HIRAO Kensho

Affiliation

Faculty of Urban Innovation, Division of Urban Innovation

Job Title

Assistant Professor

Research Fields, Keywords

Structural engineering, Non Destructive Inspection, Machine learning, Signal processing, High-strength bolted friction joints

Web Site

http://www.cvg.ynu.ac.jp/G1/Eng/index

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Education 【 display / non-display

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    2022.9

    Tokyo Institute of Technology   Doctor Course   Completed

  • 2017.4
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    2019.3

    Tokyo Institute of Technology   Master Course   Completed

Degree 【 display / non-display

  • Doctor of Engineering - Tokyo Institute of Technology

Campus Career 【 display / non-display

  • 2022.10
     
     

    Duty   Yokohama National UniversityFaculty of Urban Innovation   Division of Urban Innovation   Assistant Professor  

Academic Society Affiliations 【 display / non-display

  • 2017
     
     
     

    Japan Society of Civil Engineers

Research Areas 【 display / non-display

  • Social Infrastructure (Civil Engineering, Architecture, Disaster Prevention) / Structure engineering and earthquake engineering

  • Others / Others  / Steel structure

Qualification acquired 【 display / non-display

  • First Kind of High School Teacher License

 

Thesis for a degree 【 display / non-display

  • Quantification of Uncertain Influential Parameters Affecting the Structural Performance Evaluation of High Strength Bolted Friction Joints

    Kensho HIRAO

    2022.9

    Doctoral Thesis   Single Work    [Reviewed]

Papers 【 display / non-display

  • Evaluation for slip resistance of bolted joints including different contact surfaces with disk-type friction shims inserted

    Kensho HIRAO, Quang Vy TRAN, Hiroshi TAMURA

    Journal of Structural Engineering   70A ( 0 )   61 - 74   2024.3  [Reviewed]

    DOI CiNii Research

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    Authorship:Lead author   Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Japan Society of Civil Engineers   Joint Work  

    There is concern that the slip coefficient of high-strength bolted joints with different faying surfaces may be lower than that of conventional joints, and it has been reported that the slip coefficient is improved by inserting friction shims. In this study, shims were modified to be disk-shaped, which can be inserted into each bolt hole, for application to arbitrary bolted joints, and their slip resistance was evaluated by slip resistance tests. As a result, it was confirmed that a slip coefficient of 0.6 or higher could be expected with the insertion of shims. Failure modes of the contact surfaces were also investigated by dismantling the specimens after the test and observing the contact surfaces.

  • A study on stabilizing mechanism of flap countermeasures mitigating VIV of a box girder bridge section

    Phan Duc Tam, Hiroshi Katsuchi, Wang Jiaqi, Hiroshi Tamura, Kensho Hirao

    IOP Conference Series: Materials Science and Engineering   1289 ( 1 )   1 - 15   2023.8  [Reviewed]

    DOI

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    Language:English   Publishing type:Research paper (scientific journal)   Joint Work  

  • ULTRASONIC HIGH-STRENGTH BOLT AXIAL FORCE EVALUATION BY MACHINE LEARNING-BASED TO WAVEFORM ANALYSIS

    Kensho HIRAO, Keigo SUZUKI, Kastumi MORITA, Yuichi ITO, Kouichi TAKEYA and Eiichi SASAKI

    Journal of Japan Society of Civil Engineers, Ser. A1 (Structural Engineering & Earthquake Engineering (SE/EE))   78 ( 1 )   108 - 120   2022  [Reviewed]

    DOI

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    Authorship:Lead author   Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Japan Society of Civil Engineers   Joint Work  

    Bolt axial force of high-strength bolted joints decreases due to deterioration. One of the conventional methods to evaluate the bolt axial force is ultrasonic testing. However, quantitative evaluation of the bolt axial force is controversial in terms of accuracy, and some problems remain for practical use. This study attempts the accurate evaluation of the bolt axial force by ultrasonic testing. The time zone analysis of the ultrasonic waves indicated that the waveform in the initial time zone includes bolt axial force information. The parasitic discrete wavelet transform (P-DWT) was applied to improve the evaluation accuracy. As a result of targeting bolts manufactured in the same lot, machine learning using linear regression evaluated the unknown bolt axial force within an error of 6% or less. Therefore, it was shown that the proposed method of this study corresponds to the existing bolt and can evaluate the bolt axial force with high accuracy.

