EFFECTS OF MULTIPLE HEAT STRAIGHTENING REPAIRS ON THE STRUCTURAL PROPERTIES AND

FRACTURE TOUGHNESS OF BRIDGE STEELS

Keith Kowalkowski, Graduate Assistant and Ph.D. student

Amit H. Varma, Assistant Professor

Purdue University

January 11, 2005

TRB 2005 Annual Meeting Session, 479

Advancements in Steel Bridge Fabrication Technology

Sponsored by: Fabrication and Inspection of Metal Structures

PRESENTATION OUTLINE• INTRODUCTION, BACKGROUND, AND TESTING APPROACH

– Schematic of Typical Bridge Damage and Repair Procedure

– Relevant Prior Experimental Investigations

– Michigan High Load Hits Database

– Testing Approach

• EXPERIMENTAL INVESTIGATIONS

– Test Matrix

– Specimen Designs

– Test Setup

– Procedure, Instrumentation, and Behavior

• EXPERIMENTAL RESULTS AND CONCLUSIONS

– Elastic Modulus, Yield Stress, Ultimate Stress, % Elongation, Hardness

– A36 Fracture Toughness

– A588 Fracture Toughness

– A7 Fracture Toughness

• RECOMMENDATIONS

• ACKNOWLEDGEMENTS

INTRODUCTION, BACKGROUND, AND TESTING APPROACH

INTRODUCTION

• Over-height trucks occasionally collide with and damage the fascia beams of steel bridge structures.

• The damage of the steel fascia beam primarily includes out-of-plane bending and twisting of the beam.

• Heat straightening is a cost-effective and efficient technique for repairing steel beam bridges damaged by collisions with overheight loads.

• Currently, there is a lack of knowledge on the effects of multiple damage-heat straightening repairs on the structural properties and fracture toughness of bridge steels.

• The Michigan Department of Transportation (MDOT) funded a research project to answer these questions relating the effects of multiple heat straightening repairs.

• The damage-repair parameters considered were the damage strain (d), the restraining stress (r), and the number of damage-repair cycles (Nr).

DAMAGE INDUCED TO FASCIA BEAMS

Bottom Flange

HEAT-STRAIGHTENING REPAIR PROCEDUREa) Restraining force apparatus b) Strip heat to web

c) Vee heat to flange d) Several Vee heats to flange

RELEVANT BRIDGE STEELS• Relevant bridge steels were identified by analyzing the Michigan high

load hits database from 1976-2001 (Varma et al. 2004).

• A7 and A373 are the most relevant in this research project.

• A36 steel is the closest in chemical composition and is available commercially.

• Thus, the experimental investigations focused on A36 and A588 steels.

• Some A7 steel specimens were acquired from the web of a decommissioned W24x76 steel beam.

Steel Type Vs. Frequency of Hits(All damage-repair cases in database)

158

99

5 216

0

20

40

60

80

100

120

140

160

A7 A373 A36 A572 A588Steel Type

Fre

quen

cy

Steel Type Vs. Frequency of Hits(All damage-repair cases in database)

94

67

5 2

15

0

20

40

60

80

100

A7 A373 A36 A572 A588Steel Type

Fre

quen

cy

When the same bridge is hit multiple times, the corresponding

steel is counted multiple times

When the same bridge is hit multiple times, the corresponding

steel is counted once only.

Damage Force (Pd)

TESTING APPROACH

Restraining Force (Pr)

Two methods were considered

(Method 1)

t

PROBLEMS WITH METHOD 1• The specimen cross-section and length are subjected to

different magnitudes of damage strain, restraining stress, and heat straightening repair.

• Hinders obtaining several material specimens subjected to consistent damage-repair magnitudes and testing them to obtain statistically significant structural properties.

METHOD 2

Strip Heat

Damage Force (Pd )Repair Force (Pr )

• Specimen test-areas are subjected to consistent damage strains, restraining stresses, and heat straightening repair.

