Introduction and Objectives The focus of this study was to characterize the direct shear behavior of normal strength concrete (NSC), Cor-Tuf1 and Cor-Tuf2 ultra-high performance concretes (UHPC) under static and impact loading conditions. Objectives o Perform precision testing on NSC, Cor-Tuf1 and Cor-Tuf2 push-off specimens o Compare test data to Hawkins Direct Shear Model o Propose changes to the Hawkins Direct Shear Model if required Research Approach o Push-off specimen quasi-static testing recording relative slip with high-accuracy lasers o Push-off specimen impact testing with 300 to 5715 lb drop hammers o Post-test analysis o Propose changes to direct shear model Impact Tests Assessment of Direct Shear Behavior in Normal and Ultra-High Performance Concretes – Part 1 Static Tests Push-Off Specimen Design Specimen f` c (ksi) Reinforcement Ratio, ρ Number of Stirrups Stirrup Size NC-1A-0 4.5 0.0% 0 NA NCS-1-1 4.5 0.8% 4 #3 NCS-1-2 4.5 1.6% 8 #3 CT1-1A-0 29 0.0% 0 NA CT1S-1-1 29 0.8% 4 #3 CT1S-1-2 29 1.6% 8 #3 CT2-1A-0 29 0.0% 0 NA CT2S-1-1 29 0.8% 4 #3 CT2S-1-2 29 1.6% 8 #3 NSC Cor-Tuf2 Cor-Tuf1 Conclusions o Comparison of CT1 and CT2 specimens shows that the addition of fibers to UHPC greatly enhances its direct shear capacity in both peak shear stress and associated slips o The increase in residual capacity at the higher reinforcement ratio for CT1 suggests that a higher maximum ρf y can be utilized o The static and impact Modified Direct Shear model fairly accurately predict direct shear behavior of NSC and UHPC push-off specimens Specimen Preparation Specimen Matrix Approved for public release; distribution is unlimited SLIP (in) (ksi) 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 2.2 2.4 2.6 2.8 3 3.2 3.4 3.6 3.8 4 NCS-1-1-S-2 CT2S-1-1-S-2 CT1S-1-1-S-3 Static Test Results (ρ = 0.8%) SLIP(in) (ksi) -0.05 0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5 0.55 0.6 0.65 0.7 0.75 -0.3 0 0.3 0.6 0.9 1.2 1.5 1.8 2.1 2.4 2.7 3 3.3 3.6 3.9 4.2 4.5 4.8 NCS-1-1-D-1 CT2S-1-1-D-2 CT1S-1-1-D-2 Impact Test Results (ρ = 0.8%)