This paper provides an introduction to Smart Bridge; a railroad bridge structural integrity monitoring system based on Continuous Fiber Optic Strain Sensing (CFOSS) technology. This design concept allows for the real time observation of how a bridge responds to dynamic loading and provides for autonomous reporting of abnormal structural conditions.

The CFOSS technology can monitor the entire bridge and observe changes in the behavure of its structural elements. The structure is constantly monitored, both when the structure is at static load and when the bridge is supporting the load of a train. When significant changes are observed they can be defined by location and the degree of deviation from normal.

A Smart Bridge provides automatic notification of sudden changes to the structure in real time. These changes may be an indication of bridge impact damage. It also provides a graphical map of the changes in structural behavure over time. In both circumstances the technology will identify the specific structural element that is degrading.

Smart Bridge is based on Continuous Fiber Optic Strain Sensing technology. This technology manifests in the form of a cable that is bonded along the entire length of the structural elements of the bridge. The cable senses strain in both the axial and transverse directions. Unlike conventional strain gauge elements that are bonded to a single location, CFOSS cables run continuously along the beam, plate or tendon. The technology is able to observe the changes in the concentration of strain along a structure and identify the origin of the change.

CFOSS technology is currently under development as part of the Smart Rail project. The underlying fiber optic strain sensing cable technology is in commercial use in the oil well and petrochemical pipeline industry.

The adoption of Smart Bridge provides enhanced operational safety because it monitors the structural integrity of the bridge continuously and provides automatic status annunciations. This monitoring is active during times when the bridge is in dead load and when it is supporting the load of a passing train. Smart Bridge also improves the working safety of bridge inspectors by providing a map of structural changes that may indicate hazardous conditions. The use of Smart Bridge improves the inspection process by identifying potential structural problems that may require visual confirmation. And it provides autonomous warnings when sudden changes in the bridge structural integrity are detected.

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