the performance of curved nonnon--ferrous reinforcement...

© 2006 The University of Sheffield

Western Bank, Sheffield S10 2TN, UK Miami, Florida, U.S.A.

CICE 2006

The 3rd International Conference on FRP Composites in Civil Engineering

THE PERFORMANCE OF CURVED NON-FERROUS REINFORCEMENT FOR CONCRETE STRUCTURES

THE PERFORMANCE OF CURVED THE PERFORMANCE OF CURVED NONNON--FERROUS REINFORCEMENT FERROUS REINFORCEMENT FOR CONCRETE STRUCTURESFOR CONCRETE STRUCTURESThanongsak ImjaiThanongsak ImjaiMaurizio GuadagniniMaurizio GuadagniniKypros PilakoutasKypros PilakoutasPeter WaldronPeter Waldron

Construction Innovation Research GroupDepartment of Civil and Structural Engineering



CICE 2006


•• Why bending reinforcement?Why bending reinforcement?

•• Design of bent reinforcementDesign of bent reinforcement

•• Performance of bent Performance of bent FRPFRP’’ss

•• Experimental programExperimental program

•• Experimental resultsExperimental results

•• ConclusionsConclusions

OutlineOutline



CICE 2006


Why bending reinforcement?Why bending reinforcement?Why bending reinforcement?

•• End anchoragesEnd anchorages

•• Element connectionElement connection

•• Shear reinforcementShear reinforcement

Types of curves (BS8666)Types of curves (BS8666)Types of curves (BS8666)

Minimum number?

Minimum number?



CICE 2006



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Specification for bendingSpecification for bendingSpecification for bending

R ≥ 2d

Standardised shapes (BS8666)Standardised shapes (BS8666)

R



CICE 2006


Specification for bendingSpecification for bendingSpecification for bending

Typical steel

Typical GFRP

Plastic strain induced by bending



CICE 2006


Cold bending of FRP’sCold bending of Cold bending of FRPFRP’’ss



CICE 2006


The tensile strength of FRP bars can be largely reduced when subjected to a biaxial state of stress

Performance of bent FRP’sPerformance of bent FRP’s

Longitudinal directionTransverse

direction



CICE 2006



Premature failure at bent portionPremature failure at bent portion



CICE 2006


0.3bfb fu fu

b

rf f fd

α⎛ ⎞⎜ ⎟⎜ ⎟⎝ ⎠

= + ≤

rb is the radius of the bend in the bardb is the nominal diameter of the FRP barffu is the design strength of a straight portion …of the bar

Performance of bent FRP’sPerformance of bent Performance of bent FRPFRP’’ss

Design equation (JSCE, 1997)



CICE 2006


Use of thermoplastic FRP’sUse of thermoplastic Use of thermoplastic FRPFRP’’ss

•• Thermosetting Thermosetting FRPFRP’’ss can only be precan only be pre--bent at the bent at the factoryfactory

•• Thermoplastic Thermoplastic FRPFRP’’ss could offer a valid solution could offer a valid solution for onfor on--site bending of reinforcementsite bending of reinforcement

R/t ~ 13R/t ~ 1



CICE 2006


Use of thermoplastic FRP’sUse of thermoplastic Use of thermoplastic FRPFRP’’ss

1.48Density (g/cm3)

35Glass content (%v/v)

1.9Ultimate strain (%)

28Tensile modulus (GPa)

720Tensile strength (MPa)

Properties

GFRP thermoplastic strip (10x3mm)GFRP thermoplastic strip (10x3mm)



CICE 2006


Experimental programExperimental programExperimental program

Type 2 Type 3

Parameters Parameters (47 specimens)(47 specimens)-- R/t R/t (2 (2 –– 5)5)-- embedment length embedment length (60mm, 145mm)(60mm, 145mm)-- tail length tail length ((ttll/t/t = 5 = 5 –– 15)15)-- ffcucu (45MPa, 95MPa)(45MPa, 95MPa)-- surface treatment surface treatment (smooth, sand coated)(smooth, sand coated)



CICE 2006


Experimental resultsExperimental resultsExperimental results

0 4000 8000 12000 16000 200000%

14%

28%

42%

56%

0

100

200

300

400

strain (με)

stre

ss (M

Pa)

f / f fu

21

23

272529

Strain distribution in specimens Type 2

Failure behaviourFailure behaviour



CICE 2006


Experimental resultsExperimental resultsExperimental results

Strain Strain distributiondistribution in specimens Type 3in specimens Type 3strain (με)

0 4000 8000 12000 16000 200000%

14%

28%

42%

56%

0

100

200

300

400

f / f fu

stre

ss (M

Pa)

2123 2725

29



CICE 2006



r/t0 1 2 3 4 5 6

f / f fu

(%)

0

10

20

30

40

50

60

70

Type 2, SM, NType 2, SC, NType 2, SM, HType 2, SC, H

Bonded specimens (Type 2)

R/tr/t0 1 2 3 4 5 6

0

10

20

30

40

50

60

70

Type 2, SM, NType 2, SC, NType 2, SM, HType 2, SC, HType 3, SM, NType 3, SM, H

f / f fu

(%)

R/tr/t0 1 2 3 4 5 6

0

10

20

30

40

50

60

70

Type 3, SM, NType 3, SM, H

Unbonded specimens (Type 3)

R/t

Experimental results vs. JSCE

α=0.092

α=0.05



CICE 2006


•Thermoplastics could offer a valid solution for on-site bending

•The capacity of the bent portion is not only a function of its geometry

•Values of R/t > 4 guarantee the development of 40% of the ultimate strength

•Need for a rational design method

Final RemarksFinal Remarks

the performance of curved nonnon--ferrous reinforcement...

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