[Working detail 09.06.11] Existing facade stability system
This system stabilises the inner wall of the renovated facade and supports cleaning gantries, escape stairs, walkways, smoke extract ducts, and the fire-rated corridor on level 2.
The level 1 framework is fixed to the side of the internal circumferential beams and is connected to the two pre-stressed bolts that clamp the brick facade between these beams. Inclined tapering V-piers fabricated from steel plates support this structure and connect the facade to ground level. As tolerances are very large, telescopic steel tube connections allow sliding joints to be aligned and welded.
At levels 2 and 3 RHSs have articulated joints at each end and made-to-measure lengths were more practical and economical. To allow the level 4 running track to be flush with the internal floor, Z-shaped RHSs extend upwards to connect to the precast capping beam fixed to the original brick copings.
The setting out of the radial beams created 56 framed units at each level, corresponding to the original arches and pilasters. Curved horizontal steel frames are bolted between each radial beam and have diagonal bracing where they span the openings.
Vertical tension bars behind each brick pilaster tie together beams at levels 1 and 4, passing through others at each level. This pulls the capping beams down towards the first-floor circumferential beams, thus loading the brickwork previously subject to forces from removed galleries and seating. Between the beams of levels 3 and 4, vertical compression struts support horizontal tubular struts, stabilising the brick facade near its top where buckling under induced loading is more likely.
Two continuous 15mm flat steel belts, fixed to the inner brick facade, cover the cut-off ends of the original floor beams, tying the facade together circumferentially and increasing its stability, especially under wind loads.
James Leathem, project architect, Rogers Stirk Harbour + Partners