• Several material specimens are obtained from the test-areas and tested to obtain statistically significant structural properties.

• Method 2 was chosen in this research project.

Test Area

EXPERIMENTAL INVESTIGATIONS

EXPERIMENTAL TEST MATRIXSteel

TypeDamage

Strains (d)Restraining Stresses (r)

Number of damage-repair cycles (Nr)

No. of specimens (One spec. for each value of Nr)

A36

30 y

0.40 y 1, 2, 3, 4, 5 5

0.70 y 1, 2, 3, 4, 5 5

60 y

0.25 y 1, 2, 3, 4, 5 5

0.50 y 1, 2, 3, 4, 5 5

90 y

0.25 y 1, 3, 5 3

0.50 y 1, 2, 3, 4, 5 5

A588

20 y

0.25 y 1, 2, 3, 4,5 5

0.50 y 1, 2, 3, 4, 5 5

40 y

0.25 y 1, 2, 3, 4,5 5

0.50 y 1, 2, 3, 4, 5 5

60 y

0.25 y 1, 2, 3, 4,5 5

0.50 y 1, 2, 3, 4, 5 5

A7

30 y

0.25 y 1, 3, 5 3

0.40 y 1, 3, 5 3

60 y

0.25 y 1, 3, 3*, 5 4

0.40 y 1, 3, 5 3

90 y

0.25 y 1, 3 2

0.40 y 1, 3 2

REMOVAL OF A7 SPECIMENS

15 in. 39 in.39 in.93 in.

23.9 in.

Undamaged Material Testing

Area

• A7 specimens were fabricated from the web of the acquired approximately 24-ft. long W24x76 steel beam.

• The 24-ft. long beam was cut into three 93 in. long segments.

• Six specimens were removed from each as shown below.

TEST SPECIMEN DETAILS

7.875

3.75

5.00

3.75

3.2539.00

13.25

Test specimen thickness = 0.45 in.

A7 steel

13.25

16.88

3.75

3.75

16.88

3.25

8.00

46.25

Test specimen thickness = 1.00 in.

A36 and A588 steel

= 1.1875

5.00

Cross-section at End B

1.0 in.

0.75

in.

0.394

4 5 6

0.75

in.

0.5 in.

0.394 0.394

3.25in.Cross-section at End B

1.0 in.

0.75

in.

0.394

4 5 6

0.75

in.

0.5 in.

0.394 0.394

3.25in.

1.0 in.1.0 in.

0.75

in.

0.394

44 55 66

0.75

in.

0.5 in.

0.394 0.394

3.25in.3.25in.

Cross-section at End B

Cross-section at End B

1.0 in.

0.75

in.

0.394

4 5 6

0.75

in.

0.5 in.

0.394 0.394

3.25in.Cross-section at End B

1.0 in.

0.75

in.

0.394

4 5 6

0.75

in.

0.5 in.

0.394 0.394

3.25in.

1.0 in.1.0 in.

0.75

in.

0.394

44 55 66

0.75

in.

0.5 in.

0.394 0.394

3.25in.3.25in.

Cross-section at End B

1.0 in.

0.5 in.

0.25 in.

0.75

in. 0.394 0.394 0.394

0.75

in.

21 3

3.25 in.

Cross-section at End A

1.0 in.

0.5 in.

0.25 in.

0.75

in. 0.394 0.394 0.394

0.75

in.

2211 33

3.25 in.

Cross-section at End ACross-section at End A

1.0 in.

0.5 in.

0.25 in.

0.75

in. 0.394 0.394 0.394

0.75

in.

21 3

3.25 in.

Cross-section at End A

1.0 in.

0.5 in.

0.25 in.

0.75

in. 0.394 0.394 0.394

0.75

in.

2211 33

3.25 in.

Cross-section at End ACross-section at End A

1 2 3

0.75 0.394 0.394 0.394 0.75

5.0 in.

4 5 6

0.75 0.394 0.394 0.394 0.75

3.25 in.

End B

End A

0.50.5

2.16

5 in

. 2.

