Experiments on a Hybrid-Composite Beam for Bridge Applications

This paper details a study of the structural behavior of hybrid-composite beams (HCBs), which consist of a fiber-reinforced polymer (FRP) shell with a tied concrete arch. The HCB offers advantages in life-cycle costs through reduced transportation weight and increased corrosion resistance. Through a better understanding of system behavior, the proportion of load in each component can be determined, and each component can be designed for the appropriate forces. A long-term outcome of this research will be a general, structural analytical framework, which can be used by transportation departments to design HCBs as rapidly constructible bridge components. This study focused on the identification of the load paths and load sharing between the arch and FRP shell in an HCB and on the test of an HCB with a composite bridge deck. Tests were performed through the application of point loads on simple span beams (before the bridge deck was placed) and with a three-beam, skewed composite bridge system, which resulted in strain data for the arch and FRP shell. The test results showed that strain behavior was linear elastic at service loads, and the FRP shell had a linear strain profile. Curvature from strain data was used to find internal bending forces, and the proportion of load within the arch was found. A stress integration method was used to confirm the internal force contributions. The arch carried about 80% of the total load for the noncomposite case without a bridge deck. When composite with a bridge deck, the arch made a minimal contribution to the HCB stiffness and strength, because most of the arch was below the neutral axis and cracked under the maximum live load expected for the bridge. For this composite case, the FRP shell and prestressing strands resisted about 80% of the applied load, while the bridge deck carried the remaining 20% to the end diaphragms and bearings.