London’s One Nine Elms development was named Best Commercial Project in the 2020 Tekla Global BIM Awards. The engineering team won praise for planning the rebar under challenging conditions, using Tekla software to create a raft supporting one of the longest continuous concrete pours in the city’s history.
For a city of some 2,000 years old, London produces more than its fair share of modern architecture. The past decades have seen the city’s skyline transformed again and again by iconic structures that set new boundaries in building design.
One of the latest projects evolving London’s architecture is One Nine Elms. Set on the south bank of the Thames river, One Nine Elms is a EUR 330 million mixed-use development – combining residential, commercial and a five-star hotel – set for completion in 2022. There is also an underground carpark and an on-site energy control center.
“The use of a single, shared model certainly helped immensely the coordination and communication in this demanding project.”
Aarni Heiskanen, Construction Innovation Agent, member of the Tekla Global BIM Awards 2020 jury
The two visually striking glass towers of One Nine Elms completely transform the London borough of Wandsworth. The lower tower, which features the development’s hotel, is 160 meters high. Its counterpart reaches 200 meters, making it the tallest residential building in western Europe.
Solving the top-down challenge
One Nine Elms is significant from the Building Information Modeling (BIM) perspective for two related reasons. The project’s rebar detailers – Solve Structural Design – used Tekla’s 3D software to manage the challenges of top-down construction for the development’s three-floor basement. The steel raft they created then supported what was one of the longest continuous concrete pours in London’s history: some 5,000 m³ of concrete pumped in just 36 hours.
Developers typically choose top-down construction for its efficiency, but it does create challenges for rebar detailing. Planners need to ensure that a means of rebar continuity – such as couplers and pull-out bars – are provided in the slabs for all vertical elements, before moving to the next sub-level.
In the case of One Nine Elms, the re-bar design challenges were compounded by the fact that the core base raft for one of the buildings was constructed under very tight conditions. This meant that all equipment and materials had to be supplied through two small mole holes.
Another issue the planners had to contend with was the presence of a Victorian-era sewer – still in use – cutting across the site just beneath its surface. After consulting with London’s waterworks authorities, the developer opted to keep the sewer in place and carefully construct the slab around it.
Tekla Structures: a single source of truth
With a Tekla 3D model serving as the single source of truth, the rebar detailers were able to identify and design around the congested areas, as well as avoid costly rebar clashes. This minimized the cutting and changes typically associated with a project of this nature, which in turn kept delays to a minimum and meant on-site work was safer. All this was especially critical amid the tight conditions and considering the size and complexity of the subsequent continuous pour for the taller tower.
The project has also won praise for the way in which the various construction teams collaborated around the Tekla 3D model. Using tablets to view the model on site and Trimble Connect to communicate effectively, the different team members were able to discuss and agree on the details that kept the raft work on schedule despite the challenging conditions.