Date of Graduation
Statler College of Engineering and Mineral Resources
Civil and Environmental Engineering
Roger HL Chen
Karl E Barth
Seung H Hong
Research findings in the past have demonstrated that the heat of hydration can induce thermal cracking in early age concrete. The disproportionate thermal expansion can cause considerable tensile stresses at concrete surfaces. The minimum size of mass concrete has remained unsolved due to the complexity of the problem. In this study, a way to predict early age concrete temperature and associated thermal stresses is described, including the needed experimental testing and finite element modeling technique.;In thermal analysis, an adiabatic calorimeter was designed and built to measure the adiabatic temperature rise of the concrete. The measured adiabatic temperature rise was converted into a mathematical formulation for finite element modeling. Thermal properties including specific heat and thermal conductivity were considered to be degree of hydration dependent and determined individually for each element in the model. The interface conductance between concrete and steel formwork was determined experimentally and put in place to account for the thermal resistance from the concrete-formwork interface. External surface convection for formwork-air interface was used to calculate surface heat loss.;In order to calculate the thermal stresses, the degree of hydration was utilized to estimate the elastic modulus development. Concrete tensile creep and compressive creep behaviors were included using a step-by-step incremental calculation algorithm. Influences from loading age and temperature effect were considered in each time increment of the creep models. Based on test results from concrete cubes, the modeling method and experimental procedures used in this study were validated to exhibit reasonable accuracy in terms of temperature and strain predictions. The thermal and stress analysis models can be used to calculate the temperature profile and thermal stress development histories for early age concrete.
Lin, Yun, "Thermal Stress Analysis for Early Age Mass Concrete Members" (2015). Graduate Theses, Dissertations, and Problem Reports. 6090.