July/Aug 19 Two large barrellvaulted
the main malls
Supporting the dome are a series of rigid
joint box frames extending up from the
existing foundations, which also support
a first-floor curved walkway and a further
curved roof deck.
The two main central malls, either side
of the dome, are spanned by identical barrel
vault roof structures formed by 36m-long
curved steel rafters supporting SHS purlins.
Each of the two roofs required four rafters.
Fabricated and delivered to site in halves,
each half span is formed from a pair of
parallel plate girders battened together with
top flange bracing and detailed with a bolted
“The central section of the plate girders
were designed as Vierendeel trusses to
achieve the cellular appearance demanded
by the architectural concept,” says Mr
To resist the large horizontal base
reactions from each of the arches, tied
thrust girders have been incorporated
into the design and are supported off stub
columns extending up from the existing
More than 80 stubs were installed, with
each one requiring a break-out hole that
was drilled through the concrete flooring in
order to locate the existing steel frame. All of
this work was carried out during night time
shifts to minimise the impact on shoppers
and the mall, which has remained open
throughout the works.
A series of proprietary sliding bearing
plates have been installed to avoid any
significant lateral loads being transferred
from the roofs into the existing structure.
Four further smaller barrel vault roofs
have also been installed as part of the overall
scheme. Two 10m-wide × 20m-long roofs
continue beyond the main roof structures,
spanning narrower areas between the retail
blocks and terminating at two entrances to
Either side of the central courtyard, two
shorter, but slightly wider roof structures
will span the cross-malls of the Centre.
Summing up, both Vinci and Cameron
Darroch Associates both stress that
steelwork was the only viable option for the
works as it ensured the architectural vision
was achieved, while also minimised the
additional loads transferred to the existing
The project is due to be completed
by early 2020 with Primark having been
secured as the anchor tenant, trading
alongside existing retailers such as Next
Home, Silentnight, Homesense and the
Legoland Discovery Centre and Sea Life
Working at night
and keeping sea
Keeping the majority of Barton Square open during the
construction programme has been a key challenge for
the project team and consequently much of the work
is being undertaken outside trading hours.
All of the structural steelwork erection has been carried
out overnight by S H Structures, using cranes positioned in
the central courtyard.
An extensive clean-up operation is conducted every
morning and the cranes, along with other items of
equipment, are positioned behind hoardings during the day
to create clear circulation routes for shoppers.
“The logistics of this project have been a real challenge,”
says S H Structures Project Manager Chris Richardson.
“When we originally phased the installation of the project
we planned on using standard trailers to deliver into site
during a day shift. We very quickly realised as we got closer
to our start date that site restrictions and planned erection
all meant that we would have to switch to non-standard rear
steer trailers and deliver and erect at night.
“This required additional resources so we could reduce
loading plans per tonne but increase frequency of deliveries
into an already busy area, even at night. Each erection phase
had to be changed in design to accommodate what could
be delivered into site and when.”
As well as retail units, Barton Square also accommodates
a Legoland Discovery Centre and the Manchester Sea Life
Home to thousands of marine creatures, the latter was
identified as a key project challenge before the scheme
Vinci engaged with the attraction to identify which
creatures were most susceptible to noise and vibration. The
sharks and rays were considered to be the most sensitive
and their tanks are monitored on a 24/7 basis, to ensure no
work activities are having any adverse effects on them.
the new steelwork
roofs and dome
Image: Mott MacDonald