1. An Introduction to FRP-Strengthening of Concrete Structures
ISIS Educational Module 4:
An Introduction to FRP-Strengthening of Concrete Structures
Updated October 2010 for ISIS Canada
ISIS EC Module 4

2. Module Objectives
The use of FRPs in civil infrastructure is steadily increasing in Canada and around the world. This module is directed mainly to students to:
Provide a background and general awareness of FRP materials, their properties , their behaviour and their potential uses
Introduce the philosophies and procedures for strengthening structures with FRPs
Familiarize the students with designing using the Canadian Highway Bridge Design Code (CHBDC)
ISIS EC Module 4

3. Evaluation of Existing Structures Flexural Strengthening
Overview
Introduction
FRP Materials
Evaluation of Existing Structures
Flexural Strengthening
Shear Strengthening
Column Strengthening
Installation of FRP strengthening systems
Quality control and quality assurance
Additional applications
Field applications
ISIS EC Module 4

4. Global Infrastructure Crisis
1 - Introduction
The world’s population depends on an extensive infrastructure system
Roads, sewers, highways, buildings
The system has suffered in past years
Neglect, deterioration, lack of funding
Global Infrastructure Crisis
ISIS EC Module 4

5. Why is strengthening needed?
1 - Introduction
Why is strengthening needed?
Many structures, including bridges and parking garages, have become structurally deficient due to deterioration.
In Canada, more than 40% of the bridges currently in use were built more than 40 years ago.
Many structures are also becoming functionally obsolete due to increased loading.
ISIS EC Module 4

6. Why repair with the same materials? Why repeat the cycle?
2 - FRP Materials
Why repair with the same materials?
Why repeat the cycle?
Light weight
High Strength
FRP Materials
Easy to install
5x steel
Corrosion resistant
Highly versatile
Durable structures
Suits many projects
ISIS EC Module 4

7. FRP is a composite consisting of fibres and matrix. Fibres:
2 - FRP Materials
FRP is a composite consisting of fibres and matrix.
Fibres:
Provide strength and
stiffness
Their quality, orientation
and shape affect the
final product
Matrix (resin):
Coats the fibres
Protects the fibres from abrasion
Transfers stresses between the fibres
Strain [%]
2-8
50-90
Stress [MPa]
Fibres
FRP
Matrix
ISIS EC Module 4

8. FRP material properties are a function of:
2 - FRP Materials
FRP material properties are a function of:
Fibre quality, orientation and shape
Fibre volumetric ratio
Adhesion to the matrix
Manufacturing process (additives and fillers)
ISIS EC Module 4

9. Wide range of FRP products are available: Plates (Rigid strips)
2 - FRP Materials
Wide range of FRP products are available:
Plates (Rigid strips)
Sheets (Flexible fabric)
Rods
The fibres could be:
Carbon
Glass
Aramid
FRP sheet
ISIS EC Module 4

10. FRP advantages: Disadvantage: 2 - FRP Materials Does not corrode
High strength to weight ratio
Reduced installation time and cost
Non-conductive and non-metallic
Low maintenance requirements
Disadvantage:
High temperature is a serious concern
ISIS EC Module 4

11. FRP properties versus steel: Linear elastic behaviour to failure
3 - FRP Materials
FRP properties versus steel:
Linear elastic behaviour
to failure
No yielding
Higher ultimate
strength
Lower strain at
failure
Strain [%] 1 2 3
500
1000
1500
2000
2500
Stress [MPa]
CFRP
GFRP
Steel
ISIS EC Module 4

12. 2 - FRP Materials ISIS EC Module 4 FRP System Fiber Type Weight [g/m2]
Thickness
[mm]
Tensile
Strength [MPa]
Tensile Elastic Modulus [GPa]
Strain at Failure [%]
Fyfe Co. LLC [
Tyfo SEH51A
Glass
915
1.3
460
20.9
1.8
Tyfo SEH25A
505
0.5
417
Tyfo SCH41
Carbon
644
1.0
834 82
0.9
Hughes Brothers Inc. [
Aslan 200 --
124
Aslan 500 #2
2.0
2068
1.7
Aslan 500 #3
4.5
1965
1.5
Aslan 400 CFRP Laminates
1.4
2400
131
1.9
Sika Canada Inc. [
SikaWrap 430G
430
504
24.6
SikaWrap 100G
558
24.4
2.2
SikaWrap 230C
230
0.4
715
61.0
1.1
SikaWrap 103C
610
717
65.1
CarboDur S
2800
165
CarboDur M
210
1.2
CarboDur H
1300
300
BASF Building Systems Inc. [
MBrace S&P Laminate
2700
159
MBrace EG 900
900
0.37
1517
72.4
2.1
MBrace CF 130
0.17
3800
227
MBrace CF 160
600
0.33
MBrace CF 530
3500
373
0.94
MBrace AK 60
Aramid
0.28
2000
120
1.6
ISIS EC Module 4

13. Installation: 1) Wet lay-up system: 2 - FRP Materials
- The system is installed on the surface of the concrete element while the resin matrix is still “wet”, and the polymerization occurs on site
- Saturate sheets with epoxy adhesive, then place on the concrete surface and press with a roller
- Used with flexible sheets
- Multiple layers can be used
Epoxy
Roller
ISIS EC Module 4

14. 2) Pre-cured system: 2 - FRP Materials
- Used with FRP plates or laminates
- Used for surface bonded plates or near surface mounted reinforcements
- Not as flexible for variable structural shapes
- The pre-cured laminates should be placed on or into the wet adhesive
- Place on the concrete surface
- Multiple layers can not be used
ISIS EC Module 4

15. 3- Near Surface Mounted (NSM)
2 - FRP Materials
3- Near Surface Mounted (NSM)
It is a newer class of FRP strengthening technique.
Un-strengthened concrete T-beam
Longitudinal grooves cut into soffit
FRP strips placed in grooves
Grooves filled with epoxy grout
Research indicates that NSM reinforcement is effective and efficient for strengthening.
ISIS EC Module 4

16. FRP-Strengthening Applications :
2 - FRP Materials
FRP-Strengthening Applications :
Type
Application
Fibre Dir.
Schematic
Flexural
face of the beam
Tension and/or side
axis of the beam
Along long.
Section
Shear
Side face of the beam
(U or closed wrap)
Perpendicular
to long. axis
of the beam
Section
Confinement
Around the column
Circumferential
Section
ISIS EC Module 4

17. 3 - Evaluation of Existing Structures
Repair process includes:
Evaluation of the existing structure
 Understanding the cause and the effect of the deterioration
Determining if repair is required and its extent (quantify)
Analysis and design
Introducing a repair strategy
ISIS EC Module 4

