Evaluation of Hybrid-Composite Beam for Use in Tide Mill Bridge
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A test program for the Hybrid-Composite Beam (HCB) was conducted prior to its use for the replacement of a skewed, simply-supported bridge (Tide Mill Bridge). The HCB is an innovative combination of conventional materials and ideas in a structural beam. The beam consists of a concrete arch tied with prestressing strand that is placed within a Fiber-Reinforced Polymer (FRP) box. Behavior in individual HCBâ s and a three HCB-system was examined to determine the appropriateness of the current design methodology developed by John Hillman and the simplifying assumptions made within it. Such assumptions include strain compatibility and linear-elastic behavior. Three HCBâ s were tested at the structures laboratory at Virginia Tech. During individual beam tests, the predicted behavior of the FRP box and prestressing strand agreed with experimental results. The tests revealed the arch was susceptible to local bending and behaved far differently from predicted. Overall, the beams were shown to behave linearly. A final test was performed to apply the design live load to the system. Slight non-linear behavior was observed in the beams. Distribution factors for the system were also investigated and compared to AASHTO and Hillmanâ s model. AASHTO factors were conservative for exterior girders but unconservative for interior girders. Hillmanâ s factors were often conservative but were in agreement for the shear in the exterior girder. The current design procedure appeared to predict FRP and strand behavior well, but the behavior of the arch appeared to differ greatly from the other components of the HCB.
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