TIMBER STRUCTURES
Timber Industry Yearbook 2015 www.trada.co.uk
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Span Tables – a look back and forward Keerthi Ranasinghe, BM TRADA’s Eurocodes expert, sets the scene for the fourth edition of TRADA’s popular book Eurocode 5 Span Tables, published in 2014
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RADA’s Span Tables is a well-established, key resource in timber specification for building works. This information allows the designer to choose the size of solid, softwood, timber members necessary to give adequate support to floors, ceilings and roofs in dwellings. Now in its fourth edition, this bestselling publication from BM TRADA covers softwood species and grade combinations which satisfy strength classes C16 and C24, and is designed to supplement Approved Document A (Structural safety) (ADA) in England. The publication may also be applicable to timber design in other UK jurisdictions.
grounds for many European jurisdictions, were never meant to be like-for-like substitutions for British Standards. As such, Part 7 of BS 5268 had no successor within the Eurocodes suite of standards. In producing the first Eurocode edition of the Span Tables, the third edition in 2009, we decided to use the same calculation methods given in Part 7 of BS 5268, suitably adapted to the Eurocodes. Only the engineering principles were adopted, with all references to and parameters from BS 5268-2 substituted with information from relevant Eurocodes. However, this wasn’t the only problem to be solved during this transition period from British Standards to Eurocodes. Successful implementation of Eurocodes relies heavily on the accuracy of European Standards for materials. At the time of the third edition, some of the material standards, although published, were at an early stage of development. This meant that some of the spans presented were not the optimum that could have been
First versions of the span tables were published within the early editions of Approved Document A. However, due to representations from other material sectors these tables were subsequently taken out of the ADA. As the industry representative body, TRADA took over the ownership of the tables in 2004, with the first ‘TRADA’ edition published by TRADA Technology Ltd appearing soon afterwards. The tables continue to be referenced in the ADA as guidance material for timber buildings. The publication has come a long way since the first edition in 2004. The first and second editions were prepared to the rules and requirements of Part 2 of the then British Standard for timber design, BS 5268. Unbeknown to most designers, there was another part to BS 5268, Part 7, giving the calculation methods for the span tables, presented in seven sub-parts in equation format. Understandably, calculation programs used by TRADA Technology for the production of the span tables were prepared according to these equations. Withdrawal of the British Standards for construction, to be replaced by corresponding European Standards in 2010, meant that all these supporting documents were also made obsolescent. This presented a unique challenge for TRADA Technology in producing the third edition of the Span Tables to Eurocodes in 2009. European Standards, having to cover common
Span Tables 4th Edition