JP5441114B2 - Fatigue crack repair structure and repair method for steel structures - Google Patents

Fatigue crack repair structure and repair method for steel structures Download PDF

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JP5441114B2
JP5441114B2 JP2009263101A JP2009263101A JP5441114B2 JP 5441114 B2 JP5441114 B2 JP 5441114B2 JP 2009263101 A JP2009263101 A JP 2009263101A JP 2009263101 A JP2009263101 A JP 2009263101A JP 5441114 B2 JP5441114 B2 JP 5441114B2
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fatigue crack
crack
fatigue
peening
steel
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健太郎 山田
敏之 石川
拓巳 柿市
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Nagoya University NUC
Tokai National Higher Education and Research System NUC
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Description

本発明は鋼構造物に発生した疲労き裂の補修構造及び補修方法に関し、詳しくは鋼板の表面から裏面まで貫通した疲労き裂の補修構造及び補修方法に関するものである。   The present invention relates to a repair structure and a repair method for a fatigue crack generated in a steel structure, and more particularly to a repair structure and a repair method for a fatigue crack penetrating from the front surface to the back surface of a steel plate.

鋼橋に代表される鋼構造物が繰返し荷重を受けると、金属疲労によって鋼構造部材の表面に疲労き裂が発生する場合があり、この疲労き裂を放置すると、疲労き裂が進展し、鋼橋の耐力が維持できなくなる危険性がある。このため、鋼橋の維持・管理においては、疲労き裂の発生防止や早期発見・補修・補強などの疲労き裂対策が求められている。   When a steel structure typified by a steel bridge is subjected to repeated loads, a fatigue crack may occur on the surface of the steel structural member due to metal fatigue. If this fatigue crack is left untreated, the fatigue crack will develop, There is a risk that the strength of the steel bridge cannot be maintained. For this reason, in the maintenance and management of steel bridges, fatigue crack countermeasures such as prevention of fatigue cracks and early detection, repair and reinforcement are required.

日本では、１９６０年代からの高度経済成長に合わせて道路網が整備され、多くの鋼橋が建設されてきた。これらの鋼橋は供用開始後４０〜５０年が経過しており、様々な劣化現象が顕在化しているのに加えて、近年の交通荷重とその頻度の増加に伴って、鋼橋の溶接継手部に疲労き裂が発生しているのが発見されるようになった。   In Japan, a road network has been developed and many steel bridges have been constructed in line with the high economic growth since the 1960s. These steel bridges have been in use for 40 to 50 years, and various deterioration phenomena have become apparent. In addition, with the recent increase in traffic load and frequency, welded joints for steel bridges have been developed. It has been discovered that fatigue cracks have occurred in the parts.

図１４に鋼橋における代表的な継手構造である面外ガセット溶接継手のまわし溶接部における溶接止端に発生した疲労き裂がその周辺の鋼板部に進展していく状況を示す。面外ガセット溶接継手５０は、鋼板５１と直角にガセットプレート５２がすみ肉溶接された継手構造からなる。すみ肉溶接金属５３の特にまわし溶接部５３ａの溶接止端及びその周辺は、溶接時の熱による引張残留応力の蓄積や、溶接止端を境界に形状が急変することにより応力集中の影響を受け易いことから、疲労き裂５４が発生し易い部位となっている。   FIG. 14 shows a situation in which a fatigue crack generated at a weld toe in a turn welded portion of an out-of-plane gusset welded joint, which is a typical joint structure in a steel bridge, propagates to the surrounding steel plate portion. The out-of-plane gusset weld joint 50 has a joint structure in which a gusset plate 52 is fillet welded at right angles to the steel plate 51. The weld toe and its periphery of the fillet weld metal 53, particularly the turn welded portion 53a, are affected by stress concentration due to the accumulation of tensile residual stress due to heat during welding and the sudden change in shape at the weld toe boundary. Since it is easy, the fatigue crack 54 is likely to occur.

