15. System Identification and Displacement Profiles of Multi-Span Skewed Bridges with Seat Type Abutments

Skewed bridges are classified as irregular structures due to the geometry of the deck and bents. The evaluation of their dynamic response is challenging as it requires a combination of several modes of vibration. In this study, the results of ambient vibration tests performed on four bridges in British Columbia, Canada are used to identify the dynamic properties and the displacement profiles of multi-span skewed bridges with seat type abutments. The frequencies of vibration, the modes of vibrations and the modal dampings are identified using frequency and time domain techniques. In addition, the directionality in the transverse and longitudinal response for skewed bridges with different levels of lateral restraint and deck flexibility is discussed. This paper improves the understanding of the dynamic response of skewed bridges, in particular their lateral response to seismic loads. This understanding contributes to having a better assessment of the seismic demands that skewed structures will undergo and to the development of displacement based design methods for these structures.