Signature structure
highlights regeneration
Spanning an important London underground station and
featuring an architecturally-detailed exposed steel frame,
21 Moorfields is a feat of engineering. Martin Cooper reports.
Construction of the eagerly
anticipated Crossrail (Elizabeth
Line) scheme has been the
catalyst for the regeneration of the
previously undervalued Moorgate area of the
City of London.
A number of new and recently completed
commercial buildings have helped to breathe
new life into the area, while the western ticket
hall to Liverpool Street Elizabeth Line station,
which is adjacent to Moorgate underground
station, will ensure an increased footfall, once
the rail scheme opens in 2021.
Located directly above Moorgate’s
underground and Crossrail assets, another
commercial development known as 21
Moorfields is predicted to further regenerate
the area, while also enhancing the urban
landscape of this transportation hub with its
eye-catching exposed steelwork design.
Pre-let to Deutsche Bank as its new
London headquarters, the 17-storey building
is also a complex engineering feat, with a steel
frame that spans the full width of the station,
a distance which is equivalent in length to the
wingspan of a jumbo jet.
Prior to construction beginning, a number
of design proposals had been put forward for
the site, which had been vacant for a number
of years. But as Robert Bird Group (RBG)
Associate Director Chris Papanastasiou
explains, the current design was the most
viable.
Maximising the usable capacity of the
existing slab, which is also the station roof,
the structural design features six 7m-deep
‘Launching Trusses’, up to 55m in length, built
up from, and subsequently spanning over, the
station below to create temporary support
for the floors above during the construction
programme. In the building’s completed
form, the trusses revert to permanent features
within the circulation spaces.
The building’s first floor and main entrance
level as well as a mezzanine (second floor)
are accommodated within the truss depth.
Below the trusses, the existing slab supports
a basement, at ground floor level, for the
building’s back-of-house and plant equipment
areas.
During construction, each truss
facilitates the construction of a 10-storey
steel fabricated box section mega arch,
which in turn, once completed, enables the
construction of the concrete floor slabs and
the remaining steel frame.
The mega arches are integrated into the
building’s cores up to level 7, only exiting on
to the floorplates at levels 7 to 10, thereby
minimising the number of columns present
within each 100m long, 60m wide floorplate
to only six.
Above the mega arches, the structure
continues upwards in a more traditional
beam and column design to level 17, with
Commercial
FACT FILE
21 Moorfields, London
Main client:
Landsec
Architect:
WilkinsonEyre
Main contractor:
Sir Robert McAlpine
Structural engineer:
Robert Bird Group
Steelwork contractor:
William Hare
Steel tonnage: 17,000t
Trusses span over the
station assets
18 NSC
Feb 20
Visualisation showing
the numerous
underground
constraints
Model
showing the
trusses and
mega-arches
/Multi-storey_office_buildings
/Visually_expressed_structural_forms
/Construction
/Design
/Trusses
/Fabrication