図１４（ａ）は疲労き裂５４が発生していない状況、図１４（ｂ）はまわし溶接部５３ａの溶接止端に疲労き裂５４が発生した状況（以下、Ｎｔｏｅと呼ぶ）、図１４（ｃ）はまわし溶接部５３ａの溶接止端に発生した疲労き裂５４が進展してすみ肉溶接金属５３の溶接止端から離れ始めた状況（以下、Ｎｂと呼ぶ）、図１４（ｄ）は疲労き裂５４が鋼板５１に１０ｍｍ進展した状況（以下、Ｎ１０と呼ぶ）、図１４（ｅ）は疲労き裂５４が鋼板５１に３０ｍｍ進展した状況（以下、Ｎ３０と呼ぶ）、図１４（ｆ）は疲労き裂５４が鋼板５１に６０ｍｍ進展した状況（以下、Ｎ６０と呼ぶ）を示している。 FIG. 14 (a) shows a situation where no fatigue crack 54 has occurred, FIG. 14 (b) shows a situation where a fatigue crack 54 has occurred at the weld toe of the rotary weld 53a (hereinafter referred to as N toe ), FIG. 14 (c) situations where fatigue cracks 54 generated in the weld toe of the weld 53a turning began away from the weld toe of weld metal 53 corner progressing (hereinafter, referred to as N b), 14 ( d) situations where fatigue cracks 54 were 10mm progress in steel 51 (hereinafter, referred to as N 10), FIG. 14 (e) situations where fatigue cracks 54 were 30mm progress in steel 51 (hereinafter, referred to as N 30) FIG. 14 (f) shows a situation (hereinafter referred to as N 60 ) in which the fatigue crack 54 has advanced 60 mm to the steel plate 51.

図１４の（ｂ）〜（ｆ）に示した面外ガセット溶接継手５０を疲労き裂５４に沿って切断した断面図を図１５に示す。鋼板５１の表面５１ａに発生した疲労き裂５４が、Ｎｔｏｅ→Ｎｂ→Ｎ１０→Ｎ３０→Ｎ６０と進展するのに伴って、疲労き裂５４は、鋼板５１の厚さ方向（深さ方向）と面方向（横方向）に進展する。そして、Ｎ３０まで進展した段階において、疲労き裂５４が鋼板５１の表面５１ａから裏面５１ｂまで貫通することが多い。Ｎ３０の段階からさらに疲労き裂５４が進展すれば、鋼板５１の表面５１ａと裏面５１ｂの双方から疲労き裂５４が面方向に進展して、やがてＮ６０の段階となる。なお、Ｎ１０から先の疲労き裂５４の進展は急速であることが知られている。 FIG. 15 shows a cross-sectional view of the out-of-plane gusset welded joint 50 shown in FIGS. 14 (b) to 14 (f) along the fatigue crack 54. As the fatigue crack 54 generated on the surface 51 a of the steel plate 51 progresses in the order of N toe → N b → N 10 → N 30 → N 60 , the fatigue crack 54 increases in the thickness direction of the steel plate 51 (depth (Direction) and plane direction (lateral direction). Then, the advanced stage to N 30, the fatigue crack 54 often penetrates from the surface 51a of the steel sheet 51 to the back 51b. If progress further fatigue cracks 54 from the stage of N 30, fatigue cracks 54 from both surfaces 51a and rear surface 51b of the steel plate 51 is developed in the surface direction, eventually the phase of N 60. Incidentally, the progress of the N 10 previous fatigue crack 54 is known to be rapid.

このような鋼板の表面から裏面まで貫通した疲労き裂は、鋼橋の桁や部材の破断に繋がる危険なき裂である。このため、鋼板の面方向の疲労き裂の先端に、疲労き裂の進展を停止させるためのドリル孔（ストップホール）が設けられると共に、疲労き裂発生部分に添接板を配置して高力ボルトで摩擦接合を行うという恒久的な補修・補強対策が実施されるのが一般的である。   Such fatigue cracks penetrating from the front surface to the back surface of the steel plate are dangerous cracks that lead to breakage of the steel bridge girders and members. For this reason, a drill hole (stop hole) is provided at the tip of the fatigue crack in the surface direction of the steel plate to stop the growth of the fatigue crack. In general, permanent repair / reinforcement measures such as friction welding with force bolts are carried out.

なお、疲労き裂が小さくて鋼板の表面から裏面まで貫通しておらず、疲労き裂が危険な状況まで進展していないと判断される場合には、添接板を用いずにストップホールを設けることのみによって一時的に疲労き裂の進展を止めるという疲労き裂補修方法が実施されている。また、鋼板の表面から裏面まで疲労き裂が貫通していない段階において、疲労き裂の開口部の周辺及び直上を疲労き裂と平行にピーニングすることにより鋼板の表面に塑性変形を付与し、疲労き裂の開口部を閉じてき裂接触面を形成するという疲労き裂補修方法も発明者らによって実用化されつつある（特許文献１、非特許文献１、非特許文献２、非特許文献３）。   If it is determined that the fatigue crack is small and does not penetrate from the front to the back of the steel plate and the fatigue crack does not progress to a dangerous situation, stop holes are not used Fatigue crack repairing methods have been implemented in which the development of fatigue cracks is temporarily stopped only by providing them. In addition, at the stage where the fatigue crack does not penetrate from the surface of the steel sheet to the back surface, plastic deformation is imparted to the surface of the steel sheet by peening the periphery of the fatigue crack opening and directly above the fatigue crack, Fatigue crack repairing methods that close the opening of a fatigue crack and form a crack contact surface are also being put into practical use by the inventors (Patent Document 1, Non-Patent Document 1, Non-Patent Document 2, and Non-Patent Document 3). ).