18. 3 - Evaluation of Existing Structures
Fixing the effect without understanding the cause is likely to result in premature failure of repair. Proper repair requires an understanding of the cause to eliminate the effect.
Evaluation is important to:
Determine concrete condition
Identify the cause of the deficiency
Establish the current load capacity
Evaluate the feasibility of FRP strengthening
ISIS EC Module 4

19. 3 - Evaluation of Existing Structures
Evaluation should include:
All past modifications
Actual size of elements
Actual material properties
Location, size and cause of cracks and spalling
Location and extent of corrosion
Quantity and location of rebar
ISIS EC Module 4

20. 3 - Evaluation of Existing Structures
Problems in a structure could be due to:
Defects:
In design or material or during construction
Damage:
Due to overloading, earthquake or fire
Deterioration:
Due to corrosion or sulphate attack
ISIS EC Module 4

21. 3 - Evaluation of Existing Structures
Examples of some deficiencies:
1. Environmental effects
Wet-Dry
Chloride Ingress
Freeze-Thaw
ISIS EC Module 4

22. 2. Corrosion 3 - Evaluation of Existing Structures
A primary factor leading to extensive degradation…..
2. Corrosion
End result
Concrete
Reinforcing Steel
Moisture, oxygen and chlorides penetrate
Corrosion products form
Volume expansion occurs
Through concrete
More cracking
Through cracks
Corrosion propagation
ISIS EC Module 4

23. 3 - Evaluation of Existing Structures
Deficiencies could be due to:
Updated design loads
Updated design code procedures
Increase in traffic loads
Now
Then
ISIS EC Module 4

24. 3 - Evaluation of Existing Structures
Deficiencies could be due to:
Fire damage
Earthquakes
ISIS EC Module 4

25. 4 - Flexural Strengthening
Material resistance factors (CHBDC):
- Concrete c = 0.75
- Steel reinforcement:
- Reinforcing bars s = 0.90
- Prestressing strands p = 0.95
- Base FRP for pultruded FRP:
- AFRP FRP = (for externally bonded applications)
- AFRP FRP = (for NSMR)
- CFRP FRP = (for externally bonded applications and NSMR)
- GFRP FRP = (for externally bonded applications and NSMR)
- Non-pultruded FRP made by wet lay-up: 0.75 times base FRP
ISIS EC Module 4

26. 4 - Flexural Strengthening
Failure Modes
The analysis of the flexural strength of FRP strengthened elements is based on the following assumptions:
1) The internal stresses are in equilibrium with the applied loads.
2) Plane sections remain plane.
3) Strain compatibility exists between adjacent materials.
(ie. Perfect bond between: concrete and steel, concrete and FRP)
4) The maximum tensile strain of the FRP (eFRPt ) is
5) The maximum compressive strain in the concrete (ecu ) is
6) The contributions of FRPs in compression and of the concrete in tension are neglected.
ISIS EC Module 4

27. 4 - Flexural Strengthening
Failure Modes
The potential modes of failure are:
1) Concrete crushing before steel yielding or rupture of the FRP.
2) Steel yielding followed by concrete crushing before rupture of the FRP.
3) Steel yielding followed by rupture of the FRP.
4) Peeling, debonding, delamination or anchorage failure of the FRP (considered premature tension failures to avoid).
ISIS EC Module 4

28. 4 - Flexural Strengthening
Rectangular section without compression steel: b d
Cross Section As
Strain Distribution
eFRP ec h
bFRP es c
Stress Distribution fs
ffrp
Equiv. Stress Distribution
a = b1c
a1Φcf’c Ts
Tfrp Cc
Ts = fsAsfs
TFRP = fFRPAFRPEFRPeFRP
Cc = fca1f’cb1bc
ISIS EC Module 4

29. 4 - Flexural Strengthening
The equilibrium equations are:
1) Force equilibrium in the section:
Compression forces =Tension forces
2) Moment equilibrium in the section:
External applied moment= Internal moment
Cc = Ts + TFRP a a
Mapplied = Ts
d -
+ TFRP
h - 2 2
ISIS EC Module 4

30. 4 - Flexural Strengthening
Rectangular section with compression steel : b
ecu
a1Φcf’c d’
e’s Cs
f’s c
a = b1c
A’s Cc d h As es fs Ts
eFRP
ffrp
Tfrp
bFRP
Cross Section
Strain Distribution
Stress Distribution
Equiv. Stress Distribution
Add a compressive stress resultant
Cs = fsf’sA’s a a a
Mr = Ts d-
+TFRP h-
- d′
+Cs 2 2 2
ISIS EC Module 4

31. 4 - Flexural Strengthening
Iterative design procedure:
Assume initial strains
Select FRP material and AFRP
Assume a failure mode
If concrete crushing before steel yields, then:
ecu = and esteel < eyield
If concrete crushing after steel yields, then:
ecu = and esteel > eyield
If FRP ruptures after steel yields, then:
efrp = efrpt and esteel > eyield b ec c d h As es
efrp
bfrp
ISIS EC Module 4

32. 4 - Flexural Strengthening
Determine the compressive stress block factors (a1, b1) b
a1Φcf’c
a = b1c d Cc h As Ts
TFRP
bfrp
b1 = 0.97 – f’c > 0.67
a1 = 0.85 – f’c > 0.67
ISIS EC Module 4

33. 4 - Flexural Strengthening
Calculate c (neutral axis position)
Using equilibrium equation the following equations can be derived and used:
- Concrete crushing before steel yields (es and e’s < ey )
-Steel yielding followed by concrete crushing (es and e’s > ey )
- Steel yielding followed by FRP rupture (es and e’s > ey )
a1fc f’cb1bc2 +
fsEs ecu (As’+As)+ fFRPEFRP (ecu+efi)AFRP
c -
fsEs ecu (As'd'+Asd)+ fFRPEFRP ecuAFRP h = 0
a1fc f’cb1bc2 +
fsfy(As’-As)+ fFRPEFRP (ecu+efi)AFRP c-
fFRPEFRP ecuAFRP h = 0
fsfy(As-As’)+ fFRPEFRP eFRPtAFRP
c =
a1fc f’cb1b
ISIS EC Module 4

34. 4 - Flexural Strengthening
Check failure mode assumption with the material strains
If failure is initiated by:
Concrete crushing: FRP rupture:
- If the assumption is proven to be false, go back to step 3 and make another assumption
- If the assumption is correct, proceed to the next step
ecu=
es= ecu
eFRP = eFRPu ≤ eFRPt
(efi+eFRPu) ≤ es'= (efi+eFRPt)
(efi+eFRPu) ≤ es= (efi+eFRPt)
(efi+eFRPu) ≤ ec= (efi+eFRPt)
d - c
c-d'
c-d'
h-c
h-c c
d-c
d-c
h - c
eFRP= ecu
- efi
h-c
h-c c c c
c - d'
es'= ecu
h-c
h-c c
ISIS EC Module 4

