Bespoke structural components
NSC reports on fabricated structural components used in buildings and the capability and
capacity required by producers of these items.
Using a trusted
fabricator for
structural components
is always advisable
14 NSC
September 18
Readers of NSC will be very familiar
with projects that comprise
conventional structural steelwork.
Many of the monthly featured articles include
interesting photos of steel-framed structures
being erected. The main steel components
involved are universal beams (UBs) and
universal columns (UCs), hollow sections -
circular (CHS), rectangular (RHS) or square
(SHS) - and other typical sections.
Generally, these buildings are
straightforward in layout and in loading
characteristics. In situations where the
building is not straightforward, and
where the engineer’s requirements are
not so standard, it is likely there will be a
requirement for non-standard structural
members.
In these cases, there may be a need for
the engineer to specify items such as plate
girders, cellular beams, fabricated box girders,
or specific node / joint pieces. It has become
increasingly routine that engineers need to
adopt some of these items to meet a specific
design requirement within a structure.
Equally, it can be the case that, because
of section availability and range, floor depth
criteria or aesthetic requirements, all the
steel components used to construct the
frame are fabricated structural components.
Steelwork contractors who supply
conventional beam and column work are
well geared up for that purpose and have
invested heavily in the appropriate automatic
sawing, drilling and handling systems to
facilitate this type of work. However, for
fabricated structural components, the
equipment needed and the skills involved are
entirely different. Therefore, when fabricated
structural components are specified it is
important to choose the right supplier
with the experience, skills, capacity and
equipment to deliver the pieces efficiently
and economically, as in many cases these
can be the most critical items on the path
towards successful project delivery.
For example, where an engineer specifies
a series of very heavy box girders, these may
be, as an example, pieces weighing 1.5t/m
comprising 85mm thick top and bottom
flanges, 50mm thick web sections and a
web-to-flange joint using 15mm continuous
fillet welds. There may also be drilled holes
required for lifting points to be attached,
couplers welded to receive threaded rebar
strands, and ‘Z’ tested (through thickness)
plate specified for certain fittings. There
could be a host of specific features required
and the project inspection and testing plan
(ITP) may specifically detail hold points and
testing criteria which will not apply to any
other element in the project.
In this case the conventional steelwork
contractor may be able to make the pieces,
but may not have the lifting capability for the
85mm plate or the profiling capacity to cut
such heavy plate, and may not be familiar
with the specific quality requirements. It may
be possible to buy-in the webs and flanges
from a subcontract profiler, but there will
still be difficulties ahead with the lifting,
manipulation and welding of such heavy
plate. The more appropriate option may be to
source a suitably qualified and experienced
supplier of such complex items.
Another example may be heavy plate
girders or cellular beams. The more accepted
practice nowadays is for these beams to be
made on special purpose welding machines
where the machine ensures alignment of
the manufactured pieces and helps to limit
and control weld induced distortion. A
conventional steelwork contractor using only
manual means with jigs and fixtures could
certainly make plate girders, but it’s not
viable to do this efficiently in any volume,
without the right equipment.
Aside from the need for equipment, the
likelihood is that a specialist producer of
complex structural components will have
the required expertise and experience
and also have a relationship with an IWE
(International Welding Engineer) which can
be vitally important where there are very
complex welding issues involved.
Given that specifically designed
structural components are likely to be more
scrutinised than the conventional elements
of a steelwork project, it is sometimes the
case that an engineer will specify a higher
Execution Class for these items. This is
another reason why a conventional steelwork
contractor may choose to engage a specialist
structural component manufacturer for the
supply of such items.
Sector Focus: Structural components
Sponsors
Structural Components
Headline: Jamestown
Manufacturing Ltd
Bronze: Kloeckner Metals UK
‘’Bespoke structural components are becoming
more common in large structures nowadays.
The manufacturing and quality issues which
arise when considering such heavy structural
components are generally far more onerous
than for conventional steelwork. Therefore, it’s
critical that fabricators choose a trusted supplier
who has the expertise, experience and capability
to deliver these items.’’
Jamestown’s Managing Director Fiacre Creegan
/Steel_construction_products#Standard_open_sections
/Steel_construction_products#Structural_hollow_sections
/Box_girder_bridges
/Fabrication
/Fabrication#Circular_saws
/Fabrication#Drilling_and_punching
/Welding#Fillet_welds
/Material_selection_and_product_specification#Through_thickness_properties
/Steel_construction_products#Flat_products_-_plates
/Steel_construction_products#Cellular_beams
/Welding
/Accuracy_of_steel_fabrication#Causes_of_fabrication_distortion
/Steel_construction_products#Plate_girders
/CE_marking#Select_the_Execution_Class