Property
Codes and Standards for
Agricultural Buildings
RIDBA Technical Consultant Dr Martin Heywood is a specialist in the structural
engineering of agricultural and industrial type steel framed buildings.
» » AGRICULTURAL
buildings in the UK are
designed to a British Standard
and for the structural aspects
of the design that standard
is BS 5502-22:2013. This
standard is only the tip
of an iceberg concerning
design documents - which a
structural engineer has to use
to determine the loading on
the building, and to design a
suitable structure to carry it.
This article aims to
untangle the web of codes
and standards in use today,
explain the relationship
between them and inform
readers of changes on the
horizon.
BS 5502-22:2013
BS 5502-22:2013 is the
correct standard for the
structural design of agricultural
buildings. It provides additional
information and design
data specific to agricultural
buildings, along with reduction
factors that may be applied to
the wind, snow and imposed
loads in certain cases. BS
5502-22 was revised in 2013,
bringing it up to date with the
structural Eurocodes in use
across Europe. This enabled
structural engineers to use
the same software and design
methods that they use for
commercial and industrial
buildings, while maintaining the
reductions in loading enjoyed
by agricultural buildings in the
UK. The previous version of BS
5502-22 has been withdrawn
and is no longer a valid design
document so it must not be
used.
THE EUROCODES
The structural Eurocodes,
as they are collectively known,
are the principal design
documents for all types of
structures in the UK, ranging
from a 12m span barn to a
1200m span highway bridge.
They cover the calculation
of wind and snow loading
and the structural design of
members and frames in a
range of materials. As the
name suggests, they are
applicable for use across
Europe (and further afield),
although each nation has
its own National Annex and
is able to set Nationally
Determined Parameters (e.g.
safety factors). Contrary to
popular belief, they are not
an alternative to the old
British Standards like BS
5950; they are the current
and only British Standards
still supported by the British
Standards Institution (BSI).
‘This standard
is only the tip
of an iceberg
concerning design
documents’
At the head of the
Eurocodes’ family is EN
1990 or Eurocode 0. This
standard sets out the basis for
structural design and presents
the basic design principles.
Although for most engineers
designing simple structures,
it is the place where the load
combinations and safety
factors are obtained. The
90 Autumn 2017 www.farmers-mart.co.uk
detailed design equations and
methods are contained within
all of the other Eurocodes
starting with Eurocode 1.
EN 1991, or Eurocode 1
contains everything that the
structural engineer needs
to know about loading on
buildings and structures. It
is divided into several parts,
covering a diverse range of
loading types, including dead
and imposed loads (EN 1991-1-
1), snow loading (EN 1991-1-3),
wind loading (EN 1991-1-4) and
accidental actions (EN 1991-
1-7). Ot her parts include rules
for traffic loading on bridges,
loading from cranes and
machinery and special rules
for silos and tanks. There is a
UK National Annex for each
part.
Eurocodes 2 to 6 (EN
1992, EN 1993, EN 1994, EN
1995 and EN 1996), along
with Eurocode 9 (EN 1999),
give design rules for specific
materials, while Eurocode 7
and 8 (EN 1997 and EN 1998)
cover geotechnical design
(foundations) and earthquake
resistance respectively. For
most building structures, the
structural engineer will need
to use several Eurocodes
during the design process,
e.g. EN 1992 for the concrete
slab, EN 1993 for the steel
frame, EN 1995 for the timber
purlins and EN 1997 for the
foundations. Furthermore,
each Eurocode is divided into
several parts, giving specific
rules and recommendations.
All aspects of steelwork
design are covered by EN 1993,
including the design of the
steel frame and its members
(EN 1993-1-1), the connections
between members (EN 1993-
1-8) and light steel purlins and
cladding (EN 1993-1-3). EN
1993 replaced BS 5950 in the
UK. Although there appears
to be a bewildering number of
standards within the Eurocode
family, there is a clear hierarchy
and each part is written in a
way that complements other
members of the family. For
example, EN 1993-1-3 gives
specific rules for cold formed
steel members (e.g. light gauge
steel purlins), but builds on
the general rules given in EN
1993-1-1. This approach avoids
unnecessary repetition and
prevents contradiction between
parts.
EN 1090
Those familiar with the CE
marking of steel frames will
recognise EN 1090 as the ‘CE
marking standard for fabricating
steelwork’. However, in reality
this title should only be applied
to EN 1090-1, although to date
EN 1090-2 has featured heavily
in the CE marking process.
The difference between the
two standards is important and
is explained below:
EN 1090-1
EN 1090-1 is the Harmonised
Standard (hEN) for structural
steelwork and includes the
list of Essential Characteristics
that may be declared by the
manufacturer, along with
the all-important Annex ZA
that gives rules for the CE
mark itself. As a harmonised
standard, EN 1090-1 has one