35. 4 - Flexural Strengthening
Compute internal forces
Calculate the section moment resistance (Mr)
Compare Mr to the applied moment (Mapplied)
If Mr < Mapplied, go to step 2 and change AFRP
If Mr > Mapplied, then the design is safe
Cs = fsfsA's
Ts = fsAsfs
Tfrp = ffrpAFRPEFRPeFRP a a a
- d′
Mr = Ts d-
+TFRP h-
+Cs 2 2 2
ISIS EC Module 4

36. 4 - Flexural Strengthening
Optimized determination of AFRP
Assuming:
All the steel has yielded and combining the equilibrium equations:
Determine c using the following equation
Determine strain in FRP
a1fc f’cbwb12c2
-a 1 fc f’cbwhb1c-
Cs(h-d′)+Ts(ds-h) - Mf = 0 2
h - c
eFRP = ecu
- efi ≤ ≤ eFRPu c
ISIS EC Module 4

37. 4 - Flexural Strengthening
Determine successively:
Optimize value of AFRP
Use this AFRP as an input for the iterative design method
Cc = fca1f’cb1bc
TFRP = Cc + Cs - Ts
TFRP
AFRP =
fFRPEFRP eFRP
ISIS EC Module 4

38. 4 - Flexural Strengthening
T-section:
If the neutral axis lies in the web (c < hf), then treat it as a rectangular section with a compression zone width = be.
If the neutral axis lies outside the web
(c > hf), then treat it as a T-section.
Geometric parameters
ISIS EC Module 4

39. 4 - Flexural Strengthening= +
Geometric parameters
Factored moment subdivision
The section is treated as the summation of: flange (Mrf) and web (Mrw).
- Flange (Mrf)
a1fc f’c(be-bw)hf hf
Asf =
Mrf = fs fy Asf
d -
fsfy 2
- Web (Mrw) a a
Asw = As –Asf
Mrw = fs fy Asw
d -
+TFRP
h - 2 2
ISIS EC Module 4

40. 4 - Flexural Strengthening
Design procedure:
Select FRP material and AFRP
Determine behaviour of the section ( Rect. or T) If
Then, it is rectangular behaviour
Else, it is a T-section
Determine Asf and Mrf
Determine AFRP to obtain required Mrw
fsfyAs+fFRP EFRP eFRP A FRP
hf ≥
a1fc f’c b1be
ISIS EC Module 4

41. 4 - Flexural Strengthening
Example:
Calculate the moment resistance (Mr) for an FRP-strengthened rectangular concrete section
Section information:
b = 125 mm
h = 360 mm
2-15M bars
d = 320 mm
CFRP
f’c = 40 MPa
efrpu = 1.26 %
AFRP = 110 mm2
fy = 400 MPa
Es = 200 GPa
EFRP = 210 GPa
ISIS EC Module 4

42. 4 - Flexural Strengthening
Solution:
Step 1: Assume failure mode
Assume failure of beam due to crushing of concrete in compression after yielding of internal steel reinforcement
Thus, ecu= and esteel > eyield
ISIS EC Module 4

43. 4 - Flexural Strengthening
Step 2: Calculate concrete stress block factors
a1 = 0.85 – f’c > 0.67 a
a1 = 0.85 – (40) = 0.79
b1 = 0.97 – f’c > 0.67 a
b1 = 0.97 – (40) = 0.87
ISIS EC Module 4

44. 4 - Flexural Strengthening
Step 3: Find depth of neutral axis, c
Steel yielding followed by concrete crushing
a1fc f’cb1bc2 +
fsfy(As’-As) + fFRPEFRP (ecu+efi)AFRP
c - fFRPEFRP ecuAFRP h = 0
0.79(0.75)40(0.87)
125(c2) +
0.9(400) (0-400)+ 0.80(210000)( )110
c -
0.80(210000)
(0.0035)(110)360
= 0
(c2)-79320(c) = 0
c = mm or c = mm (rejected)
ISIS EC Module 4

45. 4 - Flexural Strengthening
Step 4: Check mode of failure
Steel yielding followed by concrete crushing
ecu=
es= ecu
ds-c =
= > 0.002(ey) c
111.7
h-c
eFRP= ecu =
= > 0.006
not O.K. c
111.7
Trial 2, assume the steel yields and the strain in the FRP is 0.006
ISIS EC Module 4

46. 4 - Flexural Strengthening
Step 5: Trial 2
Compression in concrete = Tension in ( Steel + FRP)
a1fc f’cbb1c =
fsfy As + fFRPEFRP eFRPAFRP
0.79(0.75)40(0.87)125(c) =
0.9(400) (210000)0.006(110)
c = 98.9 mm
ISIS EC Module 4

47. 4 - Flexural Strengthening
Step 6: Check mode of failure
eFRP = 0.006
es= eFRP
ds-c
= > 0.002(ey)
= 0.006
h-c c
98.9
ecu= eFRP
= 0.006
= <
O.K.
h-c
The assumed mode of failure is correct
ISIS EC Module 4

48. 4 - Flexural Strengthening
Step 7: Moment Resistance
b1c
b1c
Mr = Ts
ds-
+TFRP h- 2 2
b1c
b1c =
fsfy As fFRPEFRP eFRPAFRP
ds- h- 2 2
0.87 (98.9) =
0.9(400)400
+0.80(210000)0.006(110)
320- 2
0.87 (98.9)
360- 2
Mr = 75  106 N.mm = 75 kN.m
ISIS EC Module 4

49. 4 - Flexural Strengthening
Example:
The T-beam requires strengthening to upgrade its moment capacity to 600 kN-m. Calculate the required area of FRP (Afrp).
Section information:
f’c = 30 MPa
efrpu = 1.26 %
As = 8 x 300 mm2
fy = 400 MPa
Es = 200 GPa
Efrp = 155 GPa
ISIS EC Module 4

50. 4 - Flexural Strengthening
Step 1: Calculate concrete stress block factors
a1 = 0.85 – f’c > 0.67 a
a1 = 0.85 – (30) = 0.805
b1 = 0.97 – f’c > 0.67 a
b1 = 0.97 – (30) = 0.895
ISIS EC Module 4

51. 4 - Flexural Strengthening
Step 2: Evaluating the moment capacity of the existing section
 Assume neutral axis is inside the flange (c < hf)
Compression in concrete = Tension in steel
a1fc f’cbb1c =
fsfy As
0.805(0.75)30(0.895)650(c) =
0.9(400)(300× 8)
c = 82mm > hf
The assumption (c < hf) is wrong.
ISIS EC Module 4

52. 4 - Flexural Strengthening
Step 2: Evaluating the moment capacity of the existing section
 Assume neutral axis is outside the flange (c > hf)
a1fc f’c(be-bw)hf
Asf =
fsfy
0.805(0.75)30( )70
=1409 mm2
Asf =
0.9(400)
Asw = As –Asf = = 991 mm2 70
Mrf = 0.9 (400)1409 (510 -
) = ×106 N.mm
= kN.m 2
ISIS EC Module 4

