Durability and Cover Depth Provisions in Next Eurocode 2. Background Modelling and Calculations

Abstract

Codes contain calculation rules of general acceptance that have demonstrated to enable the building of safe enough structures with very low probability of failure. Any new method to be introduced, should be based in a consensus among experts and based in the experience. Until present, the durability is treated in the Codes following the so called “prescriptive” approach that is based in the limiting of the constituents of concrete, applying a correct curing and limiting the presence of deleterious substances as chlorides and the crack related to serviceability conditions. In the paper are described the changes introduced in the verification of durability in the new current draft of EN 1992-1-1:2010. The main changes are based in a first trial to make durability design by a performance approach to the cover depths for avoiding reinforcement corrosion that were calculated through service life models, but the covers are given in function of a new concept: the Exposure Resistance classes (ERC) which substitute the present “structural classes”. The calculations are not explicit in the Code, because they do not intrinsically imply a higher precision, but only more rational and harmonization to solve some inconsistences. In the paper is also presented the definition and scope of the ERC’s which will be regulated in a next draft standard named: EN206-100. Present method to verify the durability as indicated in present EN-206 (reproduced in Annex P of the current draft of EN 1992-1-1), will be retained for a transition period and it could continue to be applied. Providing the method introducing the ERC’s is based in a new approach and safety format, the coherence with this previous method cannot be guaranteed, but the application of one or other route will give the desired level of durability.