59945777-xiii-2386-11-iiw fatigue 2011
TRANSCRIPT
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Delegation of Japan
IIW-DOCUMENT XIII–2386-11
2011 REPORT OF WORK IN PROGRESS
ON FATIGUE STRENGTH OF WELDED JOINTS IN JAPAN
by Chitoshi MIKI
Department of Civil Engineering, Tokyo Institute of Technology
2-12-1, Ookayama, Meguro-ku, Tokyo, Japan
Takeshi MORI
Department of Civil and Environmental Engineering, Hosei University
3-7-2, Kajino-cho, Koganei-shi, Tokyo, Japan
Shozo NAKAMURA
Department of Civil Engineering, Nagasaki University
1-14, Bunkyo-machi, Nagasaki, Japan
Abstract
A survey of works in progress on the fatigue strength of welded joints in Japan was conductedon the basis of replies to a questionnaire distributed to the researchers majoring in fatigue of
welded joints as well as the members of Commission XIII of the Japanese Institute of
Welding and Fatigue Strength Committee of the Japan Welding Society. Three researches on
low cycle fatigue, five on high cycle fatigue, three on fatigue crack propagation, and five on
fatigue strength improvement and repair are included in this report.
Paper presented at Commission XIII
International Institute of Welding
17 July – 22 July 2011, Chennai, India
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1. LOW CYCLE FATIGUE
(1) Fatigue Strength Assessment of Load Carrying Cruciform Joints Based on Effective Notch StrainApproach
C. Miki, S. Kawin and T. Hanji (Tokyo Institute of Technology)
(Contact Address: Chitoshi MIKI / E-mail [email protected])
Keywords: Load carrying cruciform joints, incomplete penetration, strength mis-matching, local strain approach
The incomplete penetration and strength mis-matching are important issues to assess low and high
cycle fatigue resistance of load carrying cruciform joints. This research is aimed to evaluate the fatigue
strength focusing on the governing parameters, incomplete penetration and strength mis- matching,
using elasto-plastic analysis and effective notch concept.
Low and high cycle fatigue test have been carried out for load carrying cruciform joints. Elasto-plastic
analysis has been performed on analysis models which were built based on geometry of joint
specimens. Effective notch concept is assigned in the analysis models. Local strains along the notch of
the failure location were selected and plot against fatigue life. Unique curve can be obtained from the
local strain-fatigue life data.
Fig.1 Load-carrying cruciform joint containing incomplete penetration.
Cyclic load-
Incomplete penetration
Beam Load-carrying cruciform welded joint
Column
101
102
103
104
105
106
10710
-4
10-3
10-2
10-1
IidaMiki
Δ ε e f f
Fatigue life
Toe failure specimen
P100-O45
P100-O25-a
P100-O25-b
P100-O25-c
P100-U10
P100-U20
P100-U25
P60-O45
P60-O25-b
P60-O25-c
P50-O25-a
P50-U25
P25-O25-a
P25-U25P50-O25-a
P25-O25-a
Fig.2 Relation between local strain and fatigue life
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(2) Improvement in Low Cycle Fatigue Strength of Steel Bridge Piers by Weld Toe Grinding
T. Hanji, N. Nagamatsu and K. Tateishi (Nagoya University)
(Contact Address: Takeshi HANJI / E-mail [email protected])
Keywords: low cycle fatigue, weld toe treatment, fatigue strength improvement
This study investigated the effect of the weld toe grinding technique on the low cycle fatigue strength
of the steel bridge pier. The steel pier specimens, of which weld toe at the connection between columnand base plate was finished by grinding, were tested by applying large cyclic displacement. After
comparing the fatigue strength of the specimen in the condition of as-welded and finished toe, it was
revealed that the weld toe grinding can improve the fatigue strength of the steel pier even in low cycle
fatigue region. Then, local strains around finished weld toe were analyzed by finite element method.
The analysis results demonstrated that the local strain at as-welded toe was significantly reduced by
grinding.