53. 4 - Flexural Strengthening
Step 2: Evaluating the moment capacity of the existing section
Compression in concrete = Tension in steel (Asw)
a1fc f’cbb1c =
fsfy Asw
0.805(0.75)30(0.895)250(c) =
0.9(400)(991)
c = 88.03mm > hf
0.895 (88.03)
Mrw= 0.9 (400)991(510 -
) = ×106 N.mm
= kN.m 2
Mr= =408.8 kN.m
Moment resistance of the section
ISIS EC Module 4

54. 4 - Flexural Strengthening
Step 3: Optimized determination of AFRP
1) Determine c using the following equation:
a1fc f’cbwb12c2
- a1fc f’cbwhb1c -
Cs(h-d′)+fsfy Asw(ds-h)-(Mf -Mrf ) = 0 2
0.805(0.75)30(250)(0.895)2c2
(0.75)30(250)600(0.895)c 2
- 0.9(400)991( ) + ( )x106 = 0
c c = 0
c= (rejected) or 187mm (accepted)
ISIS EC Module 4

55. 4 - Flexural Strengthening
Step 3: Optimized determination of AFRP
2) Strain in FRP
h-c
eFRP = ecu =
= > 0.006 c
187
eFRP = 0.006
TFRP = a1fc f’cbwb1c - fsfy Asw
=0.805(0.75)30(250)0.895(187) - 400(0.9)991= N
TFRP
AFRP = =
= mm2
fFRPEFRP eFRP
0.75x0.8×155×103×0.006
Select: 2 layers b = 250mm and tFRP = 1.5mm, AFRP = 750mm2
ISIS EC Module 4

56. 4 - Flexural Strengthening
Step 4: Check the design
Assume tension failure of the FRP and yielding of steel
1) Neutral axis location
TFRP + fsfy Asw
0.75(0.8)(155000)0.006(750)+ 0.9(400)991
c = =
a1fc f’cbb1
0.805(250)0.75(30)0.895
= mm >hf …………O.K
2) Check strains c
191.3
ec= eFRP
= 0.006
= <
h-c
ds-c
es= eFRP
= 0.006
= > ey
………….O.K
h-c
ISIS EC Module 4

57. 4 - Flexural Strengthening
Step 4: Check the design
3) Moment resistance of the section
b1 c
b1 c
Mrw = Ts
ds -
+TFRP
h - = 2 2
0.895(191.3)
Mrw =
0.9(400)991
510 -
× 10-6+ 2
0.895(191.3)
0.75(155000)0.006(600)
600 -
× 10-6 2
= kN.m 70
Mrf = 0.9(400)1409(510 -
) = ×106 N.mm = kN.m 2
Mrt = Mrw + Mrf = = kN.m
ISIS EC Module 4

58. FRP sheets can be applied to increase shear resistance.
5 - Shear Strengthening
The shear resistance of the concrete element depends on the interaction between the concrete and the reinforcement.
FRP sheets can be applied to increase shear resistance.
The sheets are placed perpendicular or at an angle to the beam’s longitudinal axis. The shear capacity from the FRP stirrups is related to the angle of the cracks in the concrete, the direction and the effective strain of the FRP.
ISIS EC Module 4

59. dfrp is the effective shear depth for FRP
5 - Shear Strengthening
dfrp is the effective shear depth for FRP
sfrp is the spacing of the FRP stirrups
wFRP is the width of the FRP stirrup
 is the angle of inclination of diagonal cracks in the concrete.
b is the angle of the FRP stirrups
ISIS EC Module 4

60. Many different possible configurations:
5 - Shear Strengthening
Many different possible configurations:
1) Continuous wraps or finite width sheets (width and spacing)
2) Angle between the sheet and the beam’s axis
3) Wrap configuration with respect to the cross section
Continuous
Finite
b = 90
b  90
U-Wrap
Fully Wrapped
ISIS EC Module 4

61. Shear resistance of a beam (Vr ): 1) Existing capacity
5 - Shear Strengthening
Shear resistance of a beam (Vr ):
1) Existing capacity
- Resistance from concrete (Vc)
- Resistance from steel (Vs)
2) Additional capacity
- Resistance from FRP wraps (Vfrp)
Vr = Vc Vs
Vfrp +
ISIS EC Module 4

62. fs fyAv dv(cotq+cota)sina
5 - Shear Strengthening
Shear resistance of a beam (Vr ):
1) Resistance provided by concrete (Vc)
dv ≥ (0.72h, 0.9d)
2) Resistance provided by steel (Vs)
Vc = 2.5bvfcfcr bvdv
Vs =
fs fyAv dv(cotq+cota)sina s
ISIS EC Module 4

63. fFRP AFRP EFRP eFRPe dFRP (cotq + cotb) sinb
5 - Shear Strengthening
3) Resistance provided by FRP:
Vfrp =
fFRP AFRP EFRP eFRPe dFRP (cotq + cotb) sinb
sFRP
Afrp = 2 tfrp wfrp
efrpe is the effective strain in the FRP stirrups
dfrp is the effective depth
sfrp is the spacing of the FRP stirrups
ISIS EC Module 4

64. Tension FRP for flexure
5 - Shear Strengthening
Effective depth of FRP, dfrp: a d
Closed wrap shear FRP
No flexural FRP
Closed wrap shear FRP
Tension FRP for flexure
dfrp ≥ (0.9d, 0.72h)
dfrp ≥ 0.9h
ISIS EC Module 4

65. Tension FRP for flexure
5-Shear Strengthening
Effective depth of FRP, dfrp: a
hfrp
U-Shaped FRP stirrup
No flexural FRP
U-Shaped FRP stirrup
Tension FRP for flexure
dfrp ≥ (0.9hfrp, 0.72h)
dfrp ≥ (0.72h,hfrp)
ISIS EC Module 4

66. Effective strain in FRP, eFRPe:
5 - Shear Strengthening
Effective strain in FRP, eFRPe: a
efrpe = ≤ 0.75 efrpu (For completely wrapped sections)
efrpe = Kvefrpu ≤ (For other configurations)
where:
Kv=
K1=
K1K2Le
≤ 0.75
11900 efrpu
2/3
fc’
dfrp-Le
23300
K2 =
Le= 27
dfrp
(tfrpEfrp)0.58
ISIS EC Module 4

67. - Spacing of strips, sFRP:
5 - Shear Strengthening
Checks:
- Spacing of strips, sFRP:
sfrp ≤ wfrp +
d frp 4
- Maximum allowable shear strengthening, Vfrp :
Vc+ Vs+ Vfrp ≤ 0.25fcf’c bvdv
ISIS EC Module 4

