high performance steel reinforcing bars - nc state: …srizkal/techpapers2002...nc statenc state...

NC STATE UNIVERSITY NC STATE

High Performance Steel High Performance Steel Reinforcing Bars Reinforcing Bars

Sami Rizkalla, Raafat ElSami Rizkalla, Raafat El--HachaHachaCConstructed onstructed FFacilities acilities LLaboratory (aboratory (CFLCFL))NNorth orth CCarolina arolina SState tate UUniversity (niversity (NCSUNCSU))

and

Salem FazaSalem FazaConcrete Reinforcement TechnologiesConcrete Reinforcement Technologies

Detroit, April 22, 2002


MMFX SteelMMFX SteelHighly corrosion resistant, as a result of its patented chemical composition and microstructure during production.

High yield strength allows for design reduction of rebar quantities.


Product EvaluationProduct Evaluation

75 + years75 + years1.5 1.5 –– 1.71.7MMFXMMFX

75 + years4.3 – 4.9304 SS / 316 SS

20 – 40 years1.4 – 1.6Epoxy Coated (A615)

15 – 30 years1A615

Estimated years of

service life

Approximate ratio of installed cost of

rebar to A615 rebar

Rebar Product Classification


Testing ProgramTesting Program

Evaluate the fundamental mechanical characteristics

Validate the performance and the acceptability of the MMFX bars as reinforcement for concrete structures


Preliminary CharacteristicsPreliminary CharacteristicsMechanical properties:

TensionCompression

Shear strengthFatigue strengthTensile strength of bent barsBond strength and development lengthBehaviour as compression steel in reinforced concrete columns


Mechanical Properties in Tension Mechanical Properties in Tension

Test method follow: ASTM A370, E8, and E111

Determine the stress-strain characteristics of three MMFX bar sizes (#4, #6, and #8)

Provide the following fundamental characteristics:Modulus of elasticity: EYield strength: fyUltimate stress: fu and corresponding strainUltimate strain: εsu

NC STATE UNIVERSITY NC STATE Results of Tension TestsResults of Tension Tests

#6

#4

#8


#4MMFX Reinforcing Steel Rebar

0

20

40

60

80

100

120

140

160

180

0 0.02 0.04 0.06 0.08 0.1 0.12 0.14

Strain (in/in)

Stre

ss (k

si)

E=29000ksi

x Extensometer removed

Results of Tension TestsResults of Tension Tests

#4MMFX Reinforcing Steel RebarElastic Young's Modulus 29000 ksiYield Strength (0.2%offset) 116 ksi

STDEV 7 ksiYield Strength (0.5% strain) 107 ksi

STDEV 6 ksiUltimate Strength 165 ksi

STDEV 4 ksiStrain at Ultimate stress 4.4 %

STDEV 0.6 %Ultimate Strain 7.7 %

STDEV 1.5 %


#6MMFX Reinforcing Rebar

0

20

40

60

80

100

120

140

160

180

0 0.02 0.04 0.06 0.08 0.1 0.12 0.14

Strain (in/in)

Stre

ss (k

si)

E=29000ksi

x Extensometer removedx




STDEV 1 ksiStrain at Ultimate 5.3 %

STDEV 0.3 %Ultimate Strain 12 %

STDEV 0.3 %



#8MMFX Reinforcing Steel Rebar

0

20

40

60

80

100

120

140

160

180

0 0.02 0.04 0.06 0.08 0.1 0.12 0.14

Strain (in/in)

Stre

ss (k

si)

E=29000ksi x Extensometer removedxx xx




STDEV 1 ksiStrain at Ultimate 5.5 %

STDEV 0.3 %Ultimate Strain 9.7 %

STDEV 1.6 %



Stress-Strain Curves (2'' Gage Length)

0

20

40

60

80

100

120

140

160

180

0 0.02 0.04 0.06 0.08 0.1 0.12 0.14 0.16

Strain (in/in)

Stre

ss (k

si) 120ksi

177ksiMMFX Steel

ASTM A615 Grade 60

E =29,000ksi

failure



Mechanical Properties in Mechanical Properties in CompressionCompression

Test method follow: ASTM E9, and E111

Determine the stress-strain characteristics of three MMFX bar sizes (#4, #6, and #8)