Testing system Low cycle fatigue test results
1 100.001
0.01
0.1
Number of Cycles
N o m i n a l S t r a i n A m p l i t u d e
As–welded specimen
: P1I: P1C6: P1C3: P2C6
Finished specimen
: P1I: P1C6: P1C3: P2C6
Specimen
Cyclic large displacement
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(3) Influences of Plate Thickness on Low Cycle Fatigue Strength at Weld Toes of Cruciform WeldedJoints
K. Kinoshita and K. Ueda (Gifu University)
(Contact Address: Koji KINOSHITA/E-mail [email protected])
Keywords: low cycle fatigue strength, influences of plate thickness, cruciform welded joints
The influences of plate thickness ranging from 25mm to 40mm on low cycle fatigue strength at weldtoes of cruciform welded joints were investigated by bending fatigue tests under large plastic strain,
and its elasto-plastic FEM analysis. It was found that low cycle fatigue strength decrease with
increasing of plate thickness due to increases of local strain at weld toes by increasing plate thickness.
Moreover, the decreases of low cycle fatigue strength were evaluated based on increases of local strain
at weld toes obtained from elasto-plastic FEM analyses.
Cruciform welded joint specimenand its set-up FEM model
Low cycle fatigue strength
Evaluation of decreases of low cycle fatiguestrength based on local strain
Jack Jig
Specimen
450mm
Roller Roller
Jack Jig
Specimen
450mm
Roller Roller
Cyclic loading
0 1 2(mm)0 50 100(mm)
0.05mm
0.05mm
Minimum mesh size
0.01
0.1
1 10 100
N o m i n a l s t r a i n a m p l i t u d e
Number of cycles
25A-5%-1 25A-5%-2 25A-5%-3
25A-5%-4 40A-5%-1 40A-5%-2
40A-5%-3 40A-5%-4
Average 10.50Average 6.50
decrease by 40%
0.5
0.6
0.7
0.8
0.9
1
25 30 35 40 45
N t /
N t 2 5
Plate thickness (mm)
Fatigue test
resultsEvaluation based
on local strain
Influence of plate
thickness in high
cycle fa tigue region
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2. HIGH CYCLE FATIGUE
(1) Fatigue Strength Evaluation Method for Out-of-Plane Gusset Welded Joints Failing from WeldRoot
T. Mori (Hosei University)
(Contact Address: Takeshi MORI /Email [email protected])
Keywords: Out-of-Plane Gusset Welded Joint, Root Failure, Fatigue Strength, Hot Spot StressFatigue crack origin of out-of-plane gusset welded joints is usually weld toe with high stress concen-
tration caused by geometrical discontinuities. However, in the case of finishing weld with small weld
leg length,the stress concentration at weld root becomes higher compared with that at the toe, and
weld root may be an originating point of a fatigue failure. The fatigue strength evaluation method for
the out-of-plane gusset welded joints failing from weld root has not been made clear. In this study,
fatigue strength evaluation method for out-of-plane welded joints failing from the weld root has been
proposed using hot spot stress range through arrangement of existing fatigue test data and FEM ana-
lyses.
