Graduation Semester and Year
Summer 2026
Language
English
Document Type
Dissertation
Degree Name
Doctor of Philosophy in Civil Engineering
Department
Civil Engineering
First Advisor
Dr. Xinbao Yu
Abstract
Understanding the performance of bridge deck deicing systems under winter weather conditions is important for improving transportation safety and reducing long-term deterioration of bridge infrastructure. Bridge decks are more vulnerable to icing than ground-supported pavements because they are exposed to ambient air, wind, and radiation from multiple directions, while they do not receive thermal support from the underlying soil. Conventional deicing methods, especially chloride-based salts, can reduce ice formation in the short term, but repeated application may accelerate reinforcement corrosion, concrete damage, and environmental concerns. Therefore, shallow geothermal energy has been considered as a sustainable alternative for bridge deck deicing by using the relatively stable subsurface temperature as a renewable heat source. Although geothermal bridge deicing systems have shown promising potential, limited field-scale studies have evaluated their thermal performance, energy efficiency, ground heat exchanger behavior, and thermo-mechanical response under real operating conditions.
Therefore, this dissertation aims to provide a comprehensive field-scale evaluation of a shallow geothermal bridge deck deicing system installed on an in-service bridge in North Texas. The system was installed on an eight-span reinforced concrete flat-slab bridge on State Highway 180 in Tarrant County, Texas. It consists of sixteen vertical ground heat exchangers, four ground-source heat pumps, a transmission piping network, and externally attached hydronic heating panels installed beneath the bridge deck. Field data were collected during the 2024 and 2025 winter seasons to evaluate bridge deck temperature response, inlet and outlet fluid temperature, heat transfer efficiency, ground temperature, flow rate, heat pump performance, and strain response. The dissertation also uses numerical modeling to support the interpretation of thermo-mechanical behavior caused by localized geothermal heating.
The study first evaluates the thermal performance of the geothermal bridge deck heating system under different winter events, insulation conditions, and operation modes. Results show that the system was able to maintain heated bridge deck regions above freezing during severe winter conditions, including ambient temperatures as low as approximately −9.6°C. The comparison between insulation materials indicated that spray polyurethane foam improved heat retention and heat transfer to the bridge deck compared with geofoam. The heat transfer efficiency reached up to approximately 64% under favorable conditions, while half-capacity mode at a 30°C setpoint provided the most efficient balance between heat input and useful heat delivered to the bridge deck. Then, the study evaluates the system-level energy behavior by quantifying the energy chain from ground heat extraction to bridge deck heat delivery. Results indicate that operation mode strongly affects system performance. Half-capacity mode at 30°C produced the highest heat pump efficiency, with a load-side coefficient of performance of about 5.7 and a source-side coefficient of performance of about 4.6. The ground heat exchanger configuration also influenced thermal sustainability, where smaller active borehole groups increased short-term heat extraction but caused faster ground thermal depletion.
Finally, this dissertation examines the thermo-mechanical response of the bridge deck under geothermal system operation using field strain monitoring and three-dimensional finite element modeling. The measured strain response showed that directly heated regions had relatively stable behavior, while indirectly heated inter-panel regions experienced larger strain fluctuations due to thermal incompatibility and internal restraint between adjacent heated panels. The relationship between differential temperature and differential strain showed a strong linear correlation with a coefficient of determination of approximately 0.98 and clear hysteresis behavior. This indicates that the bridge deck response was controlled by non-uniform temperature distribution, thermal inertia, and structural restraint rather than local temperature alone. The numerical model predicted maximum thermo-mechanical stress and strain values of approximately 4 MPa and 31 με, respectively, near the interfaces between heated and indirectly heated regions. Overall, this dissertation demonstrates that shallow geothermal energy can be a technically feasible and energy-efficient method for bridge deck deicing, while also showing that insulation quality, operation mode, transmission losses, ground heat exchanger configuration, and localized thermo-mechanical effects must be considered for future design and operation of geothermal bridge deicing systems.
Keywords
Keywords: geothermal bridge deicing; shallow geothermal energy; ground-source heat pump; ground heat exchanger; bridge deck heating; heat transfer efficiency; winter maintenance; energy performance; thermo-mechanical behavior; thermal stress; thermal strain; field monitoring; finite element modeling.
Disciplines
Geotechnical Engineering
License
This work is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 3.0 License.
Recommended Citation
Fakhrabadi, Alireza, "INTEGRATED THERMAL, ENERGY, AND STRUCTURAL PERFORMANCE ASSESSMENT OF A NOVEL IN-SERVICE SHALLOW GEOTHERMAL BRIDGE DEICING SYSTEM" (2026). Civil Engineering Dissertations. 11.
https://mavmatrix.uta.edu/civilengineering_dissertations2/11