68. Example: Section information
5 - Shear Strengthening
Shear Strengthening
Example:
Example
Calculate the shear capacity (Vr) for an FRP-strengthened concrete section
Section information
f’c = 45 MPa
efrpu = 1.5%
fy = 400 MPa (re-bar & stirrup)
Steel used is 10M
Efrp = 230GPa
s = 225 mm c/c
tfrp = 1.02 mm
wfrp = 100 mm
sfrp = 200 mm
Section
b = 150 mm
hfrp = 450 mm
ds =550mm
CFRP wrap
150mm
Elevation
h=600 mm
ISIS EC Module 4

69. Solution: 1) Resistance provided by concrete (Vc) Vc = 2.5bvfcfcr bvdv
5 - Shear Strengthening
Solution:
1) Resistance provided by concrete (Vc)
Vc = 2.5bvfcfcr bvdv
fcr = 0.4* √ f’c = 0.4* √45=2.68
dv ≥ (0.72h and 0.9d)
≥ (0.72*600 and 0.9*550)
≥ (432 and 495) = 495mm
Vc = 2.5*0.18*0.75*2.68*150*495*10-3 = kN
ISIS EC Module 4

70. fs fyAv dv(cotq + cota)sina
5 - Shear Strengthening
2) Resistance provided by steel (Vs)
Vs =
fs fyAv dv(cotq + cota)sina s
Vs =
(0.9)400(200)495(cot42 + cot90)sin90
225
Vs = 175,921 N = kN
ISIS EC Module 4

71. ffrp Afrp Efrp efrpe dfrp (cotq + cotb) sinb
5 - Shear Strengthening
3) Resistance provided by GFRP (Vfrp)
Vfrp=
ffrp Afrp Efrp efrpe dfrp (cotq + cotb) sinb
sfrp
dfrp ≥ (0.9 hfrp,0.72h) ≥ (0.9 × 450, 0.72 × 600)
≥ (405,432) = 432mm
Afrp = 2 tfrp wfrp = 2(1.02)(100) = 204 mm2
ISIS EC Module 4

72. 3) Resistance provided by FRP:
5 - Shear Strengthening
3) Resistance provided by FRP:
fc’
2/3
K1= 45
2/3 = =
1.406 27 27
23300
23300 =
17.888mm
Le= =
(tfrpEfrp)0.58
(1.02 x )0.58
dfrp-Le
K2=
0.959 = =
dfrp
432
K1K2Le
(1.406)(0.959)(17.888)
0.135 < 0.75
=0.135
Kv= = =
11900 efrpu
11900 (1.5)(10-2)
ISIS EC Module 4

73. fFRP AFRP EFRPeFRPe dFRP (cotq + cotb) sinb
5 - Shear Strengthening
Effective strain in FRP, efrpe: a
efrpe ≤ 0.004
efrpe ≤ Kvefrpu = (1.5)(10-2)=
efrpe=
VFRP =
fFRP AFRP EFRPeFRPe dFRP (cotq + cotb) sinb
sFRP
VFRP =
0.6(204)(230000)( )(432)(cot42)
200(1000)
=136.8 kN
ISIS EC Module 4

74. Total resistance of the section (Vr):
5 - Shear Strengthening
Total resistance of the section (Vr):
Vr = Vc Vs
VFRP +
Vr = = kN
ISIS EC Module 4

75. 1) Maximum allowable shear strengthening, VFRP :
Checks:
1) Maximum allowable shear strengthening, VFRP :
Vc + Vs + VFRP ≤ 0.25fcf’c bvdv
379.9 ≤ 0.25(0.75)(45)(150)(495)(10-3)
379.9 ≤ kN…………………………O.K.
ISIS EC Module 4

76. 2) Spacing of strips, sFRP:
5 - Shear Strengthening
Checks:
2) Spacing of strips, sFRP:
sFRP ≤ wFRP +
d FRP 4
200 ≤ 100 +
432 4
200 ≤ 208 mm…………………….O.K
ISIS EC Module 4

77. FRP sheets can be wrapped around concrete columns to increase strength
6 - Column Strengthening
FRP sheets can be wrapped around concrete columns to increase strength
How it works:
Internal reinforcing steel
Concrete
FRP wrap
flfrp
…FRP confines the concrete…
Concrete shortens…
…and places it in triaxial stress…
…and dilates…
ISIS EC Module 4

78. 6 - Column Strengthening
The result:
Increased load capacity
Increased deformation capability
ISIS EC Module 4

79. 6 - Column Strengthening
Confinement efficiency
Best: circular cross-section
Worst: rectangular section
Areas of concrete unconfined by the small bending stiffness of FRP system
Stress concentration at corners
confined
unconfined
Uniform stress distribution in circular section
Stress distribution in rectangular section
ISIS EC Module 4

80. 6 - Column Strengthening
Slenderness of the column
If the column is not slender, then the column is designed and analyzed for axial load only (short column).
If the column is slender, then the column is designed and analyzed for combined axial load and bending moment.
ISIS EC Module 4

81. 6 - Column Strengthening
Slenderness of the column
Slenderness could be ignored if:
klu r
< M1 M2
Braced columns
klu r
< 22
Un-braced columns
Where:
k is the effective length factor for the column
lu is the unsupported length of the column
r is the radius of gyration of the section
M1 is the smaller end moment at ULS due to factored loads
M2 is the larger end moment at ULS due to factored loads
ISIS EC Module 4

82. 1 - Short column (axial load only)
6 - Column Strengthening
1 - Short column (axial load only)
ISIS EC Module 4

83. 6 - Column Strengthening
1) Confinement Pressure (flFRP):
2tFRPfFRPfFRPu
flFRP=
…………………………Eq 6-2 Dg
Where:
flFRP is the confinement pressure
tFRP is the thickness of the FRP confining system
Dg is the external diameter of the circular section or the diagonal of the rectangular section
ISIS EC Module 4

84. 6 - Column Strengthening
Confinement Limits:
To ensure adequate ductility of column
Minimum confinement pressure
Why?
Limit
flfrp ≥ 0.1fc ′
To prevent excessive deformations of column
Maximum confinement pressure
Why?
Limit
flfrp ≤ 0.33 fc ′
ISIS EC Module 4

85. 6 - Column Strengthening
2) Confined concrete strength (fcc): ′
The benefit of the confining pressure is to increase the confined compressive concrete strength, fcc ′
fcc= fc+ 2 flFRP ′ ′
…………………………Eq 6-3
Where:
fc is the unconfined specified concrete strength ′
ISIS EC Module 4

86. 6 - Column Strengthening
3) Axial Load capacity (Pr):
The factored axial load resistance for an FRP-confined reinforced concrete column, Pr is given by: ′
Pr= 0.8
a1fc fcc(Ag-As)+ fs fyAs
…………………………Eq 6-5
Where:
Ag is the gross area of the cross section
As is the total cross- sectional area of the longitudinal steel reinforcing bars
ISIS EC Module 4

