Curved Cellular Beams:
Adding Strength To Remove Weight
ellular and Porthole Beams™
have become a mainstay in
construction projects across
the world, providing added
strength, reduced weight
and convenient options for integrating
building facilities.
C
Greg North, current Regional Chairman
of the BCSA (The British Constructional
Steelwork Association) and Commercial
Director for Barnshaws, one of the UK's
leading producers of straight and curved
cellular and Porthole Beams™ lays out the
options for cellular beam construction and
the associated merits of each approach.
In the construction of modern buildings,
cellular beams are able to span wide
areas and can be made part of the design
language of the structure, enabling
architects to implement new aesthetics
into steel structures. These properties
have made the perforated beam sections
a regular feature on stadia, theatres and
public buildings – allowing steelwork to be
exposed to increase the grandeur of larger
structures.
A straight cut decision
Cellular beams can be manufactured in
straight or bent form, and usually form
part of the roof or floor support structure.
Each beam has a number of cells or
apertures / holes cut into the section at
intervals depending on the design. The
holes both reduce weight and provide
convenient access for cabling and
pipework in addition to sometimes being
used as a design feature.
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Traditional castellated cellular beams
that are characterised by the distinctive
hexagonal shape of the openings have
been superseded by the modern form
of cellular beam. Using the latest design
software and profiling techniques allows
the overall beam depth, cell diameter and
spacing to be specified to best suit the
application, including varying all aspects
across the span of the beam. These cells
can be specified to enable the integration
of electrical and data cabling, heating,
AC and ventilation systems, without
intruding into the space below the beam.
Air conditioning ducts and wires can be
passed directly through the holes in the
beam, allowing space saving throughout
the structure.
In larger, multi-floor structures, the ability
to minimise floor-to-ceiling depth by
running the various building services
through the beams can save sufficient
space for an additional floor to be
included. Compared to a more traditional
construction with universal beams,
employing cellular beams maximises the
potential space and improves the longterm profitability of the building.
Construction methods
CAD design software is used to calculate
the load bearing requirements of a
structural beam, the dimensions of which
are determined by a number of factors.
The decision to use a cellular beam will
affect what is possible, while the choice
of original steel section used to create
the new beam, plus the manufacturing
method will also have a large influence on
the beam's size and characteristics.
Essentially there a three ways of
achieving a cellular beam:
1. Cutting the required profiled holes
out of a standard sized parent 'I' beam to
create a Porthole Beam™.
2. Profiling staggered semi circles into a
standard 'I' beam before cutting it into two
halves along its length, aligning the cells
and welding the beam together to create a
deeper beam than the original.
3. Assemble a beam from three strips of
plate steel, welding one to another to
create an 'I' beam having cut holes in one
of the strips.
Each system has its advantages,
depending on the application,