effects of multiple heat straightening repairs on the structural properties and fracture toughness...
TRANSCRIPT
![Page 1: EFFECTS OF MULTIPLE HEAT STRAIGHTENING REPAIRS ON THE STRUCTURAL PROPERTIES AND FRACTURE TOUGHNESS OF BRIDGE STEELS Keith Kowalkowski, Graduate Assistant](https://reader035.vdocument.in/reader035/viewer/2022070418/56649f325503460f94c4e097/html5/thumbnails/1.jpg)
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
![Page 2: EFFECTS OF MULTIPLE HEAT STRAIGHTENING REPAIRS ON THE STRUCTURAL PROPERTIES AND FRACTURE TOUGHNESS OF BRIDGE STEELS Keith Kowalkowski, Graduate Assistant](https://reader035.vdocument.in/reader035/viewer/2022070418/56649f325503460f94c4e097/html5/thumbnails/2.jpg)
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
![Page 3: EFFECTS OF MULTIPLE HEAT STRAIGHTENING REPAIRS ON THE STRUCTURAL PROPERTIES AND FRACTURE TOUGHNESS OF BRIDGE STEELS Keith Kowalkowski, Graduate Assistant](https://reader035.vdocument.in/reader035/viewer/2022070418/56649f325503460f94c4e097/html5/thumbnails/3.jpg)
INTRODUCTION, BACKGROUND, AND TESTING APPROACH
![Page 4: EFFECTS OF MULTIPLE HEAT STRAIGHTENING REPAIRS ON THE STRUCTURAL PROPERTIES AND FRACTURE TOUGHNESS OF BRIDGE STEELS Keith Kowalkowski, Graduate Assistant](https://reader035.vdocument.in/reader035/viewer/2022070418/56649f325503460f94c4e097/html5/thumbnails/4.jpg)
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).
![Page 5: EFFECTS OF MULTIPLE HEAT STRAIGHTENING REPAIRS ON THE STRUCTURAL PROPERTIES AND FRACTURE TOUGHNESS OF BRIDGE STEELS Keith Kowalkowski, Graduate Assistant](https://reader035.vdocument.in/reader035/viewer/2022070418/56649f325503460f94c4e097/html5/thumbnails/5.jpg)
DAMAGE INDUCED TO FASCIA BEAMS
Bottom Flange
![Page 6: EFFECTS OF MULTIPLE HEAT STRAIGHTENING REPAIRS ON THE STRUCTURAL PROPERTIES AND FRACTURE TOUGHNESS OF BRIDGE STEELS Keith Kowalkowski, Graduate Assistant](https://reader035.vdocument.in/reader035/viewer/2022070418/56649f325503460f94c4e097/html5/thumbnails/6.jpg)
HEAT-STRAIGHTENING REPAIR PROCEDUREa) Restraining force apparatus b) Strip heat to web
c) Vee heat to flange d) Several Vee heats to flange
![Page 7: EFFECTS OF MULTIPLE HEAT STRAIGHTENING REPAIRS ON THE STRUCTURAL PROPERTIES AND FRACTURE TOUGHNESS OF BRIDGE STEELS Keith Kowalkowski, Graduate Assistant](https://reader035.vdocument.in/reader035/viewer/2022070418/56649f325503460f94c4e097/html5/thumbnails/7.jpg)
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.
![Page 8: EFFECTS OF MULTIPLE HEAT STRAIGHTENING REPAIRS ON THE STRUCTURAL PROPERTIES AND FRACTURE TOUGHNESS OF BRIDGE STEELS Keith Kowalkowski, Graduate Assistant](https://reader035.vdocument.in/reader035/viewer/2022070418/56649f325503460f94c4e097/html5/thumbnails/8.jpg)
Damage Force (Pd)
TESTING APPROACH
Restraining Force (Pr)
Two methods were considered
(Method 1)
t
![Page 9: EFFECTS OF MULTIPLE HEAT STRAIGHTENING REPAIRS ON THE STRUCTURAL PROPERTIES AND FRACTURE TOUGHNESS OF BRIDGE STEELS Keith Kowalkowski, Graduate Assistant](https://reader035.vdocument.in/reader035/viewer/2022070418/56649f325503460f94c4e097/html5/thumbnails/9.jpg)
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.