  • A STUDY ON ULTRASONIC MEASUREMENT OF COATING THICKNESS ON BACKSIDE OF STEEL PLATE AND THE FAYING SURFACE IN HIGH-STRENGTH BOLTED FRICTION JOINTS WITH MACHINE LEARNING

    Kensho HIRAO, Eiichi SASAKI, Yuichi ITO, Kouichi TAKEYA, Ayako AKUTSU

    Journal of Japan Society of Civil Engineers, Ser. A1 (Structural Engineering & Earthquake Engineering (SE/EE))   78 ( 3 )   508 - 519   2022  [Reviewed]

    DOI CiNii Research

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    Authorship:Lead author   Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Japan Society of Civil Engineers   Joint Work  

    <p> Recently, inorganic zinc-rich paints have been increasingly applied to the faying surfaces of high-strength bolted friction joints. The coating thickness of the faying surface is said to affect the slip coefficient of the bolted joint. If the coating thickness on faying surfaces of bolts in existing joints can be measured without disassembly the joints, it is possible to evaluate the structural performance of bolted joints on the basis of the current coating thickness on the faying surfaces and the slip coefficient. Furthermore, if it becomes possible to measure areas of high contact pressure, where the coating thickness changes after joining, this information could be useful for discussing the mechanism of structural performance of bolted joints. In this study, the construction of an ultrasonic measurement method with machine learning showed the feasibility of evaluating the coating thickness on the backside of a single steel plate. Subsequently, an attempt was made to evaluate the coating thickness on faying surfaces of bolts in existing joints without disassembly.</p>

  • APPLICABILITY OF PRETENSIONED BOLTED JOINTS INCLUDING DIFFERENT CONTACT FACES

    TAMURA Hiroshi, MINAMI Kuniaki, YOSHIOKA Natsuki, UCHIDA Daisuke, MORO Mitsuru, HAMA Tatsuya, HIRAO … Show more authors

    Journal of Japan Society of Civil Engineers, Ser. A1 (Structural Engineering & Earthquake Engineering (SE/EE))   76 ( 2 )   255 - 274   2020

    DOI CiNii Research

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    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Japan Society of Civil Engineers   Joint Work  

    <p> In frictional type pretensioned bolted joints, one specification is employed for contact faces in each joint in principle. Meanwhile, in some cases such as protection works of existing bridges and fabrication of box girders made of weathering steel without coating, introduction of usage of different contact faces in one joint might often allow labor-saving and accelerated works.</p><p> In present study, bolted joints including different contact faces are defined as a hybrid faying surfaces joint, and 33 bolted joint specimens were used in bolt pretension relaxation test and slip test. This paper reports these results and compares degree of pretension loss and slip resistance in hybrid faying surface joints with homogeneous (i.e. normal) joints. Finally, also on the basis of previous research, the applicability and slip coefficient for designing of hybrid faying surfaces joints are discussed regarding.</p>

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Review Papers 【 display / non-display

  • BIMによるデジタルツイン技術を用いた鉄道橋のメンテナンスの最適化 -オーストラリアのミナムラ鉄道橋を対象とした実証実験結果の報告-

    平尾 賢生,黒田璃紗,駒場 駿介,鹿野 光一,島田 剛気,島野 孝則,末松 慎介,土田 僚,平井 貴大,舟橋 景介,柳 博文

    橋梁と基礎   57 ( 12 )   63 - 65   2023.12  [Reviewed]  [Invited]

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    Authorship:Lead author   Language:Japanese   Publishing type:Book review, literature introduction, etc.   Joint Work  

  • 海上横断橋の設計とBIM技術の活用-中国 厦門第二東橋梁-

    桐本 翔平,平尾 賢生,倉橋 和希,黒田 璃紗,駒場 駿介,島野 孝則,末松 慎介,土田 僚,平井 貴大,舟橋 景介,柳 博文

    橋梁と基礎   58 ( 5 )   55 - 57   2024.5

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    Language:Japanese   Publishing type:Book review, literature introduction, etc.   Joint Work  

  • Asia Steel Bridge Competition 2023

    Bridge and Foundation Engineering   58 ( 3 )   53 - 55   2024.3  [Reviewed]  [Invited]

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    Language:Japanese   Publishing type:Book review, literature introduction, etc.   Joint Work  

  • GISとリモートセンシングデータを使用した橋梁の洪水リスク評価 -2020年 メディケーン「イアノス」による被害/ギリシャ-

    平井 貴大,平尾 賢生,倉橋 和希,黒田璃紗,駒場 駿介,鹿野 光一,島野 孝則,末松 慎介,土田 僚,舟橋 景介,柳 博文

    橋梁と基礎   58 ( 1 )   57 - 59   2024.1  [Reviewed]  [Invited]

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    Language:Japanese   Publishing type:Book review, literature introduction, etc.   Joint Work  

  • Asia Steel Bridge Competition 2023

    Kouichi TAKEYA, Yuichi ITO, Koji KINOSHITA, Keigo SUZUKI, Hiroshi TAMURA, Ayako AKUTSU, Kensho HIRAO

    Bridge and Foundation Engineering   57 ( 10 )   53 - 53   2023.10

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    Language:Japanese   Publishing type:Article, review, commentary, editorial, etc. (other)   Joint Work  

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Awards 【 display / non-display

