受賞区分：学会誌・学術雑誌による顕彰  受賞国：日本国

受賞区分：国内学会・会議・シンポジウム等の賞  受賞国：日本国

受賞区分：国内学会・会議・シンポジウム等の賞  受賞国：日本国

受賞区分：学会誌・学術雑誌による顕彰  受賞国：日本国

受賞区分：学会誌・学術雑誌による顕彰  受賞国：日本国

受賞区分：学会誌・学術雑誌による顕彰  受賞国：日本国

受賞区分：国内学会・会議・シンポジウム等の賞  受賞国：日本国

受賞区分：学会誌・学術雑誌による顕彰  受賞国：日本国

受賞区分：国内学会・会議・シンポジウム等の賞  受賞国：日本国

受賞区分：国内学会・会議・シンポジウム等の賞  受賞国：日本国

受賞区分：国内学会・会議・シンポジウム等の賞  受賞国：日本国

受賞区分：国内学会・会議・シンポジウム等の賞  受賞国：日本国

受賞区分：学会誌・学術雑誌による顕彰  受賞国：日本国

受賞区分：国内学会・会議・シンポジウム等の賞  受賞国：日本国

記述言語：日本語   掲載種別：研究論文（学術雑誌）  

DOI： 10.11273/jssc.31.123_57

記述言語：英語   掲載種別：研究論文（学術雑誌）  

High-frequency mechanical impact (HFMI) is a user-friendly and efficient mechanical post-weld treatment method, and the achieved fatigue life improvement is statistically proved and is attributed to HFMI-induced compressive residual stresses amongst other effects. Several studies have shown in the past that the process parameters (treatment time and working speed) have an influence on the stress state introduced by the HFMI treatment. Thus far, however, only device-specific quantitative recommendation for the HFMI treatment exists based on the instructions of each HFMI device manufacturer. It is not clear if a certain treatment time for a given intensity leads to optimum results regarding the enhanced fatigue life and the treatment parameters of the several HFMI devices cannot be directly compared with each other. For these reasons, a universal and simple definition of the HFMI treatment’s intensity based on the kinetic energy of the HFMI pin was used to quantitatively correlate the HFMI-induced compressive residual stress with the HFMI-process parameters for two different HFMI devices: pneumatical impact treatment (PIT) and high-frequency impact treatment (HiFIT). To this purpose, data from former studies of HFMI-treated base material and welded specimens are revaluated. It is shown, that the compressive residual stresses show only slight changes after reaching a threshold value of the applied kinetic energy (= 50 to 100 J/mm). This energy-based approach for the quantification of the treatment intensity was also used for a case study with PIT- and HiFIT-treated transverse stiffeners with different treatment intensities (2 J/mm and 7 J/mm). A high influence of the treatment intensity on the residual stress state was determined.

DOI： 10.1007/s40194-024-01812-7

担当区分：筆頭著者,　責任著者   記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）  

Fatigue cracks have been observed in the welded joints of end diaphragms at steel railway trough-girder bridges due to unexpected vertical movement at their supports, which was not anticipated during the design phase. Because this movement is complex and varies for each bridge depending on the damage around the support, effective retrofitting methods against these cracks have not yet been established. In this study, the influence of the vertical movement at the bridge supports on crack propagation at the end diaphragm was investigated through numerical simulation. The results indicated that the relative displacement at the bedplate affected the location of crack initiation and the direction of crack propagation, and that the stress intensity factor tended to gradually decrease after the crack reached a certain length. Furthermore, the repair effect of a hole drilled in the crack tip was numerically investigated. The results showed that the local stress around the hole edge decreases as the length of the repaired crack increases.

担当区分：筆頭著者,　責任著者   記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）  

A survey of works in progress on the fatigue strength of welded joints in Japan was conducted on 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 on fatigue behavior, two on fatigue crack propagation and three on fatigue strength improvement and repair are included in this report.

記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）  

This study developed a tap bolt joint method with tap holes in both plates as a preventive maintenance method against weld root failure in fillet-welded cover plates. The method aims to reduce the relative displacement between two plates, which is the cause of weld root crack. To evaluate the fatigue strength of the joint and the relative displacement of the plates, fatigue tests and finite element analysis were conducted to examine the fundamental characteristics of tap bolt joints. The results showed that the fatigue strength of the tap bolt joint was distributed around the JSSC-E and F strength classes under cyclic tensile axial loads, the JSSC-A class under cyclic compressive axial loads, and was significantly higher than the JSSC-S class under cyclic shear loads. Furthermore, tap bolt joints were installed in fillet-welded sole plates in plate girders, and their effectiveness was examined through fatigue tests and finite element analysis. The results showed that the tap bolt method can extend the fatigue life of the weld root of a sole plate.

記述言語：日本語   掲載種別：研究論文（学術雑誌）  

鋼橋のソールプレート溶接部には疲労き裂の発生例が多く報告されており，過去からき裂発生原因や対策方法が検討されてきた．ただし，従来は事後保全対策の検討が中心であり，これまでのところ実用的な予防保全対策は確立されていない．本研究では，ソールプレート溶接部前面に発生する止端き裂およびルートき裂に着目し，有限要素解析および疲労試験により，ピーニング処理およびタップボルトを用いた予防保全対策の検討を行った．その結果，ソールプレート溶接部に圧縮の変動応力が作用する条件下において，ピーニング処理による止端部の疲労強度改善効果，および，タップボルト工法によるルート部の疲労寿命延伸効果が得られることを明らかにした．

DOI： 10.2208/jscejj.23-00234

記述言語：日本語   掲載種別：研究論文（学術雑誌）  

DOI： 10.11273/jssc.31.121_72

記述言語：日本語   掲載種別：研究論文（学術雑誌）  

DOI： 10.11273/jssc.31.121_115

記述言語：日本語   掲載種別：研究論文（学術雑誌）  

DOI： 10.11532/structcivil.70A.521

記述言語：日本語   掲載種別：研究論文（学術雑誌）  

DOI： 10.11532/structcivil.70A.458

記述言語：英語   掲載種別：研究論文（学術雑誌）  

Numerous studies have been conducted regarding the fatigue strength of longitudinal welded gusset joints. Most studies employed relatively small specimens. Thus, this study aims to evaluate the variation of fatigue life of longitudinal welded gusset joints by using the probabilistic fracture mechanics approach, particularly for larger specimens. Although some studies claimed that lower fatigue strength is found in the thicker main plate specimens, however only a limited number of fatigue test was conducted. A probabilistic approach was employed to conquer the shortfall. In this study, fatigue crack propagation analysis was performed on the main plate thicknesses of 12, 40, and 60 mm to evaluate the effect of main plate thickness on the fatigue life of the joints. Then, a probabilistic approach is given to investigate the variation of fatigue life of the joint. In addition, fatigue tests were carried out to investigate the crack propagation behavior on larger specimens. A significant decrease in fatigue life was observed by the increase of the main plate thickness from 12 to 40 mm, however, no further decrease thereafter. The fatigue strength of longitudinal welded gusset joints with the main plate thickness of 12 mm was appertained to category F in the JSSC design curve. Meanwhile, the fatigue strength of longitudinal welded gusset joints with the main plate thickness of 40 and 60 mm falls into category G in JSSC. This condition was also confirmed by the fatigue test results, where both specimens were classified as category G in JSSC.

DOI： 10.1007/s13296-024-00812-z

担当区分：筆頭著者,　責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

The structural hot-spot stress approach is an effective method for assessing welding details when nominal stress is hard to determine due to geometric or loading complexities. Hot spots can be classified into two types: type “a,” which refers to a weld toe located on a plate surface, and type “b,” denoting one located on a plate edge. Previous studies on type “b” hot spots have mainly focused on in-plane gusset welded joints, and the applicability of type “b” hot-spot S-N curves proposed for in-plane gusset joints in IIW to the other details is not well understood. In this study, fatigue tests were conducted with a load-carrying attachment welded on a plate surface, where a crack occurred from a weld toe on the plate edge. The tests were also numerically simulated using finite element analysis. Upon evaluating the test results through the nominal stress, structural hot-spot stress (4, 8, and 12 mm method), and notch stress approaches, it was found that all the data lie above FAT71 for nominal stress, FAT100 for hot-spot stress, and FAT225 for effective notch stress.

DOI： 10.1007/s40194-024-01724-6

担当区分：責任著者   記述言語：日本語   掲載種別：研究論文（学術雑誌）  

記述言語：日本語   掲載種別：研究論文（学術雑誌）  

記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）  

Root cracks in U-rib to deck welded joints of orthotropic steel decks (OSDs) have been reported, which are two types of fatigue cracks initiating at the weld root that propagate into either the deck plate or the weld bead. For early detection of these internal cracks which may cause road surface damage, screening methods for priority inspection area in areal extent OSDs is needed. Therefore, the authors proposed a method of fatigue damage evaluation by estimating stresses to evaluate root crack initiation and propagation behavior from measurable stresses near the joints, aiming to establish a screening method. This paper examines application of the developed evaluation method for these root cracks in the actual OSDs. Field measurements were conducted in two sections with different trends of crack initiation, and a procedure was proposed to obtain the cumulative fatigue damage ratio from the measurement results and regularly obtained data. In addition, the validity of the developed evaluation method for the crack initiation and propagation direction was verified by comparing with the actual crack situation, and a screening method to select out the priority inspection area was proposed.

記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）  

Steel-concrete composite slab has rational structure consisting of bottom steel plate stiffened with ribs and concrete casted on them. In addition, the composite slab also has advantage in maintenance since there is no concern about concrete spalling. In recent years, replacement of aging slabs has been increasing, and the use of precast composite slabs is being promoted to shorten the construction period on site. When precasting concrete for composite slabs, rational joints thatachieve both strength and workability are required. Conventional bolted joints in bottom steel plate requires scaffolding to access the underside of the slab when fastening bolts and painting after fastening. Construction of scaffolding extends the whole construction period. In this study, two types of the joints that can be constructed from the top of the slab are proposed. Mechanical performance of the joints was investigated through the four-point bending tests. In addition,
evaluation method of yield resistance for each joint was discussed.

記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）  

There have been many reports on fatigue cracks at fillet welded joints of sole plates of steel bridges. When preventive maintenance management of these cracks is conducted, the screening process to determine crack-prone fillet welded joints of sole plates and prioritize to apply the countermeasures to prevent the crack is necessary. In this study, in order to propose a screening method, a method for evaluating the local stress near the fillet welded joint of sole plate based on simple calculations was investigated by finite element analysis (FEA). The results revealed that the local stress at the front fillet welded joint of sole plate is well correlated with the local cross-sectional area of the lower flange and web. Moreover, it was revealed that the horizontal reaction force additionally caused by the movability loss of bearing can affect the local stress at the fillet welded joint of sole plate. Based on these results, a simple equation for evaluating the local stress at the fillet welded joint of sole plate using the local cross-sectional area and horizontal reaction force was proposed.

担当区分：責任著者   記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）  

There are three main connection types, such as welding, bolting, and riveting. Among them, riveted joints are hardly used in current bridge assembly. On the other hand, a large number of old bridges with riveted joints still exist and its proper maintenance are required. In this study, the repair method of riveted joints by re-driving new rivets with an Induction Heating (IH) technique was considered. First, fatigue tests for riveted joints using IH technique were performed. As a result, it has similar fatigue strength to those fabricated in the traditional way. In addition, finite element analysis to simulate the replacement of the rivets under statically applying load (dead load) was performed. The analysis clarified the load-displacement relationship and load re-distribution mechanism of the joint when replacing rivets under static load.

記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）  

Anti-fatigue damage steel, in which the hard and soft phases in the microstructure of the steel are appropriately arranged by controlling the composition and manufacturing process to reduce the crack propagation rate, was developed in past studies. In this study, a steel newly developed with the concept of the existing anti-fatigue damage steel was applied to the main plate of out-of-plane gusset welded joints, and its crack propagation characteristics were clarified by plate bending fatigue tests. The results of the fatigue tests and the discussion using finite element analysis showed that the crack propagation rate of the out-of-plane gusset welded joints using the developed steel tended to be smaller than that using a structural steel conventionally used in steel bridges.

担当区分：責任著者   記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）  

When large cyclic deformations due to excessive external forces, such as those caused by an earthquake, are induced in steel bridge members, Low-cycle fatigue cracks sometimes occur in welded joints due to high strain concentration around the weld. Such cracks can lead to brittle fracture of the member. The low-cycle fatigue strength of steel members, particularly that of welded joints, should be evaluated as efficiently as possible to prevent low-cycle fatigue failure during earthquakes. In this study, as a first step to establish a simple and versatile low-cycle fatigue verification method, finite element analyses were conducted on cruciform joints of various dimensions to investigate a method to determine the local strain amplitude at the weld toe from the nominal strain amplitude by elastic analysis, and an estimation formula was developed.

担当区分：筆頭著者,　責任著者   記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）  

High-Frequency Mechanical Impact (HFMI) treatment is a technique to improve the fatigue strength of welded joints by inducing compressive residual stress. In this study, fatigue tests under variable amplitude loading were conducted on HFMI-treated welded joints to clarify its fatigue strength improvement effect. As a fundamental investigation, multi-stage amplitude block loading, which is a relatively simple waveform among variable amplitude loading, was employed. In addition, the residual stress state due to the HFMI treatment was reproduced by finite element analysis, and the change in the residual stress state around the treated area was confirmed by applying several loading patterns.

記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）  

Around the bridge bearing in steel plate girder bridge, various fatigue cracks have been found at the front fillet welded joint between lower flange and sole plate, such as toe cracks on lower flange or sole plate and root cracks. Therefore, various countermeasures are required for each of these cracks. The purpose of this study is to propose simple fatigue strength improvement methods for weld joints of sole plate. In order to verify the effect of the methods on fatigue strength, fatigue tests were conducted on a girder specimen simulating loss of movability in bearing support. As a result, it was clarified that the peening treatment had a significant improvement on the fatigue strength of the toe cracks, and the tap bolting and resin injection had a large effect on the fatigue strength of the root cracks.

記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）  

In this study, as a simple repair method for fatigue cracks, injecting a corrosion accelerator to retard crack growth was investigated. When the inner surface of a fatigue crack is corroded, corrosion products arrest crack closure. Due to this wedge effect, the crack opening displacement and crack growth rate are reduced. In this study, Nitric acid (HNO3), which has highly corrosive property and low viscosity, was adopted as the corrosion accelerator. Fatigue tests were carried out on compact tension (CT) specimens with various load range, minimum to maximum load ratio, and initial crack length at injection. The corrosion accelerator is injected to the initial crack by the dropper. After the injection, the corrosion reaction inside the crack completed approximately after 24 hours. By producing corrosion products, the strain at crack tip and crack growth rate were significantly reduced. From the test results, the crack growth retardation effect was affected by the crack length at injection and load condition.

記述言語：英語   掲載種別：研究論文（学術雑誌）  

Root cracks initiating from U-rib to deck welded joints of orthotropic steel deck bridges have become a problem for maintenance. Some fatigue strength evaluation methods for root cracks based on local stress criteria have been proposed, such as the effective notch stress method, but these methods cannot evaluate fatigue strength directly from the measurable response values of the structure. In this study, the evaluation method of crack initiation by measurable stresses was investigated by fatigue tests and FE analysis for both deck and bead propagation-type cracks, which are root cracks in U-rib to deck welded joints of orthotropic steel decks. As a result of the study, the relationship between the stress of weld root and the fatigue life was obtained by using the fillet shaped notch stress as the evaluation stress, and the S-N curve for the evaluation stress was proposed. And a method to estimate the evaluation stress of the root from the measurable stresses at four points was proposed. It was confirmed that the error of the proposed estimation method was generally within 10%. As a validation of the estimation method, it was confirmed that the fatigue test results could be properly evaluated.

DOI： 10.1007/s40194-023-01568-6

担当区分：筆頭著者,　責任著者   記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）  

The structural hot-spot stress approach is an effective method for assessing welding details when nominal stress is hard to determine due to geometric or loading complexities. Hot spots can be classified into two types: Type “a”, which refers to a weld toe located on a plate surface, and Type “b”, denoting one located on a plate edge. Previous studies on Type “b” hot-spots have mainly focused on in-plane gusset welded joints, and the applicability of Type “b” hot-spot S-N curves proposed for in-plane gusset joints in IIW to the other details is not well understood. In this study, fatigue tests were conducted with a load-carrying attachment welded on a plate surface, where a crack occurred from a weld toe on the plate edge. The tests were also numerically simulated using finite element analysis. Upon evaluating the test results through the nominal stress, structural hot-spot stress (4, 8, and 12 mm method) and notch stress approaches, it was found that all the data lie above FAT71 for nominal stress, FAT100 for hot-spot stress, and FAT225 for notch stress.

担当区分：責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

Fatigue cracks have been observed from welded joints of end diaphragms at steel railway trough-girder bridges due to vertical movement behavior at their supports that is not expected during the design phase. Since this movement behavior is complicated and varies on each bridge depending on the damage around the support, effective retrofitting methods against the crack have not been established yet. In this study, the influence of the vertical movement tendency at the bridge supports on the crack initiation location and crack propagation behavior at the end diaphragm was investigated through numerical simulation. The result indicated that the relative displacement at the bedplate affected the crack initiation location and crack propagation path, and that the stress intensity factor tended to gradually decrease after propagating a certain length.

