Introduction and ObjectivesThe 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.

Objectiveso Perform precision testing on NSC, Cor-Tuf1 and Cor-Tuf2 push-off

specimenso Compare test data to Hawkins Direct Shear Modelo Propose changes to the Hawkins Direct Shear Model if required

Research Approacho Push-off specimen quasi-static testing recording relative slip with

high-accuracy laserso Push-off specimen impact testing with 300 to 5715 lb drop

hammerso Post-test analysiso 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, ρNumber of

StirrupsStirrup Size

NC-1A-0 4.5 0.0% 0 NANCS-1-1 4.5 0.8% 4 #3NCS-1-2 4.5 1.6% 8 #3CT1-1A-0 29 0.0% 0 NACT1S-1-1 29 0.8% 4 #3CT1S-1-2 29 1.6% 8 #3CT2-1A-0 29 0.0% 0 NACT2S-1-1 29 0.8% 4 #3CT2S-1-2 29 1.6% 8 #3

NSC Cor-Tuf2Cor-Tuf1

Conclusionso 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 slipso The increase in residual capacity at the higher reinforcement ratio for CT1 suggests that a higher maximum ρfy can be

utilizedo 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)

(k

si)

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 10

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-2CT2S-1-1-S-2CT1S-1-1-S-3

Static Test Results(ρ = 0.8%)

SLIP(in)

(ks

i)

-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-1CT2S-1-1-D-2CT1S-1-1-D-2

Impact Test Results (ρ = 0.8%)