105
106
107
50
60
708090
100
200
300
400
500
N
o m i n a l S t r e s s R a n g e o n M a i n P l a t e ⊿ σ ( N / m
m 2 )
Fatigue Life (cycles)
12−14−912−10.8−8.230−16−412−12−10
12−13−9
10−
13−
1010−18−12
JSSC−G
JSSC−E
12−
12−
10
JSSC−F
A-B-C A: main plate thickness B: weld leg length on main plate sideC: weld leg length on gusset plate side
Root Failure
Hot spot
Hot spot
How to obtain hot spot stress
Finite element model
105
106
107
50
60
708090
100
200
300
400
500
H o t S p o t S t r e s s R a n g e a t W e l d R o o t ( N / m m
2 )
Fatigue Life (cycles)
12−
17−
812−14−9
12−10.8−8.212−12−10 30−16−412−13−9
5−
13−
105−18−12
JSSC−E
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(2) Fatigue Test of Misaligned Butt Welded Joints in the Bottom Flange of a Plate Girder Bridge
M. Sakano, D. Yamaoka and K. Funayama (Kansai University)
(Contact Address: Masahiro SAKANO / E-mail: [email protected])
Keywords: misalignment, butt weld, fatigue test, fatigue strength, taper, toe grinding
In the case of the plate thickness is 50mm or less, Japanese specifications for highway and railway
bridges stipulate that the misalignment of plate thickness of butt welded joints should be 10% or lessof the thinner plate thickness. In this study, we investigated the fatigue strength of butt welded joints
with 10% or more misalignment of the plate thickness, through fatigue tests using 3 steel girder spe-
cimens that have 0mm (0%), 2mm (18%) and 4mm (36%) misaligned butt welded joints in the 11mm
thick bottom flange. In addition, the effects of taper grinding and toe grinding are investigated against
those misaligned butt welded joints.
(3) Fatigue Test of Floor Beam and Stringers in an Old Deck Truss Bridge Repaired by Welded Steel
Plates
M. Sakano, T. Mizuno (Kansai University), Y. Natsuaki (Japan Bridge Association)
And K. Masuda (Ministry of Land, Infrastructure and Transport)
(Contact Address: Masahiro SAKANO / E-mail: [email protected])
Keywords: deck truss bridge, floor beam, stringer , fillet weld , fatigue strength
An 85 year old deck truss bridge has a lot of bullet wounded members repaired by welded steel plates.
In this study, their fatigue strength and cracking behaviour is investigated by fatigue tests using I beam
specimens modeled on their stringers and a floor beam wounded and repaired by welded steel plates.
Figure 1.The configurations and dimensions of the specimen
Figure.1 Configurations and dimensions of the specimen
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(4) Evaluation of Scatter in Fatigue Life of Welded Joints by Fracture Mechanics
K. Tateishi, M. Yoshida and T. Hanji (Nagoya University)
(Contact Address: Kazuo TATEISHI / E-mail [email protected]
Keywords: fatigue strength, fracture mechanics, welded joints, Monte-Carlo simulation
In this study, an evaluation method for the scatter in fatigue life of welded joints was developed by
applying linear elastic fracture mechanics and Monte-Carlo simulation technique. Fatigue crack prop-agation analysis, of which initial conditions were determined by the Monte-Carlo simulation, was
performed on non-load-carrying cruciform welded joints and out-of-plane gusset welded joints. It is
demonstrated that the estimated fatigue life by the proposed method distributes around the similar re-
gion as the fatigue test data. Consequently, the results indicate the possibility that the fatigue strength
curves of welded joints can be established by incorporating a small number of fatigue test data with
the proposed method.
Non-load-carrying cruciform welded joints Out-of-plane gusset welded joints
Simulation results and fatigue test data
10
100
1000
1.E+03 1.E+04 1.E+05 1.E+06 1.E+07 1.E+08 1.E+09
Fatigue Life N
S t r e s s
R a n g e
⊿ σ
1000
Fatigue Life (cycles)
105
100
Test Data
106 107 108 109104103
Fatigue crack
(Failure)
Median
Simulation
2.5% 2.5%
meanmean-2s.d.