DOI： 10.11532/structcivil.69A.558

記述言語：日本語   掲載種別：研究論文（学術雑誌）  

DOI： 10.11532/structcivil.69A.537

記述言語：日本語   掲載種別：研究論文（学術雑誌）  

DOI： 10.11532/structcivil.69A.568

担当区分：責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

Because low-cycle fatigue is one of the failure modes in steel structures during earthquakes, crack growth prediction in the low-cycle fatigue region has become an important factor in the evaluation of the seismic performance of steel structures. This study conducted fatigue crack growth tests with several kinds of structural steels to clarify their crack growth behaviour in the low-cycle fatigue region. These tests employed an elastic compliance technique usually used in the high-cycle fatigue region to determine crack size. Before applying the elastic compliance method to a low-cycle fatigue crack growth test, a correlation between specimen load-line crack-opening elastic compliance and crack size was analytically derived. The test results indicated that crack sizes obtained by the elastic compliance method agree relatively well with those actually measured from images. Moreover, it was revealed that the crack growth rate can be correlated with the cyclic J-integral range calculated by finite element analysis, and that the relationships between the crack growth rate and the cyclic J-integral range are similar regardless of the steel type.

DOI： 10.1007/s13296-022-00677-0

記述言語：日本語   掲載種別：研究論文（学術雑誌）  

本論文は，鋼床版のUリブとデッキプレートの溶接ルートからデッキプレートまたは溶接ビードに進展する疲労き裂に対して，交通規制が不要であり，かつ死荷重が増加しない対策方法を検討したものである．具体的には，Uリブの下フランジを切断・撤去し，Uリブ・デッキプレート溶接部をUリブ内側からも溶接する対策を提案した．まず，構造改変を伴う本対策の実現性の確認として，耐荷性能，溶接の施工性や出来形，アスファルト舗装への影響を検証した．次に，対策前後での着目溶接部周辺の局部応力やき裂先端の応力性状の変化，および他の部位への影響を有限要素解析により確認した．最後に，本対策の疲労耐久性を定点疲労試験により明らかにした．

DOI： 10.2208/jscejj.22-00231

記述言語：日本語   掲載種別：研究論文（学術雑誌）  

鋼橋の疲労き裂の対策として，ストップホール法と高力ボルトによる当て板添接を併用した場合，その疲労耐久性を定量的に評価する手法は確立されていない．本研究では，き裂を模擬したスリットにストップホールを施した鋼板に，高力ボルトにより当て板を添接した試験体に対する疲労試験を実施し，その疲労耐久性を調査した．
試験の結果，ストップホールからの疲労き裂と当て板接合面でのフレッチング疲労き裂の2つの破壊形態が確認され，前者に対して，ストップホール壁の局部応力で整理した疲労強度に対して既往研究の当て板のないストップホールの疲労強度曲線が適用できること，後者は，高力ボルト摩擦接合継手の疲労強度と同程度であることを示した．これらの結果を踏まえ，疲労耐久性を定量的に評価したうえで当て板を設計する考え方を提示した．

DOI： 10.2208/jscejseee.78.3_417

記述言語：日本語   掲載種別：研究論文（学術雑誌）  

記述言語：英語  

Over the last decade, fatigue cracks have been observed at welded joints between U-ribs and deck plates in many orthotropic steel deck bridges in Japan. This paper focuses on fatigue cracks that initiate from a weld root of rib-to-deck welded joints and propagate to a deck plate. This study examines the effect of a countermeasure that uses overlaying Ultra-High Performance Fiber Reinforced cement-based Composites (UHPFRCs) on steel decks with cracks from U-rib welds, and confirms the fatigue durability of this method. Specifically, the retardation of crack propagation and the fatigue durability of the UHPFRC itself as well as the interface between the UHPFRC and the deck plate were confirmed by a wheel running test and finite element analysis. Based on the results, it was clarified that this countermeasure has a positive effect on retarding further crack propagation compared with the method of overlaying steel fiber reinforced concrete, which is generally adopted. In addition, it was revealed that the studied countermeasure has sufficient fatigue durability.

DOI： 10.1007/s13296-022-00660-9

記述言語：日本語   掲載種別：研究論文（学術雑誌）  

本論文は，鋼床版のUリブとデッキプレートの溶接ルートからデッキプレートまたは溶接ビード方向に進展する疲労き裂を対象とし，既報にて構築した疲労評価法の実橋への応用について検討したものである．具体的には，き裂発生数の傾向が異なる2工区において応力計測を実施し，その結果と気温や大型車交通量などの定常的に得られるデータから累積疲労損傷比を求める方法を提案した．また，構築した評価法によるき裂発生有無やき裂進展方向の評価の妥当性について実き裂の状況と比較し検証した上で，重点的に点検，調査する箇所を抽出する方法を提案した．

DOI： 10.2208/jscejseee.78.2_287

記述言語：英語   掲載種別：研究論文（学術雑誌）  

High-Frequency Mechanical Impact (HFMI) is an user-friendly and efficient mechanical post-weld treatment method and the achieved fatigue life improvement is statistically proved. The achieved fatigue life improvement is attributed to HFMI-induced compressive residual stresses amongst other effects. Several studies have shown in the past that the process parameters (treatment intensity and working speed) have an influence on the stress state introduced by the HFMI treatment. Thus far however, only device-specific quantitative recommendation for the HFMI-treatment exists based on the instructions of each HFMI device’s manufacturer. It is not clear, if a certain treatment time for a given intensity leads to optimum results regarding the enhanced fatigue life. Moreover, the treatment parameters of the several HFMI devices cannot be directly compared with each other. For these reasons, a universal and simple definition of the HFMI-treatment’s intensity based on the kinetic energy of the HFMI pin was used to quantitatively correlate the HFMI-induced compressive residual stress with the HFMI-process parameters for two different HFMI devices: Pneumatical Impact Treatment (PIT) and High Frequency Impact Treatment (HiFIT). To this purpose, data from former studies of HFMI-treated base material and welded specimens are revaluated. It is shown, that the compressive residual stresses after reaching a threshold value of the applied kinetic energy show only slight changes. This energy-based approach for the quantification of the treatment intensity was also used for a case study with PIT and HiFIT treated transverse stiffeners with different treatment intensities. A high influence of the treatment intensity on the residual stress state was determined. However, only a slight influence on hardness increase and fatigue strength was shown.

担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）  

In this study, the effect of the stress state of a welded joint during application of high-frequency mechanical impact (HFMI) treatment on the resulting fatigue strength was investigated through fatigue tests and finite element analysis. A high-frequency impact treatment tool was used as the HFMI device. Longitudinal attachment welded joints were treated under a state in which a static load was applied and subsequently tested under a constant stress amplitude with stress ratios of 0 or 0.5. In addition, residual stress measurements and finite element analysis simulating welding and treatment processes were performed. The results indicate that the HFMI treatment is beneficial even when applied under a static tensile load, as the resulting compressive residual stresses are similar regardless of the stress state in the joint during treatment, meaning that the HFMI is applicable to existing structures.

DOI： 10.1201/9781003322641-262

記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）  

This paper examines a fatigue evaluation method for the cracks in the weld joints between a U-rib and a deck plate in orthotropic steel bridge decks. The crack initiates from the weld root and propagates into the deck plate or the weld bead. Fatigue tests and FE analyses were conducted in order to examine the local stresses available for fatigue assessment, and to propose a method to estimate them from some reference stresses around the weld joint. In addition, based on fatigue crack propagation analyses, a method to predict the crack propagation path was proposed.

DOI： 10.1201/9781003322641-263

担当区分：筆頭著者,　責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

There are usually two methods to evaluate the low cycle fatigue strength of a welded joint, namely the local approach and the nominal approach. Previous research has revealed the applicability of the local approach for low cycle fatigue assessment of welded joints, where fatigue cracks were initiated from a weld toe. When calculating the local strain at the weld toe, elasto-plastic finite element analysis using a fine mesh with a resolution of about 0.01 mm is usually employed, but this is not practical because of the tremendous calculation and working costs involved. In this study, finite element analyses were performed for three types of welded joints (cruciform joint, T-joint, and longitudinal attachment joint) with different dimensions, and a simple estimation method for the local elasto-plastic strain amplitude at the weld toe was developed. A feature of this method is that it correlates the local strain amplitude at the weld toe with the elastic strain distribution around the toe obtained by a simple analysis using a relatively coarse mesh. Moreover, the proposed method was verified by low cycle fatigue tests of welded joins.

記述言語：英語   掲載種別：研究論文（学術雑誌）  

Root cracks initiating from U-rib to deck welded joints of orthotropic steel deck bridge have become a road surface travel safety problem. Some fatigue strength evaluation methods for root cracks have been proposed based on local stress criteria, such as effective notch stress method, but these methods cannot be evaluated directly from the measurable response values of the structure. In order to improve the efficiency of maintenance and to predict crack initiation, it is desirable to be able to accurately evaluate fatigue strength based on information obtained from the structure for root crack initiation. This study examines a fatigue strength evaluation method for the cracks in the weld joints between a U-rib and a deck plate in orthotropic steel bridge decks. The crack initiates from the weld root and propagates into the deck plate or the weld bead. Fatigue tests and FE analyses were conducted in order to examine the local stresses available for fatigue strength assessment, and to propose a method to estimate them from some reference stresses around the weld joint.

担当区分：筆頭著者,　責任著者   記述言語：日本語   掲載種別：研究論文（学術雑誌）  

DOI： 10.11532/structcivil.68A.591

記述言語：日本語   掲載種別：研究論文（学術雑誌）  

DOI： 10.11532/structcivil.68A.580

担当区分：筆頭著者,　責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

In this study, a method for predicting residual stress introduced by high-frequency mechanical impact (HFMI) was investigated using kinetic energy of an accelerated indenter. Steel plates of different grades were treated by a high-frequency impact treatment device under different treatment conditions (such as intensity of impact, number of passes, and treatment length). In addition, the motion of the HFMI indenter was recorded using a high-speed camera during the treatment, and a simple calculation method for the kinetic energy applied to steel plates was proposed. The results confirmed that the compressive residual stress introduced to the steel plates correlated closely with the calculated kinetic energy. In addition, experiments demonstrated that the energy-based residual stress prediction is applicable to a longitudinal attachment welded joint with sufficient accuracy.

DOI： 10.1007/s40194-021-01230-z

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.11273/jssc.28.112_111

記述言語：英語   掲載種別：研究論文（学術雑誌）  

Out-of-plane gusset joints are commonly used in welded assembly structures such as bridges. The studies regarding out-of-plane gusset joint often define fatigue life of this joint as the condition when the crack has fully penetrated through the web plate. However, the time frame from crack initiation until reaching complete structural failure is unclear. In this study, extended fatigue crack propagation analysis of out-of-plane gusset joint is performed. The variation of influential parameters such as flank angle, weld toe radius, material constant, and the threshold value of stress intensity factor range was considered. The crack propagation analysis was done until the crack reaches 80% of the lower flange plate of the bridge girder. Since the crack propagation life is highly influenced by traffic conditions, the probability distribution of the number of cycles and the crack width (2b) is presented in regards to the fatigue life ratio. In estimating the failure probability of the joint, the influence of human error to detect cracks during the inspection is considered. Five cases of the probability of crack detection are assumed to represent the capability of the inspector. It was found that bridge inspection and reparation of cracks are important in controlling the failure probability.

DOI： 10.1007/s13296-021-00559-x

担当区分：筆頭著者,　責任著者   記述言語：日本語   掲載種別：研究論文（学術雑誌）  

損傷したリベット継手を補修する場合，リベットを摩擦接合用高力ボルトに取り替える方法が用いられることが多い．一部のリベットを高力ボルトに取り替えた継手では，荷重伝達機構の異なる支圧接合と摩擦接合が共存することになるが，リベットと高力ボルトを併用した継手の力学的挙動は十分に明らかにされていない．そこで本研究では，リベットと高力ボルトの配置パターンの異なる併用継手を用いた引張試験により，併用継手の力学的挙動や限界状態を明らかにした．また，引張試験を再現した有限要素解析により，併用継手内の荷重分担割合や限界状態に至るメカニズムを示した．さらに，併用継手の耐力評価法を示し，得られた結果を基に，その妥当性を検証した．

DOI： 10.2208/jscejseee.77.3_489

担当区分：筆頭著者,　責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

In this study, the effect of the stress state of a welded joint during application of high-frequency mechanical impact (HFMI) treatment on the resulting fatigue strength was investigated through fatigue tests and finite element analysis. A high-frequency impact treatment tool was used as the HFMI device. Longitudinal attachment welded joints were treated under a state in which a static load was applied and subsequently tested under a constant stress amplitude with stress ratios of 0 or 0.5. In addition, residual stress measurements and finite element analysis simulating welding and treatment processes were performed. The results indicate that the HFMI treatment is beneficial even when applied under a static tensile load, as the resulting compressive residual stresses are similar regardless of the stress state in the joint during treatment, meaning that the HFMI is applicable to existing structures.

DOI： 10.1007/s40194-021-01208-x

担当区分：筆頭著者,　責任著者   記述言語：日本語   掲載種別：研究論文（学術雑誌）  

記述言語：英語  

Damping devices such as shear panel damper (SPD) are used to ensure the soundness of the principal elements of a bridge in an earthquake. The SPD is made of low yield point steel, which absorbs seismic energy by its plastic shear deformation. Since SPD is assembled by welding, low cycle fatigue is a concern due to strain concentration at the shear panel-to-flange connection. In this study, the relationship between the weld toe radius of SPD and the low-cycle fatigue life was investigated. To examine the low cycle fatigue life and strain distribution, cyclic loading test was performed. In addition, finite element analysis was performed to investigate the influence of weld toe radius on the local strain range at the weld toe. Low cycle fatigue life was estimated from the local strain range for each weld toe radius. From the results, the effect of toe radius on the low-cycle fatigue life of SPD welded joints was quantified.

記述言語：英語  

Corner plates are often welded to cover web-to-flange joints in box girders which can hold appropriate angle between webs and flanges during construction, and enhance the buckling resistance of the web plate. The corner plates are installed by single-sided welding because circumference of corner plates can only be approached from one side. Since weld root remains in the welded joints of corner plates, many fatigue cracks found out in the weld joints of corner plates. Although the end of corner plates was cut-out and ground smoothly as a countermeasure, fatigue cracks have again occurred from weld root exposed on the cut-out surface. In this study, the fatigue durability of cut-out at corner plate ends was investigated. Fatigue tests on small-scaled specimens were performed. Two types of specimens with different angles at the corner plate ends were tested. As the results, low fatigue durability can be seen regardless of the angle at the corner plate end. In addition, fatigue strength improvement due to peening application at the weld root was investigated. Peening application increased the fatigue strength grade and fatigue limit of the joint.

担当区分：責任著者   記述言語：英語  

In this study, low cycle fatigue crack growth tests with several structural steels were performed, in which compliance method was newly introduced to determine crack size that is a technique usually used in high cycle fatigue region. The test results indicated that the crack size from the compliance method relatively agrees with that from image measurements, and the proposed relationship between the compliance and the crack size was verified. Moreover, it was revealed that the crack growth rate can correlated with the cyclic J-integral range calculated by finite element analysis regardless of the steel types.

記述言語：英語  

Over the last decade, fatigue cracks have been observed at welded joints between U-ribs and deck plates in many orthotropic steel deck bridges in Japan. Among the cracks, this paper focuses on fatigue cracks that initiate from a weld root of rib-to-deck welded joints and propagate to a deck plate. This study examines the effect of countermeasure with overlaying Ultra-High Performance Fiber Reinforced cement-based Composites (UHPFRC) on steel decks with cracks from U-rib welds, and confirms the fatigue durability of this countermeasure method. Specifically, the suppressing effect on crack propagation and the fatigue durability of UHPFRC itself and the interface between UHPFRC and the deck plate were confirmed by a wheel running test and finite element analysis. As a result, it was clarified that this countermeasure has a positive effect to retard further crack propagation compared with a countermeasure with overlaying steel fiber reinforced concrete which is generally adopted. In addition, it was revealed that this countermeasure has enough fatigue durability.

記述言語：英語  

Since orthotropic steel deck is lighter than concrete slab, it has been used for long span bridge and bridge in urban areas. Wheel loads induces the local stress reputation at weld joints between deck plate and vertical stiffener, and large number of fatigue cracks have been generated in their weld joints. In order to reduce the stress concentration, construction of semicircular notch at the top of the vertical stiffener has been suggested. In this study, construction of slit-shaped notch is suggested as enhancement of the stress reduction and retaining crack propagation.
The stress reduction at the weld joint by slit-shaped notch was investigated from finite element (FE) analysis. In addition, the crack with various size was introduced to the weld joint, and reduction in stress intensity factor (SIF) by slit-shaped notch was examined. To confirm the fatigue propagation life extension due to slit-shaped notch, fatigue tests were performed for small-scaled specimens. Fatigue life extension can be seen in most specimen while another crack was developed from the notch in a specimen.

