本四技報 HONSHI TECHNICAL REPORT

Vol.45 No.135 2020.9

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【巻頭言】Prefatory note

  • 現場の重要性

    Importance of Work in the Field

    新 一真

    Kazumasa Atarashi

【技術論文】Technical report

  • 技術開発計画(H29-R1)の成果

    Outcomes of Technological Development Project between 2017 and 2019

    荻原勝也・山口和範・遠山直樹

    Katsuya Ogihara, Kazunori Yamaguchi, Naoki Toyama

    当社では、長大橋の予防保全等を実施するために必要となる技術の開発を目的として、平成29年度から3カ年にわたる計画を策定し、取り組んできた。本報告は、この3カ年における技術開発等の成果について報告するものである。また、引き続いて実施する技術開発計画(R2-R4)の検討項目を紹介する。

    Three-year technological development project was worked on to practice preventive maintenance for long-span bridges between 2017 and 2019. This paper reports outcomes from the three-year project. The following three-year project that started in 2020 is explained as well.

  • 大三島橋の耐震補強設計

    Seismic retrofit design of Ohmishima Bridge

    山口和範・大串弘幸

    Kazunori Yamaguchi, Hiroyuki Ogushi

    大三島橋は、今後30年間に震度6弱以上の揺れに見舞われる確率が26%以上の地域にあるため、令和3年度までに耐震補強を終わらせる予定である。大三島橋の耐震性能照査の結果、道路桁(側タイ)で一部降伏し、橋台でせん断耐力の許容値を超えていた。このため、道路桁(側タイ)で当て板補強を行い、橋台では繊維シート補強を行うこととした。本文は大三島橋の耐震性能照査及び補強設計について報告するものである。

    Ohmishima Bridge is located in area where the probability of the occurrence of large earthquakes with a seismic intensity level of Lower 6 or higher in coming 30 years is 26 percent or higher. Therefore the seismic retrofit of the bridges is conducted and planned to be by 2022. As the result of seismic performance verification of the bridge, it was found that the strength of road girder (side tie) and the shear strength of abutment would be exceed the allowable range. On this account, seismic retrofit design was conducted using stiffening plate for the road girder (side tie) and fiber sheet reinforcement for the abutment. This paper presents the seismic retrofit design of the Ohmishima Bridge.

  • ASRにより劣化したPC構造物の調査と対策

    Survey and countermeasure for alkali-silica reaction occurred in prestressed concrete structure

    金田泰明・矢野賢晃・橋本龍

    Yasuaki Kaneda, Yoshiaki Yano, Ryu Hashimoto

    3径間連続複合箱桁斜張橋である生口橋のPC桁ケーブル定着部の側面において、亀甲状のひび割れや白色の析出物の発生を確認した。床版上面舗装の一部を撤去したところ、多数の橋軸方向のひび割れを確認したことから、アルカリシリカ反応によるひび割れと推定された。

    本橋梁は、建設時にアルカリシリカ反応性試験を実施し、無害の判定を確認している。このような背景から、劣化原因を特定するため、アルカリシリカ反応を念頭に置いた詳細調査を実施した。調査の結果、微小な石英を含む反応性骨材に起因する遅延膨張性のアルカリシリカ反応と判断した。

    補修は、水分の浸入を防止することを基本的な方針とし、ひび割れ注入、表面被覆、表面含浸を施工した。本論は、各種調査の結果及び当該箇所の補修方法を報告するものである。

    It was confirmed that alligator cracks and white precipitates were generated on the side surface of cable fixing part of PC girder at Ikuchi Bridge (Composite box girder cable stayed bridge with three continuous spans). It was presumed that the cracks were originally from Alkali-silica reaction, because numerous cracks on the longitudinal direction of the bridge were confirmed when a part of the concrete deck top surface pavement was removed.

    The bridge had been confirmed harmless through Alkali silica reactivity test when the bridge was constructed. For the above reasons, in order to identify the cause of deterioration, a detailed survey was conducted from the perspective of Alkali-silica reaction. As a result of the survey, it was identified that the deterioration was originally from the late expansive alkali-silica reaction that is linked to the reactive aggregate containing microcrystalline.

    Crack injection, surface coating, and surface impregnation were conducted since the basic policy for the repairmen was prevention of the water infiltration. This thesis reports the results of various surveys and the repairment methods for the relevant deteriorations.