特願２００８−２９９８８０Japanese Patent Application No. 2008-299880

山田健太郎、石川敏之、柿市拓巳、李薈、「疲労き裂を閉口させて寿命を向上させる技術の開発」、平成２０年度土木学会中部支部研究発表会講演概要集、Ｉ−５、ｐｐ．９〜１０、２００９年Kentaro Yamada, Toshiyuki Ishikawa, Takumi Sakai, Yi Peng, “Development of technology to improve fatigue life by closing fatigue cracks”, 2008 JSCE Chubu Branch Conference Presentation Summary, I-5, pp. 9-10, 2009 柿市拓巳、山田健太郎、石川敏之、李薈、「ＩＣＲ処理を用いた面外ガセット溶接継手の疲労寿命延命効果」、土木学会第６４回年次学術講演会概要集第１部、第６４巻、Ｉ−１５１、ｐｐ．３０１〜３０２、２００９年Sakai City Takumi, Yamada Kentaro, Ishikawa Toshiyuki, Lee Yong, “Fatigue Life Prolonging Effect of Out-of-Plane Gusset Welded Joints Using ICR Processing”, 64th Annual Meeting of the Japan Society of Civil Engineers, Vol. 64 I-151 pp. 301-302, 2009

しかしながら、鋼板を貫通した疲労き裂を補修の対象とする前述のストップホールと添接板による恒久的な補修・補強対策においては、多大な労力とコストがかかり、また、施工期間中は通行止めや交通制限を施す必要があるため、疲労き裂が発生している多数の鋼橋の全てに適用するのは非現実的である。   However, the permanent repair and reinforcement measures using the stop holes and attachment plates that are subject to repair of fatigue cracks that penetrate the steel plate require a great deal of labor and cost. It is impractical to apply to all of the many steel bridges where fatigue cracks occur because of the traffic restrictions.

また、添接板を高力ボルトで摩擦接合するため、添接板とボルト孔の設計が必要であり、疲労き裂を発見してから補修を開始するまでに時間を要するという問題がある。さらに、施工を行うためには、大掛かりな足場や支保工が必要となる。また、添接板や高力ボルトの重量が付加されることによって鋼橋の死荷重が増加するという問題もある。   In addition, since the attachment plate is friction-joined with high-strength bolts, it is necessary to design the attachment plate and the bolt hole, and there is a problem that it takes time until repair is started after a fatigue crack is found. Furthermore, in order to perform construction, a large scaffold and support work are required. Moreover, there is also a problem that the dead load of the steel bridge increases due to the addition of the weight of the attachment plate and the high strength bolt.

一方、ピーニングにより疲労き裂の開口部を閉じてき裂接触面を形成するという疲労き裂補修方法は、簡便かつ安価に疲労き裂を補修することが可能な方法ではあるものの、Ｎｔｏｅ、Ｎｂ及びＮ１０段階のように鋼板の片面のみに発生した疲労き裂を補修の対象としており、Ｎ３０及びＮ６０段階のように鋼板を貫通した疲労き裂に適用するには至っていない。この疲労き裂補修方法を、鋼板を貫通した疲労き裂の表面側と裏面側の両面に適用するにあたっては、以下に述べる懸案事項がある。 On the other hand, although the fatigue crack repairing method of closing the fatigue crack opening by peening and forming a crack contact surface is a method that can repair the fatigue crack easily and inexpensively, N toe , N The fatigue crack which generate | occur | produced only in the single side | surface of the steel plate like b and N 10 stage is made into the object of repair, and it has not reached to apply to the fatigue crack which penetrated the steel plate like N 30 and N 60 stage. In applying this fatigue crack repair method to both the front side and the back side of a fatigue crack penetrating a steel plate, there are the following concerns.

第一に、疲労き裂が鋼板を貫通した場合、その鋼板は疲労強度（疲労破壊強度）に達したと考えて、設計に基づいた恒久的な補修・補強対策を施すという思想が一般化されている。したがって、一時的に疲労き裂の進展を止めるという疲労き裂補修方法が受け入れられにくい風潮がある。   First, when a fatigue crack penetrates a steel plate, it is considered that the steel plate has reached fatigue strength (fatigue fracture strength), and the idea of applying permanent repair and reinforcement measures based on the design is generalized. ing. Therefore, there is a tendency that the fatigue crack repair method of temporarily stopping the fatigue crack is not accepted.

