and still evolving; as a result, there was also a lack of skilled and experienced rebar detailers, who had experience working in 3D, available too. In many ways, rebar was one of the last segments of the steel industry to truly adopt digital technology and digital workflows.
Using Tekla Structures, the level of detail and enhanced visibility that the software facilitates was critical in helping us to create this fully assured, coordinated and accurate model. In total, we have so far delivered around 60 million pieces of rebar and over 2 million embeds, all completed to 3mm tolerances. We would never have achieved this level of detail or precision without the use of BIM, with the 3D digital environment providing us with an assured, coordinated and validated design.
The completed 3D models also proved useful at other stages of the project too, both in the drawing office and on site, enabling a digital rehearsal of the works.
Using the data and information contained within the model, the team could work out how all the reinforcement elements were going to be brought together and constructed. This enabled us to optimise the construction sequence before reaching the site, helping to maximise productivity levels and improve safety.
We were also able to transfer the model to site, through the use of IFCs. We built up the model as a set of components, with each individual piece of rebar automatically tagged with three levels of assembly: Level One related to the rebar cage; Level Two dictated which wall or other structural component it helped form; and Level Three identified the overall building. This had a really positive effect on site logistics, enabling the project to fully control and manage the reinforcement, from the procurement of the rebar to the fabrication, delivery and on-site assembly. Through linking the schedules with the concrete pours, the rebar only arrived on site when it was needed and was easily bundled up into the individual ‘kits’, meaning that the contractor had easy visibility of exactly what concrete pour they needed to do and which rebar cages formed a part of that pour.
Tekla Structures is just a small part of the Trimble portfolio of products that have been used and continue to be used by BYLOR and Atkins on the construction of Hinkley Point C, one of the biggest and most complex projects in Europe.
Watch the video case study here to learn more.
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