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Numerical Modelling of Load-Induced-Thermal-Strain of Prestressed Concrete Pressure Vessels



This paper presents the implementation of a 3D Load-Induced-Thermal-Strain (LITS) model in an isotropic linear thermoelastic material law to be used for modelling concrete under transient thermal conditions. A new approach for extending to 3D uniaxial temperature-LITS curves has been proposed and adopted, capable of capturing the experimentally demonstrated dependency of LITS on the confinement of the stress state. A stress dependent confinement coefficient which amplifies uniaxial LITS curves in the case of multiaxial stress confinement was defined to capture such a dependency. Besides, a novel practice-oriented bilinear LITS model has been defined and proved to reproduce experimental curves better than the existing models in the case of triaxial stress states and temperatures up to 250°C. The model was verified, validated and calibrated by modelling experiments performed on concrete specimens. In the last part of the paper, the model has been employed to assess the effects of LITS on a Prestressed Concrete Pressure Vessel (PCPV) subjected to an accidental heatingcooling cycle. It was found that LITS plays a key role for this sort of structure, and that significant aspects of structural behavior are missed if no confinement dependency is modelled.

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