1. MECHANICAL AND STRUCTURAL BEHAVIOR of UHPFRC
Presented By: Kirllos Wahba B.Eng, M.A.Sc Candidate
Supervised By: Dr. H. Marzouk

2. Outline Objective Introduction Experimental Procedure and Analysis
UHPFRC
Experimental Procedure and Analysis
Mechanical Behavior
Fracture Energy
Tension Stiffening
Shear Friction
Structural Behavior
Flexure
Shear
Conclusion
Recommendations
Acknowledgments

3. Objective
The addition of steel fibers results in improved shear strength and ductility, owing to enhanced post-cracking tensile behavior and improved crack control characteristics. The objective of the current research is to investigate the adequacy of current design codes for UHPFRC.

4. Introduction
Definition: A Class Of Materials That Exhibits Superior Qualities To Those Of Conventional Concrete
Fibers
Use of mm long fibers
Raw
Ingredients
Precisely optimized blend of nano materials such as: silica fumes, quarts flour and silica sand
Chemical Admixture
Large dosage of high range water reducer
Introduction ♦ Fracture Energy ♦ Tension Stiffening ♦ Shear Friction ♦ Flexure Behavior ♦ Shear Behavior ♦ Conclusion

5. Introduction Addition of fibers within concrete dates back to 1980’s
Increased ductility and improved post-cracking behavior
UHPFRC is the current state of the art in concrete technology in
Bridge joint construction
Long span bridges
Structural elements where, reduced size and weight is needed
Introduction ♦ Fracture Energy ♦ Tension Stiffening ♦ Shear Friction ♦ Flexure Behavior ♦ Shear Behavior ♦ Conclusion

6. Direct Tensile Strength
Introduction
Commercially available UHPFRC in North America
Metallic Fibres
Organic Fibres
Density
2500kg/m3
2350kg/m3
Compressive Strength
Mpa
Mpa
Flexural strength
30-40 Mpa
15-40 Mpa
Direct Tensile Strength 8 5
Young’s Modulus
50 Gpa
35 Gpa
Poisson Ratio
0.2
Introduction ♦ Fracture Energy ♦ Tension Stiffening ♦ Shear Friction ♦ Flexure Behavior ♦ Shear Behavior ♦ Conclusion

7. Introduction 2% by volume of 12mm long steel fibers 0.2 mm in diameter
Introduction ♦ Fracture Energy ♦ Tension Stiffening ♦ Shear Friction ♦ Flexure Behavior ♦ Shear Behavior ♦ Conclusion

8. MECHANICAL BEHAVIOR FRACTURE ENERGY

9. Mechanical Behavior: Fracture Energy
Definition: The Energy Required to cause a unit area of a crack
Region I
Linear Elastic region representing the micro-cracking stage
Region II
Fiber bridging effect
Region
III
Softening stage corresponding to crack opening by the process of fibers pulling out
Introduction ♦ Fracture Energy ♦ Tension Stiffening ♦ Shear Friction ♦ Flexure Behavior ♦ Shear Behavior ♦ Conclusion

10. Fracture Energy: Test Specimen
Introduction ♦ Fracture Energy ♦ Tension Stiffening ♦ Shear Friction ♦ Flexure Behavior ♦ Shear Behavior ♦ Conclusion

11. Fracture Energy: Test Specimen
Introduction ♦ Fracture Energy ♦ Tension Stiffening ♦ Shear Friction ♦ Flexure Behavior ♦ Shear Behavior ♦ Conclusion

12. Fiber Optics Sensor
Fiber Bragg grating (FBG) sensors are one of many fiber optic sensor technologies that are currently being used in SHM systems.
Introduction ♦ Fracture Energy ♦ Tension Stiffening ♦ Shear Friction ♦ Flexure Behavior ♦ Shear Behavior ♦ Conclusion

13. Fracture Energy: Test Setup
Test Specimen
Data Acquisition System
FBG’s Data Acquisition System
Introduction ♦ Fracture Energy ♦ Tension Stiffening ♦ Shear Friction ♦ Flexure Behavior ♦ Shear Behavior ♦ Conclusion

14. Fracture Energy: Results and Analysis
Introduction ♦ Fracture Energy ♦ Tension Stiffening ♦ Shear Friction ♦ Flexure Behavior ♦ Shear Behavior ♦ Conclusion

15. Fracture Energy: Results and Analysis
Multiple micro cracking
Surface Cracks at 80-90% of ultimate load
Initial Condition
Initial Surface Crack
Failure Condition
Introduction ♦ Fracture Energy ♦ Tension Stiffening ♦ Shear Friction ♦ Flexure Behavior ♦ Shear Behavior ♦ Conclusion

