Doctor of Philosophy (PhD)
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Damage detection, Bridge performance, Finite element analysis, Reliability analysis, Non-contact sensors
Date of Defense
Bridge failures over the past few decades have shown conventional bridge monitoring is insufficient to effectively evaluate the safety of this important piece of infrastructure. Therefore, new methods for bridge monitoring and special considerations in bridge design are needed to ensure the health of these structures as they continue to age and prevent the possibility of catastrophic collapses. The objective of this research is to explore new means for detecting damage in bridge members during normal operations that are both accurate and affordable at the same time. However, to make any damage detection method effective and efficient, the behavior of intact and damaged bridges needs to be investigated, preferably using simple analytical models. Therefore, to achieve the objective of this research, a two-fold investigation was performed. One was to study the bridge behavior subjected to various damage scenarios and identify possible failure mechanisms. Achieving this objective leads to a method for bridge evaluation after damage and determines its level of vulnerability to such damage; in other words, it defines the redundancy and reliability of the structure. The other was to develop an effective non-destructive method for damage detection based on the bridge behavior after the damage. vii Two types of bridges were selected and studied for this purpose, twin steel box girder bridges (TSBG) that are classified as fracture critical and prefabricated bridge systems containing cast-in-place joints. These bridges are designed with distinct vulnerabilities that make them susceptible to certain types of damages.
The results of the current study confirmed that concrete deck failure is the dominant failure mode of the TSBG bridge after the occurrence of a fracture in one of the girders. Therefore, an improved simple and unified yield line analysis method was developed to determine the bridge deck capacity. An extensive analytical evaluation and availability of a simple model for load-carrying capacity developed in this study facilitated a comprehensive and coherent reliability approach to assess the safety of TSBG bridges after the complete fracture of one steel girder. Although the results of this research cannot readily be generalized for all TSBG bridges without further evaluation, this study shows that simply supported twin steel box girder bridges could indeed be safe and potentially removed from the fracture critical list. Moreover, the TSBG bridge dynamic analysis after damage showed that bridge frequencies are sufficiently sensitive for identifying partial or full-depth girder fracture in the simple span bridges. However, these significant damages may cause very small changes in the natural frequencies of continuous span bridges. The results show a significant change in the vibration mode shapes after damage in both simple and continuous span bridges. The mode shapes are sensitive enough to detect damage at the inflicted locations, in most cases providing better resolution when compared to the frequency changes.
Investigation on the performance of the full-depth precast-prestressed voided slab bridge shows the vulnerability of such bridge decks to damage at the deck longitudinal joints. Using the FE analysis and load testing results, a new damage detection method for viii structural health monitoring of bridges with precast deck panels was also introduced. This method, applicable to all bridges with modular precast deck units, can effectively identify locations and significance of potential deck joint damage based on the measured changes in bridge response and model updating. A damage detection software tool was also developed in this case that is patent pending.
Previously Published In
Abedin, M., De Caso y Basalo, F. J., Kiani, N., Mehrabi, A. B., & Nanni, A. (2022). Bridge load testing and damage evaluation using model updating method. In Engineering Structures (252:113648). Elsevier.
Abedin, M., & Mehrabi, A. B. (2021, December). Health monitoring of steel box girder bridges using non-contact sensors. In Structures (Vol. 34, pp. 4012-4024). Elsevier.
Abedin, M., & Mehrabi, A. B. (2019). Novel approaches for fracture detection in steel girder bridges. Infrastructures, 4(3), 42.
Abedin, M., Farhangdoust, S., & Mehrabi, A. (2019). Fracture detection in steel girder bridges using self-powered wireless sensors. In Risk-based Bridge Engineering (pp. 216-228). CRC Press.
Abedin, M., & Mehrabi, A. B. (2021, March). Bridge damage identification through frequency changes. In Sensors and Smart Structures Technologies for Civil, Mechanical, and Aerospace Systems 2021 (Vol. 11591, p. 1159109). International Society for Optics and Photonics.
Abedin, Mohammad, "Evaluation and Damage Detection of Highway Bridges with Distinct Vulnerabilities" (2021). FIU Electronic Theses and Dissertations. 4867.
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