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At 43 storeys and £147.9 million, Strata SE1 is the first
significant development of the planned £1.5 billion Elephant and
Castle regeneration. The structural design of the building was
fast, efficient and economic to construct and features 200mm
post-tensioned concrete slabs with a compact rectangular core.
High-strength external blade columns align with the partitions and
there are only two internal columns. At the top and bottom of the
tower the columns step in. This was achieved by ‘walking columns’ -
stepping the columns gradually to remove the need for deep transfer
structures. The slabs used C32/40 concrete whilst the columns used
C50/60 concrete, so care was taken in the design of the slab/column
junction. The foundations included 37 large-diameter bored piles
with a maximum length of 44 metres founded in the Thanet sands.
An important feature of the tower is its sustainability and the
building is targeting an EcoHomes assessment rating of “Excellent”.
Air permeability is less than half that required in current
Building Regulations, a vertical district heating system negates
the need for boilers to each apartment and the ventilation strategy
includes heat recovery to every one of the 430 apartments and with
openable panels hidden in the facade for natural ventilation.
However, it is the three wind turbines at the very top of the
building that grab the headlines.
Three five-bladed 9m diameter 19-kW wind turbines provide a
visible commitment to sustainable design. Located to take advantage
of the area’s 35mph wind speed it is anticipated that the turbines
will generate 50MWh of electricity per year equivalent to eight per
cent of Strata’s estimated total annual electricity consumption. It
would need a very large array of photovoltaics in order to generate
the same amount of energy. Each turbine is sited on a five tonne
inertia base made from concrete and steel and supported on
anti-vibration mounts to prevent vibration being transferred to the
building’s structure. The use of five blades rather than the usual
three reduces operational noise.
Strata is not the only building that plans to use wind power to
generate its own electricity. The Bahrain World Trade Centre has
wind turbines placed between its two towers and the Lighthouse
Tower in Paris’ La Defense district will have wind turbines placed
at the top when it is completed in 2015. Meanwhile, under
construction in Miami is the Cor building which features wind
towers as an integral part of the exoskeleton concrete shell (see
Concrete Quarterly Spring 2007, visit: www.concretecentre.com/cq).
Client: Brookfield Europe
Architect: BFLS Partnership
Engineer: WSP Group
Further information: Project Review by Mark Walton, WSP Group,
Issue 88, The Structural Engineer, July 2010
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Concrete Structures 10