Semester

Summer

Date of Graduation

2025

Document Type

Thesis (Campus Access)

Degree Type

MS

College

Statler College of Engineering and Mineral Resources

Department

Civil and Environmental Engineering

Committee Chair

Hung-Liang Chen

Committee Member

Onur Avci

Committee Member

Guadalupe Leon

Committee Member

Horng-Jyh Yang

Abstract

In large concrete structures, significant temperature gradients can develop due to the low thermal conductivity of concrete. This causes thermal stresses on the concrete’s surface which can lead to thermal cracking if it exceeds the concrete’s tensile strength. Therefore, researchers have extensively studied thermal stress in mass concrete structures. Often, commercially available finite element programs such as ABAQUS and ANSYS are used to implement the material properties of concrete using user subroutines. In this study, ELMER, an open-source finite element program, is used to predict the early-age thermal stress behavior of concrete. The time, temperature and location dependent material properties of concrete are implemented in ELMER using user functions and a UMAT subroutine. In thermal analysis, the concrete’s temperature distribution was modelled using user functions for thermal conductivity, specific heat and heat generation. In stress analysis, the degree of hydration dependent mechanical properties such as compressive strength and elastic modulus were incorporated using the UMAT subroutine. Creep deformation at early-age was also considered. A rectangular prism was used to validate the creep calculation under loading and unloading in the UMAT subroutine. Results indicate that ELMER can be effectively used as a tool to model early-age thermal and stress behavior of concrete.

Additionally, a comprehensive study of the thermal properties of soil samples obtained from four districts in West Virginia was conducted. The properties analyzed in this study include the soils’ moisture content, specific gravity, specific heat, compaction, and thermal conductivity. The soil samples were also classified using the Unified Soil Classification system (USCS). These properties of soil were measured in different conditions namely: non-compacted dry, compacted moist (16% moisture) and compacted dry. A three-dimensional heat conduction Green’s function solution for a rectangular prism developed in this study was shown to be able to accurately determine the thermal conductivity of soil in an experimental cube. The results indicate that the thermal conductivities of the compacted moist soil samples were the highest, followed by the compacted dry soil samples, with the non-compacted dry soil samples having the lowest thermal conductivities. The measured thermal properties of the four soil samples, namely, density, specific heat and thermal conductivity were used as a boundary condition in the thermal-stress analysis of mass concrete rectangular bridge footings in a parallel study.

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