JSSC-G S t r e s s R a n g e
Δ σ
( M
P a )
1010
100
1000
1.E+04 1.E+05 1.E+06 1.E+07 1.E+08 1.E+09
Fatigue Life N
S t r e s s
R a n g e
⊿ σ
1000
100
S t r e s s R a n g e
Δ σ
( M
P a )
Median
Simulation
2.5%
Fatigue crack
105 106 107 108 109104
Test Data
(Failure)
2.5%
JSSC-E
mean-2s.d. mean
Fatigue Life (cycles)
10
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(5) Fatigue Strength Evaluation Method for Welded Joints by New Local Stress Concept
K. Tateishi, W. Naruse, T. Hanji and I. Itoh (Nagoya University)
(Contact Address: Kazuo TATEISHI / E-mail [email protected]
Keywords: local stress approach, stress concentration, weld toe geometry, fatigue assessment
This study proposed a simple method for estimating local stresses in as-welded joints and established a
fatigue assessment method by using the estimated local stress. In this method, the local stress at theas-welded toe is calculated from the stress at the weld toe finished by the grinding technique, where
the stress can be measured by strain gauges. Fatigue tests and finite element analyses were conducted
with out-of-plane gusset welded joints under the as-welded and the finished condition. Based on the
results, the correlation of the local stress in the as-welded and finished joints was established. The
proposed local stress estimation formula for out-of-plane gusset welded joints is given as follows. It
was concluded that the fatigue strength of the as-welded joints can be evaluated by using the local
stress estimated by the proposed method with the stress measured at the finished toe.
σ l,aw= K t,aw
K t,g ×σ l,g .
.
..
..
.×σ l,g where, . .
σ l,aw is the local stress at the as-welded toe, σ l,g is the stress at the finished toe, K t,aw and K t,g are the
stress concentration factors in the as-welded and the finished joints, r aw and θ are toe radius and flank
angle in the as-welded joint, r g and d are groove radius and groove depth in the finished joint, t is main
plate thickness, h is weld size, and W is the sum of the plate thickness and weld size (= t +h).
Fatigue test results
104
105
106
107
100
1000
Number of Cycles
L o c a l S t r e s s R a n g e
( M P a )
JSSC–A
: As–welded joint
500
2000
50
: Finished joint
B
C
D
E
F
G
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3. FATIGUE CRACK PROPAGATION
(1) Fatigue Crack Growth Behaviour of A5083 Series Aluminium Alloys and Their Welded Joints
K. Gotoh, K. Murakami and Y. Noda (Kyushu University)
(Contact address: Koji GOTOH / E-mail: [email protected])
Keywords: Fatigue, Aluminium alloy A5083, RPG stress, Numerical simulation of fatigue crack
growthWe investigated the difference in fatigue behaviour between the aluminium alloys A5083-O and
A5083-H321 because they are used as structural components in ships and high speed craft. We ob-
tained S-N curves for the base materials and the welded joints made of A5083-O. The relationship
between the fatigue crack propagation rates and the stress intensity factor ranges Δ K , Δ K eff and Δ K RPG
was determined by applying the centre cracked tensile specimens.
Additionally, the evolution of fatigue crack growth for the base materials and the welded joints (cru-
ciform joints) made of A5083-O was measured. We also carried out numerical simulations of fatigue
crack growth for both base metals and their welded joints made of A5083-O. The difference in fatigue
crack growth behaviour for each alloy and the validity of the numerical simulations of fatigue crack
growth based on the RPG stress criterion proposed by Toyosada et al. in the base materials and their
welded joints was investigated.
Figure 1 Relationship between Δ K/E , Δ K eff /E and
Δ K RPG /E as well as the fatigue crack propagationrate for the A5083-O and A5083-H321 materials.
Figure 2 Comparison between the estimated fati-
gue crack growth curves and the measured curves.
