A glazed steel staircase tower in a fullyglazed enclosure
The 18-storey building has six externally expressed cores, two of which are fully glazed. The steel-framed cores gain lateral stability from the post-tensioned concrete frame. The stair design had to accommodate three different floor-to-floor heights.
Each staircase consists of a series of opposing flights separated by semi-circular half-landings and supported by two 273mm diameter chs columns between them. The access half-landings cantilever from the core structure and the inner chs column is braced back to the core with triangulated horizontal chs props.
Adjustable raking chs props (K-braces) which follow the angle of the flights, connect the outer column to the inner column; a spiralling system of kite-bracing - adjustable tensile rods - fixes the location of the outer column. The tensile rod spiral is resolved in a capping truss at the top of each tower.
The columns are connected by nodes which accommodate connections for the props and rods, and the pin joint, which is extended to act as a support for the flights. The flights consist of two sets of paired steel strings; the undersides of the folded steel treads and landings have projecting plates which slot between the strings and are bolted to them. Walking surfaces are covered with black ribbed rubber and natural anodised- aluminium nosings with a matching ribbed profile.
The glazing is suspended from six 40mm diameter pretensioned stainless- steel rods passing through stainless-steel clamps at the ends of cantilevered arms. Anodised aluminium clamps fix the aluminium T-transoms which support 12mm sheets of laminated 'extra white' glass .