担当区分：責任著者   記述言語：英語  

In riveted bridges, generally, rivets deteriorated with loosening and corrosion are replaced with high-strength friction-type bolts. In this case, both riveted and bolted connections which have different load transfer mechanism coexist in the same joint, however, the mechanical behavior and limit states of the rivet-and-bolt combination joints have not been well investigated yet. In this study, in order to clarify the mechanical behavior and limit states of the combination joints using rivets and bolts, static tensile tests were performed on specimens with different arrangement of rivets and bolts. Moreover, finite element analysis was performed to investigate load transfer mechanism in the combination joints. Based on the experiment and analysis, the evaluation method for the strength of the combination joints was indicated.

担当区分：筆頭著者,　責任著者   記述言語：日本語   掲載種別：研究論文（学術雑誌）  

本研究は，比較的短い段階の疲労き裂に対する補修方法として溶接補修に着目し，交通等による繰返し荷重作用下での溶接割れ発生条件について検討した．繰返し荷重下のスリットに対する溶接施工試験を実施し，溶接過程のルートギャップの開閉挙動を明らかにするとともに，繰返し荷重の大きさや周波数，スリットの拘束の度合いと溶接割れの発生状況を関連付けて整理した．また，熱弾塑性有限要素解析により繰返し荷重下でのスリット溶接を再現し，溶接中のルートギャップ開口変位に影響を与える因子を明らかにした．さらに，実験および解析結果に基づき，溶接前のルートギャップの開口変位と繰返し周波数，スリットの拘束度からなる繰返し荷重下での割れ発生条件式を示した．

DOI： 10.2208/jscejseee.77.2_287

記述言語：日本語   掲載種別：研究論文（学術雑誌）  

本論文は，鋼床版のUリブとデッキプレートの溶接部のルートき裂であるデッキ進展型き裂，ビード進展型き裂の双方を対象に，疲労評価方法について検討したものである．具体的には，疲労試験および有限要素解析により，ルートき裂のき裂発生寿命を評価することができる応力を明らかにするとともに，それを溶接部周辺の参照応力から推定する方法を提案した．また，き裂進展解析によりデッキ進展型き裂，ビード進展型き裂の進展挙動を再現し，いずれのき裂が発生するかを判別する手法を提案した．

DOI： 10.2208/jscejseee.77.2_255

担当区分：筆頭著者,　責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

In this study, the effect of the stress state of a welded joint during application of high-frequency mechanical impact (HFMI) treatment on the resulting fatigue strength was investigated through fatigue tests and finite element analysis. A high-frequency impact treatment tool was used as the HFMI device. Longitudinal attachment welded joints were treated under a state in which a static load was applied and subsequently tested under a constant stress amplitude with stress ratios of 0 or 0.5. The test results indicate that improved fatigue strength can be achieved even under a high stress ratio when the joint is treated under the minimum stress of fatigue loading. In addition, residual stress measurements and finite element analysis simulating welding and treatment processes indicated that the magnitude of compressive residual stress introduced to a weld toe is almost the same regardless of the stress state in the joint during treatment.

担当区分：筆頭著者,　責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

In this study, a method for predicting residual stress introduced by high-frequency mechanical impact (HFMI) was investigated using energetics. Steel plates of different grades were treated by a high-frequency impact treatment device under different treatment conditions (such as intensity of impact, number of passes, and treatment length). In addition, the motion of the HFMI indenter was recorded using a high-speed camera during the treatment, and a simple calculation method for the energy applied to steel plates was proposed. The results confirmed that the compressive residual stress introduced to the steel plates correlated closely with the calculated energy. In addition, experiments demonstrated that the energy-based residual stress prediction is applicable to a longitudinal attachment welded joint with sufficient accuracy.

担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）  

This study investigated the fatigue strength of welded joints in steel-concrete composite slabs by fatigue testing. In addition, the local stress around the welded joint was evaluated through finite element analysis. In the test, fatigue cracks occurred at the toes of boxing welds of angle-shape shear connectors as a result of stress concentration due to the local out-of-plane bending deformation of the steel plates around the boxing weld. This local deformation can be produced by the steel and concrete behaving independent of one another locally near welds when the bond at their interface is lost. The test results demonstrated that the fatigue assessment of welded joints in a composite slab can be performed using the hot-spot stress approach. Then, actual composite slabs with different structural characteristics were analyzed to investigate the local stress behavior around welded joints, and their fatigue performance was assessed based on the hot-spot stress approach.

DOI： 10.1201/9780429279119-365

記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）  

A typical repair method for fatigue cracks in steel bridge members is the splice plate method. The crack tip is drilled out and splice plates are added over the crack. For evaluating the remaining fatigue life of the repaired members, the stress at a drilled crack-arrest hole after the addition of the splice plates with high-strength bolts is required. In this study, the effect of the geometric parameters of the splice plate on stress reduction at a drilled crack-arrest hole is investigated using static loading tests and parametric finite element analyses. Based on the results, a method for predicting the stress at the drilled hole that considers the load-carrying mechanism through the bolted splice plate is proposed. It is demonstrated that the proposed method can predict stress with an error of within 10%.

DOI： 10.1201/9780429279119-478

記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）  

Fatigue cracks have been observed at welded joints between U-ribs and deck plates in many orthotropic steel decks. Considering a fatigue crack at rib-to-deck welded joints can compromise transportation safety, it is necessary to detect and repair the crack at the early development stage.
This paper presents the accuracy of crack sizing with a Phased Array Ultrasonic Testing (PAUT) scanner developed for inspection. Firstly, an internal crack propagating from a weld root was induced at rib-to-deck welded joints by using a plate bending fatigue testing machine. Subsequently, the joints were inspected with the PAUT scanner. Appropriate sizing methods were determined for the deck and weld bead propagation type cracks, respectively, and the accuracy of crack sizing was evaluated. In addition, the influence of coating on the accuracy in crack sizing was examined. As a result, it is demonstrated that the PAUT scanner had enough crack sizing performance.

DOI： 10.1201/9780429279119-540

記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）  

Carbon Fiber Reinforced Polymer (CFRP) composites, consisting of carbon fiber and matrix resin, has high stiffness and tensile strength. Recently, pultrusion method is developed for manufacturing CFRP composites. The bearing type bolted joint is typically adopted for permanent joint of CFRP composites. Due to bearing pressure around bolt hole, fatigue damage can be introduced around bolt hole in a bearing type bolted joint. In this study, fatigue performance of bearing type bolted joint with the pultruded CFRP composite was examined. To observe fatigue crack generation and propagation around bolt hole, tensile fatigue test on pultruded CFRP composites with a circular hole was performed. While fatigue crack was generated from the edge of the hole and propagates in longitudinal direction, the CFRP composites was not ruptured during the test. The fatigue test on a bearing type bolted joint for pultruded CFRP composites was also performed, and its fatigue strength was clarified. Finite element analysis (FEA) simulating multiple layer was constructed. The stress distribution around bolt hole was examined from FEA. The fatigue strength was arranged by maximum principal stress range.

DOI： 10.1201/9780429279119-496

記述言語：英語   掲載種別：研究論文（学術雑誌）  

Low cycle fatigue is a failure mode which is possibly caused by random large strains such as seismic motion. To examine the effects, this study elaborated crack propagation behavior in steel under random amplitude loading. Firstly, study on crack growth rate under constant amplitude conditions was conducted to obtain basic characteristics. Next, several patterns of random amplitude loading were applied. It is discovered that crack growth accelerated when amplitude decreased from high to low levels at tensile portions, compared to that in constant amplitude conditions. Prediction model was constructed with establishing relationship between cyclic J-integral range and crack growth rate and confirmed to give good estimation.

DOI： 10.11532/structcivil.67A.174

記述言語：日本語   掲載種別：研究論文（学術雑誌）  

DOI： 10.11273/jssc.28.109_183

記述言語：日本語   掲載種別：研究論文（学術雑誌）  

DOI： 10.11273/jssc.28.109_155

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.11273/jssc.27.108_93

担当区分：筆頭著者   記述言語：日本語   掲載種別：研究論文（学術雑誌）  

本論文は，鋼床版のUリブとデッキプレートの溶接部から生じる疲労き裂のうち，溶接ルートを起点としてデッキプレートへ進展する疲労き裂を対象として，超高性能繊維補強セメント系複合材料の敷設による疲労対策の効果と，その対策自体の疲労耐久性について検討したものである．具体的には，輪荷重走行試験および有限要素解析により，疲労き裂に対する進展抑制効果，敷設した材料やデッキプレートとの界面の疲労耐久性の確認を行い，一般に用いられる鋼繊維補強コンクリートを敷設する対策と比較して，本対策の有効性を示した．

DOI： 10.2208/jscejseee.76.3_542

担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

During the 2011 Tohoku Earthquake, a truss bridge joint structure was cracked due to large cyclic deformation, making us recognize the importance of assessing the seismic performance of joint structures in truss bridges from the viewpoint of low-cycle fatigue. In this study, seismic response analysis of an actual deck truss bridge was performed under different seismic waves, and local strain behavior generated at welded joints around a joint structure was clarified using a zooming analysis technique. The results revealed the possibility that welded joints for a lateral gusset-plate in a joint structure can be cracking sites during earthquakes. In addition, it was indicated that seismic isolation bearings can significantly reduce the local strain at the joint structure and improve its low-cycle fatigue performance. Moreover, as a simple countermeasure, weld toe treatment by grinding is also effective to decrease the possibility of low-cycle fatigue cracking at the joint structure.

DOI： 10.1007/s13296-020-00399-1

担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.11273/jssc.27.106_75

担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

This study investigated the applicability of low transformation temperature (LTT) arc welding consumables to improve fatigue strength against weld root failure. Transverse attachment joints formed by single-sided welding, similar to rib-to-deck connections in orthotropic steel bridge decks, were fabricated using an LTT welding consumable and conventional welding consumable. Fatigue tests were performed with out-of-plane bending loads using a vibration-type fatigue testing machine. The test results indicated that higher fatigue strength can be achieved in the joint with an LTT consumable compared with a conventional one. In addition, residual stresses around the weld bead were clarified by X-ray diffraction measurements and finite element analyses. The results revealed that the LTT consumable weld metal can reduce residual stress around the weld and also introduce compressive residual stress to the weld root, which can contribute to improved fatigue strength.

DOI： 10.1007/s40194-020-00915-1

担当区分：筆頭著者   記述言語：英語  

The accuracy of Miner's rule has not been verified in an extremely large strain field, corresponding to the fatigue life of less than tens cycles. In this study, low cycle fatigue tests under variable strain amplitude in the extremely large strain field were conducted with a newly developed testing system. The result revealed that the Miner's rule always predicted a longer fatigue life than the observed life. Therefore, this study proposed a simple fatigue assessment model introducing the damage mechanics concept and examined its validity as another method for predicting low cycle fatigue life.

担当区分：筆頭著者   記述言語：日本語   掲載種別：研究論文（学術雑誌）  

本研究では，L形鋼をずれ止めに用いた鋼コンクリート合成床版の溶接継手部の疲労耐久性を実験および有限要素解析により検討した．合成床版試験体に対する静的載荷試験および解析により，L形鋼溶接部周辺では鋼板が局所的に面外変形し，特にまわし溶接部で高い応力集中が生じることを示した．また疲労試験により，コンクリートにひび割れが生じない程度の荷重を繰返し載荷することでL形鋼溶接部から疲労き裂が発生することを明らかにし，その疲労強度をホットスポット応力により安全側に評価できることを示した．さらに，合成床版を有する橋梁を対象とした解析を実施し，溶接継手部に生じる実応力挙動を求め，ホットスポット応力による疲労耐久性評価を試みた．

DOI： 10.2208/jscejseee.76.5_II_50

担当区分：筆頭著者   記述言語：日本語   掲載種別：研究論文（学術雑誌）  

鋼構造物の損傷対策である高力ボルトによる当て板補修において，既設部材との干渉などから，設計基準の規定よりも狭いボルト間隔や縁端距離でボルトを配置せざるを得ないケースがあるが，それによる力学的影響については不明である．本研究では，ボルト配置を現行の基準よりも狭い配置とすることが高力ボルト摩擦接合継手の疲労強度に与える影響を明らかにすることを目的として，疲労試験および有限要素解析を行った．
疲労試験の結果，狭いボルト配置は疲労強度を1等級程度低下させること，特に，はしあきの影響が大きいことが明らかになった．解析では疲労き裂の発生位置近傍に最大の応力集中が確認され，この応力集中係数の比較により疲労強度への影響を相対的に評価できる可能性を示した．さらに，継手形状や材質が疲労強度に与える影響を分析した．

DOI： 10.2208/jscejseee.76.2_212

担当区分：筆頭著者   記述言語：日本語   掲載種別：研究論文（学術雑誌）  

DOI： 10.11532/structcivil.66A.253

担当区分：筆頭著者   記述言語：日本語   掲載種別：研究論文（学術雑誌）  

DOI： 10.11532/structcivil.66A.607

担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

This study examined the low-cycle fatigue behavior of load-carrying cruciform-welded joints containing incomplete penetration. Five types of specimens with different sizes of weld penetrations and weld leg lengths were tested under cyclic plastic strains. During testing, cracking behavior was observed on the side surface of the specimen. The test results revealed that the fatigue strength and cracking patterns depend on the ratio of the weld penetration to the main plate thickness and the ratio of the weld leg length to the 5main plate thickness, respectively. Elasto-plastic finite element analyses including the effective notch concept were then performed. The results indicate that the fatigue strength and cracking pattern of the specimens can be correlated with the local strain distribution around the effective notch.

DOI： 10.1007/s40194-019-00834-w

担当区分：筆頭著者   記述言語：日本語   掲載種別：研究論文（学術雑誌）  

担当区分：筆頭著者   記述言語：日本語   掲載種別：研究論文（学術雑誌）  

近年，引抜成形によるCFRP部材の製造が可能となり，実構造部材レベルのCFRP部材を安定供給できる環境が整備されつつある．しかし，FRP部材の接合に用いられる支圧接合については疲労特性の把握が十分でない．本研究ではCFRP引抜成形部材の有孔平板および二面せん断支圧接合継手を用いて疲労強度の評価を行った．有孔平板試験体では．公称応力範囲約260N/mm2で1000万回載荷後も破断に至らなかったが，円孔の縁から軸方向に沿ったき裂が発生・進展した．支圧接合試験体では，公称応力範囲が約70N/mm2以上のとき，ボルト孔支圧部の局所的な支圧破壊やせん断破壊が発生した．さらに有限要素解析を行いき裂が生じた円孔およびボルト孔周辺のひずみを確認した．円孔付近の最大主ひずみ範囲を用いることでCFRP部材の形状によらず，疲労寿命を評価できる可能性を示した．

担当区分：筆頭著者   記述言語：日本語   掲載種別：研究論文（学術雑誌）  

本研究では，L形鋼をずれ止めに用いた鋼・コンクリート合成床版の溶接継手部の疲労耐久性を実験および有限要素解析により検討した．合成床版試験体に対する静的載荷試験および解析により，L形鋼溶接部周辺では鋼板が局所的に面外変形し，特にまわし溶接部で高い応力集中が生じることを示した．また疲
労試験により，コンクリートにひび割れが生じない程度の荷重を繰返し載荷することでL形鋼溶接部から疲労き裂が発生することを明らかにし，その疲労強度をホットスポット応力により安全側に評価できることを示した．さらに，合成床版を有する橋梁を対象とした解析を実施し，溶接継手部に生じる実応力挙動を求め，ホットスポット応力による疲労耐久性評価を試みた．

担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

The present study examined a prediction method for the strain at drilled fatigue crack-arrest holes covered by splice plates to evaluate fatigue enhancement of the hole accompanied by the splices. Finite element analyses were performed in order to establish a method to predict the strain at a drilled hole from the strain that can be measured on a splice plate. In the present study, axially loaded center-cracked steel plates repaired by adding splice plates were analyzed for various plate thicknesses of both cracked and splice plates, bolt-hole arrangements and diameters, and crack lengths. The strain on the splice around the drilled hole was correlated with the strain at the hole. Based on the results, a prediction formula for the strain at the hole, which is a function of the pitch and diameter of bolt holes near the drilled hole, was proposed. Static tensile loading tests were conducted for several center-cracked plates repaired by adding splice plates in order to verify the proposed strain-prediction method. The test results demonstrated that the strain at the drilled hole can be predicted with enough accuracy based on the strain on the splice.

担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

The presence of tensile residual stress caused by the welding process, at weld root of rib-to-deck joint in Orthotropic Steel Deck (OSD), believed can trigger fatigue crack occurrence although the applied cycle stresses are compression. In this study, a new method to reduce tensile residual stress at the weld root of rib-to-deck joint in OSD is proposed. It was started with simulating the welding process by using Finite Element (FE) analysis. Various structural parameters are considered to examine its sensitivity in the tensile residual stress distribution at the weld root through the deck plate. It was found that high tensile residual stress is generated at the weld root and tend to be increased with the increase of deck plate thickness and welding penetration. The proposed method is simulated after welding analysis. In this method, the plastic deformation is applied around the weld root by external opening force after cutting the bottom part of the through-rib. The tensile residual stress at the weld root was dispersed when expanding the web plate of through-rib. Significant reduction of tensile residual stress can be obtained when the weld bead size is relatively small.