第二に、ピーニング処理によって疲労き裂を補修する方法としては、発明者らが実用化しつつあるエアーハンマーを用いる方法の他に、超音波振動を利用する方法もある。前者の方法では、き裂深さ４ｍｍ程度のある程度深い疲労き裂までを補修の対象としており、一方、後者の方法では、き裂深さ１ｍｍ程度の極小さな疲労き裂を補修の対象としている。このように、ピーニング処理による疲労き裂補修方法は、鋼板の片面のみに発生した小さな疲労き裂を補修の対象としていることから、鋼板を貫通する大きな疲労き裂の補修に適用するには発想の飛躍が必要である。   Secondly, as a method for repairing a fatigue crack by peening, there is a method using ultrasonic vibration in addition to a method using an air hammer which is being put into practical use by the inventors. In the former method, repair is performed up to a fatigue crack having a crack depth of about 4 mm. On the other hand, in the latter method, a very small fatigue crack having a crack depth of about 1 mm is repaired. . In this way, the fatigue crack repair method by peening treatment is intended for repairing small fatigue cracks that occur only on one side of a steel plate, so it can be applied to repair large fatigue cracks that penetrate steel plates. The leap is necessary.

第三に、鋼板を貫通した疲労き裂の表面側と裏面側の両面にピーニング処理を施してき裂接触面を形成した場合、鋼板の片面のみに発生した疲労き裂を補修する場合と同様に鋼構造物の疲労寿命の延命化効果が得られるのか未解明である。   Thirdly, when a crack contact surface is formed by performing peening treatment on both the front and back sides of a fatigue crack that penetrates the steel sheet, it is the same as when repairing a fatigue crack that occurs on only one side of the steel sheet. Whether the effect of extending the fatigue life of steel structures can be obtained is unclear.

第四に、鋼板を貫通した疲労き裂の表面側にピーニング処理を施した場合、仮に表面側の疲労き裂の開口部が閉じて表面側にき裂接触面が形成されたとしても、ピーニング時の衝撃荷重によって、裏面側の疲労き裂の開口部がさらに大きく開いてしまうのではないかという点が懸念される。   Fourth, when peening is applied to the surface side of the fatigue crack that penetrates the steel plate, even if the opening of the fatigue crack on the surface side is closed and a crack contact surface is formed on the surface side, peening is performed. There is a concern that the opening portion of the fatigue crack on the back side may be further opened by the impact load at the time.

第五に、鋼板を貫通した疲労き裂の表面側にピーニング処理を施して表面側にき裂接触面が形成された後に、裏面側のピーニング処理を施した場合、ピーニング時の衝撃荷重によって、せっかくき裂接触面が形成された表面側の疲労き裂が再度開いてしまうのではないかという点が懸念される。   Fifth, after performing peening treatment on the surface side of the fatigue crack that penetrates the steel sheet and forming a crack contact surface on the front surface side, when performing peening treatment on the back surface side, depending on the impact load during peening, There is concern that the fatigue crack on the surface side where the crack contact surface is formed may open again.

本発明は上記課題に鑑みてなされたものであり、鋼板の表面から裏面まで貫通した疲労き裂を簡便かつ安価に補修することが可能であり、疲労き裂の進展を止める、あるいは疲労き裂の進展を遅延させて鋼構造物の疲労寿命の延命化を図ることができる疲労き裂補修構造及び補修方法を提供することを目的とする。   The present invention has been made in view of the above problems, and can easily and inexpensively repair a fatigue crack that penetrates from the front surface to the back surface of a steel sheet, and stops the progress of the fatigue crack, or the fatigue crack. An object of the present invention is to provide a fatigue crack repair structure and a repair method capable of delaying the progress of the steel and extending the fatigue life of the steel structure.

以下、上記課題を解決するのに適した各手段につき、必要に応じて作用効果等を付記しつつ説明する。   Hereinafter, each means suitable for solving the above-described problems will be described with additional effects and the like as necessary.

