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“Repair/Strengthening of Concrete Bridges using Ultra-High Performance Concrete (UHPC)”

Construction Engineering and Management PhD Defense by Anthony Kodsy

1:30 pm–2:30 pm
Peter Kiewit Institute Room: 207
Kelly Johnson, (402) 554-5935,
Under the supervision of Dr. George Morcous

Abstract: Concrete bridges are subjected to environmental effects that cause premature deterioration and require structural repair/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, Ultra-High-Performance concrete (UHPC) has shown a great potential as a repair material with respect to performance, economy, and speed of construction. UHPC is a new class of concrete that has mechanical and durability properties that are far superior to those of conventional concrete (CC). Using UHPC offers several advantages, such as reduced material quantity, ease of construction, ductility, and impermeability. However, predicting the behavior of composite CC-UHPC sections in flexure and shear is challenging due to the significant differences in their tension and compression behaviors. The objective of this research is to propose new techniques for using UHPC in the flexure and shear repair/strengthening of concrete bridge components and develop prediction models for the flexural and shear strength of composite CC-UHPC components. A non-proprietary UHPC mix developed specifically for structural applications is used and its mechanical properties are evaluated. The flexure strength prediction model of composite CC-UHPC is based on the principle of strain compatibility, while the shear strength prediction model is based on the principle of effective strain. The interface shear resistance between the two materials is also predicted to design the shear connectors between the CC component and UHPC encasement. Three non-prestressed concrete beams are fabricated and tested in flexure: one CC reference beam, and two beams strengthened using UHPC. Another three non-prestressed concrete beams are fabricated and tested in shear: one CC reference beam, and two beams strengthened using UHPC. These experiments indicate the constructability of the proposed techniques and test results confirm the reliability of the prediction models.

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