87. 6 - Column Strengthening
Design steps for short column (axial load only):
1) Determine the required confined concrete (fcc) strength according to Equation 6-5.
2) Determine the required confinement pressure (flFRP) from Equation 6-3.
3) Using the properties of the selected FRP system, determine a minimal thickness for the FRP (tFRP) from Equation 6-2.
4) Check for the confinement limits. ′
ISIS EC Module 4

88. 2 - Slender Column (axial load + moment)
6 - Column Strengthening
2 - Slender Column (axial load + moment)
ISIS EC Module 4

89. 6 - Column Strengthening
Section analysis is based on stress and strain compatibility
Axial strain distribution
Cross section
FRP
Steel bars
Equivalent stress distribution
confined concrete
unconfined concrete
Internal forces
side FRP
tension face FRP ec c ec c ′ es
c-d ′
esj
dsj-c es
d-c
eFRP
h-c = = = = =
…………………Eq 6-6 ′ ′ ′
ecc ′
fcc
Ccc+ Cc+ Cs – Fsj – Ts - TFRP,side - TFRP,face = Pr ≥ Pf
= 5 -1 +1 ′ ec ′ fc
ISIS EC Module 4

90. 6 - Column Strengthening
1) Assuming concrete crushing
Internal force
Distance from the centre of the section ′ ′ ′ ′ h c
2fc+fcc
fc+fcc c ec ′
- c - ec ′
Ccc fc b c-
ecc ′
3fc+3fcc ′ ′ 2
ecc 2 h b1 c c Cc ′ ec ′ ec ′
fca1 fc b b 1
- c + 1-
ecc ′
ecc ′ 2 2 Cs ′
fs fy A s ′
h /2 -d
ecc ′ h fs
(dsj-c)
dsj -
Fsj
Es Asj
≤ fs fy A sj c 2
Ts fs fy A s or fs es Es A s if es < ey
d – h/2
ecc ′ h
(h-c)
TFRP,side fFRP
(h-c)
EFRP (h-c) tFRP - c 2 3
ecc ′ h
TFRP,face fFRP
(h-c)
EFRP btFRP c 2
ISIS EC Module 4

91. 6 - Column Strengthening′ ′
ec-ec ′
2) Assuming maximum FRP tension (eFRP = eFRPt ):
Dfc= (fcc-fc)
ecc - ec ′ ′
Internal force
Distance from the centre of the section ′ ′
fc+Dfc
h-c ′ h
h-c
3fc+Dfc
Ccc fc b c- ec
c - ec ′
eFRPt
eFRPt
6fc+3Dfc ′ 2 2
h-c h b1
h-c ′ ec ′ ec ′
Cc fca1 fc b b1
- c + 1-
eFRPt
eFRPt 2 2 h ′
- d
Cs fs fy A s or fs es Es A s if es < ey ′ ′ ′ ′ 2
eFRPt h
Fsj fs
(dsj-c)
Es Asj
≤ fs fy A sj
dsj -
h-c 2
Ts fs fy A s
d-h/2 h
(h-c)
TFRP,side fFRP fFRPu (h-c) tFRP
≤ fFRP EFRPeFRPt (h-c) tFRP - 2 3
TFRP,face fFRP fFRPu b tFRP ≤fFRP EFRPeFRPt b tFRP h 2
ISIS EC Module 4

92. 6 - Column Strengthening
Design steps for slender column:
1) Assuming a linear distribution of strain, identify the relationship of strain in the various materials as a function of the assumed failure strain.
2) Determine the resultant force for each material.
3) Calculate the position of the neutral axis using equilibrium of forces.
4) Check the validity of the assumptions of strains and stresses for all materials.
ISIS EC Module 4

93. 6 - Column Strengthening
Design steps for slender column:
5) Determine Pr as the sum of the resultant force from each material.
6) Determine Mr as the sum of the internal resultant forces multiplied by their respective distances to the centroid of the section.
ISIS EC Module 4

94. 6 - Column Strengthening
Rectangular Columns
External FRP wrapping may be used with rectangular columns. However, strengthening is not as effective and is more complex.
Confinement only in some areas
Confinement all around
ISIS EC Module 4

95. 6 - Column Strengthening
Some geometrical limitations are imposed:
Sharp edge concrete should be rounded to promote an intimate and continuous contact of the FRP with the concrete.
- minimum radius is 35 mm
The aspect ratio of the section (h/b) ≤ 1.5
The smaller cross section dimension (b) ≤ 600 mm
The equations used are the same. Dg is taken as the diagonal of the cross section.
2tFRPfFRPFFRPu
flFRP= Dg
=√ h2+b2
ISIS EC Module 4

96. 6 - Column Strengthening
Additional Considerations
External FRP wrapping may also be used with circular and rectangular RC columns to strengthen for shear.
Particularly useful in seismic upgrade situations where increased lateral loads are a concern.
ISIS EC Module 4

97. 6 - Column Strengthening
The confining effects of FRP wraps are not activated until significant radial expansion of concrete occurs.
Therefore, ensure service loads are kept low enough to prevent failure by creep and fatigue
To avoid creep failure:
PD ≤ 0.85
0.8a1fc f`c (Ag-As)+ fsAs
fs ≤ Es ≤ 0.8fy
Where:
PD is the dead load
fs is the stress in the axial steel reinforcement
ISIS EC Module 4

98. 6 - Column Strengthening
Example
Example:
Determine the number of layers of GFRP wrap that are required to increase the factored axial load capacity of the column to 3450 kN.
Information
RC column factored axial resistance (after strengthening) = 3450 kN
lu = 2500 mm
Dg = 450 mm
Ag = mm2
As = 2500 mm2
fy = 400 MPa
f’c = 30 MPa
ffrpu = 600 MPa
tfrp = 1 mm
ffrp = 0.70*0.75
ISIS EC Module 4

99. 6 - Column Strengthening
Solution:
Step 1: Check for the slenderness effect
klu r
< M1 M2
k =1.0, M1=0 and M2=0
2500
112.5
= 22.2 < 34
Thus, the slenderness effect can be ignored
ISIS EC Module 4

100. 6 - Column Strengthening
Step 2: Determine the required confined concrete strength, fcc ′
Pr = 0.8
a1fc fcc(Ag-As)+ fs fyAs ′
a1 = 0.85 – f’c > 0.67
a1 = 0.85 – (30) = 0.81
= 0.8
0.81(0.75) fcc( )+ 0.9(400)2500 ′ ′
fcc= 35.9 MPa
ISIS EC Module 4

101. 6 - Column Strengthening
Step 3: Determine the required confinement pressure (flFRP)
fcc= fc+ 2 flFRP ′ ′
35.9 = flFRP
flFRP = 2.95 MPa
Step 4: Check for the confinement limits
flfrp ≥ 0.1fc =0.1(30) = 3 MPa ′
flfrp ≤ 0.33 fc =0.33(30) = 9.9 MPa ′
flFRP = 3 MPa
ISIS EC Module 4

