Date of this Version
Kodsy, A. M. (2022). Repair and Strengthening of Concrete Bridges Using Ultra-High-Performance Concrete (UHPC) (Doctoral dissertation, The University of Nebraska-Lincoln).
Reinforced/Prestressed concrete bridges are subjected to environmental effects that cause premature deterioration and require structural repair and strengthening during their service life. Currently 42% of bridges in the United States are at least 50 years old, and 7.5% of them are structurally deficient and need to be repaired/strengthened. Recently, new repair and strengthening techniques using Ultra-High-Performance concrete (UHPC) have shown a great potential with respect to performance, economy, and speed. UHPC is a new class of concrete that has mechanical and durability properties that are far superior to those of conventional concrete (CC). In addition, UHPC offers several advantages compared to the current repair and strengthening techniques such as: ease of construction, ductility, and reduced material quantity. Limited cases of strengthening concrete bridge elements using UHPC are available in the literature. Also, predicting the behavior of composite CC-UHPC sections in flexure and shear is challenging due to the significant differences in the performance of both materials in tension and compression. The objective of this research is to develop flexure and shear prediction models of strengthened composite CC-UHPC beams. The flexure prediction model is based on strain compatibility, while shear prediction model is based on effective strain. The interface shear resistance between the two materials is also predicted to design the shear connectors between the CC beam and UHPC encasement. A non-proprietary UHPC mix is used, and its mechanical properties are evaluated. Three non-prestressed concrete beams were tested in flexure: one CC reference beam, and two beams strengthened in flexure using UHPC and different reinforcement ratios. Another three non-prestressed concrete beams were tested in shear: one CC reference beam, and two beams strengthened in shear using UHPC with different thickness. Test results were used to validate the prediction models and showed that the strengthened beams achieved their predicted strength.
Advisor: George Morcous