Full-field dynamic reconstruction and deflection field identification of bridges using System Equivalent Model Mixing

Impact vibration testing and structural identification are powerful tools for assessing structural flexibility and have been widely used in bridge load capacity evaluation. However, traditional impact tests require dense instrumentation across the entire bridge deck, which significantly limits testing efficiency and flexibility. Building a full-field dynamic model with high spatial resolution from sparse measurement configurations remains challenging. To address this, this paper proposes a framework for full-field dynamic reconstruction and deflection field identification of bridges based on System Equivalent Model Mixing (SEMM). The hybrid modeling paradigm allows extending the dynamics of an experimental model with sparse measurement degrees of freedom (DoFs) to a numerical model with a denser set of DoFs. This process yields a refined hybrid structural dynamic model that preserves the fidelity of the experimental model while leveraging the high spatial resolution of the numerical model. Subsequently, full-field modal parameters extracted from the hybrid model are used to synthesize the full-field flexibility matrix, which accurately characterizes the load-deformation relationship of the structure. Finally, the deflection field under arbitrary target loads can be reconstructed using the full-field flexibility matrix. The effectiveness of the proposed framework is validated through two numerical structures and one experimental structure. Comparisons with the classic dynamic expansion method highlight the adaptability and superiority of the proposed framework under sparse measurement configurations. This framework advances the development of full-field state perception and rapid condition assessment of bridge structures, demonstrating its potential to serve as a robust analytical tool for impact vibration testing.