10-6
10-5
10-4
10-3
10-2
10-11
10-10
10-9
10-8
10-7
10-6
F a t i g u e c r a c k
p r o p a g a t i o n r a t e : d a / d N
[ m / c y c l e ]
: O1: O2: O3 : H4
: H3: H2: H1
ΔKRPG / E [m1/2
]
: R=0.05
: R=0.3
: R=0.5
: R=0.05 (ΔKth test)
A5083-O, H321
Mild steel (SM400B)
0 2 4 6 8 100
0.1
0.2
0.3
Number of cycles: N [x105]
D i m e n s
i o n l e s s c r a c k l e n g t h : a / t
Specimen N1
Maximum load: 94.1 kNMinimum load: 47.1 kN
Curve: EstimationMark: Measurements
Fatigue crack initiation
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(2) Fatigue Crack Propagation Behaviour of Through-Thickness Crack Subjected to Out-of-PlaneBending
K. Tateishi and X. Ju (Nagoya University)
(Contact Address: Kazuo TATEISHI / E-mail [email protected])
Keywords: through-thickness crack, out-of-plane bending, crack growth rate, stress intensity
factorExperimental and numerical studies were performed on a through-thickness cracked plate to clarify
the fatigue crack propagation behaviour under out-of-plane bending. In the test, alternating loads were
applied to the specimen. It was found that the crack propagates ununiformly in the thickness direction,
forming the symmetric V shape in the fracture surface. The stress intensity factor along the crack front
was calculated by finite element analysis and correlated with the fatigue crack growth rate measured
on the specimen surfaces. Based on the results, the relationship between the stress intensity factor and
the crack growth rate under out-of-plane bending was obtained.
Specimen and loading device Crack growth rate versus stress intensity factor range
Fracture surface
1 . 0 E - 0 5
1 . 0 E - 0 4
10 100
C r a c k g r o w t h r a t e o n s u r f a c e :
d a / d N ( m m / c y c l e )
Stress intensity factor range: (MPa·m1/2)
Notch BoltRoller
Cyclic bending
Specimen
t=15
110 110
1 5 0
160
8
0.2
Unit: mm
Fix
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(3) Retardation of Fatigue Crack Propagation in Welded Joints under Plate Bending by HardeningMaterial Injection
K. Tateishi, R. Tsuboi and T. Hanji (Nagoya University)
(Contact Address: Kazuo TATEISHI / E-mail [email protected])
Keywords: fatigue crack, crack growth retardation, hardening material injection, crack opening dis-
placement A simple repair method for fatigue cracks in steel bridge members was proposed in this study. This
method can retard or arrest the crack growth by injecting hardening material into the crack to restrain
its closure. To verify the applicability of the proposed method, fatigue tests under plate bending were
conducted on out-of-plane gusset welded joints. It was indicated that the effect of the crack growth
retardation depends on when injecting the hardening material into the crack, and that the proposed
method can extend the fatigue life of the cracked welded joints regardless of the stress ratio.
Crack length versus number of cycles Nominal stress range versus fatigue life
0 1 2 3 4 50
50
100
150
Number of Cycles after Initiation (×10 )
C r a c k L e n g t h ( m m )
: No injection
6
Min. stress : 0MPa
: Injection at 80MPa
: Injection at 0MPa
Injecting hardening material
Injecting hardening material
Stress ratio : 0
Max. stress : 80MPa
105
106
107
10
100
Number of Cycles
N o m i n a l S t r e s s R a n g e
( M P a )
JSSC–C
: R=0
50
Repaired joint
: R=0
Non–repaired joint
D
E
F
G
H
: R=–1
: R=–∞ : R=–∞
: R=–1
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4. FATIGUE STRENGTH IMPROVEMENT AND REPAIR(1) Fatigue Strength Improvement by Hammer Peening Treatment under Variable Amplitude Load-
ing
C. Miki, M. Tai and K. Suzuki (Tokyo Institute of Technology)
(Contact Address: Chitoshi MIKI / E-mail [email protected])
Keywords: variable amplitude loading, peening, compressive residual stress, fatigue strength
improvement
Hammer peening treatment which introduces compressive residual stresses has been studied. The
purpose of this research is to clarify the improvement effect of fatigue strength under variable
amplitude loading (hereafter VAL).
The joint specimen with out-of-plane gusset plate is used. VAL follows the weibull distribution which
simulates the actual loading amplitude distribution. In this research, two stress patterns, where one has
constant maximum stress, called “Down”, and another has constant minimum stress, called “Up”, are
applied. Toe conditions are as-weld, cleaning and CP. Cleaning is the pre-treatment for peening using
small radius burr grinder (r=3mm) to remove undercut, and CP is the combined treatment of cleaning
and peening.
