Predicting strength of non-prestressed concrete I-beams repaired/ strengthened in flexure and shear using Ultra-High-Performance Concrete (UHPC)

The applications of Ultra-High-Performance Concrete (UHPC) have been growing significantly in the past two decades because of its superior mechanical and durability properties compared to those of conventional concrete (CC). Using UHPC as a repair and/or strengthening material for beams can offer several advantages, such as: ease of construction, protection against severe environment, high ductility, reduced encasement dimensions, and economy compared to existing repair materials. Limited repair cases were reported in the literature and a few experimental investigations were conducted on rectangular non-prestressed concrete beams repaired with UHPC in flexure and shear. In this paper, these cases and investigations are reviewed and new prediction models for the flexural and shear strength of composite CC-UHPC beams are developed. The paper also presents the testing of three non-prestressed I-beams in flexure: one control beam, and two beams strengthened with reinforced UHPC layer at the beam soffit. Three additional non-prestressed beams tested in shear are also presented: one control beam, and two beams strengthened with unreinforced UHPC layers at the two sides of the web. The construction procedure and structural behavior of the composite CC-UHPC beams up to failure are discussed. Test results showed that the strengthened I-beams achieved significantly higher strength in flexure and shear compared to those of the control beams. The average measured-to-predicted flexural and shear strength using the developed models were 1.08 and 1.32 respectively. In addition, no delamination or cracking was observed between the two materials up to failure indicating the adequacy of the interface shear resistance and design.