Composite Marine Pile Bridge Monitoring

Sponsored by: Federal Highway Administration

AITHER developed a structural health bridge monitoring system to obtain structural load data using optical fiber Bragg grating (FBG) sensors embedded in the composite shell of load carrying bridge piles. This technology has applications for structural health monitoring of bridges, piers, and other post-supported infrastructure. These sensors provide strain data for the life history of the pile including pre-installation, installation, residual strains due to the installation process, and health monitoring for the lifetime of the pile. The FBG sensors can also be used to monitor the pile’s mechanical response to static load tests, stanamic tests, and lateral load tests.

AITHER completed instrumentation and full-scale field testing of a 2-ft diameter, 60-ft long composite marine pile with embedded fiber Bragg grating (FBG) strain sensors, which was installed in the James River in Hampton, Virginia. The FBG sensors survived the initial lay-up process of the composite shell, the curing process, the cement core filling process, and the driving process, as well as all transportation events of the composite pile. The fiber optic sensors were embedded into the composite overwrap structure of the pile. A unique advantage to the use of FBG sensors is the ability to embed them directly into the composite shell material during lay-up without affecting the structural integrity of the pile. Embedding the sensors also provided a method of protection to the optical fiber and allowed for the long-term monitoring of the piles following installation and load bearing tests. Embedded fiber optic sensors in the structure can be interrogated on site by a swept laser FBG interrogation system, Micron Optics Inc.’s si425. The data recorded by the instrumentation can then be continuously uploaded, via the Internet.

An alternative approach for the data collection would be to trigger the data upload following a structural load event. With remote interrogation capability, additional cost savings can be gained by scheduling need-based maintenance, rather than preventive inspections. For more information, refer to the SPIE journal paper entitled “Structural Monitoring of Composite Marine Piles Using Multiplexed Fiber Bragg Grating Sensors: In-field Applications” in publications.