研究者詳細 - 判治　剛

論文 - 判治　剛

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Fatigue strength improvement by induction heating against weld root failure in out-of-plane gusset welded joints 査読有り

Suguru Kano, Satoshi Maeda, Kazuo Tateishi, Takeshi Hanji, Masaru Shimizu

Proceedings of the IABSE Symposium Tokyo 2025 頁： CD-ROM 2025年5月

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 improvement of fatigue strength at the weld root in out-of-plane gusset welded joints by induction heating (IH). IH works by locally heating the object with coils energized by high-frequency AC power, which can alter the residual stress distribution.
This study specifically focused on introducing tensile residual stress by locally heating the area around the boxing weld, thereby redistributing the residual stresses to introduce compressive residual stresses at the weld. This process helps transform the tensile residual stresses introduced during welding into compressive residual stresses, thus improving the fatigue strength of welded joints. Unlike other methods such as weld toe treatment, IH does not need to treat the potential crack initiation site directly, making it a promising approach for improving fatigue strength at the weld root.
The improvement in fatigue strength by IH was verified using fatigue tests under out-of-plane bending loads with a vibration-type fatigue testing machine. The results showed that the fatigue strength of the IH-treated specimens was higher than that of the specimens in the as-welded state.
Further numerical investigation based on finite element analysis to reproduce the welding and IH treatment clarified the residual stress distributions around the weld. Additionally, residual stress measurements were carried out using the X-ray diffraction method. These results confirmed that IH can reduce residual stress at the weld and introduce compressive residual stress to the weld root, which is consistent with the fatigue strength improvement against weld root failure obtained in the fatigue tests.

Fatigue strength of fillet welded T-joints using new welding materials 査読有り

Keita Asano, Takeshi Hanji, Kazuo Tateishi, Masaru Shimizu, Yuki Kotani, Toshio Takebuchi

Proceedings of the IABSE Symposium Tokyo 2025 頁： CD-ROM 2025年5月

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, fatigue tests and finite element analyses were conducted on T joints using various new welding materials to investigate the effect of enhancing fatigue strength through the application of unconventional welding materials, which are not commonly used in steel bridges. The results revealed that low transformation temperature welding materials reduced the tensile residual stress around the weld, leading to the improvement of fatigue strength. Additionally, it was found that applying additional welding method with a newly developed material for Ar-shielded MIG welding decreased stress concentration at the weld toe, resulting the improvement of fatigue strength.

Evaluation of through-thickness residual stress at T-joint weld toes using slitting method 査読有り

Yao Wu, Takeshi Hanji, Kazuo Tateishi, Masaru Shimizu

Proceedings of the IABSE Symposium Tokyo 2025 頁： CD-ROM 2025年5月

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）

Residual stress in welds is a critical factor influencing the fatigue strength of welded joints. Understanding the residual stress distribution, both on the surface and within the interior of the plates, is essential for improving the accuracy of fatigue strength evaluations in welded joints. This study aims to numerically evaluate the through-thickness residual stress at the weld toe of T-joints using the slitting method. This approach involves welding simulation, slitting simulation, and fracture mechanics to investigate the relationship between the internal residual stress and the strain changes on the plate surface near the weld toe, which occur due to stress relief during the slitting process. The results indicate that the through-thickness residual stress distributions estimated through the slitting method are consistent with those initially present in the welded joint, even under varying conditions such as different initial residual stress distributions, geometrical parameters of the joint (e.g., plate thickness, weld size), and slitting conditions (e.g., slit width and location, cutting depth ratio). Furthermore, this study identifies an optimal slitting strategy, which enhances the accuracy of residual stress evaluation.

Structural improvement of orthotropic steel decks focusing on fatigue durability and manufacturing costs 査読有り

