Modelling of the Long Term Behaviour of Prestressed Concrete Structures: the Case of Nuclear Power Plants.

The prediction of the long term behaviour of prestressed concrete structures is important in order to assess and/or extend the service life of such structures. In the case of nuclear power plants (NPPs) where the internal vessel is a biaxially prestressed structure, the prediction of the delayed deformations is also a safety concern. Indeed, in these structures, the prestressing is there to avoid tensile stresses and cracking in case of a severe accident where internal pressure and temperature could be generated. An experimental mock-up of a reactor containment building at 1/3 scale has been built near Paris by EDF in order to follow the evolution of the delayed strains and of leak tightness of the containment under aging. This mock-up named VeRCoRs (VErification Réaliste du COnfinement des RéacteurS) is highly instrumented so that its behaviour is monitored from the beginning of the construction. In this paper a modelling of the delayed strains (creep and shrinkage of concrete and relaxation of steel) based on the MC2010 is used to predict the behaviour of the mock-up. This modelling takes into account the influence of the temperature and of the relative humidity (varying under service conditions). Finally, the predicted delayed strains are compared with the measurements.