  • 瀬戸大橋長大橋(吊橋・斜張橋・トラス橋)の耐震補強工事

    Seismic retrofit of Seto-Ohashi Bridges (suspension, cable-stayed and truss bridges)

    村上博基・平山靖之

    Hiroki Murakami, Yasuyuki Hirayama

    瀬戸大橋の耐震補強工事は、平成26年度から開始し、約7年間をかけて令和2年度末に完了する予定である。ここでは、令和元年度末までに完了した吊橋3橋、斜張橋2橋、トラス橋1橋及び取付高架橋トラス部2橋の耐震補強工事の概要について報告する。耐震対策は、耐震性照査及び補強設計に基づき、鉄道直上の部材補強量及び橋全体としての補強量の最小化に留意した。それぞれの耐震補強工事の主な内容は、吊橋では、道路桁支承の補強、斜張橋では、横トラス下弦材の座屈強度改善、トラス橋4橋ではトラス部材補強、制振対策、道路桁支承の補強及び全体系の免震化などで、各橋梁に応じた耐震補強工事を行った。

    Seismic retrofit work of the Seto-Ohashi Bridges and approach viaducts started in 2014. It will be finished by the end of FY2020. This paper describes the seismic retrofit work of three suspension bridges, two cable-stayed bridges, and four truss bridges in the Seto-Ohashi Bridges. According to the result of seismic performance verification and retrofit design, seismic retrofit of these bridges was designed to minimize the volume of reinforcement work of truss members over railway tracks and of the whole bridges. Road deck bearings were reinforced in the seimic retrofit work of the suspension bridges. And, the buckling strength of the lower chords was improved for the cable-stayed bridges, and the truss bridges were retrofitted by reinforcing truss members, road deck bearings, and so on.

  • 大鳴門橋補剛桁アプローチ率向上に向けた橋梁点検補修用作業車改造の取組

    Improvement of maintenance vehicles to improve approach rate of Ohnaruto Bridge

    松尾俊宏・清原一宏・松葉真人

    Toshihiro Matsuo, Kazuhiro Kiyohara, Masato Matsuba

    大鳴門橋は、建設当時から補剛桁への接近方法を検討しており保安管理路及び橋梁点検補修用作業車(以下「桁作業車等」という。)を設置している。しかし、本州四国連絡橋の初期に建設された大鳴門橋は、保全作業の足場となる桁作業車等から補剛桁部材表面への接近面積割合(以下「アプローチ率」という。)が本州四国連絡橋の他橋に比べて著しく低い。近年、鋼床版縦桁支承等の局部的な腐食の発生や、道路法施行規則(省令)の改正に伴い、補剛桁各部材への5年ごとの近接目視点検が必須となり、アプローチ率向上が急務の課題である。これらの課題を解決するため、既設の橋梁点検補修用作業車(以下「桁作業車」という。)を効率的かつ経済的に改造した。本稿では、アプローチ率向上に向けた桁作業車改造の取組について報告する。

    In Ohnaruto Bridge, the access to the stiffening girder was examined the access method at the stage of construction, and maintenance vehicles and maintenance walkways were installed to the bridge structure. However, the accessible area of the Ohnaruto Bridge which was constructed in the early stage in the history of the Honshu-Shikoku Bridge construction projects, is extremely limited compared to those of other bridges. On the other hand, in recent years, local corrosions were confirmed in the bearings of steel deck, etc., and close visual inspection to each member of the girder was required every five years due to the revision of Road Act. Therefore, improvement of the approach rate became an urgent problem. To solve the problem, the existing maintenance vehicles were efficiently and economically modified. In this paper, efforts for the remodeling of the maintenance vehicle to improve the approach rate are reported.

【技術開発年次報告】Annual report of technology development

  • 防食分科会 塗装(鋼)WGの取組

    Report of Working Group for Metal Coating System, Anticorrosion Subcommittee

    竹口昌弘・臼田幸生・山根彰

    Masahiro Takeguchi, Yukio Usuda, Akira Yamane

  • 防食分科会 コンクリート保護工WGの取組

    Report of Working Group for concrete coating system, Anticorrosion Subcommittee

    大賀弘貴・竹口昌弘

    Hirotaka Oga, Masahiro Takeguchi

  • 疲労分科会の取組

    Report of Fatigue Subcommittee

    林昌弘・有馬敬育

    Masahiro Hayashi, Noriyasu Arima

  • 耐震分科会の取組

    Report of Seismic Subcommittee

    山口和範・大串弘幸

    Kazunori Yamaguchi, Hiroyuki Ogushi

  • 舗装分科会の取組

    Report of Pavement Subcommittee

    梶尾光邦・中山義雄

    Mitsukuni Kajio, Yoshio Nakayama

  • 点検分科会 点検技術WGの取組

    Report of Working Group for Inspection Technology, Inspection Subcommittee

    林昌弘・有馬敬育

    Masahiro Hayashi, Noriyasu Arima

  • 耐風分科会の取組

    Report of Wind-Resistance Subcommittee

    竹口昌弘・遠山直樹

    Masahiro Takeguchi, Naoki Toyama

【技術ニュース】Technical news

  • 土木学会田中賞作品部門(改築)受賞

    2019 JSCE Tanaka Award (Excellence in Bridge Design and Construction)

    臼田幸生

    Yukio Usuda

  • 塗膜劣化検出方法特許取得

    A Patent for “Evaluation method for deterioration of paint coating” was approved

    蔵森和生

    Kazuo Kuramori