165

in.

1.37

5 2.

25

1.37

5

11 22 33

0.75 0.394 0.394 0.394 0.750.75 0.394 0.394 0.394 0.75

5.0 in.

44 55 66

0.75 0.394 0.394 0.394 0.750.75 0.394 0.394 0.394 0.75

3.25 in.

End B

End A

0.50.5

2.16

5 in

. 2.

165

in.

1.37

5 2.

25

1.37

5

X Y1 2 3

0.75 0.394 0.394 0.394 0.75

5.0 in.

4 5 6

0.75 0.394 0.394 0.394 0.75

3.25 in.

End B

End A

0.50.5

2.16

5 in

. 2.

165

in.

1.37

5 2.

25

1.37

5

11 22 33

0.75 0.394 0.394 0.394 0.750.75 0.394 0.394 0.394 0.75

5.0 in.

44 55 66

0.75 0.394 0.394 0.394 0.750.75 0.394 0.394 0.394 0.75

3.25 in.

End B

End A

0.50.5

2.16

5 in

. 2.

165

in.

1.37

5 2.

25

1.37

5

X Y1 2 3

0.75 0.394 0.394 0.394 0.75

5.0 in.

4 5 6

0.75 0.394 0.394 0.394 0.75

3.25 in.

End B

End A

0.50.5

2.16

5 in

. 2.

165

in.

1.37

5 2.

25

1.37

5

11 22 33

0.75 0.394 0.394 0.394 0.750.75 0.394 0.394 0.394 0.75

5.0 in.

44 55 66

0.75 0.394 0.394 0.394 0.750.75 0.394 0.394 0.394 0.75

3.25 in.

End B

End A

0.50.5

2.16

5 in

. 2.

165

in.

1.37

5 2.

25

1.37

5

X Y1 2 3

0.75 0.394 0.394 0.394 0.75

5.0 in.

4 5 6

0.75 0.394 0.394 0.394 0.75

3.25 in.

End B

End A

0.50.5

2.16

5 in

. 2.

165

in.

1.37

5 2.

25

1.37

5

11 22 33

0.75 0.394 0.394 0.394 0.750.75 0.394 0.394 0.394 0.75

5.0 in.

44 55 66

0.75 0.394 0.394 0.394 0.750.75 0.394 0.394 0.394 0.75

3.25 in.

End B

End A

0.50.5

2.16

5 in

. 2.

165

in.

1.37

5 2.

25

1.37

5

X Y

MATERIAL COUPONS FROM TEST AREAS(A36 and A588 Specimens)

Charpy Specimens

Tension Coupons

TEST SETUP

Top Beam

Bottom Beam

Concrete Blocks

Test Specimen

Hydraulic Actuator

Split-flow valve

Electric Pump

Needle ValvePressure Gage

DAMAGE CYCLE-INSTUMENTATION

• Pressure transducers to measure actuator pressures

• Two longitudinal strain gages in test area

• Two displacement transducers to measure average strai

Gage – front Gage -back

3.25 in.

5.0 in.

Test-Area

Two displacement transducers to measure average strains in test area

TEST AREA

0

10

20

30

40

50

60

70

0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09Strain (mm/mm)

Str

ess

(ksi

)

Specimen A36-60-50-3 Target d = 0.080 in/in

Cycle 1-Longitudinal Strain Gages (Back (gray) and Front (red))

Cycle 1-Average Strain

Cycle 2 Average Strains

Cycle 3-Average Strains

Stress-strain of undamaged uniaxial tension test

EXPERIMENTAL DAMAGE BEHAVIOR(SPECIMEN A36-60-50-3)

Strain (in/in)

• Focused on shortening the specimen test area to the original length.

• The length is monitored using digital calipers and two punch marks at the edges.

• Lengths, widths, and thickness were monitored in between each heating cycle to maintain uniformity in the test area.