（１）本発明の鋼構造物の疲労き裂補修構造は、鋼板の表面から裏面まで貫通した疲労き裂の補修構造であって、前記鋼板の表面の前記疲労き裂の開口部の周辺及び／又は直上を該疲労き裂と平行にピーニングすることにより該鋼板の表面に塑性変形が付与され、該鋼板の表面の該疲労き裂の開口部が閉じられてき裂接触面が形成されていると共に、前記鋼板の裏面の前記疲労き裂の開口部の周辺及び／又は直上を該疲労き裂と平行にピーニングすることにより該鋼板の裏面に塑性変形が付与され、該鋼板の裏面の該疲労き裂の開口部が閉じられてき裂接触面が形成されていることを特徴とする。   (1) A fatigue crack repair structure of a steel structure according to the present invention is a repair structure of a fatigue crack that penetrates from the front surface to the back surface of a steel plate, and includes a periphery of the fatigue crack opening on the surface of the steel plate, and By peening immediately above and parallel to the fatigue crack, plastic deformation is imparted to the surface of the steel sheet, and the opening of the fatigue crack on the surface of the steel sheet is closed to form a crack contact surface. In addition, plastic deformation is imparted to the back surface of the steel sheet by peening the periphery and / or immediately above the opening of the fatigue crack on the back surface of the steel sheet in parallel with the fatigue crack, and the fatigue of the back surface of the steel sheet The crack opening is closed and a crack contact surface is formed.

ここで、鋼板には、鋼構造物を構成する鋼材の溶接金属とは異なる全ての部分が含まれている。例えば、鋼板には、単純な平鋼板の他、Ｈ形鋼やＩ形鋼などの構造用鋼材のフランジやウェブなどの平面部分、及び鋼管や角鋼管のように曲がり加工等が施された管材の平面部分や曲面部分も含まれている。また、疲労き裂の直上とは、疲労き裂に重なる又は重なる程度に極近接している状態を述べているのであって、上下方向の上方や、鋼板の面方向に対して垂直となる状態を述べているのではない。   Here, all the parts different from the weld metal of the steel material which comprises a steel structure are contained in the steel plate. For example, for steel plates, in addition to simple flat steel plates, flat parts such as flanges and webs of structural steel materials such as H-shaped steel and I-shaped steel, and pipe materials that are bent such as steel pipes and square steel pipes. The flat part and the curved part are also included. In addition, “immediately above the fatigue crack” refers to a state in which the fatigue crack overlaps or is in close proximity to the extent that it overlaps the fatigue crack, and is a state in which it is perpendicular to the upper and lower directions and the surface direction of the steel sheet. Is not mentioned.

表面から裏面まで貫通した疲労き裂が発生した鋼板に外力が作用して疲労き裂周辺に引張応力が作用すると、疲労き裂の対向する内側面が離れる方向に引っ張られることによって、表面側及び裏面側のき裂開口幅が広がって、疲労き裂が面方向に進展しようとする。   When an external force is applied to a steel plate in which a fatigue crack penetrating from the front surface to the back surface is applied and a tensile stress is applied to the periphery of the fatigue crack, the opposing inner surface of the fatigue crack is pulled in the direction away from the surface side and The crack opening width on the back side widens and the fatigue crack tries to propagate in the surface direction.

本発明の構成によれば、鋼板の表面及び裏面の疲労き裂の開口部が閉じて、き裂の対向する内側面同士が接触したき裂接触面が形成され、き裂接触面には少なからず圧縮残留応力が導入さている。したがって、外力による引張応力と圧縮残留応力とが相殺されることによって、鋼板の表面及び裏面の疲労き裂が開口しにくくなる、あるいはき裂開口幅が広がりにくくなる。これにより、疲労き裂の面方向への進展を止める、あるいは疲労き裂の面方向への進展を遅延させて鋼構造物の疲労寿命の延命化を図ることができる。   According to the configuration of the present invention, the fatigue crack opening on the front surface and the back surface of the steel sheet is closed, and a crack contact surface in which the inner surfaces facing each other are in contact with each other is formed. Compressive residual stress is introduced. Therefore, the tensile stress and the compressive residual stress due to the external force are offset, so that the fatigue cracks on the front surface and the back surface of the steel plate are difficult to open or the crack opening width is difficult to expand. Accordingly, the fatigue life of the steel structure can be extended by stopping the progress of the fatigue crack in the surface direction or delaying the progress of the fatigue crack in the surface direction.

また、ピーニングという簡易な方法で疲労き裂の補修を行うため、従来から実施されてきた恒久的な補修・補強対策のような多大な労力とコストは不要であり、簡便かつ安価に疲労き裂を補修することができる。また、鋼板の表面及び裏面のみに加工を施すため、鋼板への削孔等は不要であり、疲労き裂発生部位の構造や疲労き裂の進展具合を配慮することなく適用することが可能である。   In addition, since the fatigue crack is repaired by a simple method called peening, a great amount of labor and cost as in the case of permanent repair / reinforcing measures that have been used in the past is unnecessary, and the fatigue crack is easily and inexpensively performed. Can be repaired. In addition, since only the front and back surfaces of the steel plate are processed, there is no need to drill holes in the steel plate and it can be applied without considering the structure of the fatigue crack initiation site and the progress of the fatigue crack. is there.

