Further Studies of a Trussed-web Girder Composed of Reinforced Plastics

About the report:

Three single section and one trisection girder eight feet long were fabricated and load tested to determine the deflection, strain, and creep characteristics of the members. One specimen fabricated with stranded elements composed of Kevlar 49 instead of glass exhibited improved stiffness properties. The maximum load applied to a specimen was 600 psf uniformly distributed over the top plate, which caused failure of the top stiffener joints. A ratio of 107 for live load to dead weight was obtained in this test. Partial loading of the girder caused elastic buckling of some web elements. Analytical studies showed that buckling could be prevented by the addiction of dead weight as a concrete slab on the top plate. A center span deflection creep test at a load of 150 psf indicated a secondary creep rate of 0.03 inch/year, with a termination of primary creep after 30 days. The test specimens just met the center span deflection requirements of AASHTO for an 85 psf live load Computations for strains and deflections based on elastic strain-energy theories were 20% and 30% higher than experimental values for deflections and strains, respectively. Partial loading tests verified the application of the principle of superposition in the analytical procedures. It is recommended that a field study of a prototype pedestrian bridge be conducted to extend the findings of the laboratory studies.

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