• Maximum heating temperature of 1200F was enforced while repairing

REPAIR CYCLES

REPAIR CYCLE-INSTRUMENTATION

Two displacement transducers to monitor movement during heat straightening

Infrared thermometer used to measure temperature on all sides

• Pressure transducers to measure actuator pressures

• Infrared thermometer to measure surface temperature

• Two displacement transducers to measure displacement between top and bottom beam.

0

500

1000

1500

2000

2500

3000

3500

4000

4500

5000

0 500 1000 1500 2000 2500 3000 3500 4000 4500 5000

Time (s)

Pressure (psi) Temperature (F)

Right Displacement *10000 (in)

Left Displacement*10000 (in)

EXPERIMENTAL REPAIR BEHAVIOR(SPECIMEN A36-60-50-3)

REPAIR DESCRIPTION

Applying the Strip Heat Monitoring the Surface Temperature

EXPERIMENTAL RESULTS

UNIAXIAL TENSION RESULTS (A36)

0.70

0.80

0.90

1.00

1.10

1.20

1.30

1 2 3 4 5 1 2 3 4 5 1 2 3 4 5 1 2 3 4 5 1 3 5 1 2 3 4 5

Rat

io o

f E

last

ic M

od

ulu

s to

Un

dam

aged

Mat

eria

l

0.70

0.80

0.90

1.00

1.10

1.20

1.30

1 2 3 4 5 1 2 3 4 5 1 2 3 4 5 1 2 3 4 5 1 3 5 1 2 3 4 5

Ra

tio

of

Yie

ld S

tre

ss

to

Un

da

ma

ge

d M

ate

ria

l

0.70

0.80

0.90

1.00

1.10

1.20

1.30

1 2 3 4 5 1 2 3 4 5 1 2 3 4 5 1 2 3 4 5 1 3 5 1 2 3 4 5

Rat

io o

f U

ltim

ate

Str

ess

to U

nd

amag

ed M

ater

ial

0.70

0.80

0.90

1.00

1.10

1.20

1.30

1 2 3 4 5 1 2 3 4 5 1 2 3 4 5 1 2 3 4 5 1 3 5 1 2 3 4 5

Ra

tio

of

%E

lon

ga

tio

n t

o U

nd

am

ag

ed

Ma

teri

al

d = 30y

r =0.40y d = 30y

r =0.70y d = 60y

r =0.25y d = 60y

r =0.50y d = 90y

r =0.25y

d = 90y

r =0.50y

Number of damage-repairs (Nr)

d = 30y

r =0.40y d = 30y

r =0.70y d = 60y

r =0.25y d = 60y

r =0.50y d = 90y

r =0.25y d = 90y

r =0.50y

Number of damage-repairs (Nr)

Number of damage-repairs (Nr)

d = 30y

r =0.40y d = 30y

r =0.70y d = 60y

r =0.25y d = 60y

r =0.50y d = 90y

r =0.25y d = 90y

r =0.50y d = 30y

r =0.40y d = 30y

r =0.70y d = 60y

r =0.25y d = 60y

r =0.50y d = 90y

r =0.25y d = 90y

r =0.50y

ELASTIC MODULUS YIELD STRESS

ULTIMATE STRESS DUCTILITY % ELONGATION

0.50

0.60

0.70

0.80

0.90

1.00

1.10

1 2 3 4 5 1 2 3 4 5 1 2 3 4 5 1 2 3 4 5 1 2 3 1 2 3 4 5

Rat

io o

f %

Elo

ng

atio

n t

o U

nd

amag

ed M

ater

ial

0.50

0.60

0.70

0.80

0.90

1.00

1.10

1 2 3 4 5 1 2 3 4 5 1 2 3 4 5 1 2 3 4 5 1 2 3 4 5 1 2 3 4 5

Rat

io o

f %

Elo

ng

atio

n t

o U

nd

amag

ed M

ater

ial

DUCTILITY OF A36, A588, AND A7 STEEL d = 30y

r =0.40y d = 30y

r =0.70y d = 60y

r =0.25y d = 60y

r =0.50y d = 90y

r =0.25y d = 90y

r =0.50y

Number of damage-repairs (Nr)

d = 30y

r =0.40y d = 30y

r =0.70y d = 60y

r =0.25y d = 60y

r =0.50y d = 90y

r =0.25y d = 90y

r =0.50y

A588 STEEL

Number of damage-repairs (Nr)