担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

Low cycle fatigue, is one of the main failure modes in steel structures due to the earthquake. Earthquake acceleration leads to contribute irregular and high plastic deformation to the affected structures. However, the low cycle fatigue durability under irregular loading has not been clarified. The objective of this research is to obtain crack propagation pattern and low cycle fatigue life prediction under various loading histories. Two types of controlled displacement sequences with mixed amplitude were applied to the CT specimen. One was the series with uniform value at constant high and constant low displacement. The remain was the series with changing amplitude from high to low displacement and from low to high displacement. Experimental work and Finite Element (FE) analysis conducted gave ΔJ-integral following applied cyclic loading histories trends and predicted fatigue life curve resulted showed non linear relationship for the crack growth rate during additional value of ΔJ-Integral.

担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

This study examined low cycle fatigue behavior of load-carrying cruciform welded joints containing incomplete penetration. Six types of specimens with different sizes of weld penetrations and weld leg lengths were tested under cyclic plastic strains. During testing, cracking behavior was observed on the side surface of the specimen. The test results revealed that the fatigue strength and cracking patterns depend on the ratio of the weld penetration to the main plate thickness and the ratio of the weld leg length to the main plate thickness, respectively. Then, elasto-plastic finite element analyses including the effective notch concept were performed. The results indicate that the fatigue strength and cracking pattern of the specimens can be correlated with the local strain distribution around the effective notch.

担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

This study investigated the applicability of low transformation temperature (LTT) consumables to improve fatigue strength against weld root failure. Transverse attachment joints formed by single-sided welding, similar to rib-to-deck connections in orthotropic steel bridge decks, were fabricated using an LTT welding consumable and conventional welding consumable. Fatigue tests were performed with out-of-plane bending loads using a vibration-type fatigue testing machine. The test results indicated that higher fatigue strength can be achieved in the joint with an LTT consumable compared with a conventional one. In addition, residual stresses around the weld bead were clarified by X-ray diffraction measurements and finite element analyses. The results revealed that the LTT consumable can reduce residual stress around the weld and also introduce compressive residual stress to the weld root, which can contribute to improved fatigue strength.

担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

Under out-of-plane bending and shearing force, a crack develops in the thickness direction with an inclination toward the axial direction. Typically, three types of crack propagation behaviors can be observed; the crack develops in thickness direction up to the opposite surface, the crack is arrested after inclining toward an axial direction, and a counter crack comes from the opposite surface. In this study, the occurrence condition of each crack propagation behavior was investigated. Cyclic bending fatigue tests were conducted for notched steel plates. Furthermore, the crack propagation and counter crack occurrence were evaluated from finite element analysis. The crack propagation pass tends to be affected by the ratio between bending stress and shear stress near the crack. Also, in the case that the counter crack was generated, the strain on the opposite surface yielded.

記述言語：英語  

Fatigue strength of longitudinal welded joints is used to be less focused since the other joints are considered more critical. However, the presence of blowholes in the fillet welds can be a weak point and cause unpredicted fatigue crack. For determining the appropriate period of inspection, it is important to understand the crack growth behavior in longitudinal welded joint of the primary member. In this study, fatigue strength of longitudinal welded joints with the presence of blowholes is studied. To obtain the crack propagation life, crack propagation analysis for large-scaled girder containing blowhole in its welded joint between web and flange is performed. In the end, the analysis results associated with the traffic volume data is employed to predict how long will it takes from the moment crack initiates from blowholes until reach member failure.

担当区分：責任著者   記述言語：英語  

This study examined low cycle fatigue behavior of load-carrying cruciform welded joints containing incomplete penetration. Six types of specimens with different sizes of weld penetrations and weld leg lengths were tested under cyclic plastic strains. During testing, cracking behavior was observed on the side surface of the specimen. The test results revealed that the fatigue strength and cracking patterns depend on the ratio of the weld penetration to the main plate thickness and the ratio of the weld leg length to the main plate thickness, respectively. Then, elasto-plastic finite element analyses including the effective notch concept were performed. The results indicate that the fatigue strength and cracking pattern of the specimens can be correlated with the local strain distribution around the effective notch.

担当区分：責任著者   記述言語：英語  

Steel truss bridges are widely used for intermediate spans because of its light weight and high load-carrying capacity. Failure accidents of truss bridge have shown that fracture of some members can lead to collapse of the whole bridge, called fracture critical member (FCM). In this study, from the viewpoint of low cycle fatigue, dynamic behavior of FCM under great earthquake was discussed. The results of finite element analysis indicated that large strains were locally occurred at the end of fillets of a gusset plate and around the boundary between the gusset and main chords, which have the possibility to become cracking sites due to low cycle fatigue.

記述言語：英語  

担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

This study examined the fatigue strength of cruciform joints and longitudinal joints fabricated with laser-arc hybrid welding. Load-carrying and non-load-carrying cruciform welded joints with plate thicknesses of 8, 16, and 25 mm were tested under tensile cyclic loads and out-of-plane bending cyclic loads. In longitudinal joints, four-point bending fatigue tests were performed on plate girders with flanges and a web connected by laser-arc hybrid welding. When assembling the plate girder, tack welds were installed at the flange-to-web connection to clarify their effect on the fatigue strength of the longitudinal joints. Measurements of weld toe profiles and residual stress were also conducted. The residual stress was measured using X-ray diffraction. The test results revealed that the fatigue strengths of hybrid welded joints are equivalent to those of arc welded joints and satisfy the fatigue design curves specified by the Japanese Society of Steel Construction. In addition, the effect of plate thickness on the fatigue strength was observed in hybrid welded joints as well as in arc welded joints.

DOI： 10.1007/s40194-019-00745-w

担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

In current design codes, the minimum bolt spacing and edge distance for high-strength bolted friction joints are specified based on the bolt diameter, regardless of the plate thickness or steel strength. However, the mechanical performance of joints with a more compact bolt spacing than that given in the current design specifications has been little examined. In this study, the slip and ultimate strength of high-strength bolted joints with a compact bolt spacing and edge distance were investigated. Tensile tests were conducted on friction-type joints with various bolt arrangements. The use of a compact bolt arrangement was not observed to have a negative influence on the slip strength in these tests. The estimated strengths corresponding to the experimentally observed failure modes were found to agree fairly well with the experimental results within a 10% error. A parametric finite element analysis was also conducted to investigate the influence of the bolt arrangement on the slip coefficient. It was concluded that the bolt spacing and edge distance have little influence on the slip coefficient.

DOI： 10.1007/s13296-018-0199-3

担当区分：筆頭著者   記述言語：日本語   掲載種別：研究論文（学術雑誌）  

DOI： 10.2207/qjjws.37.99

担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

This study investigated the applicability of low transformation temperature (LTT) consumables to improve fatigue strength against weld root failure. Transverse attachment joints formed by single-sided welding, similar to rib-to-deck connections in orthotropic steel bridge decks, were fabricated using an LTT welding consumable and conventional welding consumable. Fatigue tests were performed with out-of-plane bending loads using a vibration-type fatigue testing machine. The test results indicated that higher fatigue strength can be achieved in the joint with an LTT consumable compared with a conventional one. In addition, residual stresses around the weld bead were clarified by X-ray diffraction measurements and finite element analyses. The results revealed that the LTT consumable can reduce residual stress around the weld and also introduce compressive residual stress to the weld root, which can contribute to improved fatigue strength.

担当区分：筆頭著者   記述言語：日本語   掲載種別：研究論文（学術雑誌）  

鋼床版のUリブ・デッキプレート溶接部を対象として，デッキプレート方向もしくは溶接ビード方向に進展する内在き裂を検出できる非破壊検査手法と，その測定精度について検討した．本研究では，鋼床版に磁石で固定でき，バッテリ駆動のモータにより橋軸方向に電動走行できる治具を取り付けたフェーズドアレイ超音波探傷装置を用いた．本装置によりデッキプレートおよび溶接ビードに内在する疲労き裂を同時に探傷することが可能である．振動式疲労試験機により，様々な寸法のデッキ進展型もしくはビード進展型の疲労き裂を導入した試験体を製作し，測定方法の検討，測定精度の検証，塗膜の影響の確認を行い，本手法が十分な検出性能を有していることを示した．

DOI： 10.2208/jscejseee.74.516

担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.11273/jssc.25.100_73

担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

担当区分：筆頭著者   記述言語：日本語   掲載種別：研究論文（学術雑誌）  

担当区分：筆頭著者   記述言語：日本語   掲載種別：研究論文（学術雑誌）  

DOI： 10.2207/qjjws.36.219

担当区分：筆頭著者   記述言語：日本語   掲載種別：研究論文（学術雑誌）  

鉄道橋Iビーム桁の支点部において，ウェブと下フランジの境界部に沿って疲労き裂が発生する事例が報告されている．このき裂に対しては，応急対策としてストップホールが施されることが多いが，比較的早期にき裂が再発生した報告もあり，その延命効果を定量的に評価する手法の確立が望まれている．そこで本研究では，Iビーム桁支点部の疲労き裂に対するストップホールの効果を疲労試験と有限要素解析により検討した．疲労試験は，供用後に撤去されたIビーム桁を用い，き裂が発見された支点まわりの挙動を模擬して行った．その結果，補修後の疲労寿命がストップホール縁の応力範囲により整理できることを示した．さらに解析により，補修時のき裂長とストップホール縁の応力範囲の関係を明らかにし，実橋に施したストップホールの疲労寿命予測を試みた．

DOI： 10.2208/jscejseee.74.290

担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

This study examined the low cycle fatigue behavior of load-carrying cruciform welded joints containing incomplete penetration. Five types of specimens with different sizes of weld penetrations and weld leg lengths were tested under cyclic plastic strains. During testing, cracking behavior was observed on the side surface of the specimen. The test results revealed that the fatigue strength and cracking patterns depend on the ratio of the weld penetration to the main plate thickness and the ratio of the weld leg length to the main plate thickness, respectively. Elasto-plastic finite element analyses including the effective notch concept were then performed. The results indicate that the fatigue strength and cracking pattern of the specimens can be correlated with the local strain distribution around the effective notch.

担当区分：筆頭著者   記述言語：日本語   掲載種別：研究論文（学術雑誌）  

DOI： 10.11273/jssc.25.97_61

担当区分：筆頭著者   記述言語：日本語   掲載種別：研究論文（学術雑誌）  

DOI： 10.11532/structcivil.64A.445

担当区分：筆頭著者   記述言語：日本語   掲載種別：研究論文（学術雑誌）  

DOI： 10.11532/structcivil.64A.435

担当区分：筆頭著者   記述言語：日本語   掲載種別：研究論文（学術雑誌）  

DOI： 10.11273/jssc.24.96_17

担当区分：筆頭著者   記述言語：日本語   掲載種別：研究論文（学術雑誌）  

担当区分：筆頭著者   記述言語：英語  

As for bolt spacing and edge distance of high strength bolted joints, minimum values are specified as a function of bolt diameter D, regardless of plate thickness and steel strength. That is, the minimum value is not clearly defined by mechanical performance of the joint. Moreover, there is little knowledge on the performance of the joint with the bolt spacing more compact than given in the current design specifications. This study investigates slip and fracture strength of high strength bolted joints with compact bolt spacing and edge distance. Tensile coupon tests on frictional joints with various bolt arrangement were conducted. It was not clearly observed the negative influence of compact bolt arrangement on the slip strength. The fracture strengths estimated from the cross
sectional area where the fracture occurred and steel strength of the plate agreed with the experimental results within 10% error in all fracture modes. Parametric analyses were also conducted to investigate the influence of the bolt arrangement to the slip coefficient. It was concluded that the bolt spacing and edge distance have small influence on the slip
coefficient.

担当区分：筆頭著者   記述言語：英語  

This study newly proposed a low cycle fatigue assessment method for steel members which can predict their low cycle fatigue life from nominal strain history calculated with a beam analysis. After establishing a fatigue strength curve for base joints in steel bridge piers, seismic response analyses with beam elements were conducted to assess their low cycle fatigue performance against earthquakes. The analysis results revealed that some of the piers, even though they satisfy with the current seismic design code, have possibility to fail due to low cycle fatigue under earthquake.

担当区分：筆頭著者   記述言語：英語  

Fatigue cracks have been reported in I-beam ends of railway steel bridges, which occur at a lower end of an I-beam web. As a temporary measure, the crack is typically repaired with drilling holes at its tips, called a stop-hole method. In the cracked I-beam ends, however, the effect of life extension due to a stop-hole has not been clearly evaluated yet. In this study, fatigue tests of I-beams repaired with a stop-hole were conducted. And also, in order to make sure local stress distribution around the stop-hole in the test, a finite element analysis was performed. As a result, it was proven that the fatigue life of the repaired I-beam can be predicted from the local stress range at the stop-hole edge. Furthermore, several case studies on life extension of an I-beam due to the stop-hole method were performed.

担当区分：筆頭著者   記述言語：英語  

Shear panel damper possess high energy absorption capacity by its hysteresis damping. However, repetition of high strain concentration around welding joint could lead to low cycle fatigue. To avoid the low cycle fatigue, estimation method should be established. So far, a prediction method of low cycle fatigue initiation life based on the local strain range has been proposed. However, the calculation of local strain usually needs much time and effort to build finite element model. In this study, the relationship between mean shear strain range and local strain range at crack initiation point was examined for various shear panel damper. From the relation, prediction equation of local strain range was established. In addition, low cycle fatigue strength curve based on mean shear strain range was developed. Comparing fatigue strength curve for several shear panel damper, fatigue crack initiation life was discussed.

担当区分：筆頭著者   記述言語：英語  

In this study, fatigue lives of corroded reinforcing steel bars were investigated. Several kinds of rebars consisting of different yield stress and rib shapes were used. The rebar was galvanically corroded to three levels, which are considered as a percentage of mass reduction of 5%, 10% and 15% respectively. Fatigue tests were carried out under constant stress amplitude. The test results revealed that the fatigue life of the corroded rebar decreases as the corrosion level increases. Then, 3D elasto-plastic finite element analyses were conducted with models reflecting surface profiles of the corroded rebar. The analysis results indicated that a cross section where the maximum local strain occurs corresponds to a cracking site observed in the test. Finally, the fatigue life of the corroded rebar was predicted by crack propagation calculations based on linear fracture mechanics. There are relatively good agreements between the prediction and the test results.

担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

Low-cycle fatigue is one of the failure modes in steel structures during earthquakes. With a focus on crack growth in the low-cycle fatigue region, this study developed a fatigue crack growth curve and verified its applicability to crack growth prediction in welded joints. Fatigue crack growth tests under highly plastic conditions were performed using compact tension specimens with side grooves. The results indicate that the crack growth rate in the low-cycle fatigue region correlates with the cyclic J-integral range, which can be calculated using finite element analysis. Additionally, the results for both plain steel and weld metal were distributed in the same region within a narrow band. Based on the results, a formula for the fatigue crack growth rate under large cyclic strains was proposed. Low-cycle fatigue tests were then performed on welded joints to clarify their crack growth behavior, and the crack growth observed in these tests was compared with the crack growth calculated using the proposed formula. The calculation results were found to be in relatively good agreement with the experimental results, verifying the applicability of the formula.

DOI： 10.1007/s40194-017-0504-3

担当区分：筆頭著者   記述言語：日本語   掲載種別：研究論文（学術雑誌）  

DOI： 10.11273/jssc.24.95_25

担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

This study examined the fatigue strength of cruciform joints and longitudinal joints fabricated with laser-arc hybrid welding. Load-carrying and non-load-carrying cruciform welded joints with plate thicknesses of 8, 16 and 25 mm were tested under tensile cyclic loads and out-of-plane bending cyclic loads. In longitudinal joints, four-point bending fatigue tests were performed with plate girders to which flanges and a web were connected with laser-arc hybrid welding. When assembling the plate girder, tack welds were installed at the flange-to-web connection to clarify their effect on the fatigue strength of longitudinal joints. Measurements on weld toe profiles and residual stress were also conducted. The test results revealed that the fatigue strengths of hybrid welded joints are equivalent to those of arc welded joints and satisfy the fatigue design curves specified in Japanese Society of Steel Construction. In addition, the effect of plate thickness on fatigue strength was observed in hybrid welded joints as well as in arc welded joints.

担当区分：筆頭著者   記述言語：日本語   掲載種別：研究論文（学術雑誌）  

DOI： 10.11532/structcivil.63A.646

担当区分：筆頭著者   記述言語：日本語   掲載種別：研究論文（学術雑誌）  

担当区分：筆頭著者   記述言語：日本語   掲載種別：研究論文（学術雑誌）  

担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

In this study, focusing on crack growth in low cycle fatigue region, a fatigue life prediction method was proposed and its applicability to a crack in welded joints was verified through fatigue tests. First, a fatigue crack growth curve under large cyclic strains, which is a relationship between crack growth rate, da/dN, and cyclic J-integral range, ΔJ, was proposed for plain steel materials and weld metal. Then, crack growths in welded joints obtained in experiments were predicted by crack growth calculation with the proposed curve. Finally, the validity of the fatigue life prediction method proposed in this study was confirmed by comparing the test results and the predictions.

担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

Fatigue cracks have been reported in I-beam ends of railway steel bridges. The crack occurs around a rounded part between a web and a lower flange. Previous studies have revealed that out-of-plane bending deformation of a web plate due to non-uniform settlement of a support is a main trigger of the crack. On the other hand, its propagation characteristics which becomes useful information to decide a repair method have not been clarified yet. In this study, fatigue tests were performed with specimens which were cut out from I-beams in an actual railway bridge to investigate occurrence and propagation behavior of the crack. As a result, it was revealed that a crack occurs along the rounded part between the web and the lower flange and grows straight along the rounded part when cyclic load was applied just above the support. Furthermore, the result demonstrated that the crack tends to change its propagation from horizontally to downward as it approaches the sole plate end, and also that there is a possibility that this tendency was independent on loading positions.

