研究者詳細 - 判治　剛

論文 - 判治　剛

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鋼床版垂直補剛材上端への切欠きの施工による応力低減効果の簡易推定査読有り Open Access

清水優，舘石和雄，判治剛，末次宏基，長谷川秀也

構造工学論文集 72A 巻頁： 484-494 2026年3月

鋼床版Uリブの形状変更によるデッキ進展き裂の疲労強度改善査読有り Open Access

前田諭志，舘石和雄，判治剛，清水優，髙田耕庸

土木学会論文集 82 巻 ( 2 ) 頁： 25-00223 2026年2月

記述言語：日本語掲載種別：研究論文（学術雑誌）

本論文は，閉断面リブ鋼床版に発生するデッキ進展き裂に対し，Uリブの形状変更による疲労強度改善を検討したものである．まず，有限要素解析を用いてUリブの幅およびUリブ同士の間隔がき裂発生点の応力に与える影響を確認し，従来のUリブを用いた構造に比べて疲労強度の改善が期待できる構造を提案した．次に提案構造に対して交差部定点疲労試験および輪荷重走行試験を行い，その疲労強度を確認した．最後に，実橋を対象とした解析的検討により，供用環境下における疲労寿命を定量評価した．これらの検討により，Uリブ形状の変更はデッキ進展き裂の疲労強度改善に有効であることを示した．

DOI： 10.2208/jscejj.25-00223

Open Access

送電用鉄塔部材に用いられる鋼管割込み継手の曲げ疲労強度査読有り Open Access

早田直広，舘石和雄，判治剛，清水優

鋼構造論文集 32 巻 ( 128 ) 頁： 163-178 2025年12月

Fatigue life evaluation of root failure in welded joints based on displacement around the weld root 査読有り国際誌 Open Access

Erik Wahyu Pradana, Kazuo Tateishi, Takeshi Hanji, Masaru Shimizu

Welding in the World ?? 巻 ( ?? ) 頁： ???-??? 2025年12月

記述言語：英語掲載種別：研究論文（学術雑誌）

Unanticipated load transfer in load-carrying cruciform and butt-welded joints with incomplete penetration can initiate fatigue cracks from the weld root. Conventionally, the fatigue life of such joints is assessed using the nominal stress approach. However, this method is often inadequate for geometrically complex joints, particularly when the weld throat nominal stress cannot be clearly defined due to non-uniform stress distribution. Although the effective notch stress (ENS) method provides an alternative, it is computationally demanding and relies on an assumed notch radius which lacks a well-defined physical basis. This study proposes an alternative fatigue evaluation method based on displacement around the weld root, offering a physically meaningful and mesh-insensitive fatigue damage parameter. A linear-elastic finite element model with a 1 mm mesh around the unfused zone was employed to evaluate the displacement at a reference point 1 mm from the weld root. A dataset comprising 398 fatigue test results from specimens with incomplete penetration exhibiting root failure was extracted from the literature to validate the proposed method. A correction factor was introduced to normalize the fatigue damage parameter into a dimensionless form, allowing direct comparisons across specimens of varying sizes and geometries. The relationship between the normalized fatigue damage parameter and fatigue life was presented on logarithmic scales, resulting in the normalized Δd–N curve. This curve not only demonstrates improved predictive accuracy and reliability compared to the conventional S–N curve but also offers a physically interpretable approach applicable to complex welded joint geometries.

DOI： 10.1007/s40194-025-02293-y

Open Access

Fatigue life evaluation of deck propagation crack in orthotropic steel deck and effect of temperature 査読有り国際誌

Satoshi Maeda, Kazuo Tateishi, Takeshi Hanji, Masaru Shimizu, Koyo Takata

Proceedings of the ISSS and PSSC 2025 頁： 798-801 2025年11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 often used for long-span bridges or urban highways in Japan due to their light weight and rapid construction. However, fatigue cracks can initiate from the weld root in the closed rib to deck plate welded joints and potentially propagate to the deck surface (deck propagation cracks). Since these cracks can lead to pavement damage and reduced road traffic safety, accurate evaluation of crack initiation and propagation is necessary. This study quantitatively evaluated the fatigue life of deck propagation cracks using finite element analysis (FEA). Furthermore, as stress is greatly affected by seasonal changes in pavement stiffness, the influence of temperature on fatigue life was estimated. Based on the results of FEA, a relationship was formulated between temperature and stress range, indicating that a 1C increase in temperature could reduce fatigue life by 9%. Additionally, the fatigue life was estimated to potentially range from half to three times that in Japan in countries with different climates.

Fatigue life extension of trough girder railway bridges using crack-arrest holes 査読有り国際誌

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

Proceedings of the ISSS and PSSC 2025 頁： 482-485 2025年11月

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）

Fatigue cracks have been observed in the welded joints of end diaphragms in steel trough girder railway bridges. These fatigue cracks are thought to result from deterioration of the bridge supports and uneven settlements induced by train loads passage. As a simple repair method, crack-arrest holes are often drilled at the crack tips. However, their effectiveness remains unclear. In this study, a fatigue test was conducted on an end diaphragm from a trough girder bridge under support conditions simulating those of an actual bridge. Crack propagation behavior and the effectiveness of the crack-arrest hole repair were examined through fatigue test and numerical analysis. In addition, finite element analysis was performed to clarify the effects of various parameters on the local stress at the edge of the crack-arrest hole in actual bridges.

