Steady-state stresses in concrete structures subjected to sustained temperatures and loads: Part I. Cases of uniaxial stress

Abstract

The influence of creep and temperature on the behaviour of concrete structures is discussed with restriction to cases of uniaxial stress. Under the combined effects of non-uniform temperature and stress it is shown that redistribution takes place and that eventually stresses may reach stationary values if the temperature and load conditions are sustained. These steady-state stresses together with the initial values form upper and lower bounds. Theorems are presented that enable the steady-state stresses, moments and forces to be calculated directly and without reference to the elastic or thermal expansion properties of concrete, for structures in which member sections remain plane. A worked example is given and some experimental support to the theory is provided from data relating to two-span continuous prestressed concrete beams subjected to temperature-crossfalls. Application of the theory to three-dimensional stressing is mentioned and it is concluded that the ability to calculate steady-state stresses is of importance in the design of heated concrete structures. The present paper serves as a basis for a following article on an important problem in the desing of prestressed concrete reactor pressure vessels: The calculation of steady-state stresses in a concrete hollow sphere and a long hollow cylinder subjected to sustained pressure and temperature loading.