担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

Multiple steel columns consist of four steel pipes and connection beams between them. A shear panel in a connection beam is expected to absorb and disperse seismic energy by its plastic deformation. Some experiments on a shear panel have revealed that there is a possibility that low cycle fatigue crack could occur at welded joints in the panel. Therefore, it is needed to make clear conditions when low cycle fatigue cracks occur. Previous study has indicated that low cycle fatigue life of a shear panel can be assessed based on local strain amplitude at a crack initiation point. In this study, influential factors on low cycle fatigue of a shear panel were investigated through finite element analyses, and then, a simple assessment method for low cycle fatigue at a boxing weld of a scallop in a shear panel was proposed. By using the method, low cycle fatigue assessments under seismic motions were conducted. The results indicated that the method can estimate fatigue life in more conservative than the local strain based method.

担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

In orthotropic steel deck systems, traffic loads lead to local deformation around welded joints repeatedly, which causes fatigue cracks. Specifically, a large number of fatigue cracks have been found around a cutout between a longitudinal closed rib (U-rib) and a transverse rib web. This study focuses on a crack generated from a weld toe on a U-rib web in a cutout. This crack is mainly caused by local out-of-plane bending deformation of a U-rib, so the connection can be regarded as an out-of-plane gusset welded joint under bending loads. However, thickness of a U-rib, which is regarded as a main plate of the gusset joint, is thinner than that used in conventional joints. Therefore, there may be difference in fatigue strength improved by conventional techniques. In this study, fatigue tests were conducted with out-of-plane gusset welded joints under bending load which simulates deformation in a U-rib web. The test result indicated that conventional improvement methods, such as improving weld toe configuration and introducing compressive residual stress techniques, can increase the fatigue strength of the joint with the thin main plate as well.

担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

Tensile residual stress existing near a weld reduces fatigue strength of welded joints. A peening technique is one of the methods to reduce tensile residual stress and introduce compressive residual stress at a cracking point, which can improve fatigue strength. In a peening method, the improvement on fatigue strength is considered to be related to the magnitude of introduced compressive residual stress. And also, it is considered that the magnitude of compressive residual stress by peening depends on the static strength of base material. Therefore, the fatigue strength of welded joints improved by peening may depend on the static strength of steel used in the joint.
This study focuses on UIT (Ultrasonic Impact Treatment), which is one of the peening methods, and investigated the effect of static strength of steel on the fatigue strength improvement of welded joints. First of all, introduced compressive residual stress due to UIT was measured by X-ray diffraction method, and the measurements were correlated with the static strength of materials. The results indicated a tendency that higher compressive residual stress can be induced by UIT as the static strength increases. In addition, fatigue tests on out-of-plane gusset welded joints made with different grades of steels were performed to reveal the effect of the static strength on fatigue strength improvement. As a result, it was confirmed that the fatigue strength of welded joints can be improved by UIT and its effect slightly varies depending on the static strength of steel.

担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

In this study, the improvement effect by Carbon-Fiber Reinforced Polymer (CFRP) repair to a crack was quantified. In order to make clear opening behavior of a crack under CFRP, tensile tests for butted steel plates which were bonded with CFRP plates were performed. The test results indicated that local peel-off around a crack needs to be introduced in a finite element model when analyzing the opening behavior of a crack under CFRP. Secondary, in order to estimate the effect of CFRP repair, stress intensity factor of a crack covered with various sizes and numbers of lamination of CFRP sheet was calculated through finite element analyses. As a result, it was indicated that length of CF sheet can affect reduction of stress intensity factor and even shorter sheet can achieve adequate improvement. In addition, fatigue tests of out-of-plane gusset welded joints repaired with CF sheets were carried out under bending load. The test results demonstrated that fatigue life of the joint is considerably improved by using CFRP.

担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

Laser-arc hybrid welding, which is combined with laser welding and arc welding, has been recently developed. Laser welding commonly requires less heat-input than ordinary arc welding, additionally it achieves deep penetration even in fast welding operation. On the other hand, an allowable root gap of a joint by the laser welding is smaller than that by arc welding due to thick weld bead. The laser-arc hybrid welding has the advantage of the laser welding and also improves the allowance of the gap, meaning that it can provide deep weld penetration, high processing speeds and wider allowance of the gap. Meanwhile, fatigue strength of the laser-arc hybrid welding has not been clarified. In addition, stress concentration and residual stress after the welding have not been deeply investigated yet. In this study, tensile and plate bending fatigue tests were carried out to examine the fatigue strength of load-carrying cruciform welded joints with the laser-arc hybrid welding. Furthermore, their residual stresses and weld toe configurations affecting the stress concentration were measured.

担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

Low cycle fatigue is one of the main failure modes in steel structures during earthquake. In this study, focusing on crack growth in low cycle fatigue region, a fatigue crack growth curve was proposed and its applicability to a crack growth prediction in welded joints was verified. Fatigue crack growth tests under large plastic condition were performed by using compact tension specimens with side grooves. The results indicated that crack growth rate in low cycle fatigue region correlates with cyclic J-integral range which is calculated by finite element analysis. Besides, the results in both plain steel material and weld metal distribute in the same region with narrow band. Based on the result, a formula of fatigue crack growth rate under large cyclic strains was proposed. Then, low cycle fatigue tests for welded joints were performed to clarify their crack growth behavior, and the crack growth obtained in the experiments were compared with the prediction based on crack growth calculation with the proposed curve. The prediction was in relatively good agreement with the experiments, which can verify the applicability of the curve.

担当区分：筆頭著者   記述言語：日本語   掲載種別：研究論文（学術雑誌）  

DOI： 10.11532/structcivil.62A.667

担当区分：筆頭著者   記述言語：日本語   掲載種別：研究論文（学術雑誌）  

DOI： 10.11273/jssc.23.89_85

担当区分：筆頭著者   記述言語：日本語   掲載種別：研究論文（学術雑誌）  

担当区分：筆頭著者   記述言語：英語  

This paper presents a new fatigue strength evaluation method for root failure in fillet weld joints, based on the displacement at unfused root gap. The displacement at the spot 1mm away from the weld root on unfused gap surfaces, obtained by FEA with 1mm size elements, was used as a parameter for fatigue strength evaluation. The accuracy of the method was verified with fatigue test results. A unique relationship was found between the displacements and the fatigue lives regardless of joint type and joint size and loading modes.

担当区分：筆頭著者   記述言語：英語  

This study proposed a method for estimating weld crack initiation in weld repair under cyclic loading through welding tests and thermal elasto-plastic finite element analyses. Sectional observations after the welding test revealed that the initiation of a weld crack highly depends on the magnitude of root gap opening displacement, especially in welding process. Then, through the simulation of welding under cyclic loading, this study proposed a prediction equation for the root gap opening displacement during welding. As a result of the experimental and analytical investigations, an estimation method for the crack initiation in weld repair under cyclic loading was established.

担当区分：筆頭著者   記述言語：英語  

Extremely low cycle fatigue, which is caused by large cyclic deformation with small number of loading repetition, is one of the main failure modes in steel structures during earthquake. In this study, crack propagation behavior of structural steels for welded structures (not only plain material but also weld deposit) under large cyclic deformation was investigated. As a result, a prediction equation for crack propagation under large deformation was proposed based on cyclic J-integral range. Besides, the proposed equation was verified through low cycle fatigue tests of corner welded joints.

担当区分：筆頭著者   記述言語：英語  

Weld toe grinding is known to have relatively large variations in its improvement effects of fatigue strength. On the other hand, the residual stress distribution near the ground groove has not been revealed although it has a significant influence on the fatigue strength. In this research, X-ray stress measurements and finite element analyses were conducted in order to reveal the redistribution behavior of welding residual stress resulting from weld toe grinding.

担当区分：筆頭著者   記述言語：英語  

As a new repair method, Carbon-Fiber Reinforced Polymer (CFRP) adhesive repair has been getting attention. In this study, the effect of CFRP adhesive repair for a fatigue crack in a steel plate was investigated experimentally and analytically. The fatigue tests revealed that the propagation rate of a crack repaired with CFRP was reduced comparing with that without repair. Based on the results, a fatigue life prediction method for a crack with CFRP was proposed.

担当区分：筆頭著者   記述言語：英語  

Multiple Steel Columns can absorb seismic energy by shear deformation of shear panel. Due to large shear deformation in the shear panel, however, the low cycle fatigue crack could occur at the welding joint of shear panel. In this study, a cyclic loading test of Multiple Steel Columns was simulated by finite element analysis. Further, prediction method for crack initiation and propagation of low cycle fatigue in a welding joint of shear panel was developed.

担当区分：筆頭著者   記述言語：英語  

In welded steel structures, there are some cases when weld-lines exist close to each other. As an example in steel highway bridges in Japan, a vertical stiffener is connected to a web plate close to an end of a horizontal stiffener. In this case, stress concentrations due to each joint may be superposed, and consequently, fatigue strength of the stiffeners may become lower compared with typical welded joints. In this study, fatigue tests and finite element analyses were performed on plate girders where vertical and horizontal stiffeners attached with a small gap between them. The result revealed that the stress concentration at the end of the horizontal stiffener slightly varied with the distance between the stiffeners, resulting in small difference of the fatigue strength.

担当区分：筆頭著者   記述言語：日本語   掲載種別：研究論文（学術雑誌）  

すみ肉溶接継手のルート破壊に対しては，のど断面応力を用いた疲労照査法が示されているが，実際にはのど断面応力が定義できない場合も多い．本研究では，これに代わる手法として，有限要素解析で求めた未溶着部の開口変位を用いる方法について検討した．未溶着部の変位は，応力と比較して要素サイズによる影響が小さく，比較的粗い要素分割によっても安定的な値が得られる．解析結果に基づき，1mmの要素を配置して解析を行い，未溶着部先端から1mmの位置での変位に着目することを提案した．き裂進展解析および過去に行われた疲労試験の結果をその変位で整理した結果，変位と疲労強度には高い相関があり，のど断面応力による方法と同等の精度で疲労強度を推定できることが明らかとなった．

DOI： 10.2208/jscejseee.71.315

担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

This study investigated fatigue strength evaluation methods based on the structural hot spot stress concept, focusing on a crack at a crossing between a longitudinal closed rib and a cross-beam (transverse rib) web cutout in an orthotropic steel bridge deck. The results indicated the possibility that the fatigue strength of the connection can be evaluated with the hot spot stress range. And also, it was revealed that the hot spot stress range hardly decreases with increasing of deck plate thickness and decreasing of transverse rib distance.

担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

Extremely low cycle fatigue, which is caused by large cyclic deformation with small number of loading repetition, is one of the main failure modes in steel structures during earthquake. In this study, crack propagation behaviour of structural steel in extremely low cycle fatigue region was evaluated based on a non-linear fracture mechanics parameter calculated by analyses. The results demonstrated that crack propagation rate in extremely low cycle fatigue region can be estimated by using cyclic J-integral.

担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

As a simple repair method for fatigue cracks in steel bridges, the resin injection method has been proposed. The method can decrease fatigue crack growth rate by injecting resin into a crack. In this study, the applicability of the method for cracks occurred by cyclic compressive loading was investigated by experiments and finite element analyses. The results revealed that the crack growth retardation can be expected even under the compressive loading when enough elastic modulus and infiltration of resin are achieved.

担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

This paper presents an assessment method for extremely low cycle fatigue cracks from corner joints in concrete-filled steel piers. Low cycle fatigue tests indicated that one of the main failure modes of concrete-filled steel piers are a fatigue crack from corner joints, which is caused by out-of-plane bending deformation of flange and web plates. In the previous study, authors had proposed extremely low cycle fatigue strength curves for the corner joints based on the effective notch strain approach. In this study, the proposed method was applied to the experiment of the concrete-filled piers and it is demonstrated that extremely low cycle fatigue life of the pier can be predicted by using the method.

DOI： 10.11532/structcivil.61A.662

担当区分：筆頭著者   記述言語：日本語   掲載種別：研究論文（学術雑誌）  

DOI： 10.11532/structcivil.61A.627

担当区分：筆頭著者   記述言語：日本語   掲載種別：研究論文（学術雑誌）  

DOI： 10.11532/structcivil.61A.767

担当区分：筆頭著者   記述言語：日本語   掲載種別：研究論文（学術雑誌）  

担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

Low cycle fatigue strengths of corner welded joints with single bevel groove welding were studied. Low cycle fatigue tests were performed with three types of specimens which have different sizes of weld root face. The test results indicated that the low cycle fatigue strength of the corner welded joints strongly depends on the weld root size. Then, the fatigue strength of the corner joints was evaluated based on the effective notch strain at the weld root tip which was calculated by elasto-plastic finite element analyses. A unique relationship between the effective notch strain and the fatigue life of the joint was observed regardless of the weld root size. Therefore, it was revealed that the effective notch strain approach is applicable to evaluate the low cycle fatigue strength of the corner welded joints.

DOI： 10.1007/s13296-014-3015-8

担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

One of the main failure modes of steel bridge piers is low cycle fatigue. In a concrete-filled steel pier with a box section, it has been reported that low cycle fatigue cracks are often initiated from longitudinal welds connecting flange and web plates (called corner joint) when it is subjected to large cyclic deformation. In this study, low cycle fatigue strengths of the corner joints were investigated. Low cycle fatigue tests were performed with corner joint specimens with different weld root sizes. Then, the fatigue strength of the corner joints was evaluated based on the effective notch strain at the root tip which was calculated by elasto-plastic finite element analyses. The results indicated a unique relationship between the effective notch strain range and the fatigue life of the joint regardless of the weld root size. Besides, the test results of the corner joints located in the same region as those of load-carrying cruciform joints. Therefore, it was demonstrated that the effective notch strain approach is applicable to evaluate the low cycle fatigue strength of welded joints regardless of the joint types.

担当区分：筆頭著者   記述言語：日本語   掲載種別：研究論文（学術雑誌）  

DOI： 10.11273/jssc.21.81_47

担当区分：筆頭著者   記述言語：日本語   掲載種別：研究論文（学術雑誌）  

DOI： 10.11532/structcivil.60A.587

担当区分：筆頭著者   記述言語：日本語   掲載種別：研究論文（学術雑誌）  

DOI： 10.11532/structcivil.60A.651

担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

Weld joint with a cope hole has relatively low fatigue strength, since high stress concentration is generated due to local shear deformation inside the cope hole. In this study, fatigue strength improvement for the cope hole joint by burr grinding is investigated. I-section beams with cope holes, of which boxing weld toes were smoothly finished by burr grinding, were tested and analyzed in order to know the fatigue strength and the local stress behavior of the joint. Test and analysis results demonstrated that the benefit of grinding on fatigue strength improvement is relatively small when shear stress is largely applied to the cope hole detail.

DOI： 10.1007/s13296-013-4009-7

担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

This study revealed low cycle fatigue strength of deformed bars and proposed a strain based fatigue strength evaluation method based on fatigue tests and FE analyses. The low cycle fatigue strength of the material of deformed bars is equivalent to that of structural steels. The low cycle fatigue strength of a deformed bar depends on the shape of ribs, but can be evaluated by using the strain amplitude at the cracking site and fatigue strength curve for the material.

担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

Recently, a lot of fatigue cracks have been found in steel bridges in Japan. It is therefore urgent to develop a simple repairing and retrofitting method for such fatigue cracks. A new repair method named Impact Crack Closure Retrofit treatment (ICR treatment) was developed, which induces compressive residual stress and closes a crack by hammering around the crack. In this study, improvement of the method was investigated by finite element analyses and fatigue tests. As the result of the analysis, stress intensity factor of the crack treated by the ICR decreased. The test results also showed that fatigue life was extended by the ICR treatment under cyclic tensile load.

担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

For low cycle fatigue assessment of steel members, strain behavior in the member should be accurately estimated. In this study, the strain behaviors of steel bridge piers subjected to several types of long duration ground motions were investigated, and low cycle fatigue performances of the pier were assessed by a proposed strain based method. Parametric analyses with various geometry configurations of the pier were conducted. Nominal strain amplitudes in effective failure length of the pier were obtained by nonlinear dynamic analyses, and then fatigue damage index was calculated from the strain by using nominal strain based fatigue strength curves proposed for the piers.

担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

In this study, the fatigue performance on the welded joints of the newly developed steel called Steels for Bridge High Performance Structures (simply called SBHS) was investigated. In order to clarify the fatigue crack growth characteristic of the SBHS, the crack propagation tests were performed with compact tension type specimens. Then, the fatigue strengths of out-of-plane gusset welded joints and non-load-carrying cruciform welded joints of the SBHS were investigated. Plate girder specimens, in which gusset plates were attached on their webs, were also fabricated with the SBHS and tested. The fatigue test results revealed that the fatigue performances of the welded joints of the SBHS are almost the same as those of the conventional steel.

