From the early conceptual design stage, the AKT II team worked on forming a structure that is stiff and resilient. Every piece and surface within Vessel either provides the strength for the structure to withstand large crowds of people (1,500 people at the same time) or provide stiffness, for it to be rigid enough to avoid excessive vibration when occupied – whether that be people dancing on the structure or in the event of an emergency evacuation.
“This project highlights a distinct game-change taking place in our industry. The design has been enabled using pioneering interoperable modelling, where geometry, structural performance and material are controlled, manipulated and optimised in one single modelling environment. Vessel is probably one of the first built examples designed using a shared workflow between the wider design team.”
Edoardo Tibuzzi, Associate Director AKT II (p.art®)
In designing the structure, we developed a workflow with Heatherwick Studio based on a parametric model, which created both the structural and the architectural models that allowed building regulators to ensure Vessel was compliant regarding stairs and rises.
Because the structure is not conventional, with no floors and columns – the structure is comparable to a massive pseudo spring – it is more susceptible to vibration and footfall of crowds. To counter this, the AKT II team had to carry out sophisticated, non-linear dynamic analysis to assess the level of comfort people would experience when occupying it. Due to the structure’s unique nature, there was no precedence or comparison to draw upon; whilst the dynamics are similar to a football stadium, there is no real similarity.
The structure stands 46 metres tall, 46 metres in diameter with only a 15-metre wide footprint (Thomas Heatherwick was keen to maintain the slenderness of the base). We also worked on the design of a parabolic elevator within the structure, to carry those unable to climb the stairs. In order to mitigate the vibrations, tuned mass dampers were installed in the landings within the top section of Vessel, mounted on springs, to counterbalance the oscillations produced by visitors.
“Vessel’s performance was assessed under extreme conditions of vertical and horizontal accelerations due to the response of the structure to an asymmetric jumping simulation of a group of people at the very top rings. Tuned mass damper positions were optimised to reduce the acceleration response of the structure under these conditions.”
Alessandro Margnelli, Technical Director AKT II