Condition Assessment of FRP Composite Bridge Components Using Infrared Thermography

This paper presents the findings of an experimental study on the use of Infrared Thermography for nondestructive evaluation of subsurface delaminations in Fiber Reinforced Polymer (FRP) composite bridge decks and concrete columns wrapped with FRP jackets. Composite bridge deck specimens were constructed in the laboratory with varying subsurface delamination conditions such as sizes, thicknesses and filler materials. These simulated delaminations were placed between the 3/8 inches thick wearing surface and the top of the FRP deck. The laboratory specimens were tested using an infrared imaging system. The infrared images from the delaminated specimens were compared with solid (undamaged) specimens to study the effect of subsurface delaminations on the infrared images under controlled laboratory conditions. In addition, field tests were conducted using infrared thermography on the FRP composite decks of two bridges (Wickwire Run and Laurel Lick) located in West Virginia. The field tests were used to detect subsurface delaminations and study the effect of environmental parameters on the infrared images. As an additional example, infrared testing was conducted to evaluate FRP wrapping and detect debonding between the FRP wraps and concrete columns in the Pond Creek Bridge in West Virginia. This study shows that the infrared thermography technique can be used effectively for rapid evaluation of subsurface condition of FRP composite bridge decks and wrapped columns. The study also shows how the environmental conditions (e.g., shadow, oil spill, and angle of reflection of solar rays) can affect the output infrared images.