Numerical prediction of low cycle fatigue life in cruciform welded joints 査読有り国際誌

Kyung-mo Lim, Takeshi Hanji, Kazuo Tateishi, Masaru Shimizu

Proceedings of the ISSS and PSSC 2025 頁： 366-369 2025年11月

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）

Welded structures are essential in civil structures such as bridges, offshore platforms, and high-rise buildings, where they are frequently exposed to severe cyclic loading conditions. Under such conditions, low-cycle fatigue (LCF) becomes a critical failure mode, particularly during seismic events that induce large plastic strains. In a previous study, a LCF test was conducted on load-carrying cruciform welded joint with incomplete weld penetration to confirm its LCF performance. Based on the experiment, this study proposes a numerical method for predicting LCF crack propagation life of welded joints by employing the cyclic J-integral as the primary crack driving force. The cyclic J-integral is computed by extracting the output components in finite element analysis, numerical post processing, incorporating elasto-plastic material behavior to capture cyclic deformation effects. The modified Paris law, which describes the relationship between cyclic J-integral and crack growth rate, was used to predict fatigue life. The prediction results closely matched the crack propagation curves obtained from the experiment, demonstrating the potential applicability of LCF life assessment not only for plain materials but also for welded joints.

Hot-spot stress fatigue strength curves for welded joints with toe crack at plate edge 査読有り国際誌

Moku Takeshi, Takeshi Hanji, Kazuo Tateishi, Masaru Shimizu

Proceedings of the ISSS and PSSC 2025 頁： 358-361 2025年11月

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 the nominal stress approach is difficult to apply for fatigue strength evaluation, the hot-spot stress approach is effective. Hot-spots are classified into two types: Type "a", which refers to weld toes located on the plate surface, and Type "b", which refers to those located at the plate edge. In this study, fatigue test data on joints where Type "b" cracks occur were collected across several different joint types. Finite element analysis was performed to compute hot-spot stress, with variations in element type and element size near the reference points used for hot-spot stress calculation. When the 4-8-12 mm method, recommended in the IIW recommendation, was employed for hot-spot stress calculation, the lower limit considering data scatter, defined as the mean minus two times standard deviations, was 95.4 N/mm2. This finding indicates that fatigue test results for welded joints occurring Type "b" cracks can collectively be assessed using FAT90. Additionally, it was confirmed that variations in element size within the range recommended in IIW near the reference points, as well as changes in element type, had negligible effects on the hot-spot stress assessment.

Effectiveness of patch plate reinforcement for bead-through cracks at longitudinal rib–crossbeam intersections in orthotropic steel decks 査読有り国際誌

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

Proceedings of the ISSS and PSSC 2025 頁： 478-481 2025年11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, the reinforcement with patch plates from the top of the deck plate against bead-through fatigue cracks at the intersection of crossbeam was investigated by FEM analysis. The analysis was performed for different bolt arrangements and thicknesses of the patch plate, and the stress reduction at the root were examined. The analysis results showed that bead-through cracks are more likely to occur when the weld penetration is 25% or less. Adding bolts to the inside of the U-ribs reduces the stress at the root, and the greater stress reduction can be achieved when the thickness of the patch plate is increased.

Weld root fatigue life assessment of load-carrying cruciform joints based on crack opening displacement 査読有り国際誌

Erik Wahyu Pradana, Kazuo Tateishi, Takeshi Hanji, Masaru Shimizu

Proceedings of the ISSS and PSSC 2025 頁： 370-373 2025年11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）

Fatigue failure initiating at the weld root in welded joints with incomplete penetration is conventionally assessed by the nominal stress approach. However, this method is often unsuitable for geometrically complex joints, where non-uniform stress distribution near the weld root prevents accurate definition of nominal stress at the weld throat. Although the effective notch stress (ENS) method overcomes this limitation, it requires a high-resolution mesh and depends on a fictitious notch radius that lacks a clear physical justification. This study proposes an alternative fatigue assessment approach based on crack opening displacement (COD). COD reflects local cyclic deformation at the weld root and provides a physically meaningful parameter for fatigue assessment. This study proposes COD measurement through finite element analysis using 1 mm mesh at a reference point 1 mm from the weld root within the unfused zone. Analogous to the S−N curve, a u−N curve relating COD to fatigue life was established from 235 published fatigue test results on root failure in axially loaded cruciform welded joints with incomplete penetration. Furthermore, COD was normalized by a correction factor (F) derived from crack propagation analysis to eliminate specimen size effects on fatigue life. As a results, the u−N curve yielded a correlation coefficient (R = 0.88), demonstrating high predictive accuracy and practical value as an alternative to the nominal stress approach.

