Description
Output-only system identification of a large post-tensioned concrete bridge using hybrid excitation was conducted. To boost ambient excitations, a dynamic force induced by two light-weight electro-dynamic shakers was adopted for hybrid testing. The bridge modal characteristics were identified using three output-only identification methods: auto-regressive (AR) time series model, eigensystem realization algorithm with observer/Kalman identification (ERA-OKID) and data-driven stochastic subspace identification method (SSI-data). The accuracy and efficacy of the system identification algorithms when applied to hybrid dynamic responses were investigated and benchmarked against the results obtained from pure ambient vibration testing. The study demonstrated that using output-only identification algorithms on vibration responses produced by hybrid excitations can be used for extracting more accurate and reliable modal parameters with enhanced accuracy and reliability for large-scale structures due to enhanced excitation energy and better coverage of relevant frequency bands. More modes were identified at a reduced computational cost from voluminous data of multi-channel measurements.