Length of the specimens = 2dBAR

Provide the following fundamental characteristics:Modulus of elasticity: EYield strength: fy´


Test SetTest Set--UpUp

Top Loading Plate

Bottom Loading Plate

Universal Testing Machine


StressStress--Strain CurvesStrain Curves

145ksi

0

20

40

60

80

100

120

140

160

180

200

-0.03-0.025-0.02-0.015-0.01-0.00500.0050.010.0150.02

Transvers Strain (in/in) Longitudinal

Com

pres

sive

Str

ess

(ksi

)

E=29,000ksi

A615 #8 Grade 60A615 #8 Grade 60

#6&8 MMFX#6&8 MMFX


Failure ModeFailure Mode

#4MFFX #6MFFX #8MFFX


Shear Strength Shear Strength Determine the Shear Strength of three bar sizes (#4, #6, #8) using five specimens for each size. The test specimen is subjected to double shear action

Shear strength is determined based on the failure load


Results of Shear StrengthResults of Shear Strength#4MMFX Shear Strength

specimen ksi1 110.62 108.63 108.94 109.95 111.8

Average 110.0st.dv. 1.3

#6MMFX Shear Strengthspecimen ksi

1 111.22 111.83 111.84 110.25 111.2


#8MMFX Shear Strengthspecimen ksi

1 107.22 111.83 110.64 112.9


Shear Strength MMFX = 110.7 ksi st.dv. = 1.5 ksi


Fatigue StrengthFatigue StrengthTest method follow: ASTM E466

Determine the endurance limit for bar sizes #4 & #6

Determine the stress-number of cycles curve (S-N curve) for each bar size

The maximum tensile stress level varied: 90%, 80%, 75%, 70%, and 65% of the yield strengthThe minimum tensile stress level was set at 20% of the yield strength


S-N Diagrams

0

20

40

60

80

100

120

10000 100000 1000000

Fatigue life, N, Cycles

Stre

ss (k

si)

#6MMFX

#4MMFX

SS--NN DiagramDiagram


Tensile Strength of Bent BarsTensile Strength of Bent BarsExamine the bend effect on the strength of the MMFX reinforcing steel bent bars

Two different bar sizes (#4, and #6) were used

The radius of the bent is 90° (ACI 318-99)

20 Hydraulic Jack

Load Cell

#4 MMFX

18

Plastic tube

1212

Concrete BlockConcrete Block


Bend Effect on Tensile StrengthBend Effect on Tensile Strength

Plastic tube for debonding


Test SetTest Set--upup#4MMFX#4MMFX

Bend Effect on Tensile StrengthBend Effect on Tensile Strength


Tensile Strength of Bent BarsTensile Strength of Bent Bars#4MMFX Reinforcing Steel Bars

0

20

40

60

80

100

120

140

160

0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08

Strain (in/in)

Stre

ss (k

si)

165ksi


#6MMFX Reinforcing Steel Bars

177 ksi

0

20

40

60

80

100

120

140

160

180

0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08

Strain (in/in)

Stre

ss (k

si)

Tensile Strength of Bent BarsTensile Strength of Bent Bars


Bond Strength and Bond Strength and Development Length Development Length

Evaluate the bond strength and the development length of bar sizes #4, #6, and #8.

Different embedment length of 8db, 18db, 38db, 58db, 78db and 98db were examined for each selected size (db is the diameter of the bar).


Bond Test SpecimenBond Test Specimen

12inLVDT

Load Cell

Jack

Elevation

Development length

Plan


Bond SpecimensBond Specimens

Specially designed RC TSpecially designed RC T--sectionsection

Concrete T-section heavily reinforced with Grade 60 steel

Plastic tubesPlastic tubes



self-reacting steel frame against the flange of the T-section

Jack Load Cell

NC STATE UNIVERSITY NC STATEResults of Bond TestsResults of Bond Tests

#4MMFX Embedment Length = 4in (8d)

2.2ksi, 0.0198in)

0

0.5

1

1.5

2

2.5

0 0.02 0.04 0.06 0.08 0.1 0.12 0.14

Slip at the Free End (in)

Bon

d St

ress

(ksi

)

