The challenges of building on a cliff edge

The engineering challenge of replicating the natural environment in an ambitious location was realised using 3D design modelling software

Inspired by large sculptures and the rocky outcrops of nearby Dartmoor, the Hux Shard from architects Squirrel Design – as seen on Channel 4’s Grand Designs – has a striking geometric appearance and provided TWP Consulting Engineers with a significant challenge.

With the building’s geometric architecture inspired by Dartmoor’s wild granite tors, the Hux Shard’s exterior walls are formed of 34 shard-shaped sculptural panels, set in a jagged 70-metre line following the contours of the hill on which the property stands. It is the combination of these immense shards and the exposed rural landscape that was perhaps one of the key challenges for TWP as the structural engineers appointed to successfully deliver the project.

The building’s design required a series of large concrete pad foundations and short steel columns, which in turn support the gigantic timber frame’s floor structure and roof. The primary building frame consists of 282 glulam timbers, which were bolted together with steel brackets to form a wooden skeleton over seven metres high. The property’s exterior walls were then formed from 34 insulated timber shards, each around 600mm thick and clad in zinc, and interspersed with 46 equally complex glazed panels. As if that wasn’t enough of a challenge, the whole structure is also partially suspended, raised 0.5-1.5m off the ground. 

Nick Drew, Director at TWP explains: “Perhaps the main challenge on this project was the shard-shaped panels that form the building exterior and which serve to create the dramatic geometric impact of the overall building. Due to the intended architectural aesthetic, there is no uniformity to the panels, no parallel elements and no true 90-degree angles. Each of the shards is wholly individual; they are all at different angles to one another, and the whole property was also slightly curved on plan.

“As if those design complexities weren’t challenging enough, the shards were also incredibly large – some as tall as a two-storey house. Given the exposed and elevated hilltop location, the concern was that the shards would effectively act as sails, capturing a lot of wind and putting more stress into the primary structure itself. As engineers, we had to ensure that this wind loading was accounted for in the engineered design and that the shards wouldn’t place unnecessary strain and deflection on the primary structure and glazing.”

Design technology

TWP turned to its trusted Tekla Structural Designer software for help in bringing the client and architect’s dramatic vision to life. “Fortunately for us, it has an automated wind loading feature, meaning that we were able to quickly and automatically model and calculate full-building wind loads,” Nick says.

“In turn, this gave us a far better economy for an optimised design – rather than the alternative of manually considering the loads, which is often based on the worst-case scenarios and doesn’t necessarily provide the whole picture.”

Given that every timber shard is unique, with different heights, raking lengths and angles, each panel had to be modelled and constructed individually within the Tekla modelling environment.

“This, combined with the jagged layout of the shards and the uneven ground level, provided us with another challenge – namely, how to create clear layers in the software,” Nick says. “It was imperative that we were able to create clear layers and gridlines, as well as ensuring that the gridlines were named correctly, as this information then referenced back to the gridline’s respective shard. Without the ability to clearly and concisely complete and model this in the software, it would have presented some serious difficulties and confusion that would have affected the whole project delivery.”

In addition to the timber panels, 46 equally large glass panels are interspersed throughout the building’s exterior walls and roof, designed to help draw natural light into the property. “A priority for us was stability, and ensuring the overall building is stiff enough,” Nick says. “Given the combination of glass and timber, it was vital that there were no differential variations between the frames, as this would run the risk of the glass shards cracking or shattering. Again, we were able to efficiently model and analyse all of this in the software, viewing all of the loads, deflections and stresses present in the building design.”

While the Tekla software is more known for its use with concrete and steel design, its capabilities are expanding for timber design. Indeed, as the emphasis on sustainability and the embodied carbon value of buildings continues, timber will inevitably become a more popular building material among clients, engineers and contractors.

“More and more timber is being used on construction projects such as this as people focus more on sustainability,” Nick says. “With the Tekla software, we’re able to analyse the timber building design and understand all forces and potential stresses. Then the software’s integration and interoperability enables us to export the data on the timber beams directly into Tekla Tedds, saving us considerable time.

“When you’re working on a project of this complexity, the ability to spin the 3D model around and interact with it, really understanding how it all relates, fits and connects together, is invaluable. Thanks to the software and the 3D environment that it provides, we were able to finish our engineering work within a three-month period – without it, I can only imagine how long it would have taken.

“It was certainly a fascinating and an ambitious project, with a significant reliance on engineering principles to create and bring the vision to life.”

More details at huxshard.uk, tekla.com/uk  and twpeng.com. For more inspired architecture, visit squirrel-design.co.uk

Image credit | Squirrel Design | Tekla

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