Field Study of a Glass-Reinforced Plastic Pedestrian Bridge: Interim Report

About the report:

Discussed are the design, fabrication, and load testing of girders composed entirely of glass-reinforced polyester (GRP) resin. The girders were 4.9 m (16 ft.) long and had geometric features which included trussed webs, a solid flange plate, and a triangular-shaped cross section. Three of the girders were attached laterally by a GRP cover plate in the laboratory to provide a complete superstructure for a pedestrian bridge 4.9 m (16 ft.) long by 2.1 m (7 ft.) wide. The lightweight, high strength, and formability of the GRP materials permitted fabrication and handling of both the components and the completely assembled structure without the use of heavy equipment. The weight of the GRP bridge superstructure was approximately 364 kg (800 lb.). An exposed aggregate concrete deck and wooden handrails will be used for the bridge to blend with the natural setting of the recreational area site for the bridge. Outdoor live load tests were performed to measure strains, deflections, and the creep behavior of one full-scale girder exposed to prevailing climatic conditions in Charlottesville. A finite element analysis was conducted for the single girder to provide comparisons between experimental load test data and analytical predictions. The experimental results were approximately 25% lower than the predicted values for deflections. Creep test results from a laboratory specimen indicate mid-span deflections to be less than 0.88 mm/year (0.03 in./year) under a live load greater than the AASHTO design value of 4,063 N/m²(85 psf). Observations of the bridge are planned for a period of five years to monitor its structural behavior, the effects of weathering, and user abuse.

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