（２）本発明の鋼構造物の疲労き裂補修構造は、前記き裂接触面に作用する圧縮残留応力が設計引張応力以上であることが好ましい。   (2) In the fatigue crack repair structure of a steel structure according to the present invention, the compressive residual stress acting on the crack contact surface is preferably equal to or greater than the design tensile stress.

き裂接触面に作用する圧縮残留応力が、設計荷重によって発生する引張応力（設計引張応力）以上であれば、設計荷重に対して疲労き裂が開口することがない。したがって、疲労き裂の進展を止める、あるいは疲労き裂の進展を遅延させて鋼構造物の疲労寿命の延命化を図る効果を十分に得ることができる。   If the compressive residual stress acting on the crack contact surface is equal to or greater than the tensile stress generated by the design load (design tensile stress), the fatigue crack will not open against the design load. Therefore, it is possible to sufficiently obtain the effect of stopping the fatigue crack growth or delaying the fatigue crack propagation to prolong the fatigue life of the steel structure.

さらに好ましくは、前記き裂接触面に作用する圧縮残留応力が降伏応力と同程度又はそれ以上であるとよい。   More preferably, the compressive residual stress acting on the crack contact surface is equal to or higher than the yield stress.

許容応力度法で設計された既設の鋼構造物は、設計引張応力が鋼材の許容引張応力以内に収まるように設計されている。設計では許容引張応力を降伏応力の１／１．７程度としており、実際に作用する引張応力は許容引張応力のさらに１／２程度と考えられている。したがって、圧縮残留応力が降伏応力と同程度又はそれ以上となっていれば、疲労き裂の進展を確実に防ぐことが可能である。   Existing steel structures designed by the allowable stress method are designed so that the design tensile stress is within the allowable tensile stress of the steel material. In the design, the allowable tensile stress is set to about 1 / 1.7 of the yield stress, and the actually applied tensile stress is considered to be about 1/2 of the allowable tensile stress. Therefore, if the compressive residual stress is equal to or higher than the yield stress, it is possible to reliably prevent the development of fatigue cracks.

なお、鋼構造物はある程度の寿命（耐用年数）を想定して設計されており、疲労き裂等の補修や塗装の塗替えなどの部分的な維持補修を行いながら全体構造としての健全性が維持されている。したがって、疲労き裂を補修する場合には、構造物の耐用年数を超えるほどの強固な補修を施す必要はなく、疲労き裂の進展を止める、あるいは残存寿命が十分に確保できる程度に進展を遅延することができればよい。このような観点からは、本発明の疲労き裂補修方法も、一時的な疲労き裂補修対策ではなく、恒久的な疲労き裂補修対策と見なすこともできる。   Steel structures are designed with a certain life expectancy (life expectancy), and the overall structure is sound while repairs such as fatigue cracks and partial maintenance repairs such as repainting are performed. Maintained. Therefore, when repairing a fatigue crack, it is not necessary to perform a strong repair that exceeds the service life of the structure, and the progress is made to the extent that the fatigue crack can be stopped or the remaining life can be secured sufficiently. It suffices if it can be delayed. From this point of view, the fatigue crack repair method of the present invention can also be regarded as a permanent fatigue crack repair measure rather than a temporary fatigue crack repair measure.

（３）鋼板の表面から裏面まで貫通した疲労き裂を補修の対象とする本発明の鋼構造物の疲労き裂補修方法は、前記鋼板の表面の前記疲労き裂を挟んだ両側のうち少なくとも一側を該疲労き裂と平行にピーニングすることにより該鋼板の表面に塑性変形を付与し、該鋼板の表面の該疲労き裂の開口部を閉じてき裂接触面を形成する疲労き裂周辺ピーニング工程と、前記鋼板の裏面の前記疲労き裂を挟んだ両側のうち少なくとも一側を該疲労き裂と平行にピーニングすることにより該鋼板の裏面に塑性変形を付与し、該鋼板の裏面の該疲労き裂の開口部を閉じてき裂接触面を形成する疲労き裂周辺ピーニング工程と、を有することを特徴とする。   (3) The method for repairing a fatigue crack of a steel structure according to the present invention, which is intended for repairing a fatigue crack penetrating from the front surface to the back surface of the steel sheet, includes at least one of both sides of the surface of the steel sheet sandwiching the fatigue crack. Peripheries of fatigue cracks that impart plastic deformation to the surface of the steel sheet by peening one side parallel to the fatigue crack, and close the opening of the fatigue crack on the surface of the steel sheet to form a crack contact surface A peening step and peening at least one side of the back surface of the steel sheet sandwiching the fatigue crack in parallel with the fatigue crack to impart plastic deformation to the back surface of the steel sheet; A fatigue crack peripheral peening process for closing the fatigue crack opening and forming a crack contact surface.

