Eurocode 2 introduces new span/depth rules for the design of reinforced concrete beams and slabs. These are investigated from practical and theoretical points of view and serious problems found. The present UK National Annex imposes requirements which are impossible to comply with, making EC 2 unusable in the UK until it is revised. The proposed EC 2 recommendations offer a choice between an over-conservative simple table, or a formula for calculating allowable ratios which is impractical to use and contains serious errors. In particular its wording is ambiguous, which makes the effects of varying steel stress unclear, and it exaggerates the effect that increasing concrete strength has on deflection. Until these problems are sorted out, it is recommended that present BS 8110 limits are retained but it is recommended that an error in these should be corrected to improve economy.
Alasdair N Beal BSc CEng MICE FIStructE
Thomasons LLP, Leeds