0.50

0.60

0.70

0.80

0.90

1.00

1.10

1 3 5 1 3 5 1 3 3* 5 1 3 5 1 3 1 3

Rat

io o

f %

Elo

ng

ati

on

to

Un

dam

ag

ed

Ma

teri

al d = 30y

r =0.40y d = 30y

r =0.70y d = 60y

r =0.25y d = 60y

r =0.50y d = 90y

r =0.25y d = 90y

r =0.50y

A7 STEEL

Number of damage-repairs (Nr)

A36 STEEL

CONCLUSIONS–STRUCTURAL PROPS.

• Multiple damage-heat straightening repair cycles have a slight influence (±15%) on the elastic modulus, yield stress, ultimate stress, and surface hardness of A36, A588, and A7 bridge steels.

• The yield stress and surface harness increase slightly and the ultimate stress and elastic modulus are always within ±10% of the undamaged values.

• However, the % elongation of damaged-repaired steel is influenced significantly.

• The ductility (% elongation) of A36 and A588 steel decreases significantly but never lower than minimum values according to AASHTO requirements.

• The ductility of A7 steel subjected to five damage-repair cycles is extremely low.

FRACTURE TOUGHNESS RESULTS (A36)

0.00

0.25

0.50

0.75

1.00

1.25

1.50

1.75

2.00

2.25

0 1 2 3 4 5 0 1 2 3 4 5

Fra

ctu

re T

ough

nes

s/ T

ough

nes

s U

nd

amag

ed A

36

d = 30y r = 0.40y d = 30y r = 0.70y

Number of damage-repairs (Nr)

95% low

95% high

Mean

95% high

Mean

95% low

0 = undamaged0.00

0.25

0.50

0.75

1.00

1.25

1.50

1.75

2.00

2.25

0 1 2 3 4 5 0 1 2 3 4 5Fra

ctur

e T

ough

ness

/ Tou

ghne

ss U

ndam

aged

A36

95% high

Mean

95% low

95% high

Mean

95% low

d = 60y r = 0.25y d = 60y r = 0.50y

Number of damage-repairs (Nr)

0 = undamaged

0.00

0.25

0.50

0.75

1.00

1.25

1.50

1.75

2.00

2.25

0 1 3 5 0 1 2 3 4 5 4Fra

ctu

re T

ough

nes

s/ T

ough

nes

s U

nd

amag

ed A

36

95% high

Mean

95% low

95% high

Mean

95% low

d = 90y r = 0.25y d = 90y r = 0.50y

Number of damage-repairs (Nr)

0 = undamaged

• Fracture toughness of damaged-repaired specimens analyzed statistically mean toughness and 95% confidence interval (CI) high and low toughness values

• The 95% CI Low, mean, and 95% CI high toughness values of the damaged-repaired specimens were normalized with respect to the undamaged mean toughness of the corresponding steel.

• The normalized fracture toughness values for the damaged-repaired specimens are shown and the effects of parameters d, r, and Nr are evaluated.

CONCLUSIONS – A36 TOUGHNESS

• The fracture toughness of A36 steel is much lower than the undamaged fracture toughness.

• The mean fracture toughness of specimens damaged to 30y becomes less than 50% after two damage-repair cycles.

• The fracture toughness of specimens damaged to 60y becomes less than 50% after three damage-repair cycles.

• The mean fracture toughness of specimens damaged to 90y was found to have significant scatter.

• Higher restraining stress appear to decrease the fracture toughness slightly.