Axial stress = 70.6ksiMaximum Laod = 13830lb


Results of Bond TestsResults of Bond Tests#6MMFX Embedment Length = 7in (9d)

(2.24ksi, 0.04975in)

0

0.5

1

1.5

2

2.5

0 0.04 0.08 0.12 0.16 0.2 0.24

Slip at Free End (in)

Bon

d St

ress

(ksi

)

Axial stress = 83.8ksiMaximum Laod = 36875lb


Results of Bond TestsResults of Bond Tests4in 9in 19in 29.25in 39in 49in8d 18d 38d 58.5d 78d 98d

Maximum Load (lb) 13830 31940 34820 32725 33526 33418Bond Stress (ksi) 2.2 2.26 1.16 0.71 0.55 0.43Axial Stress (ksi) 70.6 163 178 167 171 170.5Slip at Free End (in) 0.019804 0.038281 0.003812 0.000342 0.000150 0.000014Failure Mode Slip Slip Rupture Rupture Rupture Rupture

Embedment Length

#4MMFX

#6MMFX7in 14in 29in 44in 59in 74in9d 19d 39d 59d 79d 99d

Maximum Load (lb) 36875 71626 74084 75572 65951 ---Bond Stress (ksi) 2.24 2.10 1.08 0.73 0.47 ---Axial Stress (ksi) 84 163 168 172 150 ---Slip at Free End (in) 0.04975 0.04891 0.02927 0.01247 0.00156 ---Failure Mode Slip Slip Rupture Rupture Didn't Fail not tested

Embedment Length

(test in progress)

#8MMFX8in 18in 38in 57in 78in 98in8d 18d 38d 57d 78d 98dEmbedment Length


Development LengthDevelopment Length

c

ybd ff

dl′

=25αβλ

(ACI 318 –99)

fc´ : compressive strength of concrete = 7000 psiGrade 60 steel: Grade 60 steel: ffyy = 60,000 psi = 60,000 psi →→ lldd = 29= 29ddbbMMFX steel: MMFX steel: ffyy = 120,000 psi = 120,000 psi →→ lldd = 57= 57ddbb

MMFX Rebar9in 19in 14in 29in18d 38d 19d 39d

Failure Mode Slip Rupture Slip Rupture

#6Embedment Length

#4


Compression Steel in Short Compression Steel in Short RC ColumnRC Column

Two RC concrete columns were constructed:C1: 6#6MMFX longitudinal reinforcing barsC1: 6#6MMFX longitudinal reinforcing bars

C2: 6#6 Grade 60 longitudinal reinforcing barsC2: 6#6 Grade 60 longitudinal reinforcing bars

Columns are laterally reinforced with #3 Grade 60Columns are 3ft. long and 12in. diameter

Columns were tested under axial compression up to failure

The concrete strength = 5000psi


Details of Short ColumnsDetails of Short Columns

#6 MMFX#6 MMFX 6# Grade 606# Grade 60

#3 Grade 60

8in3ft

12in



PI gagePI gage


Results of RC ColumnsResults of RC Columns12in. Reinforced Concrete Columns

0

100,000

200,000

300,000

400,000

500,000

600,000

-0.005-0.0045-0.004-0.0035-0.003-0.0025-0.002-0.0015-0.001-0.00050

Strain (in/in)

App

lied

Axi

al L

oad

(lb)

MMFX

Grade 60


Failure ModeFailure Mode

6# Grade 606# Grade 60#6 MMFX#6 MMFX


Flexural TestingFlexural Testing(UNF & WVU)(UNF & WVU)


Effect of Reinforcement RatioEffect of Reinforcement Ratio

0

20

40

60

80

100

120

140

-0.5 0 0.5 1 1.5 2 2.5 3 3.5

Deflection (in)

Load

(kip

s)

Beam B2-1

Beam B3-1

Beam B1-1

As = 2.012 in2

As = 1.246 in2

As = 0.623 in2


ConclusionConclusion

Research in Progress


Typical MMFX ApplicationsTypical MMFX Applications

Pennsylvania DOT Bridge DeckOklahoma DOT

Bridge Girders

Florida Residential Construction

Kentucky DOT Bridge Deck


Thank YouThank You

high performance steel reinforcing bars - nc state: …srizkal/techpapers2002...nc statenc state...

Documents