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Exploring structural identification as a tool for characterization of bridge substructures
Dissertation   Open access

Exploring structural identification as a tool for characterization of bridge substructures

Qiang Mao
Doctor of Philosophy (Ph.D.), Drexel University
Oct 2019
DOI:
https://doi.org/10.17918/b1gr-1324
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Abstract

Bridges--Foundations and piers Bridges--Evaluation Bridges--Maintenance and repair Civil Engineering
Insufficient information on existing bridge substructures and foundations poses significant challenges for structural condition evaluation and can cause significant uncertainties for the safety and serviceability of bridges. Characterization and condition evaluation of bridges substructures and foundations will not only help to decrease the vulnerability to natural hazards, but it could also provide opportunities for their reuse with considerable benefits. In this thesis, the feasibility of leveraging structural identification techniques to characterize bridge substructures and foundations is studied. The challenges and limitations of implementing structural identification on bridge substructure characterization are also explored. In addition, the counter measurements for these challenges are also investigated. A 3-span simply supported bridge located in Mossy, WV is used as a case study. Multi-Reference Impact Testing is applied to this bridge with two different sensor layouts designed to investigate different unknowns of the bridge substructure, and to increase spatial information to be leveraged in the following study. Modal analysis and finite element model updating techniques are used to comprehend the uncertainties and conditions of the substructure. An updated finite element model for this structure provides valuable information for bridge condition assessment and proves how structural identification is a viable tool for the case considered. Several difficulties of implementing structural identification on this bridge substructure is also discussed including: (a) identifying substructure modes from Experimental Modal Analysis results; (b) identifying unknown variables with parameter coupling effect (between foundation depth and SSI); (c) mode pairing during automated FEM calibration process. A physical scaled bridge model is designed and studied to provide more flexibility to explore the application of structural identification on the bridge substructures. The scaled bridge model is designed as a scaled phenomenological model considering similitude requirements and distortions. Three experimentation cases are designed for EMA on the scaled bridge model: a case where aluminum bearings are installed with bolts to connect superstructure and substructure, a case where rubber bearings are installed with bolts and a case where rubber bearings are installed with epoxy. Based on the study on the scaled bridge model, structural identification shows the potential to characterize bridge substructures. The counter measurements for the major challenges met in the WV bridge study are explored and verified in the study for the scaled bridge model. In addition, recommendations for the application of structural identification on real bridge substructures are given based on the results presented in this thesis.

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