![Page 10: EFFECTS OF MULTIPLE HEAT STRAIGHTENING REPAIRS ON THE STRUCTURAL PROPERTIES AND FRACTURE TOUGHNESS OF BRIDGE STEELS Keith Kowalkowski, Graduate Assistant](https://reader035.vdocument.in/reader035/viewer/2022070418/56649f325503460f94c4e097/html5/thumbnails/10.jpg)
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
![Page 11: EFFECTS OF MULTIPLE HEAT STRAIGHTENING REPAIRS ON THE STRUCTURAL PROPERTIES AND FRACTURE TOUGHNESS OF BRIDGE STEELS Keith Kowalkowski, Graduate Assistant](https://reader035.vdocument.in/reader035/viewer/2022070418/56649f325503460f94c4e097/html5/thumbnails/11.jpg)
EXPERIMENTAL INVESTIGATIONS
![Page 12: EFFECTS OF MULTIPLE HEAT STRAIGHTENING REPAIRS ON THE STRUCTURAL PROPERTIES AND FRACTURE TOUGHNESS OF BRIDGE STEELS Keith Kowalkowski, Graduate Assistant](https://reader035.vdocument.in/reader035/viewer/2022070418/56649f325503460f94c4e097/html5/thumbnails/12.jpg)
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
![Page 13: EFFECTS OF MULTIPLE HEAT STRAIGHTENING REPAIRS ON THE STRUCTURAL PROPERTIES AND FRACTURE TOUGHNESS OF BRIDGE STEELS Keith Kowalkowski, Graduate Assistant](https://reader035.vdocument.in/reader035/viewer/2022070418/56649f325503460f94c4e097/html5/thumbnails/13.jpg)
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.
![Page 14: EFFECTS OF MULTIPLE HEAT STRAIGHTENING REPAIRS ON THE STRUCTURAL PROPERTIES AND FRACTURE TOUGHNESS OF BRIDGE STEELS Keith Kowalkowski, Graduate Assistant](https://reader035.vdocument.in/reader035/viewer/2022070418/56649f325503460f94c4e097/html5/thumbnails/14.jpg)
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
![Page 15: EFFECTS OF MULTIPLE HEAT STRAIGHTENING REPAIRS ON THE STRUCTURAL PROPERTIES AND FRACTURE TOUGHNESS OF BRIDGE STEELS Keith Kowalkowski, Graduate Assistant](https://reader035.vdocument.in/reader035/viewer/2022070418/56649f325503460f94c4e097/html5/thumbnails/15.jpg)
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
![Page 16: EFFECTS OF MULTIPLE HEAT STRAIGHTENING REPAIRS ON THE STRUCTURAL PROPERTIES AND FRACTURE TOUGHNESS OF BRIDGE STEELS Keith Kowalkowski, Graduate Assistant](https://reader035.vdocument.in/reader035/viewer/2022070418/56649f325503460f94c4e097/html5/thumbnails/16.jpg)
TEST SETUP
Top Beam
Bottom Beam
Concrete Blocks
Test Specimen
Hydraulic Actuator
Split-flow valve
Electric Pump
Needle ValvePressure Gage
![Page 17: EFFECTS OF MULTIPLE HEAT STRAIGHTENING REPAIRS ON THE STRUCTURAL PROPERTIES AND FRACTURE TOUGHNESS OF BRIDGE STEELS Keith Kowalkowski, Graduate Assistant](https://reader035.vdocument.in/reader035/viewer/2022070418/56649f325503460f94c4e097/html5/thumbnails/17.jpg)
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
![Page 18: EFFECTS OF MULTIPLE HEAT STRAIGHTENING REPAIRS ON THE STRUCTURAL PROPERTIES AND FRACTURE TOUGHNESS OF BRIDGE STEELS Keith Kowalkowski, Graduate Assistant](https://reader035.vdocument.in/reader035/viewer/2022070418/56649f325503460f94c4e097/html5/thumbnails/18.jpg)
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)
![Page 19: EFFECTS OF MULTIPLE HEAT STRAIGHTENING REPAIRS ON THE STRUCTURAL PROPERTIES AND FRACTURE TOUGHNESS OF BRIDGE STEELS Keith Kowalkowski, Graduate Assistant](https://reader035.vdocument.in/reader035/viewer/2022070418/56649f325503460f94c4e097/html5/thumbnails/19.jpg)
• 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
![Page 20: EFFECTS OF MULTIPLE HEAT STRAIGHTENING REPAIRS ON THE STRUCTURAL PROPERTIES AND FRACTURE TOUGHNESS OF BRIDGE STEELS Keith Kowalkowski, Graduate Assistant](https://reader035.vdocument.in/reader035/viewer/2022070418/56649f325503460f94c4e097/html5/thumbnails/20.jpg)
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.