16. Fracture Energy: Results and Analysis
According to the Japanese Concrete Institute Standard (2003),
GF= (0.75W0+W1)/Alig Eq.2
Specimen
Name
fc’
(MGa) Pu
(kN)
εpu
x 10-6 GF
(N/m)
ft’
(MPa)
FE1
163
100.25
3500
8.68
FE2
137
97.5
1700
8.44
Introduction ♦ Fracture Energy ♦ Tension Stiffening ♦ Shear Friction ♦ Flexure Behavior ♦ Shear Behavior ♦ Conclusion

17. Fracture Energy: Characteristic length
Material property representing the size of the fracture zone
Used in theoretical guidelines for shear strength of RC
lch=Ec GF/ ft2 (mm) Eq. [3]
lch = 600(fc’)-0.3 (mm) Eq. [4]
lch = -3.84fc’+580 (mm) Eq. [5]
fc’
(MPa)
lch, Eq. [3]
(mm)
lch, Eq. [4]
lch, Eq. [5] 40
500
198.39
426.4 55
742
180.31
368.8 74
478
164.96
295.84
137
769
137.13
53.92
163
693
130.16
-45.92
Introduction ♦ Fracture Energy ♦ Tension Stiffening ♦ Shear Friction ♦ Flexure Behavior ♦ Shear Behavior ♦ Conclusion

18. MECHANICAL BEHAVIOR TENSION STIFFENING

19. Mechanical Behavior: Tension Stiffening
Definition: Stresses carried by concrete after cracking to improve a RC member’s response
Introduction ♦ Fracture Energy ♦ Tension Stiffening ♦ Shear Friction ♦ Flexure Behavior ♦ Shear Behavior ♦ Conclusion

20. Tension Stiffening: Test Specimen
Specimen Name
Cross Sectional Area
(bxb mm2)
Length, L
(mm)
Reinforcement
Ratio (%)
TS1
180x180
2000
1.5
TS2
160x160 2
Introduction ♦ Fracture Energy ♦ Tension Stiffening ♦ Shear Friction ♦ Flexure Behavior ♦ Shear Behavior ♦ Conclusion

21. Tension Stiffening: Test Setup
Load Application
Fixed Connection
Introduction ♦ Fracture Energy ♦ Tension Stiffening ♦ Shear Friction ♦ Flexure Behavior ♦ Shear Behavior ♦ Conclusion

22. Tension Stiffening: Results and Analysis
Initial Crack of TS1 & TS2 at 140 & 100 kN, respectively
Introduction ♦ Fracture Energy ♦ Tension Stiffening ♦ Shear Friction ♦ Flexure Behavior ♦ Shear Behavior ♦ Conclusion

23. Tension Stiffening: Results and Analysis
Average tensile stress at initial crack 3.4 MPa
Introduction ♦ Fracture Energy ♦ Tension Stiffening ♦ Shear Friction ♦ Flexure Behavior ♦ Shear Behavior ♦ Conclusion

24. Tension Stiffening: Results and Analysis
High post-cracking stiffness
Fiber Bridging action
Introduction ♦ Fracture Energy ♦ Tension Stiffening ♦ Shear Friction ♦ Flexure Behavior ♦ Shear Behavior ♦ Conclusion

25. Tension Stiffening: Results and Analysis
Specimen
Name
Reinforcement
Ratio (%)
f’c
(MPa)
Number of Cracks
Elongation
(mm)
Average Crack
Width (mm)
TS1
1.5
159.8 17
2.22
0.13
TS2 2
157.5 19
3.22
0.17
Introduction ♦ Fracture Energy ♦ Tension Stiffening ♦ Shear Friction ♦ Flexure Behavior ♦ Shear Behavior ♦ Conclusion

26. MECHANICAL BEHAVIOR SHEAR FRICTION

27. Mechanical Behavior: Shear Friction
Definition: The transformation of shear stresses across an interface between two members that are free to move relative to each other
Load
Horizontal
Shear
Deck
Girder
Introduction ♦ Fracture Energy ♦ Tension Stiffening ♦ Shear Friction ♦ Flexure Behavior ♦ Shear Behavior ♦ Conclusion

28. Shear Friction: Test Specimen
Name
Shear Area
(mm2)
Reinforcement
Ratio (%)
SF1
305x101.5
SF2
0.5
SF3 1
Introduction ♦ Fracture Energy ♦ Tension Stiffening ♦ Shear Friction ♦ Flexure Behavior ♦ Shear Behavior ♦ Conclusion

