036 RCI 0717

RCI July 2017

CLADDING & SHEETING Codes and Standards for agricultural buildings explained 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 The previous version of BS 5502-22 has been 036 JULY 2017 RCIMAG.COM withdrawn and is no longer a valid design document so it must not be used.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). 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 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). Other 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 By RIDBA technical consultant Dr Martin Heywood Dr Martin Heywood, technical consultant for RIDBA: “Many of the changes currently being discussed will have little impact on agricultural buildings. However, there is talk of replacing the equations used to combine snow and wind loading, with possible consequences for design loads”


RCI July 2017
To see the actual publication please follow the link above