The structure is a
propped portal frame
A steel-framed solution
is a proven method for
This plant is located adjacent to the
Huntstown Power Station and, once
operational, it will generate up to 3.8MW
of electricity to supply 7,500 homes from
90,000t of food waste per annum.
The main processing area for any AD
facility is usually housed within one large
structure and at Huntstown this structure
measures 90m-long × 43m-wide.
This steel-framed building will house
the waste disposal/reception area and
pre-treatment zones, where the product
is sorted prior to being pumped into the
facility’s six primary digestion tanks where
the bio-fuel is created.
“We’ve been involved in a number of AD
plants and they’ve all had a steel-framed
pre-processing treatment building,” says
DBFL Director Colm Doyle.
“Steel is the ideal material to form these
structures as they are always long span
DBFL are the project’s structural
engineer and worked on the initial design
for the main building. County Wexfordbased
steelwork contractor Fox Bros.
Engineering were then subsequently
contracted to the scheme on a design and
“This is the third AD plant we have
done and they are all similar open-plan
structures,” explains Fox Bros. Director
John O’Hara. “Once we were brought on
board we value engineered the steel frame
to make it as cost-efficient as possible.”
Supported on pad foundations, the
Huntstown facility’s building is an
asymmetric propped portal frame, with
its centre line of columns located slightly
off centre, in order to accommodate the
internal equipment layout.
As well as having portalised bays for
stability, the frame also makes use of
bracing located in the gable ends. In
these areas, the steel frame is founded on
concrete walls, and uses their rigidity to
add further stability to the overall frame.
The majority of the central spine
columns are arranged in a hit and miss
configuration, whereby only every other
bay features a column. Consequently, some
roof rafters span the entire 43m width
unsupported, while others span 18m and
25m, either side of the off centre spine
Fox Bros. had to bring the roof rafters
to site in three pieces, which were then
assembled on site before being lifted into
place in one piece.
All of the project’s steelwork has been
galvanized to protect it against the highlycorrosive
atmosphere that arises inside
an AD facility. No steel member on this
project is longer than 16m, because the
beams and columns all needed to fit into
the galvanizing contractor’s tank.
The structure also incorporates an
internal two-storey office which is situated
along one main elevation. Measuring
approximately 50m-long × 18m-wide, its
internal partition, separating it from the
reception part, is formed by the off centre
The Huntstown AD facility is due to be
operational by late 2019.
Various forms of
stability are used
including the structural