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.
1. Brownjohn, J., A. De Stefano, Y.-L. Xu, H. Wenzel and A. Aktan. “Vibration-based monitoring of civil
infrastructure: challenges and successes,” Journal of Civil Structural Health Monitoring, Vol. 1, pp. 79-95,
2011.
2. Friswell, M. and J. Mottershead. Finite Element Model Updating in Structural Dynamics, Dordrecht,
Netherlands: Kluwer Academic Publishers, 1995.
3. Catbas, F., S. Ciloglu, O. Hasancebi, K. Grimmelsman and A. Aktan. “Limitations in Structural Identification of
Large Constructed Structures,” Journal of Structural Engineering, Vol. 133, No. 8, pp. 1051-1066, 2007.
4. Hong, A., F. Ubertini and R. Betti. “Wind Analysis of a Suspension Bridge: Identification and Finite-Element
Model Simulation,” Journal of Structural Engineering, Vol. 137, No. 1, pp. 133-142, 2011.
5. Peeters, B. “Continuous Monitoring of the Øresund Bridge: Data Acquisition and Operational Modal Analysis,”
in Encyclopedia of Structural Health Monitoring, West Sussex, UK, John Wiley & Sons Ltd, 2006, pp. 2159-
2174, 2009.
6. Ahn, I.-S. and S. Chen. “Nonlinear Model-Based System Identification of Lead-Rubber Bearings,” Journal of
Structural Engineering, Vol. 134, No. 2, pp. 318-328, 2008.
7. Weng, S.,Y. Xia, Y.-L. Xu and H.-P. Zhu. “Substructure based approach to finite element model updating,”
Computers and Structures, Vol. 89, No. 9-10, pp. 772-782, 2011.
8. Whelan, M. “Design and Application of a Wireless Sensor Network for Vibration-Based Performance
Assessment of a Tied Arch Bridge,” Structural Health Monitoring 2011: Condition-based Maintenance and
Intelligent Structures, Lancaster, PA, DEStech Publications, Inc., pp. 709-716 2011.
9. Hietbrink, C. and M. Whelan. “System Identification of a Tied Arch Bridge using Reference-Based Wireless
Sensor Networks,” in Smart Sensor Phenomena, Technology, Networks, and Systems Integration, San Diego,
CA, 2012.
Figure 7: Nonlinear least-squares fitting to the analytical solution for the transverse cable response.
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10. Wenzel, H. and D. Pichler. Ambient Vibration Monitoring, West Sussex, UK: John Wiley & Sons, 2006.
11. Zui, H., T. Shinke and Y. Namita. “Practical Formulas for Estimation of Cable Tension by Vibration Method,”
Journal of Structural Engineering, Vol. 122, no. 6, pp. 651-656, 1996.
12. Mehrabi, A. and S. Tonon. “Unified Finite Difference Formulation for Free Vibration of Cables,” Journal of
Structural Engineering, Vol. 124, No. 11, pp. 1313-1322, 1998.
13. Ren, W., H. Liu and G. Chen.“Determination of cable tensions based on frequency differences,” International
Journal for Computer-Aided Engineering and Software, Vol. 25, No. 2, pp. 172-189, 2008.