Health monitoring of FRP bridge decks: Fid-Bau Portal

Health monitoring of FRP bridge decks

Miceli, Marybeth / Horne, Michael R. / Duke, John C.

Statistics released in the fall 1989 show that 238,357 (41%) of the nation's 577,710 bridges are either structurally deficient or functionally obsolete. New materials are being explored for use in bridge systems to solve this problem. These materials are less affected by corrosive environmental conditions than conventional civil engineering materials and thus, require less maintenance and potentially provide a longer life span. A material being considered for these applications is glass fiber reinforced vinyl ester matrix composites. Fiber reinforced plastic (FRP) composite deck systems made of this material are favorable potential replacements for deteriorating conventional bridge decks. The decreased specific weight of the FRP greatly reduces the dead load of the superstructure helping avoid load posting of bridges. However there is a lack of long-term durability data concerning this material system in typical bridge environments. Thus, an efficient and effective method must be devised to monitor the health of an FRP structure in-situ. This paper will discuss the use of Infrared Thermography as a means of detecting structural imperfections -- delaminations, disbonds, voids -- caused by conditions encountered both in fabrication and in the field. As forced convection hot air is circulated through the bridge deck, delaminations and disbonds in the top of the deck appear cold while defects in the bottom of the deck give rise to areas with higher temperatures. The discontinuities in thermal propagation patterns are detected with a thermal imaging system and indicate present and possible future structural deficiencies. Laboratory results revealing fabrication/installation problems and those from field tests will be presented.