The project comprises the demolition of an existing six storey RC framed superstructure with the single storey basement retained. A new seven storey steel framed structure is to be constructed and designed to BCO standards.
The site is located close to St Paul's Cathedral and has frontage along Cannon Street. To allow maximum flexibility, the proposed structural grid is in the order of 15m x 9m, and the floor construction comprises of a 150mm thick metal decked slab designed to act compositely with 600mm deep Westock beams. The diameter of the cells within the Westock beams are 400 to 450mm to allow M&E services to pass through them, which has reduced the overall structural/services zone.
The upper floors are set back from Cannon Street to maintain the viewing corridor to St Paul's which was a key planning requirement. The set backs have required the introduction of a number of transfer structures at the upper floors. Options including full height trusses were explored by the team, and in the end, in order to achieve the agreed planning sightlines
a cascade of offset columns were introduced, with these upper columns sitting on steel transfer beams.
The proposed building is to have extensive plant situated in the basement. The depth of the existing basement is limited and design requires the basement to be deepend in certain areas to accommodate the proposed plant.
The site is located close to the Waterloo and City Line and requires LUL approval.