Hot‑spot stress fatigue strength curves for weld toe on plate edges 査読有り国際誌 Open Access

Takeshi Hanji, Kazuo Tateishi, Moku Takeshi, Masaru Shimizu

Welding in the World ?? 巻 ( ?? ) 頁： ???-??? 2025年11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（学術雑誌）

Hot-spots are classified into two types: Type "a", which refers to weld toes located on the plate surface, and Type "b", which refers to weld toes located at the plate edge. In this study, fatigue test data on joint details in which Type "b" cracks occur were collected from 25 published papers, comprising a total of 264 data points across several different joint details. Finite element analysis was performed to compute hot-spot stress, with variations in element type and element size near the reference points used for hot-spot stress calculation. When the data were organized according to the nominal stress range, significant scatter was observed in the S–N diagram due to variations in fatigue strength among different joint details. In contrast, when analyzed based on the 4–8–12 mm method, as recommended in the IIW Designer's Guide, the scatter was significantly reduced. Taking into account data scatter, the lower limit, which is defined as the mean minus two standard deviations, was 95.4 N/mm2. These findings indicate that fatigue test results for in-plane gusset welded joints, as well as other joint details, can collectively be assessed using the fatigue design curve of FAT90. Additionally, it was confirmed that variations in element size within the range of 1 mm to 4 mm near the reference points, as well as changes in element type, had negligible effects on the hot-spot stress assessment.

DOI： 10.1007/s40194-025-02244-7

Open Access

鋼床版デッキプレート－垂直補剛材溶接部の垂直補剛材側止端に生じるき裂の発生条件と進展経路に関する検討査読有り

清水優，上山広己，舘石和雄，判治剛

鋼構造年次論文報告集 33 巻頁： 558-564 2025年11月

ACFM法による塗膜上からの疲労き裂検知に関する基礎検討査読有り

近藤光一，判治剛，舘石和雄，清水優

鋼構造年次論文報告集 33 巻頁： 593-599 2025年11月

高周波誘導加熱処理による面外ガセット溶接継手ルート部の疲労強度向上効果査読有り

清水優，村井航平，加納俊，舘石和雄，判治剛

鋼構造論文集 32 巻 ( 127 ) 頁： 72-82 2025年9月

Hot-spot stress fatigue strength curves for weld toe on plate edges 査読有り

Takeshi Hanji, Kazuo Tateishi, Moku Takeshi, Masaru Shimizu

The 78th Annual Assembly of International Institute of Welding 頁： XIII-3176-2025 2025年6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）

Hot‐spots are classified into two types: Type "a", which refers to weld toes located on the plate surface, and Type "b", which refers to weld toes located at the plate edge. In this study, fatigue test data on joint details in which Type "b" cracks occur were collected from 25 published papers, comprising a total of 264 data points across several different joint details. Finite element analysis was performed to compute hot‐spot stress, with variations in element type and element size near the reference points used for hot‐spot stress calculation. When the data were organized according to the nominal stress range, significant scatter was observed in the S–N diagram due to variations in fatigue strength among different joint details. In contrast, when analyzed based on the 4–8–12 mm method, as recommended in the IIW Designer's Guide, the scatter was significantly reduced. Taking into account data scatter, the lower limit, which is defined as the mean minus two standard deviations, was 95.4 N/mm2. These findings indicate that fatigue test results for in‐plane gusset‐welded joints, as well as other joint details, can collectively be assessed using the fatigue design curve of FAT90. Additionally, it was confirmed that variations in element size within the range of 1 mm to 4 mm near the reference points, as well as changes in element type, had negligible effects on the hot‐spot stress assessment.

Fatigue crack propagation and repair using crack-arrest holes in trough girder railway bridges 査読有り

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

The 78th Annual Assembly of International Institute of Welding 頁： XIII-3178-2025 2025年6月

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）

Fatigue cracks have been observed in the welded joints of end diaphragms in steel trough girder railway bridges. These fatigue cracks are thought to result from deterioration of the bridge supports and uneven settlements induced by train loads passing over them. As a simple repair method, crack‐arrest holes are often drilled at the crack tips. However, their effectiveness remains unclear, and in some cases, the cracks tend to re‐initiate and propagate. In this study, a fatigue test
was conducted on an end diaphragm from a trough girder bridge under support conditions simulating those of an actual bridge. Crack propagation behavior and the effectiveness of the crack‐arrest hole repair were examined through fatigue test and numerical analysis. In addition, finite element analysis replicating real bridge conditions was performed to clarify the effects of various parameters on the local stress at the edge of the crack‐arrest hole. Furthermore, the effect of inserting a bolt into the hole on reducing the local stress at the hole edge was also investigated.

2025 Report of work in progress (WIP) on fatigue strength of welded joints in Japan 査読有り

Takeshi Hanji, Eiichi Sasaki

The 78th Annual Assembly of International Institute of Welding 頁： XIII-3180-2025 2025年6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. Two on fatigue behavior, two on fatigue crack propagation, and one on fatigue crack prevention are included in this report.

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.

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