担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

A large number of fatigue cracks have been reported at the connection between longitudinal closed ribs and cross-beam webs in orthotropic steel decks because of high stress concentrations due to complicated local deformations of the rib and the web. In this study, the local stress behaviors around the weld end adjacent to the cross-beam cutout were analytically investigated. Finite element analyses were conducted by using a full scale model of an actual bridge, where plenty of cracks were detected around the cross-beam cutout, to investigate the deformation modes causing the cracks. Then, the effective cutout configurations to reduce the crack-inducing local stresses were investigated by comparing the local stress in different cutout types.

記述言語：英語   掲載種別：研究論文（学術雑誌）  

Fatigue strength category of out-of-plane gusset welded joint was determined based on large number of previous fatigue tests and is categorized with gusset length. However, the variety of the joint size of specimens used in previous researches is very limited and the size is much smaller than the joints in bridge structures. In this study, stress analyses with out-of-plane gusset welded joint models having large variety of joint size like from small joint specimen to joint in steel bridges were conducted, and existing fatigue test results of joint specimen and girder specimen with out-of-plane gusset weld joint were analyzed. From these analysis and survey, the following points are discussed.
(1) Change in stress (toe stress, hot spot stress and stress at the area adjacent to the boxing weld toe) with change in joint geometry not only of base plate thickness and gusset length but also base plate width and gusset height of out-of-plane gusset weld joint; In this part, size effect in fatigue strength and in toe stress concentration factor, relationship between toe stress and hot spot stress, and nominal stress evaluation were mainly discussed.
(2) Fatigue strength of out-of-plane gusset weld joint in bridge structures; In this part, using hot spot stress approach and existing fatigue test data, fatigue strength of large scale out-of-plane gusset weld joint was analytically evaluated.

担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

Since a large number of fatigue cracks have been detected in steel bridges and its number is expected to increase more and more in the future, simple repair methods are strongly required. Repair by welding will be more cost efficient and shorten work period comparing with a conventional bolted splice method, because the weld repair requires no additional members. On the other hand, the weld repair has a possibility to induce weld defects, especially when applied in service condition. Vehicle loads generate cyclic deformation of members and opening and closing behaviour of cracks. In order to employ the weld repair in actual bridges, therefore, it is necessary to make clear appropriate weld repair conditions to achieve sound weld quality under cyclic loading.
In this study, experiments were performed to investigate weld repair quality in service condition. Specimens with a fictitious crack in their mid-width were repaired by arc-welding under cyclic loading. Several series of the tests were carried out with changing magnitude of root gap opening displacement, load frequency, welding position and groove geometry etc. After the repair welding, sections of the specimen were observed to detect weld cracks. From the observations in some specimens, the weld crack was detected in weld deposit. The experiments demonstrated that occurrence of the weld crack under the cyclic loading strongly depends on the magnitude of the root gap opening displacement and the load frequency.

担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

It is well known that reduction of tensile residual stress around cracking sites is effective to improve fatigue strength of welded joints. Several methods to improve the fatigue strength, such as burr grinding, peening, and TIG-dressing techniques, have been proposed and applied to actual steel structures. Recently, a new welding material called low-temperature transformation welding material (LTT), which can induce compressive residual stress has been developed and examined about its applicability.
In this study, thermo-elasto-plastic analyses were carried out to clarify fatigue strength improvement mechanism when applying LTT from the view point of introduction of compressive residual stress. Residual stress distribution in an out-of-plane gusset welded joint when applying LTT or a conventional welding wire was identified. In the analyses, in order to simulate actual welding procedures, heat was applied with moving its location. The analysis results indicated that compressive residual stress was introduced around a weld toe in case that LTT was used for welding. As for a weld root, it was revealed that tensile residual stress is deceased by LTT in case that LTT was used for first layer and a conventional material was the second layer.

担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

A large number of fatigue cracks have been reported in orthotropic steel decks, especially at the connection between longitudinal closed ribs and cross-beam webs, because of high stress concentration due to complicated local deformations of the rib and the web. In this study, the local stress characteristics around the weld end adjacent to the cross-beam cutout were analytically investigated. Finite element analyses were conducted by using a full scale model of an actual bridge, where plenty of cracks were detected around the cross-beam cutout, to figure out the deformation modes causing the cracks. Then, the effective cutout configurations to mitigate the crack-inducing deformations were investigated by comparing the local stress behaviors in different cutout types.

担当区分：筆頭著者   記述言語：日本語   掲載種別：研究論文（学術雑誌）  

DOI： 10.11273/jssc.20.77_15

担当区分：筆頭著者   記述言語：日本語   掲載種別：研究論文（学術雑誌）  

DOI： 10.11532/structcivil.59A.781

担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

During the Hyogo-ken Nanbu Earthquake in 1995, two types of failure modes were observed in steel bridge piers; one is a local buckling and the other is a brittle fracture triggered by a low cycle fatigue. A large number of researches on the local buckling have conducted after the earthquake and proposed several methods to prevent the local buckling of the pier, such as filling concrete in the steel pier. The concrete-filled steel pier has high deformation capacity since the internal concrete can constrain local deformation of flange and web plates, and even with an origination of the buckling, the concrete can restrain its growth. When the pier endures large cyclic plastic deformations, the low cycle fatigue will be an issue. There are, however, few researches which investigating the concrete-filled steel pier in terms of the low cycle fatigue. In this study, the low cycle fatigue behavior of the concrete-filled steel pier was experimentally investigated. The concrete-filled pier specimens were fabricated and tested under large cyclic displacement. The test results revealed the crack initiation and propagation behavior in the concrete-filled pier and the effect of the axial loading on the low cycle fatigue strength of the pier.

担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

The authors previously proposed a fatigue strength evaluation method based on the effective notch strain concept and reported that the fatigue strength of load-carrying cruciform joints can be assessed by the effective notch strain regardless of the mismatching and the incomplete penetration ratio from the low- to the high-cycle fatigue region. However, in applications to actual structures, this method has difficulty in modeling and analysis because it requires extremely fine meshing around the welds. Therefore, in this paper, an estimation method of the effective notch strain from nominal strain is proposed.

DOI： 10.1016/j.ijfatigue.2012.01.021

担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

This study examined the applicability of the effective notch concept to the low- and high-cycle fatigue regions for load-carrying cruciform joints. Low- and high-cycle fatigue tests were performed on specimens with various strength matching conditions and incomplete penetration ratio. Fatigue test results revealed that the effect of strength matching becomes obvious in low cycle fatigue region, while, it was negligible in high cycle fatigue region. Different failure patterns can be observed for specimen with different strength mismatching condition in the low cycle fatigue tests. Elasto-plastic finite element analyses were performed under the same conditions as the experiments. The effective notch strains were determined at the crack initiation points. A unique relationship between effective notch strain and fatigue life was obtained regardless of matching condition and incomplete penetration ratio.

DOI： 10.1016/j.ijfatigue.2011.12.016

担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

This study investigated the low- and high-cycle fatigue strength of load-carrying cruciform joints containing incomplete penetration and strength mismatch between base metal and weld deposit, and proposed an assessment method based on the local approach. Low- and high-cycle fatigue tests were performed on specimens with varying mismatch and sizes of incomplete penetration. The test results revealed that the crack initiation life was extremely small for this type of joint. In fractographs, dimples observed around the crack initiation site provided evidence of ductile crack propagation. Also, it was found that strength mismatch had a negligible effect on the high-cycle fatigue strength but that under-matching reduced the low-cycle fatigue region. However, a unique relationship was found between local strain around a weld root tip calculated by elasto-plastic finite element analysis and both the low- and high-cycle fatigue life of the specimen.

DOI： 10.1007/BF03321357

担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

In Japan, more than 5000 steel piers exist in elevated bridges in urban area, which play an important part in transportation. The Kobe Earthquake in 1995 caused enormous damage to steel bridge piers, such as collapse, buckling and brittle fracture. It has been revealed two types of main failure modes in the pier, which are local buckling and low cycle fatigue. Therefore, both local buckling and low cycle fatigue are key issues to prevent the piers from damaging and also to secure the public safety.
In this study, we focused on the low cycle fatigue failure occurring from base joints of the pier. The low cycle fatigue assessment method based on the nominal strain approach was proposed for the base joints of the pier. The nominal strain can be simply calculated by finite element analysis with a beam element. Fatigue tests with steel pier specimens demonstrated that the proposed fatigue assessment method could provide fatigue life estimation with enough accuracy.

担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

When repairing fatigue damage by welding, the fatigue strength of cracked joints needs to be restored and also improved to prevent the reoccurrence of cracks. In this study, a new welding wire called low temperature transformation (LTT) welding wire, which enables the introduction of compressive residual stresses around a weld bead and the reduction of weld deformation, was applied to the weld repair. Its applicability was investigated by fatigue tests with compact tension specimens and a plate girder specimen. The compact tension specimens revealed that compressive residual stresses introduced by LTT welding wire have positive effects on crack initiation and propagation behaviour. The plate girder specimen indicated that the fatigue lives of cracked joints are restored and also improved by weld repair with LTT welding wire. Therefore, weld repair with LTT welding wire makes it possible to improve the fatigue strength of cracked joints.

DOI： 10.1007/BF03321334

担当区分：筆頭著者   記述言語：日本語   掲載種別：研究論文（学術雑誌）  

DOI： 10.11532/structcivil.58A.647

担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

The fatigue strengths of load-carrying cruciform joints with incomplete penetration and a strength mismatch between the base metal and the deposit metal were studied. Low- and high-cycle fatigue tests were performed on specimens with five matching conditions and two sizes of incomplete penetration. The test results revealed that the failure life was governed by crack propagation in both the low-cycle and high-cycle fatigue regions, and the crack propagation paths differed according to the matching and loading conditions. In addition, the fatigue strengths of the joints were compared for the degree of strength matching and the size of incomplete penetration in the low- and high-cycle fatigue regions. It was found that the effect of strength matching on the fatigue strength is negligible in the high-cycle fatigue region, but it becomes large in the low-cycle fatigue region and significantly reduces the fatigue life of the specimen in the under-matched joints.

DOI： 10.1007/s13296-011-4002-y

担当区分：筆頭著者   記述言語：日本語   掲載種別：研究論文（学術雑誌）  

担当区分：筆頭著者   記述言語：日本語   掲載種別：研究論文（学術雑誌）  

担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

The number of fatigue cracks at in steel bridges is increasing, while it is difficult to repair all cracks just after detecting them. In this study, a simple repair method for cracks in steel bridges was proposed. 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 repaired by the hardening material injection. 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 regardless of the stress ratio.

担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

Local stress approach has been proposed as the fatigue strength evaluation method of welded joints without any classifications by the joint types and verified in the past studies. Generally, since it is difficult to directly measure the local stresses at the crack initiation point, ex. weld toe, the stress analysis helps us to estimate them, which requires establishing a model with weld toe geometry in fine mesh and great amounts of time. Thus, this study proposed the simple method for estimating the local stress in as-welded joints. In this method, the local stress at the as-welded toe is estimated from the stress at the toe finished by the grinding technique, where the strain gauge measurement is applicable. Fatigue tests and finite element analyses were conducted with out-of-plane gusset welded joints of as-welded and finished condition, respectively. Based on the results, the correlation of the local stress in the as-welded and finished joints was established. Consequently, it was demonstrated that the fatigue strength of the as-welded joints can be evaluated by using the local stress estimated by the proposed method.

担当区分：筆頭著者   記述言語：日本語   掲載種別：研究論文（学術雑誌）  

DOI： 10.2207/qjjws.29.162

記述言語：英語   掲載種別：研究論文（学術雑誌）  

In this study, the validity of the assumption made for the crack propagation analysis, that fatigue crack propagates in the plane perpendicular to the loading direction, was discussed. The comparison of stress intensity factor obtained by the conventional method and analytical codes were made. In addition, fatigue tests with out-of-plane gusset welded joints were carried out and the front profile of fatigue crack originated in out-of-plane gusset welded joint was closely observed.

担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

This study investigated the effect of the extremely low cycle fatigue strength improvement on steel pier by weld toe grinding. Low cycle fatigue tests on the steel pier specimens, of which base joints were ground smoothly, were performed, and their results were compared with those of the specimens under as-welded condition. It was revealed that the burr grinding is applicable to increase the fatigue strength in extremely low cycle fatigue region. Local strain around finished weld toe was analyzed by finite element analysis. It was confirmed that it is possible to estimate the extremely low cycle fatigue life by using local strain at a crack initiation point and proposed fatigue strength curves. Moreover appropriate grinding areas were considered by the analysis.

担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

In this study, an evaluation method for the scatter in the fatigue life of the welded joints was developed with employing LEFM and Monte-Carlo simulation technique. Fatigue crack propagation 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 was demonstrated that the estimated fatigue life by the proposed method distributes around the similar region 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.

担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

Local stress approach has been proposed and verified in past studies as the fatigue strength evaluation method of welded joints without any classifications by the joint types. Even though the local stress approach is valid for assessing the fatigue life of the joints, it is difficult to measure the local stresses at the as-welded toe directly. The stress analysis makes it possible to estimate the local stresses, which requires establishing a model with weld toe geometry in fine mesh. This study proposed the simple estimation method for the local stress in as-welded joints. In this method, the local stress at as-welded toe is estimated from the stress measured at the toe finished by the grinding technique. Fatigue tests and finite element analyses were conducted with out-of-plane gusset welded joints in as-welded and finished condition, respectively. Based on the analysis results, a correlation between the stress at the finished groove and the local stress at the as-welded toe was established. Then, fatigue test results verified that the fatigue strength of out-of-plane welded joints can be uniformly evaluated by using proposed local stress based fatigue assessment method.

担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

In present, the upper and lower flanges of outrigger bracket are attached to main girder by using full penetration welding. However, the full penetration weld of lower flange might be mainly subjected compressive stress by live load, and also the generated stress level is relatively low. This study investigated the possibility to change the full penetration weld joint of lower flange to partial penetration weld joint considering fatigue strength. In this study, fatigue test was carried out on partial penetration welded cruciform joint under compressive cyclic load which simulates new welding joint of the lower flange. Moreover, finite element analysis was performed to identify the stress distribution around the welded joint outrigger bracket. The results revealed the possibility to change the full penetration welds of lower flange to partial penetration welds.

担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

Load carrying cruciform joints with incomplete penetration have two fatigue cracking points which are the weld root and toe. The crack initiation point in high cycle fatigue region depends on only weld leg size and incomplete penetration ratio, while the strength mis-matching between the base and deposit metal becomes important when considering it in low cycle fatigue region. Elasto-plastic analysis was performed on load carrying cruciform joints regarding the size of weld leg and incomplete penetration, and strength matching. The effective notch was assigned at the weld root and toe, and the strains around both notches were compared. It was demonstrated that the cracking points estimated from the analysis agreed with the experimental results.

担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

This study newly defined effective notch strain and examined its applicability in elastic and elasto-plastic condition for load carrying cruciform welded joints. Low and high cycle fatigue tests were performed on specimens with different strength matching conditions and incomplete penetration sizes. To calculate the effective notch strain of the specimen, elasto-plastic finite element analyses were performed under the same condition as experiments. The unique relation between the effective notch strain and fatigue life can be obtained regardless of the matching condition and incomplete penetration size. Furthermore, the simple method for estimating effective notch strain was proposed and verified by the experiments.

担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

Fatigue behaviors of load-carrying cruciform joints containing incomplete penetration and strength under-matching between base metal and weld deposit were studied. Low and high cycle fatigue tests were performed on specimens with five matching conditions and two sizes of incomplete penetration. Observation of the specimens revealed that crack propagation paths differ by low and high cycle loading conditions and that failure life was dominated by crack propagation. Besides, it was found that the effect of the strength under matching on the fatigue strength becomes large in low cycle fatigue region by significantly reducing fatigue life of the specimen. Moreover, local strain obtained from analysis model can be governing parameter to fatigue life of specimens.

担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

Previous research suggested that driver's reaction during earthquake, which is responsible for driving safety, is related to velocity response of bridge deck. To reduce the velocity response of the deck, conventional devices like rubber bearings, base isolators and dampers system are employed. Analytical results reveals that rubber bearings, while more commonly used than dampers, cannot not reduce velocity response even though they can be effective in controlling strain response of steel bents.

担当区分：筆頭著者   記述言語：日本語   掲載種別：研究論文（学術雑誌）  

鋼橋に生じた疲労き裂に対して溶接により補修を行うことは，当て板等の補強部材を必要としないため工期や費用を抑えることができ，またボルト添接が不可能な狭隘部に対して有効である．しかしその一方で，溶接補修部においては溶接欠陥や残留変形が生じてしまい疲労強度が低下する恐れがある．さらに，き裂が生じた継手部には疲労強度の低い継手ディテールが採用されていることが多く，たとえ健全な補修溶接により元の状態に回復できたとしても，補修後の疲労強度を補修前より向上させなければき裂が再発する可能性がある．そこで本研究では，溶接後の冷却過程にて圧縮残留応力を導入でき，かつ溶接変形を抑制できる低変態温度溶接材料に着目し，それを用いた溶接補修の有効性について検討した．

DOI： 10.2208/jsceja.66.836

担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

This study investigates the applicability of local approach to assess the fatigue strength of load carrying cruciform joints containing incomplete penetration and strength mismatching. Low and high cycle fatigue tests were conducted. Test results indicate that the effect of the strength mismatch on the fatigue strength is negligibly small in high cycle fatigue region but becomes large in low cycle fatigue region. Elasto-plastic FE analysis was performed, where the concept of effective notch was assigned at weld root tip. Different types of notch shapes were investigated. It is clear that local strain obtained from FE model can be used to arrange fatigue strength of load carrying cruciform joints. A unique curve can be established from low to high cycle fatigue regions.

