Comparison of deflection calculations and span-to-depth ratios in BS 8110 and Eurocode 2

Abstract

The current paper proposes a procedure for calculating deflections with Eurocode 2, which is subsequently used to evaluate the span-to-effective-depth rules in Eurocode 2 and British Standard (BS) 8110. The theoretical background to span-to-depth rules is examined. The Eurocode 2 span-to-depth rules were derived by curve-fitting the results of a parametric study in which deflections were calculated in simply supported beams under a permanent load equal to half the design ultimate load. The loading assumed in the derivation of the Eurocode 2 span-to-depth rules is unrealistic for lightly reinforced slabs where self-weight can exceed half the design ultimate load. The procedure used to modify the Eurocode 2 span-to-depth rules for different stress levels is also shown to be questionable. An amendment is proposed that is shown to improve the accuracy of the Eurocode 2 span-to-depth rules.