![Page 21: EFFECTS OF MULTIPLE HEAT STRAIGHTENING REPAIRS ON THE STRUCTURAL PROPERTIES AND FRACTURE TOUGHNESS OF BRIDGE STEELS Keith Kowalkowski, Graduate Assistant](https://reader035.vdocument.in/reader035/viewer/2022070418/56649f325503460f94c4e097/html5/thumbnails/21.jpg)
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)
![Page 22: EFFECTS OF MULTIPLE HEAT STRAIGHTENING REPAIRS ON THE STRUCTURAL PROPERTIES AND FRACTURE TOUGHNESS OF BRIDGE STEELS Keith Kowalkowski, Graduate Assistant](https://reader035.vdocument.in/reader035/viewer/2022070418/56649f325503460f94c4e097/html5/thumbnails/22.jpg)
REPAIR DESCRIPTION
Applying the Strip Heat Monitoring the Surface Temperature
![Page 23: EFFECTS OF MULTIPLE HEAT STRAIGHTENING REPAIRS ON THE STRUCTURAL PROPERTIES AND FRACTURE TOUGHNESS OF BRIDGE STEELS Keith Kowalkowski, Graduate Assistant](https://reader035.vdocument.in/reader035/viewer/2022070418/56649f325503460f94c4e097/html5/thumbnails/23.jpg)
EXPERIMENTAL RESULTS
![Page 24: EFFECTS OF MULTIPLE HEAT STRAIGHTENING REPAIRS ON THE STRUCTURAL PROPERTIES AND FRACTURE TOUGHNESS OF BRIDGE STEELS Keith Kowalkowski, Graduate Assistant](https://reader035.vdocument.in/reader035/viewer/2022070418/56649f325503460f94c4e097/html5/thumbnails/24.jpg)
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
![Page 25: EFFECTS OF MULTIPLE HEAT STRAIGHTENING REPAIRS ON THE STRUCTURAL PROPERTIES AND FRACTURE TOUGHNESS OF BRIDGE STEELS Keith Kowalkowski, Graduate Assistant](https://reader035.vdocument.in/reader035/viewer/2022070418/56649f325503460f94c4e097/html5/thumbnails/25.jpg)
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
![Page 26: EFFECTS OF MULTIPLE HEAT STRAIGHTENING REPAIRS ON THE STRUCTURAL PROPERTIES AND FRACTURE TOUGHNESS OF BRIDGE STEELS Keith Kowalkowski, Graduate Assistant](https://reader035.vdocument.in/reader035/viewer/2022070418/56649f325503460f94c4e097/html5/thumbnails/26.jpg)
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.
![Page 27: EFFECTS OF MULTIPLE HEAT STRAIGHTENING REPAIRS ON THE STRUCTURAL PROPERTIES AND FRACTURE TOUGHNESS OF BRIDGE STEELS Keith Kowalkowski, Graduate Assistant](https://reader035.vdocument.in/reader035/viewer/2022070418/56649f325503460f94c4e097/html5/thumbnails/27.jpg)
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.