単に疲労き裂の直上のみをピーニングするだけでは、疲労き裂の開口部付近の対向する内側面を近づける方向に塑性変形を付与しにくいため、効率よくき裂接触面を形成することができない。本発明においては、疲労き裂周辺ピーニング工程によって疲労き裂の開口部付近の対向する内側面を近づける方向に塑性変形を付与することができるため、効率よくき裂接触面を形成することができる。その他の作用効果については、上述した（１）の作用効果と同様である。   By simply peening just above the fatigue crack, it is difficult to provide plastic deformation in the direction in which the inner surfaces facing each other near the opening of the fatigue crack are close to each other, so that a crack contact surface cannot be formed efficiently. In the present invention, the crack contact surface can be formed efficiently because plastic deformation can be imparted in a direction in which the opposing inner surfaces near the opening of the fatigue crack are brought closer by the fatigue crack peripheral peening process. . About another effect, it is the same as that of the effect of (1) mentioned above.

（４）本発明の鋼構造物の疲労き裂補修方法は、必要に応じて、前記鋼板の表面及び／又は裏面に対する前記疲労き裂周辺ピーニング工程の後工程として、前記疲労き裂の直上をピーニングすることにより前記鋼板の表面及び／又は裏面に塑性変形を付与し、前記き裂接触面の接触面積及び／又は接触圧力を増加する疲労き裂直上ピーニング工程を施すことができる。   (4) The method for repairing a fatigue crack of a steel structure according to the present invention includes, if necessary, directly above the fatigue crack as a post-process of the fatigue crack peripheral peening process for the front surface and / or the back surface of the steel plate. By peening, plastic deformation can be imparted to the front surface and / or back surface of the steel sheet, and a peening process immediately above a fatigue crack can be performed to increase the contact area and / or contact pressure of the crack contact surface.

疲労き裂周辺ピーニング工程によってき裂接触面を形成した後に、疲労き裂直上ピーニング工程を施すことによって、き裂接触面の接触面積や接触圧力が増加する。これにより、き裂接触面の広い範囲で高い圧縮残留応力を導入することができるため、疲労き裂を開口しようとする引張応力に抵抗する効果はさらに高くなる。   After the crack contact surface is formed by the fatigue crack peripheral peening process, the contact area and contact pressure of the crack contact surface are increased by performing the peening process immediately above the fatigue crack. Thereby, since a high compressive residual stress can be introduced in a wide range of the crack contact surface, the effect of resisting the tensile stress that attempts to open a fatigue crack is further enhanced.

なお、一般には疲労き裂直上ピーニング工程によって、き裂接触面の接触面積と接触圧力の両方が増加することが想定されるが、ピーニングの方法によっては、接触面積が変わらずに接触圧力のみが増加する場合や、接触圧力が変わらずに接触面積のみが増加する場合や、部分的に接触面積や接触圧力が減少する場合も想定される。   In general, it is assumed that both the contact area and the contact pressure of the crack contact surface are increased by the peening process immediately above the fatigue crack, but depending on the peening method, only the contact pressure is maintained without changing the contact area. It is also assumed that the contact area increases or the contact pressure increases without changing the contact pressure, or the contact area or the contact pressure partially decreases.

このような場合であっても、接触面積と接触圧力を掛け合わせた合力として、疲労き裂を開口しようとする引張応力に抵抗する効果が高くなれば、疲労き裂周辺ピーニング工程の後工程として疲労き裂直上ピーニング工程を実施することの利点が得られる。   Even in such a case, if the effect of resisting the tensile stress that tries to open a fatigue crack becomes high as a resultant force obtained by multiplying the contact area and the contact pressure, as a subsequent process of the peening process around the fatigue crack The advantage of performing the peening process directly above the fatigue crack is obtained.

（５）本発明の鋼構造物の疲労き裂補修方法は、前記疲労き裂と平行に設置したガイドにより前記ピーニングの軌道を案内しながら、該ピーニングを行うことが好ましい。   (5) In the method for repairing a fatigue crack of a steel structure according to the present invention, it is preferable to perform the peening while guiding the peening trajectory with a guide installed in parallel with the fatigue crack.

