The majority of concrete structures have to fulfil a number of structural functions beyond that of simple resistance. These include behavioural requirements for: stability, reinforced concrete cracking, deformability, water and air leak-tightness, and sustainability.
Most European concrete structures today are designed in accordance with Eurocode 2 (EC2), which uses a performance-based approach related to durability and functionality at Serviceability Limit State (SLS).
For massive and more general special structures, the EC2 standard rules do not fully reflect the complete behaviour of massive elements, for which Thermo-Hydro-Mechanical (THM) effects, scale effects and structural effects induce crack pattern such as crack spacing and crack width. For massive slabs and walls, shrinkage and creep are prevalent at an early and long-term age. This approach may lead to structures that are not optimised, especially for concrete reinforcement.
To address these concerns, the French Civil Engineering Community decided in 2008 to launch a joint national research programme project, CEOS.fr, with the aim of making a significant step forward in the engineering capabilities for predicting the expected crack pattern of special structures Under anticipated in-service or extreme conditions.
The aims of the CEOS.fr project are to:
- Develop numerical non linear and damage models, to simulate concrete behaviour Under load and imposed deformation;
- Provide engineering guidelines to optimise the design of special concrete structures;
- Propose further rules for crack width and crack spacing assessment in special concrete structures, in addition to EC2 or fib Model Code 2010 (MC2010).
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Are considered as “special” structures: structures that are not covered by the conventional engineering practice:
- Very massive h0 ≥ 400 mm, where h0 is the notional size of the cross section (cf. EC2-1 § 3.1.4)
- Unusual in-service requirements (life duration, leak tightness …)
- Unusual requirements relating to the protection against external threats or hazards