102. 6 - Column Strengthening
Step 5: Determine the minimal thickness for the FRP (tFRP) and number of layers
2tFRPfFRPFFRPu
flFRP = Dg
2tFRP(0.70×0.75)600
3 =
450
tFRP = 2.14 mm
Since tGFRP = 1.0 mm, 3 layers of GFRP are required.
ISIS EC Module 4

103. 6 - Column Strengthening
Example
Example:
Check the design of the following column. It is required to resist a factored axial load of 6000 kN and a factored moment of 1600 kN.m.
Information 75
325
800
600
Axial FRP
2 layers
Hoop FRP
6 layers
Steel bars
Ast = 4000 mm2
fy = 400 MPa
f’c = 30 MPa
ffrpu = 3450MPa
tfrp = mm
efrpu = 0.015
ISIS EC Module 4

104. 6 - Column Strengthening
Step 1: Determine the properties of the confined concrete
Equivalent diameter: h
= 1.25 ≤ 1.5
b < 800 b
Dg=√ b2+h2 =√ = 1000 mm
Confining pressure:
2tFRPfFRPfFRPu
2(6 × 0.167)(0.75 ×0.70)3450
flFRP = =
= 3.63 MPa Dg
1000
Confinement limits:
0.33 fc ≥ flfrp ≥ 0.1fc
10 ≥ flfrp ≥ 3………………….O.K ′ ′
ISIS EC Module 4

105. 6 - Column Strengthening
Step 1: Determine the properties of the confined concrete
Confined concrete strength:
fcc = fc+ 2 flFRP ′ ′
fcc= 30+2×3.63 = MPa ′
Concrete strain: ′ ′
ecc
fcc
= 5 -1 +1 ec ′ fc ′
37.26
ecc ′
= ( ) = 30
ISIS EC Module 4

106. 6 - Column Strengthening
Step 2: Determine the equations of the resultant forces
The following assumptions were made:
- Compression failure (concrete crushing)
- fc varies linearly from f’c to fcc
- Yielding of both tension and compression steel
- Intermediate steel in elastic domain ′
a1 = 0.85 – f’c > 0.67
a1 = 0.85 – (30) = 0.805
b1 = 0.97 – f’c > 0.67
b1 = 0.97 – (30) = 0.895
ISIS EC Module 4

107. 6 - Column Strengthening
Assuming concrete crushing: ′ ′
fc+fcc c
c ×
0.0035 ′
Ccc= fc b c- ec
= 0.75
600
c -
ecc ′ 2 2
0.0077
c ×
0.0035
c - =
0.0077 c ′ ′ ec
c ×
0.0035
Cc= fca1 fc b b 1
ecc ′
= 0.75(0.805)30(600)0.895
0.0077
c ×
0.0035 =
0.0077 ′
Cs=fs fy A s
= 0.9(400)1500 = N
ISIS EC Module 4

108. 6 - Column Strengthening
ecc ′
0.0077
Fsj = fs
(dsj-c)
Es Asj
= 0.9
(400-c)
×1000 c c
0.0077
(400-c)
=180 × 106 c
Ts= fs fy A s = 0.9 (400) 1500 = N
ecc ′
0.0077
TFRP,side= fFRP
(h-c)
EFRP (h-c) tFRP = 0.75×0.70
(800-c) 2
× 0.334 c c
0.0077 =
(800-c) 2 c
ecc ′
0.0077
TFRP,face= fFRP
(h-c)
EFRP btFRP= 0.75×0.70
(800-c)
×600 ×0.334 c c
0.0077 =
(800-c) c
ISIS EC Module 4

109. 6 - Column Strengthening
Step 3: Determine the position of the neutral axis, c:
Ccc+Cc+Cs-Fsj-Ts-TFRP,side-TFRP,face= Pr
c ×
0.0035
c ×
0.0035
c -
0.0077
0.0077
0.0077
0.0077
(400-c)
-180 × 106
(800-c) 2 c c
0.0077
(800-c)
= 6000 × 103 c
c = 472 mm
ISIS EC Module 4

110. 6 - Column Strengthening
Step 4: Check the assumptions for strains:
ecc c ′
472-75
472 ′ es ′
(c-d )
= ×
= >  OK =
ecc c ′
472
esj
(dsj-c)
= ×
= < ±  OK =
472
ecc c ′ es
(d-c )
= ×
= >  OK =
ecc c ′
472
(h-c )
eFRP
= ×
= <  OK =
c ec
ecc ′
472
0.0077 c ′
= ×
= mm = ′
ISIS EC Module 4

111. 6 - Column Strengthening
Step 5: Determine Pr:
Pr = Ccc+Cc+Cs-Fsj-Ts-TFRP,side-TFRP,face =
214.5
-180 × 106
0.0077
( ) 2
472
0.0077
( )
= 5997 × 103 N
472
ISIS EC Module 4

112. 6 - Column Strengthening
Step 6: Determine Mr: h c
2fc+fcc ′ ′
Ccc
- c - ec ′
ecc ′ ′ ′
3fc+3fcc 2
800 2X
3X30+3X37.3
= 1075 X 106 N.mm = 2 h b1 c Cc ec ′
- c + 1-
ecc ′ 2 2
800
0.895 = 1-
X 214.5
= 97 X 106 N.mm 2 2 h
800 ′ Cs
- d =
-75
= 176 X 106 N.mm 2 2
ISIS EC Module 4

113. 6 - Column Strengthening
Step 6: Determine Mr: h
Fsj dsj -
= 0 N.mm 2 h
800
Ts d - =
= 176 X 106 N.mm 2 2 h
(h-c)
800
( )
TFRP,side
= 71400
= 21 X 106 N.mm - - 2 3 2 3 h
800
TFRP,face =
= 52 X 106 N.mm 2 2
Total = 1597 X 106 N.mm
The flexural resistance is adequate Mr = 1597 kN.m ≈1600 kN.m
ISIS EC Module 4

114. 7 - Installation of FRP Strengthening Systems
Includes:
1) Approval of FRP materials
2) Handling and storage of FRP materials
3) Staff and contractor qualifications
4) Concrete surface preparation
5) Installation of FRP systems
6) Curing the FRP system
7) Protection and finishing for FRP system
ISIS EC Module 4

115. 7 - Installation of FRP Strengthening Systems
1) Approval of FRP materials:
The use of certified FRP materials is recommended.
Qualification testing can be used for the approval of the FRP materials.
2) Handling and storage of FRP materials:
- Must be carried out in accordance with manufacturer specifications.
- Contractor and supplier must ensure that FRP materials are shipped in adequate conditions. Do not use opened or damaged containers.
- FRP components must be stored in clean & dry area, sheltered from sun rays.
- Do not use material that has exceeded its shelf life.
- Material safety data sheet for all FRP materials and components should be obtained from the manufacturer and should be accessible at the job site.
ISIS EC Module 4