![Page 28: EFFECTS OF MULTIPLE HEAT STRAIGHTENING REPAIRS ON THE STRUCTURAL PROPERTIES AND FRACTURE TOUGHNESS OF BRIDGE STEELS Keith Kowalkowski, Graduate Assistant](https://reader035.vdocument.in/reader035/viewer/2022070418/56649f325503460f94c4e097/html5/thumbnails/28.jpg)
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.
![Page 29: EFFECTS OF MULTIPLE HEAT STRAIGHTENING REPAIRS ON THE STRUCTURAL PROPERTIES AND FRACTURE TOUGHNESS OF BRIDGE STEELS Keith Kowalkowski, Graduate Assistant](https://reader035.vdocument.in/reader035/viewer/2022070418/56649f325503460f94c4e097/html5/thumbnails/29.jpg)
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.
![Page 30: EFFECTS OF MULTIPLE HEAT STRAIGHTENING REPAIRS ON THE STRUCTURAL PROPERTIES AND FRACTURE TOUGHNESS OF BRIDGE STEELS Keith Kowalkowski, Graduate Assistant](https://reader035.vdocument.in/reader035/viewer/2022070418/56649f325503460f94c4e097/html5/thumbnails/30.jpg)
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.
![Page 31: EFFECTS OF MULTIPLE HEAT STRAIGHTENING REPAIRS ON THE STRUCTURAL PROPERTIES AND FRACTURE TOUGHNESS OF BRIDGE STEELS Keith Kowalkowski, Graduate Assistant](https://reader035.vdocument.in/reader035/viewer/2022070418/56649f325503460f94c4e097/html5/thumbnails/31.jpg)
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.
![Page 32: EFFECTS OF MULTIPLE HEAT STRAIGHTENING REPAIRS ON THE STRUCTURAL PROPERTIES AND FRACTURE TOUGHNESS OF BRIDGE STEELS Keith Kowalkowski, Graduate Assistant](https://reader035.vdocument.in/reader035/viewer/2022070418/56649f325503460f94c4e097/html5/thumbnails/32.jpg)
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.
![Page 33: EFFECTS OF MULTIPLE HEAT STRAIGHTENING REPAIRS ON THE STRUCTURAL PROPERTIES AND FRACTURE TOUGHNESS OF BRIDGE STEELS Keith Kowalkowski, Graduate Assistant](https://reader035.vdocument.in/reader035/viewer/2022070418/56649f325503460f94c4e097/html5/thumbnails/33.jpg)
• 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
![Page 34: EFFECTS OF MULTIPLE HEAT STRAIGHTENING REPAIRS ON THE STRUCTURAL PROPERTIES AND FRACTURE TOUGHNESS OF BRIDGE STEELS Keith Kowalkowski, Graduate Assistant](https://reader035.vdocument.in/reader035/viewer/2022070418/56649f325503460f94c4e097/html5/thumbnails/34.jpg)
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)
![Page 35: EFFECTS OF MULTIPLE HEAT STRAIGHTENING REPAIRS ON THE STRUCTURAL PROPERTIES AND FRACTURE TOUGHNESS OF BRIDGE STEELS Keith Kowalkowski, Graduate Assistant](https://reader035.vdocument.in/reader035/viewer/2022070418/56649f325503460f94c4e097/html5/thumbnails/35.jpg)
QUESTIONS
![Page 36: EFFECTS OF MULTIPLE HEAT STRAIGHTENING REPAIRS ON THE STRUCTURAL PROPERTIES AND FRACTURE TOUGHNESS OF BRIDGE STEELS Keith Kowalkowski, Graduate Assistant](https://reader035.vdocument.in/reader035/viewer/2022070418/56649f325503460f94c4e097/html5/thumbnails/36.jpg)
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.
![Page 37: EFFECTS OF MULTIPLE HEAT STRAIGHTENING REPAIRS ON THE STRUCTURAL PROPERTIES AND FRACTURE TOUGHNESS OF BRIDGE STEELS Keith Kowalkowski, Graduate Assistant](https://reader035.vdocument.in/reader035/viewer/2022070418/56649f325503460f94c4e097/html5/thumbnails/37.jpg)
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.