Sensor Technologies



Verify Composite Reinforcement Integrity:

The Challenge

Composite over-wraps are applied as reinforcements to concrete bridge structures that have been damaged by internal corrosion or over-loading. These over-wraps are composed of polymers with fiber reinforcements of fiberglass or carbon fibers. It is essential that delamination of the reinforcement does not occur, or the benefit of adding the strengthening element is lost. Environmental factors, such as wide thermal excursions and moisture ingress, can lead to failure at the bond line. A significant advantage is gained if a cost-effective monitoring system is used to watch for signs of the delamination of these bonded reinforcements, especially in critical applications where the need for safety is high and structural failure is a potential risk.

Is there a sensor system that can monitor bond integrity? Can the system be applied to existing structures that have protective coatings? Can the sensors survive a wide range of environmental conditions? Is the system safe to use in flammable environments?

The Solution

FOX-TEK ’s FT fiber optic sensors have these capabilities. They are light weight, flexible, and are easily bonded to concrete, steel, polymers and composites. The sensors are passive, non-electrical devices and are immune to electromagnetic interference (EMI). For outdoor applications where lightning strikes pose a hazard, these sensors are an ideal choice. Although the sensors are quite rugged by themselves, additional protection from environmental is easily achieved with hermetic coatings.

FT sensors measure structural displacement and are readily compensated for thermal effects. When a bonded over-wrap delaminates, the fiber optic sensor detects a loss of strain transfer between the structure and the reinforcement. Periodic site visits or continuous monitoring of the FT sensor strain signals are convenient ways to assess the structural health of the repaired structure in comparison to the installed state.

Summary of Benefits

  • E arly detection of bond failure
  • Timely repairs to minimize further corrosion/structural damage
  Cost Savings
  • M aintenance/repair schedules based on integrity of over-wraps
  • Reduced risk of premature structural failure
  • Reduction in unnecessary repairs
  • Assessment of bond integrity after abnormal load events
  • Data provides reliable performance metrics
  • Reduced risk of structural failure and injury to users