NSC 17
Feb 20 disrupted the visual aspect of the project,
where removed.
The original building had three atria, one
has been infilled to create more floor space,
while the other two have been reconfigured
to create one new larger atrium in the centre
of the building. This atrium has a glazed roof
to allow natural light to penetrate the inner
parts of the structure. Cantilevering breakout
spaces, that are positioned at various points
within the void, will give the space some
architectural interest.
By opting to reuse as much of the existing
steel frame as possible, a number of the
original columns and beams had to be
surveyed in order to determine whether they
could carry the additional loads from the
new floors.
“Only 60 of the existing columns,
which equates to about 10%, needed to be
strengthened to carry the additional loads,”
explains Heyne Tillett Steel (HTS) Engineer
Jimmy Reading.
“While below ground, our investigations
and detailed analysis helped us increase the
allowable load capacity of the existing piles.
The only area of the project that required
new piles was for the new core.”
Most of the steelwork, new and existing,
will be left exposed within the new scheme,
giving the office floors a modern industrial
look. The old building’s steelwork was
encased in concrete and this had to be
broken out in order to shot blast, prime and
then apply a high-spec paint to the existing
steelwork.
Because the steelwork will be exposed
and on show in the final scheme, all of the
strengthening work needed to be done with
the upmost care and diligence.
Mr Boorer says: “Initially, the design
for the building did not include exposed
internal steelwork and so the columns that
needed strengthening would have had extra
plates welded between the flanges of the
UC column, effectively turning a traditional
column into a box section, which would have
been easier to plasterboard over.
“Once the design changed, we decided
to weld strengthening plates to the outside
of the flanges, thereby keeping the column’s
original shape, which is a better option for
steelwork that will be on show.”
The majority of the reconfigured floors
offer approximately 4,000m2 of office space,
however this decreases slightly floor-byfloor,
as there are roof terraces from level six
upwards along two elevations.
The new upper floors all have large
landscaped outdoor terraces that are up to
10m-deep in places. Steelwork contractor
Severfield had to install a series of large
transfer beams, up to 10t in weight, in order
to create the structural frame’s steps and the
subsequent change in column positions.
On top of the uppermost office floor,
Severfield has also erected a large plant deck.
In summary, Severfield Project Manager
David McGurk says: “Tying into an existing
steel frame meant a substantial amount
of new connections were required on site
(either drilled or welded) to support the new
framing.
“To get this right meant a heavy reliance
on extensive site surveys and photographic
information fed back to our drawing office,
so that connections could be designed to
adapt to the pre-existing steel framing.
“With that in mind, tying into
the existing, 30-year old and partially
demolished, steel frame meant that existing
levels sometimes didn’t marry up with new
theoretical floor levels. The resolution to
these issues required extensive collective
input from Skanska, HTS, EPR Architects
and ourselves to ensure the project was
delivered on time and to the required
specification.”
60 London Wall is due to complete in
June 2020.
Commercial
New steelwork (blue)
has been added to the
existing steel frame
New floorplates have been
created by infilling atria
The new central atrium
will have a glazed roof
/Steel-supported_glazed_facades_and_roofs#Atrium_Roofs_and_Sky_lights
/Recycling_and_reuse#Reuse
/Visually_expressed_structural_forms
/Surface_preparation#Abrasive_blast_cleaning
/Paint_coatings
/Welding
/Steel_construction_products#Flat_products_-_plates
/Construction#Steel_erection
/Simple_connections
/Steelwork_specification