Full project details
The 224 metre building is one of the most recognisable in the square mile, occupying a prominent site directly opposite the distinctive Lloyd’s of London headquarters.
Design and engineering
The structure’s distinct asymmetrical shape – a response to planning requirements to maintain views of St Paul’s Cathedral – meant settlement both in the foundations and through compression of its elements would be irregular. The solution was to design the building to be erected slightly off the vertical so that it would settle in its correct form. This made the construction process exceptionally challenging. Working with tall building expert, Bill Baker of Skidmore, Owings & Merrill, Laing O’Rourke came up with an innovative alternative. Now, when the building reaches the 19th floor, steel along the sloping face will be tensioned to pull the structure back to the vertical. This process will be repeated every seven storeys.
An iconic building
The development’s tapering shape, which when viewed from the west appears to ‘lean away’ from St Paul’s Cathedral, delivers varied sizes of floor plates, all offering spectacular views over London. Practical completion of the shell and core is scheduled for mid-2014. Exceptional engineering skills were necessary therefore, to develop a construction methodology that enabled the building to stay upright – with tolerances of plus or minus 20mm required on all but five of its floors.
Using multidimensional Building Information Modelling (BIM) technology, Laing O’Rourke devised an innovative delivery strategy that harnesses the benefits of offsite manufacturing. This ‘virtual construction’ approach allowed the client to visualise our solution in intricate detail. Critically, by integrating data from the architects and structural engineers, the team was able to achieve the early design coordination needed to meet such a challenging programme. The model also combines information from key trades to ensure the compatibility of the different packages.
Logistics and DfMA
The intense public interest in the development leaves no room for logistical error. Its high-profile location – characterised by narrow and densely populated streets – along with the site’s remarkably tight footprint, represent considerable obstacles. To work around these constraints, much of the structure – including the cores, basement and building services – will be constructed off site. However, with components of up to 26 metres in length this creates its own challenges. Once again, the team used BIM to perfect its strategy for just-in-time assembly.