Performance of High-Strength Steel Reinforcement in Shear Friction Applications

US Transportation Collection2020PDFTech ReportBarbosa, AndreTrejo, DavidMatus, NicolasVaddey, Naga PavanOregon State University. School of Civil and Construction EngineeringOregon. Dept. of Transportation. Research SectionUnited States. Department of Transportation. Federal Highway AdministrationOregon. Dept. of Transportation. Research SectionUnited StatesBridge designConcrete structuresHigh strength steelLaboratory testsLoad factorReinforcement (Engineering)Reinforcing barsShear strengthSurface preparationFHWA-OR-RD-21-02SPR-805Final ReportThe use of high strength steel reinforcement has the potential to provide economic and constructability benefits when used in reinforced concrete structures. Current design provisions limit the nominal yield strength of reinforcing steel bars to 60 ksi (420 MPa) for many bridge design applications. This report presents results from a laboratory testing program designed to evaluate the performance of concrete interface shear reinforced with ASTM A706 Grade 60 (420 MPa), ASTM A706 Grade 80 (550 MPa), ASTM A615 Grade 100 (690 MPa), and ASTM A1035 Grade 120 (830 MPa) reinforcing steel bars. Results are reported on the influence of reinforcing steel bar size, reinforcing steel bar spacing, shear interface surface preparation, and nominal concrete strength on shear friction performance. This report provides a summary of previous research regarding shear friction theory, a description of the test specimen design, and an overview of the materials used. Results indicate that using high-strength steel reinforcing bars did not have a significant impact on the peak loads reached, however they did allow for the development of greater post-peak sustained loads due to dowel action in the post-peak stage of the test specimen responses. Significant variation was observed when analyzing the effect of surface preparation. Additionally, in some cases, an exposed aggregate surface preparation enhanced the aggregate interlock and allowed it to contribute to the post-peak shear capacity. Overall, the results presented indicate that an increase in allowable nominal yield strength to 80 ksi (550 MPa) maintains a conservative design per AASHTO and ACI 318-14 code provisions.109