When using modified Miner’s rule for evaluating equivalent stress range, for as-weld and cleaning,
both fatigue lives under VAL are longer than those under constant amplitude loading (hereafter CAL).However, in the case of CP, fatigue life is extremely short compared to CAL. In other words, the
improvement effect under VAL is much less than that under CAL.
(a) Down (b) UpFig.2 Examples of stress pattern
Fig.1 Test Specimen
Fig.3 Test results
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(2) Influence of Steel Static Strength on Fatigue Strength Improvement of Out-of Plane GussetWelded Joints by UIT
T. Mori (Hosei University), H. Shimanuki and M. Tanaka (Nippon Steel)
(Contact Address: Takeshi MORI / Email [email protected])
Keywords: Fatigue Strength, Out-of-Plane Gusset welded Joint, UIT, Static Strength of Steel
It has been confirmed through a lot of experimental researches that UIT (Ultrasonic Impact Treatment)gives excellent improving effect on fatigue strength of welded joints. Main factor to increase the fati-
gue strength is considered to be introduction of compressive residual stress. It is expected to be able to
introduce higher compressive residual stress and realize further improvement of fatigue strength by
increasing the static strength of steel used.
The purpose of the present study is to clarify the influence of static strength on the fatigue strength of
out-of-plane gusset welded joints with UIT. For this purpose, the fatigue tests on SBHS700 steel (yield
stress higher than 700N/mm2) specimens have been performed under constant amplitude stress and
maximum stress being constant, and their results are compared with test results of SBHS500 steel
(yield stress higher than 500N/mm2) specimens.
Appearances of Weld Beads
x
0 2 4 6 8 10−800
−600
−400
−200
0
200
400
AW(SBHS700)
UIT(SBHS700)
Distance from weld toe x (mm)
R s i d u a l s t r e s s ( N / m m
2 )
AW(SBHS500)
UIT(SBHS500)
Specimen
Residual Stress Distribution
Fatigue Tests Results
105
106
107
40
50
60708090
100
200
300
400
500
SBHS700
SBHS500
Fatigue Life N (cycles)
S r e s s R a n g e ⊿ σ (
N / m m
2 )
As−
Welded Specimens(AW Specimens)
105
106
107
40
50
60708090
100
200
300
400
500
UIT (SBHS700)
UIT (SBHS500)
Fatigue Life N (cycles)
S t r e s s R a n g e ⊿ σ ( N m m 2 )
AW試験体
UIT Specimens
(maximum stress:352N/mm2
)
105
106
107
40
50
60708090
100
200
300
400
500
UIT (SBHS700)
UIT (SBHS500)
Fatigue Life N (cycle)
S t r e s s R a n g e ⊿ σ ( N m m 2 )
AW試験体
UIT Specimens
(maximum stress: 300N/mm2)
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(3) Influence of Grinding Depth on Fatigue Strength of Out-of-Plane Gusset Welded Joints
T. Mori (Hosei University)
(Contact Address: Takeshi MORI / Email [email protected])
Keywords: Fatigue Strength, Out-of-Plane Gusset welded Joint, Finishing Weld Toe, Grinding
Depth
Finishing the weld toe by burr grinder is usually used for improving the fatigue strength of welded joints because it makes weld toe profile smooth and decreases stress concentration there. In order to
get the certain effect by this method, the toe must be finished so that as-welded toe line does not
remain. In this case, weld toe is prone to be grinded to some depth. When the depth is large, the
fatigue strength is considered to be low, so the limit of depth is specified to 1mm in the IIW
Recommendations and 0.5mm in the Japanese Specifications.
In this study, aiming to clarify the influence of grinding depth on fatigue strength of out-of-plane
gusset welded joints with finished weld toe by burr grinder, fatigue tests on model specimens and
FEM analyses have been performed.
