Prediction of thermal stresses in mass concrete structures with experimental and analytical results

Abstract

Accurate prediction of concrete properties is needed for the thermal stress analysis of mass concrete structures because analysis results are mainly dependent on concrete properties. However, it is uneconomic or impractical to evaluate directly concrete properties, such as thermal expansion coefficient, elastic modulus, shrinkage and creep etc. by experiments because the concrete properties at early ages drastically change with time and curing conditions, which cause thermal deformation of the specimens and the experimental devices. The purpose of this study is to predict thermal stresses in mass concrete structures by the proposed method, which uses experimental and analytical results. To achieve this goal, experiments of elastic modulus, stress-independent strain and thermal stresses are suggested and conducted. Elastic modulus and stress-independent strain are used for elastic analysis, while thermal stresses are used to evaluate the creep effects on thermal stresses. Based on the step-by-step method, thermal stresses in mass concrete structures are obtained by integrating the incremental stresses which are the sum of elastic stress and the stress affected by creep. For the verification, the predicted stresses are compared to the stresses measured from the experiments of mass concrete structures with internal and external restraints. As a result of the comparison, it showed good prediction results for compressive stresses, while the tensile stresses at the surface showed the difference from measured stresses due to the surface cracking in concrete.