Structural identification of highway bridges, as well as individual components, through vibration-based
measurement techniques may provide promising alternatives for in-service characterization of infrastructure
health. This approach is particularly compelling since it links distributed dynamic response measurements to the
global mechanics of the structure, whereas alternative nondestructive test methods provide very localized measures
of structural change. In the present study, a tied arch bridge was instrumented using a high-rate wireless sensor
network providing thecapability to measure real-time accelerations at 48 locations across the bridge. Referencebased
testing was used to extract modal parameters for the full structure with high-resolution mode shapes
constructed from hundreds of sampled locations. The spatial density was resolved fine enough that local response of
plate modes in the rib arches were reconstructed, which may offer advantages for long-term diagnostic monitoring.
Supplemental impulse-response testing was performed on the hanger cables of the bridge to extract estimates of
the tension force in each cable through structural identification for further characterization of the structure. The
estimation of cable force in tied arch bridge hangers presents a particular challenge since the cable slenderness
ratios typically preclude use of approximation formulas. A summary of the applied experimental approach,
extraction of a subset of modal parameters, and discussion of cable force estimation in the hangers is provided.
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