29. Shear Friction: Test Setup
Load Cell
Test Specimen
LPDT
Roller Support
MTS Machine
Introduction ♦ Fracture Energy ♦ Tension Stiffening ♦ Shear Friction ♦ Flexure Behavior ♦ Shear Behavior ♦ Conclusion

30. Shear Friction: Test Results
Specimen
Name
Shear Area
(mm2)
Reinforcement
Ratio (%)
Cracking load
Vcr (kN)
Ultimate load
Vu (kN)
Maximum Displacement
Δmax (mm)
SF1
305x101.5
400
445
2.3
SF2
0.5
N/A
524
3.6
SF3 1
530
1.5
Introduction ♦ Fracture Energy ♦ Tension Stiffening ♦ Shear Friction ♦ Flexure Behavior ♦ Shear Behavior ♦ Conclusion

31. Shear Friction: Test Results
SF1
Vu = 445 kN
Δmax =2.3
Vu = 524 kN
Δmax = 3.6
Vu = 530kN
Δmax = 1.5
Shear Friction: Test Results
Introduction ♦ Fracture Energy ♦ Tension Stiffening ♦ Shear Friction ♦ Flexure Behavior ♦ Shear Behavior ♦ Conclusion

32. Shear Friction: Test Results
Introduction ♦ Fracture Energy ♦ Tension Stiffening ♦ Shear Friction ♦ Flexure Behavior ♦ Shear Behavior ♦ Conclusion

33. Shear Friction: Design Guide Lines
Shear Stress
vu = c + μρvfy (MPa) CSA A23.3
vu = μρvfy(MPa) ACI-318
vu = 0.05 f’c ρvfy ≤ 0.2 f’c Khan and Mitchell (2002)
Introduction ♦ Fracture Energy ♦ Tension Stiffening ♦ Shear Friction ♦ Flexure Behavior ♦ Shear Behavior ♦ Conclusion

34. Shear Friction: Analysis of Results
Introduction ♦ Fracture Energy ♦ Tension Stiffening ♦ Shear Friction ♦ Flexure Behavior ♦ Shear Behavior ♦ Conclusion

35. Analysis of Results: Fiber Effect
Af = ½ VfDb
Aeff =αη2 Af
For Fibers having L=30 mm & d= 0.55mm
Orientation Factor; α = 3/8 (Aoude et al. 2012)
Length Factor; η1 = 1/2 (Aoude et al. 2012)
Introduction ♦ Fracture Energy ♦ Tension Stiffening ♦ Shear Friction ♦ Flexure Behavior ♦ Shear Behavior ♦ Conclusion

36. Shear Friction: Analysis of Results
vu = 0.05 f’c ρvfy ≤ 0.2 f’c Khan and Mitchell (2002)
vu = 0.05 f’c [ρvfy + αη2ρfffy] ≤ 0.2 f’c Eq. 4-6
Introduction ♦ Fracture Energy ♦ Tension Stiffening ♦ Shear Friction ♦ Flexure Behavior ♦ Shear Behavior ♦ Conclusion

37. STRUCTURAL BEHAVIOR

38. Structural Behavior: Specimen Specifications
Beam
Name
Span, L
(mm)
Cross Section
(mm2)
Shear Span
a/d
Steel Ratio ρw (%)
SB1
1830
178x305
2.3
SB2
1.25
SB3
3660
4.6
SB4
2.5
SB5
Beam
Name
Span, L
(mm)
Cross Section
(mm2)
Shear Span
a/d
Steel Ratio ρw (%)
Introduction ♦ Fracture Energy ♦ Tension Stiffening ♦ Shear Friction ♦ Flexure Behavior ♦ Shear Behavior ♦ Conclusion

39. Structural Behavior: Test Setup
Hydraulic Pump
Load Cell
Steel Spacers
Loading Beam
Test Specimen
Introduction ♦ Fracture Energy ♦ Tension Stiffening ♦ Shear Friction ♦ Flexure Behavior ♦ Shear Behavior ♦ Conclusion

40. Structural Behavior: Results and Analysis
Introduction ♦ Fracture Energy ♦ Tension Stiffening ♦ Shear Friction ♦ Flexure Behavior ♦ Shear Behavior ♦ Conclusion

41. Result and Analysis: Effect of Reinforcement Ratio
SB1 ρw=0
Maximum Load 90 kN
SB2 ρw=1.25 Maximum
Load 235 kN
SB4 ρw=2.5
Maximum Load 330 kN
Introduction ♦ Fracture Energy ♦ Tension Stiffening ♦ Shear Friction ♦ Flexure Behavior ♦ Shear Behavior ♦ Conclusion

