Mode Shape-Based Damage Detection of Twin Skewed Bridges Based on OMA and FE Model Updating

Abstract

A comparative study of the dynamic behavior of twin single-span bridges was carried out based on operational modal analysis and a linear finite element model updating with the aim of finding a potential damage indicator. The bridges are skewed, 30 m long and with prestressed concrete girders as the main support structure, but one of them were collided and suffered damage in two of its I-shape girders. Ambient vibration tests were conducted by deploying 14 uniaxial accelerometers along the sidewalks, experimental modal parameters were identified using the COVariance-driven Stochastic Subspace Identification method (SSI-COV). Six vertical modes were clearly identified for each structure. Additionally, some extra modes with non-proportional damping were identified. It was found that the modal frequencies are sensitive to the support conditions and the overall stiffness of the bridge but not to the localized girder damage, which, on the contrary, is reflected in the discrepancy in the fundamental bending mode shape amplitude between the lateral sides of the bridge, and a so-called Continuous Symmetry Measure adopted as a symmetry index seems to be a good damage indicator for this type of straight-alignment simply supported bridges, given the symmetric nature of the bending mode shapes and the asymmetric nature of the damage.

Keywords:

• structural dynamics
• stochastic subspace identification
• damage detection
• prestressed concrete bridges
• finite element model updating

Acknowledgements

This research was financed within the framework of the powers assigned to the LanammeUCR through Article 6 of Law No. 8114. It is also recognized the contributions of Eng. Juan Luis López Agüero and Eng. Shasly Otárola Ortega in the development of the initial FE model of the bridge within their final graduation project, and special thanks to Eng. Pablo Agüero Barrantes Ph.D. in the planning and support of the field instrumentation and data collection, and also thanks to the review and suggestions from the engineers of the Bridge Unit of LanammeUCR for the improvement of this paper.

Disclosure Statement

No potential conflict of interest was reported by the author(s).

Data Availability Statement

The data that support the findings of this study are available from the corresponding author, Y.C. Liu ([email protected]), and LanammeUCR ([email protected]), upon reasonable request.