Leach initially erected
the steel core
NSC 23
Mar 20
can cause havoc to our deliveries.”
Unlike many commercial schemes, Eleven
York Street has a steel braced core, which
accommodates staircases, lifts, risers and
toilets. It also provides the building’s main
frame with its stability, and was chosen
over a more traditional concrete core for
commercial reasons.
“It may have been difficult to get a
contractor to install a concrete core as there
is so much construction work underway in
the city,” says Mr Harmston. “Plus, a steel
core has programme benefits, whereby
the project team didn’t have to wait for a
concrete contractor to finish its work before
beginning the steel erection as it was all part
of the same programme.”
For this reason, the steel braced core was
the initial part of the building to be erected.
It was installed to its full height and once
completed, it then allowed the remainder of
the structure to be installed by providing the
frame’s stability.
Although centrally-positioned, the core is
offset and located along one of the building’s
main elevations, thereby creating more
valuable floor space.
After the core, Leach Structural Steelwork
erected the main steel frame by dividing the
structure into two further phases, with each
one erected bay-by-bay and to the full height
of the building.
Radiating out from the core, each of the
floor’s long clear spans are formed by a
series of Westok cellular beams, up to 15m
in length. The choice of using Westok beams
was made because the cellular sections are
able to fully integrate the services within
their depth, maximising the structure’s
floor-to-ceiling heights, while also being
economic as they are lighter than traditional
UB sections.
The Westok beams were optimised to
adhere to the strict 660mm-depth restriction
imposed on the floorplate. To facilitate the
passage of the services, a cell pattern of
425mm-diameter holes at 600mm centres
was provided, along with some discreet
wider elongated cells.
Kloeckner Metals UK Westok Design
Team Manager John Callanan commented,
“We continue to see a steady stream of clearspan
commercial office developments in
Manchester and Salford, and it was great to
work with the project team on this job.”
The building’s design contains just one
solitary internal column, located in an area
where the span would have been greater
than 15m. Without this column, the span
would have needed a beam with dimensions
much greater than the other beams, and this
would have interfered with the structure’s
overall floor-to-ceiling heights. For this
reason, the decision was taken to allow the
one column to invade the otherwise openplan
floorplates.
All of the steelwork has been erected
using the project’s one tower crane, and so
all individual sections had to be within the
crane’s capacity. To this end, the heaviest
pieces of steelwork, other than the cellular
beams which weigh up to 9t, is a series of
transfer plate girders. The heaviest of these
is 9.6t and it is positioned close to the core,
where the structural loads are deemed to be
too great for a cellular beam to support.
There is another 5t plate girder positioned
at the underside of the second-floor level
that creates a cantilever over the entrance’s
double-height space, while a further transfer
girder is positioned at sixth floor level to
form a set-back in the structure along its
northern elevation to form an outdoor
maintenance terrace.
Eleven York Street is due to be complete
by the end of the year.
Commercial
FACT FILE
Eleven York Street,
Manchester
Main client:
Kier Property
Architect:
AHR Architects
Main contractor: Kier
Structural engineer:
Tier Consult
Steelwork contractor:
Leach Structural
Steelwork
Steel tonnage: 890t
A large plate girder
creates the columnfree
entrance
/Concept_design#Concrete_or_steel_cores
/Concept_design#Structural_options_for_stability
/Construction#Steel_erection
/Steel_construction_products#Cellular_beams
/Service_integration
/Steel_construction_products#Standard_open_sections
/Design
/Construction#Tower_cranes
/Steel_construction_products#Plate_girders