0.00

0.25

0.50

0.75

1.00

1.25

1.50

1.75

2.00

2.25

0 1 2 3 4 5 0 1 2 3 4 5Fra

ctu

re T

ough

nes

s/ T

ough

nes

s U

nd

amag

ed A

588

FRACTURE TOUGHNESS RESULTS (A588)

Number of damage-repairs (Nr) Number of damage-repairs (Nr)

0.00

0.25

0.50

0.75

1.00

1.25

1.50

1.75

2.00

2.25

0 1 2 3 4 5 0 1 2 3 4 5Fra

ctu

re T

ough

nes

s/ T

ough

nes

s U

nd

amag

ed A

588

Quarter Average

Mid Average

Quarter Average

Mid Average

d = 20y r = 0.25y d = 20y r = 0.50y

0 = undamaged

Quarter Average

Mid Average

Quarter Average

Mid Average

d = 40 y r = 0.25 y d = 40 y r = 0.50 y

0 = undamaged

Number of damage-repairs (Nr)

0.00

0.25

0.50

0.75

1.00

1.25

1.50

1.75

2.00

2.25

0 1 2 3 4 5 0 1 2 3 4 5Fra

ctu

re T

ough

nes

s/ T

ough

nes

s U

nd

amag

ed A

588

d = 60 y r = 0.25 y

Quarter Average

Mid Average

Quarter Average

Mid Average

d = 60 y r = 0.50 y

0 = undamaged

• Fracture toughness of damaged-repaired specimens analyzed statistically mean quarter and mid thickness values were used

• The mean values of the damaged-repaired specimens were normalized with respect to the undamaged mean toughness (quarter or mid) of the corresponding steel.

• The normalized fracture toughness values for the damaged-repaired specimens are shown and the effects of parameters d, r, and Nr are evaluated.

CONCLUSIONS – A588 TOUGHNESS

•The fracture toughness of damaged-repaired A588 steel is greater than or close to the undamaged fracture toughness in several cases.

•The fracture toughness never decreases below 50% (even after five damage-repair cycles).

• Increasing the restraining stress reduces the fracture toughness of A588 steel significantly.

FRACTURE TOUGHNESS RESULTS (A7)

Number of damage-repairs (Nr)Number of damage-repairs (Nr)

Number of damage-repairs (Nr)

0.00

0.25

0.50

0.75

1.00

1.25

1.50

1.75

2.00

2.25

0 1 3 5 0 1 3 5Fra

ctu

re T

ough

nes

s/ T

ough

nes

s U

nd

amag

ed A

7

95% high Mean

95% lowMean

95% low

95% high

d = 60y r = 0.25y d = 60y r = 0.40y

0 = undamaged0.00

0.25

0.50

0.75

1.00

1.25

1.50

1.75

2.00

2.25

0 1 3 5 0 1 3 5

Fra

ctu

re T

ough

nes

s/ T

ough

nes

s U

nd

amag

ed A

7

95% high

Mean

95% low

Mean

95% low

95% high

d = 30y r = 0.25y d = 30y r = 0.40y

0 = undamaged

0.00

0.25

0.50

0.75

1.00

1.25

1.50

1.75

2.00

2.25

0 1 3 0 1 3Fra

ctu

re T

ough

nes

s/ T

ough

nes

s U

nd

amag

ed A

7 d = 90y r = 0.25y d = 90y r = 0.40y

95% high

Mean

95% low

Mean

95% low

95% high

0 = undamaged

• Fracture toughness of damaged-repaired specimens analyzed statistically mean toughness and 95% confidence interval (CI) high and low toughness values

• The 95% CI Low, mean, and 95% CI high toughness values of the damaged-repaired specimens were normalized with respect to the undamaged mean toughness of the corresponding steel.

• The normalized fracture toughness values for the damaged-repaired specimens are shown and the effects of parameters d, r, and Nr are evaluated.

CONCLUSIONS – A7 TOUGHNESS

• The fracture toughness of A7 steel decreases with an increase in r and Nr and with a decrease d.

• The fracture toughness of steels damaged to 30y reduces to 50% of the undamaged toughness after three damage-repairs.