担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

This study investigated effects of incomplete penetration and strength mismatch between base metal and weld deposit on fatigue strength of load-carrying cruciform welded joints. Low and high cycle fatigue tests were performed on specimens with changing matching conditions and sizes of in-complete penetration. Test results revealed that fatigue life was dominated by crack propagation, and that crack propagation directions vary according to strength matching and loading conditions. In fractographs, dimples were observed around the crack initiation point which produces an evidence of ductile crack propagation. Also, it was found that the effect of the strength under matching, in which yield strength of weld deposit is lower than that of base metal, on the fatigue strength is negligibly small in high cycle fatigue region but becomes large in low cycle fatigue region by significantly reducing fatigue life of the joints.

担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

This study presents a newly developed web database for fatigue damage and repairing cases. Authors use a new platform “PukiWiki" for the web data base instead of html documents. The new platform includes two advantages. One is the editing language, the simple structure of which enhances easy updating; hence, it is possible for the researchers and engineers who are unfamiliar with editing a web page to use it. Another advantage is multi-editor system. Authorized researchers and engineers can edit and update the web at any time from anywhere; that is, we can skip the process of collecting, editing and updating information by a web administrator. It means the platform enables to less laborious editing and quick updating. We expect to enlarge new information on the web; also, expand professional judgment and outlooks to the world from the new database.

担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

The weld repair requires no additional member such as splice plates, therefore it will be more cost efficient and shorten the work period comparing with the conventional bolted splice method. However, the weld repair has possibility to induce weld defects or residual deformation which may reduce the fatigue strength of the repaired joints. Besides, even though fatigue cracked joints are restored to the initial condition with sound weld repairs, cracks will reoccur in the repaired part, because the fatigue strength of cracked joints is originally low in most of the cases. In this study, a new welding wire named low temperature transformation (LTT) welding wire, which enables to introduce compressive residual stress in the vicinity of the weld bead and reduce weld deformation, was applied to the weld repair. The applicability of LTT welding wire to the weld repair was investigated by the fatigue tests with compact tension specimens and a plate girder specimen.

担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.2208/jsceja.66.219

担当区分：筆頭著者   記述言語：日本語   掲載種別：研究論文（学術雑誌）  

DOI： 10.11532/structcivil.56A.671

担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

In this study, fatigue behavior of load-carrying cruciform joints with incomplete penetrations under cyclic plastic strains, corresponding to the fatigue life is less than hundreds cycles, was experimentally investigated. In all specimens, fatigue cracks initiated from the weld root and propagated into the weld deposit. Crack initiation life was rather small compared with crack propagation life. This means that the propagation life is dominant in the fatigue life of the joints. Fracture surfaces under cyclic plastic strains contained dimples, which can produce an evidence of ductile crack propagation.

担当区分：筆頭著者   記述言語：日本語   掲載種別：研究論文（学術雑誌）  

DOI： 10.11273/jssc.16.64_21

担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

The improvement of extremely low cycle fatigue strength of welded joints by TIG dressing and burr grinding was investigated. The weld toes of T-shape welded joints were improved by TIG dressing or burr grinding and tested under displacement control conditions. The crack initiation life of finished specimens was at least threefold longer than that of as-welded specimens. There was no clear difference in improvement between TIG dressing and burr grinding. We also analysed the local strain around the cracking point by finite element analysis, and performed local strain-based fatigue assessment. The results indicated that extremely low cycle fatigue strength of the joints improved by TIG dressing and burr grinding can be assessed by evaluating the local strain and referring to the extremely low cycle fatigue strength curve.

DOI： 10.1007/BF03321135

担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

Fatigue crack propagation simulations on T-shape welded joints were carried out. Main plate of the joint was supported at ends and tensile and bending loads were applied to an attached rib. An initial crack of 0.5 mm in length was given at weld toe on the main plate. Five kinds of stresses, i.e. nominal bending stress, membrane stress and average shear stress in the main plate, nominal bending stress and membrane stress in the attached rib, were picked up as parameters. With changing these parameters, the crack propagation simulation was performed. Simulation results demonstrated that the crack direction at the beginning was influenced by the parameters, particularly the average shear stress in the main plate. These results were supported by fatigue test results conducted under the same conditions as the simulation. Finally, the relationship of the average shear stress and the crack direction at the beginning were presented.

記述言語：英語   掲載種別：研究論文（学術雑誌）  

The purpose of this study is to evaluate the fatigue strength of load carrying cruciform welded joints which contain incomplete penetration in both high and low cycle fatigue regions. Cyclic loading experiment was carried out in this study, and failure surfaces were investigated in order to verify the crack propagation and initiation point.

担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

In this paper, fatigue strength of welded joints with incomplete penetrations was experimentally investigated overall from low-cycle to high-cycle fatigue regions, corresponding to the fatigue life is from tens cycles to millions cycles. Fatigue tests on load-carrying cruciform joints containing root discontinuities were carried out. In all specimens, fatigue cracks initiated from the weld root and propagated into the weld metal. Fracture surfaces of the specimen were observed in order to verify the crack initiation point and propagation behavior.

記述言語：英語   掲載種別：研究論文（学術雑誌）  

The purpose of this research is to guess the behavior of member causing fatigue damage at joint part in Railway Truss Bridge using wireless acceleration sensor devices and local strain measurement, and to suggest the countermeasure for the prospective fatigue crack. In this paper, the experimental measurement in actual bridge was conducted, then the behavior of member causing the fatigue damage when train passed through the target panel point was verified by the local strain data from strain gauge and acceleration data from wireless sensor. Finally, from the measurement results, the countermeasure is suggested.

記述言語：英語   掲載種別：研究論文（学術雑誌）  

記述言語：英語   掲載種別：研究論文（学術雑誌）  

In this paper, fatigue crack propagation analysis on T-shape welded joints under out-of-plane plate bending was carried out. Main plate of the joint was supported at the ends, and tensile and bending loads were applied to an attached rib. We picked up five kinds of stresses as parameters, i.e. nominal bending stress, membrane stress and average shear stress in the main plate and nominal bending stress and membrane stress in the attached rib. We performed the analysis with changing these parameters and investigated the crack propagation path. The analysis results indicated that the crack angle at the beginning was influenced by these parameters, particularly the average shear stress in the main plate. These results were verified by fatigue tests conducted in the same conditions as the analysis. Finally, we presented the correlation between the average shear stress in the main plate and the crack angle at the beginning.

担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

Tip echo is scattered wave which radiates all direction from the sharp tip of reflection source such as fatigue cracks. Tip echo has been utilized for sizing defects as tip echo method and also may apply to identify fatigue cracks from other defects. The radiation characteristics of tip echo were examined experimentally and the relationship between incident wave directions and directivity of echo and dumping of echo due to fatigue crack closure were shown. The steering and focusing functions of linear phased array ultrasonic testing system was applied to send waves to the tip of crack with various angles and to receive echo waves from various directions. Then, the tip echo method was applied to a crack to grasp crack tip opening and closing behaviour in the residual stress field.

記述言語：英語   掲載種別：研究論文（学術雑誌）  

In this study, we analyzed the local strain around the cracking point of the finished joint and the as-welded joint by FEA, and demonstrated that the local strain could be affected by the toe geometry parameters, such as radius, depth of the groove, and the main plate thickness. Then, we presented an example way to determine the desirable shape of the finished zone for satisfying the fatigue performance requirement of the welded joint.

担当区分：筆頭著者   記述言語：日本語   掲載種別：研究論文（学術雑誌）  

担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

In the Great Hanshin Awaji Earthquake (1995), steel bridge piers were damaged by extremely low cycle fatigue, which has raised concerns about the seismic performance of the piers. However, researches on extremely low cycle fatigue strength of structural steel members have been limited and no design guidelines have been established for bridge structures. The authors have already conducted a series of researches on extremely low cycle fatigue strength of structural steel members and proposed a simple assessment method for extremely low cycle fatigue strength of the steel bridge piers. In this study, steel pier specimens were fabricated and tested under large cyclic deformation, and the proposed assessment method was verified by the test results.

担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

In this study, the improvement of extremely low cycle fatigue strength by toe finishing was investigated. T-shape welded joints, which are in as-welded, TIG dressed or burr ground condition, were tested under displacement control conditions. The test results indicated that crack initiation lives of finished specimens were much longer than those of as-welded specimens. Between TIG dressing and burr grinding, no clear difference on improvement was observed. We also performed elasto-plastic finite element analyses to calculate local strain around the cracking point, and assessed the fatigue strength of the finished specimen based on the local strain. The results demonstrated that the fatigue strength of TIG dressed and burr ground joints can be reasonably assessed using the local strain at the cracking point and the extremely low cycle fatigue strength curves.

担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

In this study, fatigue crack propagation analyses on T-shape welded joints subjected to plate bending were carried out. We picked up five kinds of stresses as parameters, i.e. nominal bending stress, membrane stress and average shear stress in the main plate, nominal bending stress and membrane stress in the attached rib. We analyzed the crack propagation path with changing these parameters. Analysis results indicated that the crack angle at the beginning was influenced by these parameters, especially the average shear stress in the main plate. These results were supported by fatigue test results conducted on T-shape welded joints with the same conditions used in the analysis. Finally, we presented the relationship of the average shear stress and the crack angle at the beginning.

担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

The improvement of extremely low cycle fatigue strength of welded joints by TIG dressing and burr grinding was investigated. The weld toes of T-shape welded joints were improved by TIG dressing or burr grinding and tested under displacement control conditions. The crack initiation life of finished specimens was at least threefold longer than that of as-welded specimens. There was no clear difference in improvement between TIG dressing and burr grinding. We also analysed the local strain around the cracking point by finite element analysis, and performed local strain-based fatigue assessment. The results indicated that extremely low cycle fatigue strength of the joints improved by TIG dressing and burr grinding can be assessed by evaluating the local strain and referring to the extremely low cycle fatigue strength curve.

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.2208/jsceja.64.288

担当区分：筆頭著者   記述言語：日本語   掲載種別：研究論文（学術雑誌）  

担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

A number of transportation agencies throughout the world have adopted and implemented the bridge management system with advanced asset management decision-making capabilities. However, there are still significant room for improvement in the information and data upon which the bridge management systems are based, and on the results and decision-making that occurs based on the output of these systems. In order to address some of gaps in knowledge, the Federal Highway Administration (FHWA) of the U.S. Department of Transportation is initiating a Long-Term Bridge Performance (LTBP) program in 2006. In this paper, we will introduce the recent bridge management systems and the LTBP program in the States.

担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

Several steel piers suffered low cycle fatigue damage in the Great Hanshin Earthquake (1995), which raises concerns about their performance in future earthquakes. However, researches on the low cycle fatigue of civil structures in extremely large strain region, corresponding to a strain magnitude of more than 10% and a fatigue life of less than ten cycles, are limited and design guidelines have not been established. In order to provide the benchmark data for extremely low cycle fatigue assessment, thick-walled steel piers with box section were fabricated and subjected to incremental or constant amplitude cyclic loading. During the test, fatigue cracks were initiated from weld toe at the corner. With the loading repetition, the cracks propagated along the weld toe. Finally, oblique cracks formed both in flange and web plate, and the pier was ruptured without local buckling. Although the cracks occurred at relatively early stage of the test, the loading capacity hardly decreased before failure. In other words, the crack propagation occupied the most part of life of the specimen. After the test, the low cycle fatigue strength of steel pier specimens was assessed based on the strain near the crack initiation point.

記述言語：英語   掲載種別：研究論文（学術雑誌）  

In a seismic event, steel piers may undergo large strain fluctuations of typically one to tens of cycles. That will possibly result in fracture of base end joints or beam-column joints, namely extremely low cycle fatigue. In this paper, thick walled un-stiffened box section steel piers subjected to incremental cyclic loading are analyzed by a three-dimensional elastic-plastic finite element analysis with shell and solid elements to investigate the behavior of local strain at weld toe. Several parameters, such as width thickness ratio, slenderness ratio, weld toe radius and axial loading, are taken into account. From engineering point of view, it is preferable to employ a simple parameter reflecting the local strain behavior. Here, the local strain is correlated to nominal strain, which is average strain along effective failure length by fiber model. Finally, a simple approach to extremely low cycle fatigue assessment is proposed and applied to test results.

担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

As a method to predict fatigue strength of welded joints in extremely low cycle fatigue region, local strain based approach was discussed in this paper. Low cycle fatigue tests were conducted on T-shaped welded joints in order to find the crack initiation point and to obtain the fatigue life. On the other hand, local strain field around welded toe, where fatigue cracks were formed in fatigue tests, was analyzed by elasto-plastic finite element analysis, and the local strain amplitude at the cracking point was quantified. Based on the fatigue life obtained by fatigue test and the local strain amplitude by FEA, fatigue test results were compared with the low cycle fatigue strength curve, i.e., strain versus fatigue-life diagram. Test data were consistent with the strength curve. Consequently, it was demonstrated the fatigue assessment method based on local strain approach is available to predict the fatigue strength of welded joints even in extremely large strain region.

担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

Miner's rule has been accepted as a simple and effective method for predicting the low cycle fatigue life under variable strain amplitude. However, in an extremely large strain field, corresponding to the fatigue life of less than 10 cycles, the accuracy of Miner's rule has not been verified. In this study, low cycle fatigue tests under variable strain amplitude in an extremely large strain field were conducted with a newly developed testing system. Miner's rule always predicted a longer fatigue life than the observed life. A simple model introducing the damage mechanics concept was proposed and its validity was examined as another method for predicting low cycle fatigue
life.

DOI： 10.1016/j.ijfatigue.2006.08.001

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.11273/jssc1994.13.52_73

担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

Miner's rule has been accepted as a simple and effective idea for predicting the low cycle fatigue life under variable strain amplitude. However, in an extremely large strain field, corresponding to the fatigue life of less than ten cycles, the accuracy of Miner's rule has not been verified. In this study, low cycle fatigue tests under variable strain amplitude in an extremely large strain field were conducted with a newly developed testing system. Since test results indicated that Miner's rule always predicted a longer fatigue life than the observed life, we proposed a modified life prediction model introducing the damage mechanics concept and investigated its validity.

担当区分：筆頭著者   記述言語：日本語   掲載種別：研究論文（学術雑誌）  

DOI： 10.11273/jssc1994.13.50_27

担当区分：筆頭著者   記述言語：日本語   掲載種別：研究論文（学術雑誌）  

本研究では，極低サイクル疲労領域における溶接継手の低サイクル疲労強度を推定するための手法として，局部的なひずみを基準とする疲労強度評価手法に着目した．溶接継手の例として，T字溶接継手試験体を対象とした極低サイクル疲労試験を行った．一方，弾塑性有限要素解析により，溶接部周辺のひずみ分布を明らかにし，き裂発生点における局部的なひずみを求めた．局部的なひずみにより疲労試験結果を整理した結果，全ての試験データがき裂発生点である溶接金属部の疲労強度曲線と一致し，極低サイクル疲労領域においてもき裂発生点の局部的なひずみを用いることにより疲労強度を推定することが可能であることが明らかとなった．

DOI： 10.2208/jsceja.62.101

担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

As an estimation method of fatigue strength of welded joint in extremely low cycle fatigue region, peak strain based fatigue assessment method was verified. T-shape welded joints were employed for the verification test. The specimen was analyzed by elasto-plastic finite element method in order to quantify the local strain field around welded portion and the peak strain at the cracked point. On the other hand, fatigue life of the specimen was experimentally obtained by low cycle fatigue tests. The relationship between the peak strain and the fatigue life was consistent with the fatigue strength curve proposed by the authors. Consequently, it was demonstrated that the fatigue assessment method by peak strain approach was available even in extremely low cycle fatigue region.

担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

Extensive experiments on low cycle fatigue for plain steel material have been conducted and obtained some important results. However there are few studies for extremely low cycle fatigue, corresponding to the strain more than 0.10.
In this study, a new low cycle fatigue testing system, in which a steel plate specimen was subjected to bending deformation and the image technique was introduced to measure the strains in the specimen, was developed. The testing system has enabled the low cycle fatigue test with introducing extremely large strains into the specimen. Low cycle fatigue tests on plain steel plates under constant and variable strain amplitude were conducted by using the system. Based on the test results, an estimation method for low cycle fatigue strength in extremely low cycle fatigue region was proposed.

担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

The improvement of extremely low cycle fatigue strength of welded joints by TIG dressing was investigated. T-shape welded joint specimens of which weld toes were finished by TIG dressing were tested. The fatigue test results were compared with that of as-weld specimens tested in the same conditions. The test results indicated that TIG dressing could substantially increase the extremely low cycle fatigue strength of welded joints.

担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

A new low cycle fatigue testing system has been developed, in which a steel plate specimen is subjected to bending deformation, and strains of the specimen are measured by image technique. In this study, the low cycle fatigue tests of steel welded joints under constant and variable strain amplitude, particularly the fatigue life less than ten cycles in extremely large strain field, was conducted by using the newly developed testing system. On the basis of the test results, the applicability of low cycle fatigue life prediction model was confirmed, which has been developed for plain steel material, to welded portion, such as deposit metal and heat affected zone (HAZ).