Satoshi Maeda, Takayuki Kawakami, Hironori Ishii, Takeshi Hanji, Kazuo Tateishi

Proceedings of the IABSE Symposium Tokyo 2025 頁： CD-ROM 2025年5月

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）

Orthotropic steel decks (OSDs) are widely used for long-span bridges or urban expressways because they are lightweight and allow rapid construction. However, an OSD designed according to Japanese specifications for highway bridges has several issues. For example, an OSD with closed ribs (CRD) requires a minimum deck plate thickness of 16 mm, but it has been revealed that this does not completely prevent fatigue crack initiation from the weld root in the rib to deck plate welded joints under heavy traffic loads. In contrast, an OSD with open ribs (ORD) has fewer fatigue problems, but the dead load (steel weight) and manufacturing cost tend to be higher due to the smaller spacing between transverse ribs compared to CRDs. This study investigated improved OSD structures that ensure fatigue durability while reducing the dead load and manufacturing cost.
For a conventional CRD, two improved structures were designed that reduce stress at both the cross-beam intersection and general section by reducing the width and spacing of U-ribs, even with a thinner deck plate. The improved CRDs reduced the steel weight compared to a conventional CRD, and had a similar manufacturing cost.
For a conventional ORD, an improved structure was designed that expands the cross-beam spacing to 4.0 m by using L-shaped steel for longitudinal ribs. The improved ORD reduced both the steel weight and manufacturing cost compared to those for a conventional ORD.

Investigation on the rational cut-out shape for fatigue countermeasure in vertical stiffeners of orthotropic steel decks 査読有り

Masaru Shimizu, Kazuo Tateishi, Takeshi Hanji, Hideya Hasegawa, Hiroki Suetsugu

Proceedings of the IABSE Symposium Tokyo 2025 頁： CD-ROM 2025年5月

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 orthotropic steel bridge decks, many fatigue cracks have been found at the weld joint between deck plate and vertical stiffeners. As a countermeasure for the fatigue crack, semi-circular cut-out is introduced in the top of vertical stiffener to reduce the stress concentration around boxing weld. However, more effective cut-out geometry should be considered from viewpoint of fatigue improvement and constructability. In this study, stress reductions were investigated for newly developed slit-like cut-out and sigma-shaped cut-out.
For various cut-out shapes, the stress reductions were investigated from finite element analysis. Significant reduction in stress was found when the cut-out length was long and the distance from the upper edge of the cut-out to the bottom surface of the deck plate was short. Fatigue life extension was verified through fatigue tests on a welded joint specimen consisting of deck plate and vertical stiffeners. A cut-out dimensions were adopted as 20mm from the upper edge of the cut-out to the bottom surface of the deck plate, a length of 118.5 mm, and a hole diameter of 100 mm. As a result, the fatigue life extension for welded joint between deck plate and vertical stiffener at the crack initiation stage was more than 12 times that of a specimen without a cut-out. In addition, crack propagation was also retarded after introducing the cut-out in the vertical stiffener.

既設鋼床版のUリブ・デッキプレート溶接部に対する床版下面からの疲労対策の耐久性検証査読有り

服部雅史，舘石和雄，判治剛，寺沢拓哉

土木学会論文集 81 巻 ( 2 ) 頁： 24-00187 2025年2月

記述言語：日本語掲載種別：研究論文（学術雑誌）

鋼床版のUリブとデッキプレートの溶接ルートから発生する疲労き裂に対して，筆者らは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提案した．一方で，その対策方法には，横リブ交差部を除く一般部の疲労耐久性が不明であることや，対策のうちピーニング処理の範囲が不明瞭であるとした課題が残されている．本報告は，それら課題の解決を試み，その疲労対策の耐久性を検証したものである．具体的には，はじめに，既設鋼床版のUリブ・デッキプレート溶接部の一般部において，疲労き裂を再現することができる試験方法を調査した．次に，試験方法の調査結果を踏まえ，輪荷重走行試験により本対策の一般部の疲労耐久性を明らかにするとともに，ピーニング処理範囲の決定に必要なデータを得た．最後に，提案されている対策方法の改良案を示した．

DOI： 10.2208/jscejj.24-00187

Extending fatigue life of weld roots in fillet-welded cover plates by installing tap bolt joints 査読有り国際誌

Yuichiro Niwa, Kazuo Tateishi, Takeshi Hanji, Masaru Shimizu

Welding in the World ?? 巻 ( ?? ) 頁： ???-??? 2025年2月

記述言語：英語掲載種別：研究論文（学術雑誌）

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 class under cyclic tensile axial loads and 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 joint method can extend the fatigue life of the weld root of a sole plate.

