Theoretical model of high temperature effects on uniaxial concrete member under elastic restraint

An analytical solution to a uniaxial benchmark problem of a concrete member restrained by an elastic spring and subject to heating and subsequent cooling is given. The model demonstrates the effect of load-induced thermal strain, which has so far only been described through experiments. Heating a concrete specimen under constant compressive load shows a significant contraction rather than expansion, which would be the case if the specimen were heated without any constraints. The magnitude of this contraction is beyond that of conventional creep and mechanical strain even though the stiffness degradation from high temperature exposure is taken into account. Thus, it is attributed to a special thermo-mechanical coupling, taking place during the first transient heating process. Furthermore, the analytical model describes the tensile stresses, developing during cooling, including non-linear material behaviour arising from fictitious cracking. Through several examples the effect of the various parameters is ev...