THE BUILDING FAÇADE COMPRISES A
DOUBLE-GLAZED UNIT SKIN, A SIMPLE
AND COST-EFFECTIVE SOLUTION
DESIGNED TO CONTROL SOLAR GAINS
AND PREVENT OVERHEATING.
Due to the asymmetric core, inclined north façade and sharply
trapezoidal plan form, the core’s centre of stiffness was eccentric
to the centre of load from wind and the centre of mass. It becomes
even more eccentric as the low rise and mid and high rise lift banks
reduced (from three serving the lower floors to only one servicing mid
and upper floors) and the core shrinks towards the south east corner
of the building, opening up valuable upper floor plates. To counteract
twisting, the building needed torsion stiffness. Columns were placed
at 6m centres in the perimeter to coincide with the planning module.
There are four internal columns in the lowest level of the tower. As the
floor plates reduce in size the columns drop off. By level 26 the floor
plate is column free.
The interaction between the angular building shape and the prevailing
wind was also a structural design factor. Inspired by the engineering
methods used to limit wobbling on the Millennium Bridge, the building
has ‘integral viscous damping’ where oil filled dampers are built into
the stability system, absorbing the energy of motion that builds up
during a wind storm to make the building comfortable even on the
windiest days. This innovative design solution negates the need for a
TMD, saving more than £2M and 1100sqf of lettable space.
The engineering team developed an algorithm that led to every beam
being unique. This led to saving 700 tonnes of steel, and as a result,
saving 1,300 tonnes of embodied carbon dioxide and £1.4 million in
manufacturing costs.