Education
Academic design exposed
A famous London seat of learning has chosen to use an aesthetically-pleasing exposed
steel frame for its latest redevelopment project. Martin Cooper reports.
26 NSC
May 18
The world-renowned London School
of Economics’ (LSE) continuing
redevelopment of its central London
properties currently includes the
Central Building Redevelopment (CBR)
that will create a state-of-the-art flexible and
highly sustainable academic and teaching
building.
Situated just south of Lincoln Inn
Fields, and just a short walk from the LSE’s
Academic Building (see NSC May 2007), the
CBR project replaces four previous buildings
that were demolished as they were deemed to
be no longer fit-for-purpose.
Once complete the project will offer a
slightly smaller gross internal floor area of
15,507m2 as the scheme also includes a new
landscaped public square.
A modern and stylish environment
will be created by leaving much of the
new building’s steel frame largely exposed,
a design that has required a number of
bespoke steelwork elements in order to fulfil
the project’s architectural vision.
Another part of the architectural
intent is to provide a slimmed down floor
construction, in order to maximise available
space. This design has been achieved by
using RHS or plated floor beams, featuring
bottom plates to support the building’s long
span precast floor units which sit within the
depth of the beams.
As exposed steelwork plays such an
important role within the design, the
fabrication process had to rise to the
challenge accordingly as Mace Project
Director Frank Connolly explains.
“Billington, our steelwork contractor, was
tasked with making sure that the majority of
the steel connections were hidden from view
in accordance with the client’s requirements.
“Flush connections are the order of the
day, or alternatively they have positioned
end-plates to help create shadow gaps
which, in turn, are then used as repeating
architectural features.”
Shear forces and torsional moments
applied to the RHS beams, in conjunction
with the desire to avoid site welding, led to
the bespoke hidden connection design. Many
of the steel members have an internal bolted
connection, hidden from view and accessed
via a hatch.
Having the steel frame and the ductwork
exposed not only creates an aesthetic
environment within the completed building,
it also brings ventilation advantages.
“Exposed steelwork supporting exposed
precast flooring planks creates a flat soffit
and contributes to the building’s MEP
strategy via the material’s high thermal mass
qualities,” explains AKT II Director Ricardo
Baptiste.
Overall, the building consists of two
conjoined parts; the 13-storey Tower Block
and the six-storey Houghton Block. At either
end of the blocks, that sit side-by-side for
just under half of their lengths, exposed
The steel frame will
remain exposed
SHS bracings bookend the project and form
another highly visible exposed steelwork
element.
This exo-skeleton bracing, which sits
approximately 300mm outside of the
building envelope, is not just an aesthetic
element as it is also a structural requirement,
sharing the stability with two concrete cores.
Significant forces are transferred both
within and into the SHS bracing system,
and so bespoke cruciform node joints were
engineered with machined flush plates to
ensure the correct standard of finish was
achieved.
Full stability to the structure was only
achieved once the entire frame was erected
and all of the precast flooring was installed.
Until that point was reached Billington had
to install temporary bracing to each floor,
which was only removed once each level was
fully complete.
According to Billington Structures
Managing Director Mark Smith, to allow
flexibility in the overall build sequence the
temporary stability system was developed to
largely ignore any benefit that the concrete
cores may have offered.
“Due to the architecturally sensitive
nature of the exposed frame, we had to be
mindful of the subsequent impact of any
of the connection points for the temporary
bracing, and so bolted cleats were used to
negate the need for any removal of welded
plates,” he says.
The majority of the project’s steelwork
begins at ground floor level, however
in order to form a large subterranean
auditorium two large plate girders had to
Model of the steel
frame and foundations
/Education_buildings
/Education_buildings
/Design
/Floor_systems#Shallow_floors
/Floor_systems#Shallow_floors
/Floor_systems#Precast_units
/Fabrication
/Simple_connections
/Simple_connections#Flexible_end_plate_connections
/Steel_construction_products#Structural_hollow_sections
/Construction#Site_welding
/Thermal_mass
/Visually_expressed_structural_forms#Expression_of_bracing
/Concept_design#Structural_options_for_stability
/Concept_design#Concrete_or_steel_cores
/Construction#Temporary_works
/Steel_construction_products#Plate_girders