• The fracture toughness of specimens damaged to 60y and repaired with 0.25y is excellent. However, increasing r has a significant adverse effect on the fracture toughness.

• The fracture toughness of specimens damaged to 90y is close to the undamaged toughness after three damage-repair cycles.

• Based on the changes in fracture toughness and ductility (% elongation), it is recommended that A36 and A7 steel beams should be limited to three damage-heat straightening repair cycles. Smaller damage strains are more detrimental to A36 and A7 steel as compared to larger damage strains.

• A588 steel is an extremely resilient material that can be subjected to several (up to five) damage-repair cycles without significant adverse effects on the structural properties, ductility, and, fracture toughness.

• Lower restraining stresses should be used preferably.

RECOMMENDATIONS

ACKNOWLEDGEMENTS

• Conducted within the Department of Civil and Environmental Engineering at Michigan State University.

• Funded by the Michigan Department of Transportation. The MDOT program manager and the research advisory panel are acknowledged for their help and support.

– Roger Till (Program Manager)

– Christopher Idusuyi (Bridge Maintenance)

– Corey Rogers (Bridge Maintenance)

– Steve Cook (MDOT Engineer)

– Steve Beck (MDOT Engineer)

• Significant contribution was provided at MSU by the following:

– Jason Shingledecker (MSU Undergraduate Student)

– Siavosh Ravanbakhsh (MSU Civil Engineering Lab Manager)

– Sig Langenberg (Langenberg Machine Products)

QUESTIONS

RELEVANT EXPERIMENTAL TESTS

• Avent et al. conducted experimental investigations to determine the effects of one damage-heat straightening repair cycle on the structural properties of ASTM A36 steel plate specimens.

–The plates were damaged by bending about the major axis and repaired using Vee heat patterns.

–The experimental results indicated that (a) the elastic modulus decreases by up to 30%, (b) the yield stress increases by up to 20%, (c) the ultimate stress increases by up to 10%, and (d) the % elongation decreases by up to 30%.

• Avent et al. also conducted experimental investigations on four W6x9 beams made from A36 steel by subjecting them to 1, 2, 4, and 8 damage-heat straightening repair cycles.

–The experimental results indicated similar relationships as for the plate specimens.

65

321

4

section at End A and B

3.25in.3.25in.Cross

0.394

1, 4

0.394

2, 5

0.394

3, 6

0.750

X0.750

Y0.44 in.

65

321

4

section at End A and B

3.25in.3.25in.3.25in.3.25in.3.25in.Cross

0.394

1, 4

0.394

2, 5

0.394

3, 6

0.750

X0.750

Y0.44 in.

65

321

4

X Y

5.0

in.

2.16

5 in

. 2.

165

in.

0.75 0.75

0.394 0.394 0.394

0.394 0.394 0.394

8.0

in.

End B

End A

65

321

4

X Y

5.0

in.

2.16

5 in

. 2.

165

in.

0.75 0.75

0.394 0.394 0.394

0.394 0.394 0.394

8.0

in.

65

321

4

X Y

5.0

in.

2.16

5 in

. 2.

165

in.

0.75 0.75

0.394 0.394 0.394

0.394 0.394 0.394

8.0

in.

End B

End A

MATERIAL COUPONS FROM TEST AREAS(A7 Specimens)

Charpy Specimens

Tensile Coupons

65

321

4

X Y

5.0

in.

2.16

5 in

. 2.

165

in.

0.75 0.75

0.394 0.394 0.394

0.394 0.394 0.394

8.0

in.

End B

End A

65

321

4

X Y

5.0

in.

2.16

5 in

. 2.

165

in.

0.75 0.75

0.394 0.394 0.394

0.394 0.394 0.394

8.0

in.

65

321

4

X Y

5.0

in.

2.16

5 in

. 2.

165

in.

0.75 0.75

0.394 0.394 0.394

0.394 0.394 0.394

8.0

in.

End B

End A

0.45 in

3.25 in.