Seismic Evaluation of Bridge Systems Using Novel Opensees-Integrated Graphical User Interfaces
Open Access DepositedThis thesis presents the development of the "Bridge Analysis Program Version 2024" (BAP2024), a MATLAB-based tool designed to analyze the response of girder bridges subjected to seismic events and other external excitations, such as harmonic or impulse loads. BAP2024 features intuitive Graphical User Interfaces (GUIs) integrated with custom MATLAB functions and the Open System for Earthquake Engineering Simulation (OpenSees). Its primary objectives are to simplify the preprocessing of bridge data for OpenSees and streamline the postprocessing of analysis results, eliminating the need for manual scripting in Tcl or external tools like Microsoft Excel for response evaluation.In the pre-processing phase, BAP2024 allows users to input bridge data through GUIs, automatically calculating critical parameters, such as non-composite and composite section properties, confined concrete characteristics, and plastic hinge lengths. It also generates a finite element model of the bridge, including nodes, elements, and fiber sections. Elemental loads and nodal masses are determined based on self-weight and tributary area superimposed loads. Users can customize analysis settings directly through the GUIs. The program then produces Tcl files for OpenSees, containing all the necessary data to analyze the finite element model. In the post-processing phase, BAP2024 imports OpenSees results and visualizes them via GUI-based diagrams, such as shear force-displacement plots, force-time histories, and displacement-time histories. It also provides detailed superstructure displacement profiles at each time step. Users can identify column yield displacements by selecting points on the shear force-displacement diagram. Using yield and maximum displacement values during seismic events, the program enables the evaluation of column ductility levels, aiding in repair or replacement decisions. As an application tool, BAP2024 was implemented in the analysis of two prototype bridges, referred to as Prototypes A ( a six-span bridge) and B (a two-span bridge). In these prototypes, circular reinforced concrete (RC) columns were designed individually using force-based methods and response spectrum analysis. BAP2024 facilitated the modeling and performance analysis of the prototypes under five scaled earthquake records, assuming soil classification D, to capture the seismic demands on the columns. The analytical results reveal that the RC circular columns in Prototype A exceed Caltrans ductility limits and present an unacceptable risk of collapse. In contrast, the RC circular columns in Prototype B exhibited lower ductility demands, indicating superior performance with minimal risk of severe damage or negligible failure. These results underscore a critical limitation in the traditional approach of designing structural components as individual members, rather than considering their behavior within the context of a full bridge system. While force-based methods and response spectrum analysis provide a robust framework for initial design, they may overlook complex interactions between bridge components. This can lead to inconsistencies in the predicted performance of individual elements and the overall structure. By bridging the gap between member-level and system-level design, tools like BAP2024 provide valuable insights for improving seismic design methodologies and achieving more reliable and sustainable bridge structures. From an educational tool, BAP2024 is user-friendly and has potential as a teaching aid in the "Structural Design to Resist Natural Hazards" course at George Washington University. This course trains graduate students in designing bridge columns for seismic forces using force- and displacement-based methods. BAP2024 can supplement instruction by validating column designs for target ductility levels within multi-degree-of-freedom (MDOF) systems in three-dimensional contexts. Future enhancements to the program could focus on expanding its versatility in modeling complex bridge structures by incorporating additional bridge types, such as box girder bridges, and integrating pushover analysis into BAP2024. This would facilitate the identification of potential failure points and enable the evaluation of structural performance beyond the elastic range. Additionally, conducting analyses under varying bridge constraints, boundary conditions, and soil classifications is recommended to further investigate their effects at the system level. Validating component-level column designs using the Displacement-Based Design (DBD) method at the system level is also advised to provide comparative insights against results obtained from the Force-Based Design (FBD) method.
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Charoenwong_gwu_0075M_17097.pdf | 2025-04-11 | Open Access |
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