  • Best Presentation Award

    2024.4   The 70th Symposium on Structural Engineering   Evaluation for slip resistance of bolted joints including different contact surfaces with disk-type friction shims inserted

    Individual or group name of awards:Kensho HIRAO

Other external funds procured 【 display / non-display

  • Loose bolt detection by nut rotation history using AI image processing

    2023.7 - 2024.6

    Investigator(s):Kensho HIRAO

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    Authorship:Principal investigator 

  • Evaluation of the existing performance of high-strength bolted friction joints considering the effect of uncertainty

    2022.6 - 2023.5

    Investigator(s):Kensho HIRAO

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    Authorship:Principal investigator 

  • Evaluation of the existing performance of high-strength bolted friction joints considering the effect of uncertainty

    2021.6 - 2022.5

    Investigator(s):Kensho HIRAO

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    Authorship:Principal investigator 

Presentations 【 display / non-display

  • Proposal of ultrasonic bolt axial force evaluation method using machine learning and signal processing

    Kensho HIRAO

    IABSE  2022.5 

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    Event date: 2022.5

    Language:English   Presentation type:Oral presentation (general)  

    Venue:Prague, Czech Republic   Country:Czech Republic  

    It has been confirmed that bolt axial force of high-strength bolted joints decreases due to various effects. Generally, evaluating the bolt axial force of existing bolts has been an important issue. In a conventional ultrasonic bolt axial force evaluation method, bolt length change due to the change of bolt axial force is evaluated. However, bolt length can include uncertainty due to manufacturing errors. Hence, in this study, attention was paid to the deformed shape of the bolt head, which has a little dependency on the bolt length, and application of signal processing and machine learning was attempted. It was shown that the waveform data obtained from the bolt head by ultrasonic testing included characteristic signals indicating the bolt axial force. The target characteristic signal was detected by the parasitic discrete wavelet transform (P-DWT). A highly accurate bolt axial force evaluation method was proposed by applying machine learning to characteristic signals.

  • Applicability of disk-type friction shim in high-strength bolted joints including different faying surface

    Kensho Hirao, Yuki Goka, Hiroshi Tamura, Jiaqi Wang, Hiroshi Katsuchi

    JSCE 2023 Annual Meeting  2023.9  JSCE

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    Event date: 2023.9

    Language:Japanese   Presentation type:Oral presentation (general)  

    Venue:Hiroshima   Country:Japan  

    There is concern that the slip coefficient of high-strength bolted joints with different faying surfaces may be lower than that of conventional joints, and it has been reported that the slip coefficient is improved by inserting friction shims with electroless nickel and diamond treatment into the faying surfaces. In this study, shims were modified to be disk-shaped so that they can be inserted into each bolted joint hole, and their applicability to arbitrary bolted joints was evaluated by slip tests. The results of slip resistance tests confirmed that a slip coefficient of 0.65 or higher can be expected with the insertion of shims, indicating the applicability of the shims to arbitrary bolted joints.

  • Effect of steel strength on load carrying capacity of high-strength bolted joints under compression

    Kensho HIRAO

    12th Pacific Structural Steel Conference  2019.11 

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    Event date: 2019.11

    Language:English   Presentation type:Oral presentation (general)  

    Venue:Tokyo, Japan   Country:Japan  

    In this research, the steel strength of the high-strength bolted frictional joint, i.e., the strength and thickness configuration of the base plate and the splice plate were investigated. In order to clarify the effect on the load carrying capacity of high-strength bolted frictional joints under compressive load, compressive loading experiment and numerical analysis were conducted. In the experiment, the mechanism up to the post-slip behavior was confirmed for joints of yield precedence type, and it was shown that hybrid joints of slip precedence type can secure the design slip resistance calculated by the general slip coefficient and the design bolt axial force. In the analysis, it was confirmed that the stress distribution of the homogeneous joint and some hybrid joints in pre-slip was almost the same.

  • Influence of Steel Strength on Load Carrying Capacity of High-Strength Bolted Frictional Joints Under Compression

    Kensho HIRAO

    2019.9 

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    Event date: 2019.9

    Language:Japanese   Presentation type:Oral presentation (general)  

    Country:Japan  

 

Charge of on-campus class subject 【 display / non-display

  • 2024   Experiment in Civil Engineering B

    College of Urban Sciences

  • 2024   Exercises on Structural Mechanics

    College of Urban Sciences

Charge of off-campus class subject 【 display / non-display

  • 物理1及演習

    2024.4 Institution:法政大学

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    Level:Undergraduate (specialized) 

 

Committee Memberships 【 display / non-display

  • Japan Steel Bridge Engineering Association "Working Group on Joints of Steel Bridges"

    2022.11  Academic Member

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    Committee type:Academic society 

  • Bridge and Foundation Engineering

    2022.10 

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    Committee type:Other