Simulation of the thermal stress in mass concrete using a thermal stress measuring device

Abstract

An experimental study is conducted to simulate the thermal stresses generated in mass concrete. Accurate prediction of the thermal stresses by analysis is quite difficult particularly at early ages, due to uncertain age-dependent properties of concrete. A series of tests was conducted in which the amount of restraint in a thermal stress device (TSD) was varied. The effect of aging and the amount of restraint on stress development that can occur in realistic structures was evaluated. The influence of the uncertain early-age properties of concrete (i.e., elastic modulus, thermal dilation, autogenous deformation and transitional thermal creep), on the generation of thermal stresses was incorporated using a TSD due to the simultaneous development of temperature and the corresponding stress in a restrained specimen from the very beginning of the process. The effect of various amounts of restraint on the generation of thermal stress was pronounced. Numerical simulations of the thermal stress setup were also performed using the finite element code DIANA to verify and extend the experimental interpretation and to determine the maximum value of restrained stress which would occur under highest level of restraint. Adopting this methodology may simplify the complexity of thermal stress analyses (i.e., more precise 3-D thermal stress analysis can be performed using material properties achieved from 1-D uniaxial tests) due to the difficulty of accurately determining the early-age properties of concrete.