Abstract
The paper presents a novel thermomechanical 3D Load-Induced Thermal Strain (LITS) model that captures the experimentally demonstrated behavior of concrete in the case of heating under multiaxial mechanical load, for temperatures up to 250 °C. In contrast to the models available in the literature, the new model takes into account the observed dependency of LITS on stress confinement. Such a dependency is introduced through a confinement coefficient which makes LITS directly proportional to the confinement of the stress state. Also, a new practical bilinear LITS model is proposed and proved to be suitable for fitting the general trend of the curves experimentally obtained for different loading conditions. The presented model is embedded in a thermoelastic material constitutive law, and then verified and validated against experiments performed on concrete specimens subjected to transient temperatures up to 250 °C under uniaxial, biaxial and triaxial compressive stress states. Once calibrated and validated, the constitutive model is used to evaluate the effects of LITS on the structural behavior of a Prestressed Concrete Pressure Vessel (PCPV) of a typical Advanced Gas cooled Reactor (AGR) subjected to a heating-cooling cycle simulating a temporary fault in its cooling system. The results of this study indicate that the development of LITS significantly influences the stress redistribution in the structure. Moreover, it is shown that in the case of PCPVs (and by extension similar structures) it is crucial to consider the LITS dependence on the stress confinement.
Highlights
Load induced thermal strain, or Load-Induced Thermal Strain (LITS), is a strain component that develops when concrete is heated while subjected to compressive stress states
LITS may be seen as the difference between the thermal strains developing in the cases of concrete subjected to constant compressive stress and stress-free concrete
If LITS is not included in the model, an increase in tension develops on heating, due to the difference in thermal expansion of steel and concrete
Summary
LITS, is a strain component that develops when concrete is heated while subjected to compressive stress states. Little attention has been paid to the development of LITS in bulk concrete structures where the stress state is expected to be multiaxial, such Prestressed Concrete Pressure Vessels (PCPV) of nuclear reactors, tunnels and vaults With this in mind, the present paper presents a novel and robust 3D LITS material model which overcomes some of the shortcomings of the models available in the literature. Experimental evidence shows that if heated concrete is subjected to uniaxial compressive stress, a smaller thermal strain occurs in the direction of the load than in the case of free thermal expansion. It is this additional thermal strain component, which is defined as LITS. LITS may be seen as the difference between the thermal strains developing in the cases of concrete subjected to constant compressive stress and stress-free concrete
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