42. Flexural Behavior: Material Property
Introduction ♦ Fracture Energy ♦ Tension Stiffening ♦ Shear Friction ♦ Flexure Behavior ♦ Shear Behavior ♦ Conclusion

43. Flexural Behavior: Fiber Effect
Af = ½ VfDb
Aeff = αη2 Af
For Fibers having L=30 mm & d= 0.55mm
Orientation Factor; α = 3/8 (Aoude et al. 2012)
Length Factor; η1 = 1/2 (Aoude et al. 2012)

44. Flexural Behavior: Fiber Effect
Mr = Msteel + Mfiber
Introduction ♦ Fracture Energy ♦ Tension Stiffening ♦ Shear Friction ♦ Flexure Behavior ♦ Shear Behavior ♦ Conclusion

45. Structural Properties: Shear Strength
Compressive Strength
Flexural Reinforcement
a/d Ratio
Introduction ♦ Fracture Energy ♦ Tension Stiffening ♦ Shear Friction ♦ Flexure Behavior ♦ Shear Behavior ♦ Conclusion

46. Structural Properties: Shear Strength
Material Property
vu = λβ√fc’ (MPa) CSA A23.3
vu = 1/6 √fc’ (MPa) ACI-318
vu = k ft’(d/a)0.5 (Mpa) Sharma (1986)
Fiber
Effect
vu = e (0.24 fspfc + 80ρ a/d) + vb Narayanan (1987)
vu = (0.7√fc’ + 7F)+17.2ρ a/d Ashour et al. (1992)
vu = 3.7e (fspfc)2/3 (ρ d/a)1/ vb Kwak(2002)
Introduction ♦ Fracture Energy ♦ Tension Stiffening ♦ Shear Friction ♦ Flexure Behavior ♦ Shear Behavior ♦ Conclusion

47. Structural Properties: Shear Strength
Beam
f’c
(MPa) Vc
Ashour (kN)
Kwak et al. (kN)
Narayanan et al. (kN)
Experimental (kN)
SB1
168.15
168.25
7.7533
286.11
90.5
SB2
145.14
160.90
381.99
297.65
235.5
SB3
160.38
84.07
100.38
112.42
113.5
SB4
167.08
174.99
526.94
378.67
330.5
SB5
172.08
88.62
131.09
127.27
169
Introduction ♦ Fracture Energy ♦ Tension Stiffening ♦ Shear Friction ♦ Flexure Behavior ♦ Shear Behavior ♦ Conclusion

48. Structural Properties: Shear Strength
Beam
f’c
(Mpa) Vc
CSA (kN)
ACI (kN)
Japan (kN)
Experimental (kN)
SB1
168.15
105.25
92.33
297.18
90.5
SB2
145.14
97.79
85.78
303.71
235.5
SB3
160.38
102.79
90.17
303.93
113.5
SB4
167.08
104.92
92.03
305.92
330.5
SB5
172.08
106.48
93.40
306.01
169
Introduction ♦ Fracture Energy ♦ Tension Stiffening ♦ Shear Friction ♦ Flexure Behavior ♦ Shear Behavior ♦ Conclusion

49. Conclusion
The introduction of fiber reinforcement proves to increase, significantly, the ductility of the concrete
R/C, R/ECC and R/UHPFRC showed significant differences in their tension stiffening behavior
The combination of ordinary reinforcement and fiber reinforcement proved to significantly improve the tension stiffening response of reinforced concrete
In order to utilize the superior qualities of UHPFRC; high grade steel should be used
Introduction ♦ Fracture Energy ♦ Tension Stiffening ♦ Shear Friction ♦ Flexure Behavior ♦ Shear Behavior ♦ Conclusion

50. Conclusion Both CSA A23.3 and ACI 318 proved to be rather conservative
The proposed Eq. [7] & [8] predict, with high accuracy, the flexural capacity of UHPFRC beams
The Japanese society for civil engineers recommendation for design of UHPFRC proved to be the most accurate for the shear capacity of the tested members
When dealing with UHPFRC; the tensile strength and fiber reinforcement ratio are of a greater importance than the compressive strength
Introduction ♦ Fracture Energy ♦ Tension Stiffening ♦ Shear Friction ♦ Flexure Behavior ♦ Shear Behavior ♦ Conclusion

51. National Science and Engineering Research Council of Canada
Acknowledgment
National Science and Engineering Research Council of Canada
Lafarge North America
Ryerson University

52. Thank You For Listening
Questions
Thank You For Listening