Modification Studies for a Bridge Girder of Reinforced Plastics

About the report:

Several modifications were made in the design of a glass-reinforced plastic girder in an effort to improve its load-deflection performance characteristics. The addition of lateral ties between the lower chords of adjacent girders in a trisectional structure significantly reduced the horizontal displacements of the sections due to vertical loads. Considerable improvement was also made in vertical deflections by the replacement of glass strands with Kevlar 49 strands in the tension elements. The replacement of pin-connected stiffener assemblies with rigid stiffeners did not indicate improved performance in a load test. Secondary creep deflections were estimated to increase at a rate of 0.03 inch per year in a trisectional structure loaded to 100 psf. Ultimate load tests indicated a safety factor of 8 based on AASHTO design loads for pedestrian bridges. Criteria for the design of triangular trussed girder structures should be based on limiting deflections, mechanical protection of stressed elements from degrading environmental factors, automated fabrication procedures, and the use of combinations of materials to effect cost benefits.

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