Three hybrid composite beam (HCB) bridges were recently constructed in Missouri, USA. HCB is an innovative idea that incorporates traditional construction materials (steel and concrete) with fiber reinforced polymer (FRP) composites in such a manner to optimize the performance of the beam constituents. The HCB consists of self-consolidating concrete (SCC) poured in classical arch shape and tied at the ends by conventional prestressing strands. The concrete and steel are tucked inside durable fiberglass shell and the voids are filled with polyiso foam. An integrated study was implemented on the three bridges to investigate the HCB in-service behavior. The study included quality control/quality assurance (QC/QA) testing program. As a part of this research study, an innovative infrared (IR) thermal imaging approach was developed to detect the voids in the concrete arch section during its casting. The approach is found to be an ideal solution for QC/QA of the concrete arch concrete placement. A series of load tests on the bridges together with meticulous theoretical and numerical analyses were executed. The first finite element analysis (FEA) for a HCB bridge superstructure was accomplished. The analysis was used to provide better understanding for the girder behavior and to emphasize the areas that need more examination. Based on the FEA results the existing flexural design methodology and assumptions were tested. The methodology was found unable to detect the maximum compressive stress in the concrete arch, and the strain compatibility assumption was found invalid. However, the experimental measurements along with the mathematical calculations indicate that the HCB owns abundant nominal bending and shear strength to withstand the expected loads during its lifetime. A modified methodology that is based on the same assumptions as the existing one was produced. The methodology was found to achieve significant enhancement in predicting the stresses under the service loads. The durability of the HCB was tested through subjecting the composite shell to different aging regimes. The testing results indicate that the HCB possesses excellent durability in relation to the expected weathering exposure in Missouri. Longer exposure regimes are under implementation to assure these results.
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