Determination of Temperature Stresses during Construction of the Monolithic Thick-Walled Cylindrical Shells

Abstract

Introduction. The thick-walled cylindrical shells are widely used in the hydraulic structures, protective structures of nuclear power plant reactors and missile system launchers. Due to the internal heat emission of concrete in massive monolithic structures, there is a high risk of early-age cracking. Computer modeling methods can be used to develop the preventive measures against it. Previously, modeling of temperature stresses within a construction process was carried out for the massive foundation slabs and walls, whereas the thick-walled cylindrical shells were not studied. The aim of the present work is to develop a methodology for calculating the temperature stresses during construction of the monolithic thick-walled cylindrical shells. Materials and Methods. Stress calculations were made in a one-dimensional axisymmetric formulation. The dependence of the mechanical properties of concrete on the degree of its maturity was taken into account. The stress-strain state (hereinafter — SSS) calculation problem was reduced to a second-order differential equation relative to the radial stress, which was solved numerically by a finite difference method. The SSS calculation was preceded by the temperature field calculation, which was deemed independent from the stress state. The authors carried out the numerical solution in the MATLAB environment.Results. At the first stage of testing, the developed methodology was compared with calculations made in the ANSYS software package under a time-constant modulus of elasticity of concrete that confirmed its reliability. Also, the calculation results, which took into account the dependence of the modulus of elasticity of concrete on degree of its maturity were presented. Moreover, compared to calculations under the time-constant mechanical properties of concrete, in the stress-strain state, the picture became radically different. Discussion and Conclusion. Calculations under a time-constant modulus of elasticity of concrete by means of the standard software packages, as opposed to the author’s methodology, leads to the overestimated circumferential stress values, and hinders calculation of the residual stresses. In the case of a time-constant modulus of elasticity of concrete, the temperature stresses are completely reversible.