116. 7 - Installation of FRP Strengthening Systems
3) Staff and contractor qualifications:
The workers must have a basic knowledge of all stages of the installation of the FRP systems. The minimum required knowledge includes:
An understanding of the security instructions
Mixing proportions of resins
Application rates
Pot life and curing times
Installation techniques
ISIS EC Module 4

117. 7 - Installation of FRP Strengthening Systems
4) Concrete surface preparation:
Repair of existing substrate:
- The concrete surfaces must be free of particles and pieces that no longer adhere to the structure.
- The surface must be cleaned from oil residuals or contaminants.
- Rough surface should be smoothed.
- Sections with sharp edges must be rounded.
- Surface preparation for contact critical applications
- A continuous contact between the concrete and the FRP confinement system should be guaranteed.
- Rounding of corners, filling holes and elimination of depression are of prime importance.
ISIS EC Module 4

118. 7 - Installation of FRP Strengthening Systems
5) Installation of FRP systems:
- Primer, putty, saturating resin and fibres should be a part of the same system.
- All equipment should be clean and in good operating condition
- Ambient air and concrete surface temperature should be 10°C or more
- The mixing of resins should be done in accordance with the FRP system manufacturer recommended procedure. All components should be mixed at a proper temperature and in the correct ratio until there is a uniform mix, free from trapped air.
- The installation of FRP is either hand wet applied system or precured system.
ISIS EC Module 4

119. 7 - Installation of FRP Strengthening Systems
6) Curing the FRP system
FRP materials should be cured according to the recommendations of the manufacturer unless the curing process is accelerated by heating, chemical reactant or other external supply.
The curing time should not be less than 24 hours before further work is done on the repaired surface.
Chemical contamination from gases, dust or liquid must be prevented during the cure of all materials.
ISIS EC Module 4

120. 7 - Installation of FRP Strengthening Systems
7) Protection and finishing for FRP system
When the surface of the FRP materials is sufficiently dry or hard, a protection system and/or paint compatible with the installed reinforcement can be added.
The coating must dry for a minimum of 24 hours .
A certificate of compatibility of the protection system with the selected type of FRP reinforcement must be obtained from the manufacturer of the FRP materials.
ISIS EC Module 4

121. 8 - Quality Control and Quality Assurance
The FRP material suppliers, the FRP installation contractors and all others associated with the FRP strengthening project should maintain a comprehensive quality assurance and quality control program.
1) Material qualification and acceptance:
The FRP manufacturer, distributor or their agent should provide information demonstrating that the proposed FRP meets all mechanical, physical and chemical design requirements.
 Tensile strength, type of fibres, resins, durability, etc.
2) Qualification of contractor personnel:
The selection of contractors should be based on evidence regarding their qualifications and experience for FRP strengthening projects.
ISIS EC Module 4

122. 8 - Quality Control and Quality Assurance
3) Inspection of concrete substrate:
- The concrete surface should be inspected and tested before application of FRP. The inspection should include:
- Smoothness or roughness of the surface
- Holes and cracks
- Corners radius
- Cleanliness
- Pull-off tests should be performed to determine the tensile strength of the concrete for bond-critical applications.
ISIS EC Module 4

123. 8 - Quality Control and Quality Assurance
4) FRP material inspection:
Inspection of the FRP materials shall be conducted before, during and after their installation.
- Before Construction
The FRP supplier should submit certification & identification of all the FRP materials to be used. The installation procedure should be submitted as well.
- During Construction
Keep records for:
- Quantity and mixture proportions of resin
- The date and time of mixing
- Ambient temperature & humidity
- All other useful information
Visual inspection of fibres orientation and waviness should be carried out.
ISIS EC Module 4

124. 8 - Quality Control and Quality Assurance
4) FRP material inspection:
- At completion of the project:
A record of all final inspection and test results related to the FRP material should be retained.
Samples of the cured FRP materials should be retained as well.
5)Testing:
- Qualification testing:
It is a specification for the product certification of FRPs used for rehabilitation. It includes some guidelines as:
- FRP systems whose properties have not been fully established should not be considered
- Constituent materials, fibres, matrices and adhesives, should be acceptable by the applicable code and known for their good performance.
ISIS EC Module 4

125. 8 - Quality Control and Quality Assurance
5) Testing:
- Field testing:
Confirmatory test samples of the FRP material systems should be prepared at the construction site and tested at an approved laboratory.
In-place load testing can be used to confirm the behaviour of the FRP strengthened member.
ISIS EC Module 4

126. 9 - Additional Applications
Prestressed FRP Sheets
One way to improve FRP effectiveness is to apply prestress to the sheet prior to bonding
This allows the FRP to contribute to both service and ultimate load-bearing situations
It can also help close existing cracks, and delay the formation of new cracks
Prestressing FRP sheets is a promising technique, but is still under development
ISIS EC Module 4

127. Maryland Bridge - Winnipeg, Manitoba - Constructed in 1969
10 - Field Applications
Maryland Bridge
- Winnipeg, Manitoba
- Constructed in 1969
- Twin five-span continuous precast prestressed girders
- CFRP sheets to upgrade shear capacity
ISIS EC Module 4

128. John Hart Bridge - Prince George, BC
10 - Field Applications
John Hart Bridge
- Prince George, BC
- 84 girder ends were shear strengthened with CFRP
Locations for FRP shear reinforcement
- Increase in shear capacity of 15-20%
- Upgrade completed in 6 weeks
ISIS EC Module 4

129. Country Hills Boulevard Bridge
10 - Field Applications
Country Hills Boulevard Bridge
- Calgary, AB
- Deck strengthened in negative bending with CFRP strips
- New wearing surface placed on top of FRP strips
ISIS EC Module 4

130. (Currently under revision)
Design Guidance
CAN/CSA-S806-02: Design and Construction of Building Components with Fibre Reinforced Polymers
(Currently under revision)
A Canadian code exists for the design of FRP-strengthened concrete members
CAN/CSA-S6-10: Canadian Highway Bridge Design Code
ISIS EC Module 4

131. Additional Information
Available from
ISIS EC Module 1: Mechanics Examples Incorporating FRP Materials
ISIS EC Module 2: An Introduction to FRP Composites for Construction
ISIS EC Module 3: An Introduction to FRP-Reinforced Concrete
ISIS EC Module 5: Introduction to Structural Health Monitoring
ISIS EC Module 6: Application & Handling of FRP Reinforcements for Concrete
ISIS EC Module 7: Introduction to Life Cycle Engineering & Costing for Innovative Infrastructure
ISIS EC Module 8: Durability of FRP Composites for Construction
ISIS EC Module 9: Prestressing Concrete Structures with Fibre Reinforced Polymers
ISIS EC Module 4