DOI： 10.1007/s40194-025-01986-8

鋼床版横リブ交差部ビード進展き裂に対するデッキプレート上面からの当て板補強に関する解析的検討査読有り

寺沢拓哉，清水優，舘石和雄，判治剛，長谷川秀也，末次宏基

鋼構造年次論文報告集 32 巻頁： 1-9 2024年11月

AE計測によるルートき裂の検知に関する基礎的検討査読有り

清水優，舘石和雄，判治剛

鋼構造年次論文報告集 32 巻頁： 39-46 2024年11月

新しい溶接材料を用いたT形すみ肉溶接継手の疲労強度査読有り

浅野景太，判治剛，舘石和雄，清水優，小谷祐樹，竹渕敏郎

鋼構造年次論文報告集 32 巻頁： 77-88 2024年11月

Evaluation of fatigue damage ratio for slotted tubular joints of overhead transmission tower with fatigue cracks 査読有り

Naohiro Soda, Kazuo Tateishi, Takeshi Hanji, Masaru Shimizu

Proceedings of the 18th East Asia-Pacific Conference on Structural Engineering and Construction 頁： E0054 2024年11月

記述言語：英語掲載種別：研究論文（学術雑誌）

To systematically maintain a large number of overhead transmission towers, it is important to understand the mechanism of fatigue failure and its evaluation methods. In this study, we evaluate the fatigue damage ratios for a case involving fatigue cracks in the slotted tubular joints of a testing tower to discuss the application range of the evaluation method and factors affecting the fatigue damage ratio. The fatigue damage ratios are calculated using wind data observed near the tower, a response estimation method for vortex-induced vibration (VIV), and previous fatigue strength data for slotted tubular joints. The results show that the fatigue damage ratios of horizontal and web members on the north side of the tower, directly exposed to strong winds, exhibited good agreement with the actual failure state. However, the accuracy of the results for members in the cross-arm sections was diminished, primarily due to the stress range induced by VIV nearing the cut-off limit. Additionally, the wind acting on these members were disturbed by the other members located upwind of them. Furthermore, the slenderness ratio of a member with a high fatigue damage ratio was limited to a specific range.

疲労き裂進展抵抗を高めた鋼材の活用による橋梁鋼床版のデッキ貫通き裂の疲労寿命改善の検討査読有り

ドアンティーフィン，栗原康行，兵藤義浩，﨑本隆洋，判治剛，田川哲哉

鋼構造論文集 31 巻 ( 123 ) 頁： 13-22 2024年9月

高力ボルトにより当て板添接されたストップホールの組合せ応力作用下での応力集中低減効果査読有り

清川昇悟，舘石和雄，判治剛，趙茂伶，川上峻幸

鋼構造論文集 31 巻 ( 123 ) 頁： 57-68 2024年9月

Quantifying the intensity of high frequency mechanical impact treatment 査読有り国際共著国際誌

Jan Schubnell, Takeshi Hanji, Kazuo Tateishi, Stefanos Gkatzogiannis, Thomas Ummenhofer, Majid Farajian

Welding in the World 69 巻 ( 1 ) 頁： 125-137 2024年7月

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

Numerical simulation of fatigue crack propagation and repair with drilled hole in trough-girder bridges 査読有り

Takeshi Hanji, Kazuo Tateishi, Miki Shibata, Masaru Shimizu, Makoto Yamaguchi, Yuichiro Niwa

The 77th Annual Assembly of International Institute of Welding 頁： XIII-3083-2024 2024年7月

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.

2024 Report of work in progress (WIP) on fatigue strength of welded joints in Japan 査読有り

Takeshi Hanji, Eiichi Sasaki

The 77th Annual Assembly of International Institute of Welding 頁： XIII-3088-2024 2024年7月

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.

Extending fatigue life of weld roots in fillet-welded cover plates by installing tap bolt joints 査読有り

Yuichiro Niwa, Kazuo Tateishi, Takeshi Hanji, Masaru Shimizu

The 77th Annual Assembly of International Institute of Welding 頁： XIII-3084-2024 2024年7月

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.

鋼橋ソールプレート溶接部の疲労き裂の予防保全対策査読有り

丹羽雄一郎，舘石和雄，判治剛，清水優

土木学会論文集 80 巻 ( 5 ) 頁： 23-00234 2024年5月

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

鋼床版Uリブ・デッキプレート溶接継手におけるルートの局部応力による疲労強度評価査読有り

清水優，判治剛，内田大介，服部雅史，吉田黎

鋼構造論文集 31 巻 ( 121 ) 頁： 72-87 2024年3月

タップボルト継手の疲労強度および材間相対変位の評価査読有り

丹羽雄一郎，舘石和雄，判治剛，清水優

鋼構造論文集 31 巻 ( 121 ) 頁： 115-126 2024年3月

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