担当区分：筆頭著者   記述言語：日本語   掲載種別：研究論文（学術雑誌）  

DOI： 10.11273/jssc1994.12.46_27

担当区分：筆頭著者   記述言語：日本語   掲載種別：研究論文（学術雑誌）  

担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

In this study, we investigated the low cycle fatigue strength of welded joints using a new fatigue testing system in which the image analysis technique was used to measure the strains in specimens. After checking the validity of the testing system, we used this new system to conduct fatigue tests on welded joint specimens. The test results indicate that the fatigue strength of welded material (weld deposit and heat affected zone) is much lower than that of the plain material.

DOI： 10.1016/j.ijfatigue.2004.03.016

担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

Authors have developed a new low cycle fatigue testing method, in which a specimen is subjected to bending deformation and strain of the specimen is measured by image analysis. The advantage of this method is to be able to induce extreme large strain in steel plate even if it includes welding. In this study, the fatigue strength of welded joints in extreme large strain field was investigated by a newly developed testing system. The test results indicated that the fatigue strength of welded joints was much lower than that of plain material, and heat affected zone (HAZ) was the weakest spot.

担当区分：筆頭著者   記述言語：日本語   掲載種別：研究論文（学術雑誌）  

変動振幅ひずみ下での鋼材の低サイクル疲労強度については，従来より，Miner則を用いることにより比較的精度よく予測できるといわれている．しかし，これは疲労寿命が数百回以上の領域での検討結果に基づいており，極低サイクル疲労領域における寿命予測手法は確立されていないのが現状である．本研究では新たに開発した低サイクル疲労試験システムを用い，極低サイクル疲労領域における変動振幅ひずみによる低サイクル疲労試験を行った．その結果，極低サイクル疲労領域ではMiner則は危険側の予測結果を与えることが明らかとなった．そこで極低サイクル疲労領域における新たな疲労寿命予測モデルを提案し，試験結果と比較した結果，提案モデルにより精度よく疲労寿命を推定できることが明らかとなった．

DOI： 10.2208/jscej.2004.773_149

担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

Extensive experiments on the low cycle fatigue for plain steel material have been conducted and obtained some important results. There are few studies, however, on the low cycle fatigue in the extreme large strain field, corresponding to the fatigue life less than ten cycles.
In this study, we developed a new low cycle fatigue testing system, in which a specimen was subjected to bending deformation and the strain in the specimen was measured by image analysis technique. Low cycle fatigue tests on plain steel plates under constant and variable strain amplitude were conducted by using the testing system. Based on the test results, an estimation method for low cycle fatigue strength in the extreme large strain field was proposed.

担当区分：筆頭著者   記述言語：日本語   掲載種別：研究論文（学術雑誌）  

本研究では，従来の砂時計型試験体では困難とされている，溶接部の低サイクル疲労強度を実験的に明らかにすることを目的とし，新たな試験システムとして，画像計測を用いたひずみ制御低サイクル曲げ試験システムを開発した．あらかじめ，画像計測面近傍にひずみゲージを貼付し，それにより測定できた範囲内で画像計測値とゲージ値を比較することで本計測手法の精度を確認した．本手法を用いて素材試験体と突合わせ溶接継手試験体の疲労試験を行った結果，素材試験体に関しては過去の研究におけるデータと同様の傾向を示した．一方，溶接継手試験体では，素材試験体の疲労強度を大幅に下回っており，溶接継手の低サイクル疲労強度は著しく低下することを明らかにした．

DOI： 10.2208/jscej.2004.752_277

担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

Since Great Hanshin-Awaji Earthquake caused low cycle fatigue failures at base joints and beam-to-column connections in steel piers, it is important to investigate the low cycle fatigue strength of welded joints in civil structures. In this study, low cycle fatigue strength of welded joints was investigated by means of a new fatigue testing system in which image analysis technique was introduced to measure the strain of specimens. It was validated that the strains measured by the image analysis were almost equal to those by strain gauges, and the low cycle fatigue strength of plain steel plate was in good agreement with the result reported in the former studies. The low cycle fatigue tests carried out on welded joint specimens indicated that the fatigue strength of the welded joints was much lower than that of plain material.

担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

Almost all the low cycle fatigue cracks observed in Hanshin-Awaji Earthquake were initiated from welded joints. In this study, a new testing system was developed, which enables the investigation on the low cycle fatigue strength of welded joints. In this testing system, a specimen was subjected to bending deformation, and the strain in the specimen was measured by means of image analysis technique. It was shown that the strains measured by the image analysis were almost equal to those measured by strain gauges, and the low cycle fatigue strength of plain steel material obtained by this testing system was in good agreement with the results reported in former studies.

担当区分：筆頭著者   記述言語：日本語   掲載種別：研究論文（学術雑誌）  

DOI： 10.11273/jssc1994.8.31_11

記述言語：英語   掲載種別：研究論文（学術雑誌）  

記述言語：英語   掲載種別：研究論文（学術雑誌）  

記述言語：日本語   掲載種別：研究論文（学術雑誌）  

記述言語：日本語

記述言語：日本語

記述言語：日本語

記述言語：日本語

記述言語：日本語

記述言語：日本語

開催年月日： 2024年9月

記述言語：日本語   会議種別：口頭発表（一般）  

国名：日本国  

開催年月日： 2024年9月

記述言語：日本語   会議種別：口頭発表（一般）  

国名：日本国  

開催年月日： 2024年9月

記述言語：日本語   会議種別：口頭発表（一般）  

国名：日本国  

開催年月日： 2024年9月

記述言語：日本語   会議種別：口頭発表（一般）  

国名：日本国  

開催年月日： 2024年9月

記述言語：日本語   会議種別：口頭発表（一般）  

国名：日本国  

開催年月日： 2024年9月

記述言語：日本語   会議種別：口頭発表（一般）  

国名：日本国  

開催年月日： 2024年9月

記述言語：日本語   会議種別：口頭発表（一般）  

国名：日本国  

開催年月日： 2024年9月

記述言語：日本語   会議種別：口頭発表（一般）  

国名：日本国  

開催年月日： 2024年7月

記述言語：英語   会議種別：口頭発表（一般）  

開催地：Rhodes Island   国名：ギリシャ共和国  

開催年月日： 2024年7月

記述言語：英語   会議種別：口頭発表（一般）  

開催地：Rhodes Island   国名：ギリシャ共和国  

開催年月日： 2024年7月

記述言語：英語   会議種別：口頭発表（一般）  

開催地：Rhodes Island   国名：ギリシャ共和国  

開催年月日： 2023年11月

記述言語：日本語   会議種別：口頭発表（一般）  

国名：日本国  

開催年月日： 2023年11月

記述言語：日本語   会議種別：口頭発表（一般）  

国名：日本国  

開催年月日： 2023年11月

記述言語：英語   会議種別：口頭発表（一般）  

国名：大韓民国  

開催年月日： 2023年11月

記述言語：英語   会議種別：口頭発表（一般）  

国名：大韓民国  

開催年月日： 2023年11月

記述言語：英語   会議種別：口頭発表（一般）  

国名：大韓民国  

開催年月日： 2023年11月

記述言語：英語   会議種別：口頭発表（一般）  

国名：大韓民国  

開催年月日： 2023年11月

記述言語：英語   会議種別：口頭発表（一般）  

国名：大韓民国  

開催年月日： 2023年11月

記述言語：英語   会議種別：口頭発表（一般）  

国名：大韓民国  

開催年月日： 2023年11月

記述言語：英語   会議種別：口頭発表（一般）  

国名：大韓民国  

開催年月日： 2023年11月

記述言語：英語   会議種別：口頭発表（一般）  

国名：大韓民国  

開催年月日： 2023年11月

記述言語：英語   会議種別：口頭発表（一般）  

国名：大韓民国  

開催年月日： 2023年9月

記述言語：日本語   会議種別：口頭発表（一般）  

国名：日本国  

開催年月日： 2023年9月

記述言語：日本語   会議種別：口頭発表（一般）  

国名：日本国  

開催年月日： 2023年9月

記述言語：日本語   会議種別：口頭発表（一般）  

国名：日本国  

開催年月日： 2023年9月

記述言語：日本語   会議種別：口頭発表（一般）  

国名：日本国  

開催年月日： 2023年9月

記述言語：日本語   会議種別：口頭発表（一般）  

国名：日本国  

開催年月日： 2023年9月

記述言語：日本語   会議種別：口頭発表（一般）  

国名：日本国  

開催年月日： 2023年9月

記述言語：日本語   会議種別：口頭発表（一般）  

国名：日本国  

開催年月日： 2023年9月

記述言語：日本語   会議種別：口頭発表（一般）  

国名：日本国  

開催年月日： 2023年9月

記述言語：日本語   会議種別：口頭発表（一般）  

国名：日本国  

開催年月日： 2023年9月

記述言語：日本語   会議種別：口頭発表（一般）  

国名：日本国  

開催年月日： 2023年7月

記述言語：英語   会議種別：口頭発表（一般）  

開催地：Singapore   国名：シンガポール共和国  

開催年月日： 2023年5月

記述言語：日本語   会議種別：口頭発表（一般）  

国名：日本国  

開催年月日： 2022年11月

記述言語：日本語   会議種別：口頭発表（一般）  

国名：日本国  

開催年月日： 2022年9月

記述言語：日本語   会議種別：口頭発表（一般）  

国名：日本国  

開催年月日： 2022年9月

記述言語：日本語   会議種別：口頭発表（一般）  

国名：日本国  

開催年月日： 2022年9月

記述言語：日本語   会議種別：口頭発表（一般）  

国名：日本国  

開催年月日： 2022年9月

記述言語：日本語   会議種別：口頭発表（一般）  

国名：日本国  

開催年月日： 2022年9月

記述言語：日本語   会議種別：口頭発表（一般）  

国名：日本国  

開催年月日： 2022年9月

記述言語：日本語   会議種別：口頭発表（一般）  

国名：日本国  

開催年月日： 2022年7月

記述言語：英語   会議種別：口頭発表（一般）  

開催地：Tokyo   国名：日本国  

開催年月日： 2022年7月

記述言語：英語   会議種別：口頭発表（一般）  

開催地：Tokyo   国名：日本国  

開催年月日： 2022年7月

記述言語：英語   会議種別：口頭発表（一般）  

開催地：Tokyo   国名：日本国  

開催年月日： 2022年7月

記述言語：英語   会議種別：口頭発表（一般）  

国名：スペイン  

DOI： 10.1201/9781003322641-263

開催年月日： 2022年7月

記述言語：英語   会議種別：口頭発表（一般）  

国名：スペイン  

DOI： 10.1201/9781003322641-262

開催年月日： 2022年4月

記述言語：日本語   会議種別：口頭発表（一般）  

国名：日本国  

開催年月日： 2022年4月

記述言語：日本語   会議種別：口頭発表（一般）  

国名：日本国  

開催年月日： 2021年11月

記述言語：日本語   会議種別：口頭発表（一般）  

国名：日本国  

開催年月日： 2021年11月

記述言語：英語   会議種別：口頭発表（一般）  

国名：大韓民国  

開催年月日： 2021年11月

記述言語：英語   会議種別：口頭発表（一般）  

国名：大韓民国  

開催年月日： 2021年11月

記述言語：英語   会議種別：口頭発表（一般）  

国名：大韓民国  

開催年月日： 2021年11月

記述言語：英語   会議種別：口頭発表（一般）  

国名：大韓民国  

開催年月日： 2021年11月

記述言語：英語   会議種別：口頭発表（一般）  

国名：大韓民国  

開催年月日： 2021年11月

記述言語：英語   会議種別：口頭発表（一般）  

国名：大韓民国  

開催年月日： 2021年9月

記述言語：日本語   会議種別：口頭発表（一般）  

国名：日本国  

開催年月日： 2021年9月

記述言語：日本語   会議種別：口頭発表（一般）  

国名：日本国  

開催年月日： 2021年9月

記述言語：日本語   会議種別：口頭発表（一般）  

国名：日本国  

開催年月日： 2021年9月

記述言語：日本語   会議種別：口頭発表（一般）  

国名：日本国  

開催年月日： 2021年9月

記述言語：日本語   会議種別：口頭発表（一般）  

国名：日本国  

開催年月日： 2021年9月

記述言語：日本語   会議種別：口頭発表（一般）  

国名：日本国  

開催年月日： 2021年9月

記述言語：日本語   会議種別：口頭発表（一般）  

国名：日本国  

開催年月日： 2021年7月

記述言語：英語   会議種別：口頭発表（一般）  

開催地：Online   国名：日本国  

開催年月日： 2021年7月

記述言語：英語   会議種別：口頭発表（一般）  

開催地：Online   国名：日本国  

開催年月日： 2021年4月

記述言語：日本語   会議種別：口頭発表（一般）  

国名：日本国  

開催年月日： 2021年4月

記述言語：英語   会議種別：口頭発表（一般）  

国名：日本国  

DOI： 10.1201/9780429279119-365

開催年月日： 2021年4月

記述言語：英語   会議種別：口頭発表（一般）  

国名：日本国  

DOI： 10.1201/9780429279119-540

開催年月日： 2021年4月

記述言語：英語   会議種別：口頭発表（一般）  

国名：日本国  

DOI： 10.1201/9780429279119-496

開催年月日： 2021年4月

記述言語：英語   会議種別：口頭発表（一般）  

国名：日本国  

DOI： 10.1201/9780429279119-478

開催年月日： 2020年9月

記述言語：日本語   会議種別：口頭発表（一般）  

国名：日本国  

開催年月日： 2020年9月

記述言語：日本語   会議種別：口頭発表（一般）  

国名：日本国  

開催年月日： 2020年9月

記述言語：日本語   会議種別：口頭発表（一般）  

国名：日本国  

開催年月日： 2020年9月

記述言語：日本語   会議種別：口頭発表（一般）  

国名：日本国  

開催年月日： 2020年9月

記述言語：日本語   会議種別：口頭発表（一般）  

国名：日本国  

開催年月日： 2020年9月

記述言語：日本語   会議種別：口頭発表（一般）  

国名：日本国  

開催年月日： 2020年9月

記述言語：日本語   会議種別：口頭発表（一般）  

国名：日本国  

開催年月日： 2019年11月

記述言語：日本語   会議種別：口頭発表（一般）  

国名：日本国  

開催年月日： 2019年11月

記述言語：英語   会議種別：口頭発表（一般）  

国名：日本国  

開催年月日： 2019年11月

記述言語：英語   会議種別：口頭発表（一般）  

国名：日本国  

開催年月日： 2019年11月

記述言語：英語   会議種別：口頭発表（一般）  

国名：大韓民国  

開催年月日： 2019年11月

記述言語：英語   会議種別：口頭発表（一般）  

国名：大韓民国  

開催年月日： 2019年11月

記述言語：英語   会議種別：口頭発表（一般）  

国名：大韓民国  

開催年月日： 2019年11月

記述言語：英語   会議種別：口頭発表（一般）  

国名：大韓民国  

開催年月日： 2019年11月

記述言語：英語   会議種別：口頭発表（一般）  

国名：日本国  

開催年月日： 2019年11月

記述言語：英語   会議種別：口頭発表（一般）  

国名：日本国  

開催年月日： 2019年11月

記述言語：英語   会議種別：口頭発表（一般）  

国名：日本国  

開催年月日： 2019年11月

記述言語：英語   会議種別：口頭発表（一般）  

国名：日本国  

開催年月日： 2019年11月

記述言語：英語   会議種別：口頭発表（一般）  

国名：日本国  

開催年月日： 2019年11月

記述言語：英語   会議種別：口頭発表（一般）  

国名：日本国  

開催年月日： 2019年9月

記述言語：日本語   会議種別：口頭発表（一般）  

国名：日本国  

開催年月日： 2019年9月

記述言語：日本語   会議種別：口頭発表（一般）  

国名：日本国  

開催年月日： 2019年9月

記述言語：日本語   会議種別：口頭発表（一般）  

国名：日本国  

開催年月日： 2019年7月

記述言語：英語   会議種別：口頭発表（一般）  

国名：スロバキア共和国  

開催年月日： 2018年11月

記述言語：日本語   会議種別：口頭発表（一般）  

国名：日本国  

開催年月日： 2018年11月

記述言語：日本語   会議種別：口頭発表（一般）  

国名：日本国  

開催年月日： 2018年8月

記述言語：日本語   会議種別：口頭発表（一般）  

国名：日本国  

開催年月日： 2018年8月

記述言語：日本語   会議種別：口頭発表（一般）  

国名：日本国  

開催年月日： 2018年8月

記述言語：日本語   会議種別：口頭発表（一般）  

国名：日本国  

開催年月日： 2018年8月

記述言語：日本語   会議種別：口頭発表（一般）  

国名：日本国  

開催年月日： 2018年8月

記述言語：日本語   会議種別：口頭発表（一般）  

国名：日本国  

開催年月日： 2018年8月

記述言語：日本語   会議種別：口頭発表（一般）  

国名：日本国  

開催年月日： 2018年7月

記述言語：英語   会議種別：口頭発表（一般）  

国名：インドネシア共和国  

開催年月日： 2018年4月

記述言語：日本語   会議種別：口頭発表（一般）  

国名：日本国