THERMOPLASTICITY MODEL FOR CONCRETE UNDER TRANSIENT TEMPERATURE AND BIAXIAL STRESS

In the past, the theory of thermoplasticity has been confined to metal type materials exhibiting an elastic-perfectly-plastic behaviour. This paper describes the application of this theory to modelling the response of a nonlinear hardening material (concrete in the present case) under transient temperature and stress. The difficulties arising from the application of the theory of thermoelastoplasticity to modelling the behaviour of concrete at elevated temperatures are discussed, together with the inadequacy of the existing algorithms that were proposed for perfectly plastic materials, to cope with a nonlinear hardening case. An integration scheme derived from the Euler backward scheme is used to integrate the rate equations. The resulting model is used to analyse existing biaxial data and investigate the effect of a sustained load on the deformational response of concrete under biaxial loading and elevated temperature.