Specimen Weld toe radius Grinding depth SCF
AW (as-welded) 1.1mm ‐ 4.13
3RS 3.4mm 0.14mm 2.77
3RD 3.9mm 0.48mm 2.73
5RS 5.2mm 0.14mm 2.40
5RD 5.2mm 0.49mm 2.49
SCF : Stress Concentration Factor
Specimen
Steel: SM40YAYield strength : 418 – 438 N/mm2 Tensile strength : 529-560 N/mm2
Elongation : 21 – 27 %
Type of Specimen
105
106
107
50
100
200
S t r e s
s R a n g e Δ σ ( N / m m
2 )
Fatigue Life N(cycles)
3RS3RD
AW
105
106
107
50
100
200
S t r e s s
R a n g e Δ σ ( N / m m
2 )
Fatigue Life N(cycles)
5RS5RD
AW
3RS
3RD
Fatigue Test Results
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(4) Fatigue Test of Orthotropic Steel Deck Specimen with Trough Ribs Retrofitted by TIG Welding
M. Sakano, D. Yamaoka, K. Asane (Kansai University),
N. Kanjo, H. Sugiyama(Hanshin Expressway Co.)
H. Sakoda, Y. Tanba (Hanshin Expressway Management Technology Center)
(Contact Address: Masahiro SAKANO / E-mail [email protected])
Keywords: orthotropic steel deck, trough rib, fatigue crack, fillet weld, TIG welding
In the orthotropic steel deck with trough ribs, deck plate and ribs are usually connected by the fillet
weld from the only outside of trough ribs. Most of existing structures have those outside fillet welds
with so poor penetration that a number of fatigue cracks developed at the root of fillet welds. In this
study, we try to reproduce bead-propagating cracks, and investigate the effect of repair TIG welding
through fatigue tests using an actual size specimen.
Figure 1. Specimen and Loading position
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0
50
100
150
200
-80 -60 -40 -20 0 20 40
SM490(EBW無し)SM490(B=13mm)SM490(B=4mm)
(5) Fracture Toughness Test with Stop-Hole-Size Core
K. Ono (Osaka University), K. Anami and M. Oikawa (Shibaura Institute of Technology)
(Contact Address: Kengo ANAMI / E-mail )
Keywords: repair and retrofit, fracture toughness, Charpy Test
In order to consider maintenance methods, repair and retrofit, for existing fatigue damaged steel bridge
structures, it is also necessary to obtain information of mechanical and chemical properties of steel ofdamaged members or joints. However, for the aging bridges, it is sometimes difficult to obtain such
kinds of information from design articles. For such case, a sample material might be taken from the
structures, but the sample should be as small as possible. This study examines the use of a core, which
is taken from stop-hole (for prevention of crack propagation) or bolt-hole (for retrofit with splice
plate), for tests of material properties, especially fracture toughness tests (e.g. charpy test). Figure 1
explains the fabrication process of charpy test specimens. Materials tested in this study are 1920~30’s
steel taken from a displaced bridge structure and present steel (JIS-SM490), and present steels
(JIS-SM490 and SM570) are laser welded to test materials to fabricate charpy test specimens. The
parameter of this series of charpy test is the width of test material, B. An example of charpy test results
is shown in Fig.2, and the results indicate the influences of heat input and constraint of plastic
deformation around the notch tip can be eliminated when the width, B is larger than 13mm. The
observation of heat-affected area, measurement of hardness change and a series of FEM analysesregarding to the constraint effect are also carried out in this study.
Core fromstop hole
Fig.1 Fabrication of Charpy Test Specimen
Test material
One side ( B=13)
Another side ( B=13)
One side laser welding isconducted
Temperature (℃)
□ No weld ▲ B=13mm◆ B=4mm
Fig.2 Result of Charpy Test (JIS-SM490)
B
B=4, 9, 13mm
Test-material
laser weldlaser weld