疲労き裂に沿って設置したガイドによりピーニングの軌道を案内すれば、疲労き裂に平行して正確な軌道でピーニングを行うことができる。したがって、ピーニングによって鋼板に付与する塑性変形の精度を確保することができる。   If the peening trajectory is guided by a guide installed along the fatigue crack, the peening can be performed with an accurate trajectory parallel to the fatigue crack. Therefore, it is possible to ensure the accuracy of plastic deformation applied to the steel sheet by peening.

（６）本発明の鋼構造物の疲労き裂補修方法は、前記き裂接触面に作用する圧縮残留応力が設計引張応力以上であることが好ましい。作用効果については、上述した（１）の作用効果と同様である。   (6) In the fatigue crack repair method for a steel structure according to the present invention, it is preferable that a compressive residual stress acting on the crack contact surface is equal to or greater than a design tensile stress. The operational effect is the same as the operational effect (1) described above.

本発明の鋼構造物の疲労き裂補修方法によれば、鋼板を貫通した疲労き裂を補修の対象とした従来の恒久的な補修・補強対策であるストップホールと添接板による方法と比べて、作業時間及び労力が大幅に削減される。   According to the fatigue crack repair method for steel structures of the present invention, compared to the conventional method of permanent repair / reinforcement with stop holes and attachment plates for repairing fatigue cracks that penetrate through steel plates. Thus, work time and labor are greatly reduced.

本発明の鋼構造物の疲労き裂補修構造及び補修方法によれば、鋼板の表面から裏面まで貫通した疲労き裂を簡便かつ安価に補修することが可能であり、疲労き裂の進展を止める、あるいは疲労き裂の進展を遅延させて鋼構造物の疲労寿命の延命化を図ることができる。   According to the fatigue crack repair structure and repair method for a steel structure of the present invention, it is possible to repair a fatigue crack penetrating from the front surface to the back surface of the steel plate easily and inexpensively, and stop the progress of the fatigue crack. Alternatively, the fatigue life of the steel structure can be extended by delaying the progress of the fatigue crack.

一実施形態における疲労き裂補修方法を説明する斜視図であって、（ａ）は鋼板の表面に疲労き裂が発生した状況、（ｂ）は鋼板の表面から裏面まで疲労き裂が進展した状況、（ｃ）は鋼板の表面に疲労き裂周辺ピーニング工程を実施している状況、（ｄ）は鋼板の表面に疲労き裂直上ピーニング工程を実施している状況、（ｅ）は鋼板の裏面に疲労き裂周辺ピーニング工程を実施している状況、（ｆ）は鋼板の裏面に疲労き裂直上ピーニング工程を実施している状況を示している。It is a perspective view explaining the fatigue crack repair method in one Embodiment, (a) is the situation where the fatigue crack generate | occur | produced on the surface of the steel plate, (b) is the fatigue crack progressed from the surface of the steel plate to the back surface. The situation, (c) is a situation where a fatigue crack peripheral peening process is performed on the surface of the steel sheet, (d) is a situation where a fatigue crack directly peening process is performed on the surface of the steel sheet, and (e) is a condition of the steel sheet. The situation where the fatigue crack peripheral peening process is carried out on the back surface, and (f) shows the situation where the fatigue crack directly peening process is carried out on the back surface of the steel sheet. 本発明の一実施形態における疲労き裂補修方法を説明する斜視図であって、ガイドによりピーニングの軌道を案内しながら疲労き裂周辺ピーニング工程を実施している状況を示している。It is a perspective view explaining the fatigue crack repair method in one Embodiment of this invention, Comprising: The condition which is implementing the fatigue crack periphery peening process, guiding the peening track | orbit with a guide, is shown. 疲労き裂補修を行わない場合の疲労き裂の進展状況を模式的に説明する説明図であって、（ａ）は鋼板の表面から裏面まで疲労き裂が進展した状況を説明する斜視図、（ｂ）は（ａ）の鋼板の両端に下向きの曲げ荷重が作用して鋼板の表面付近に引張応力が発生した状況を説明する断面図、（ｃ）は（ａ）の鋼板の両端に上向きの曲げ荷重が作用して鋼板の裏面付近に引張応力が発生した状況を説明する断面図、（ｄ）は（ｂ）及び（ｃ）に示した曲げ荷重の繰返しによって疲労き裂がさらに進展した状況を説明する斜視図を示している。It is explanatory drawing which illustrates typically the progress situation of the fatigue crack when not performing fatigue crack repair, (a) is a perspective view explaining the situation where the fatigue crack has progressed from the front surface to the back surface of the steel sheet, (B) is a cross-sectional view illustrating a situation in which a downward bending load is applied to both ends of the steel plate of (a) and tensile stress is generated near the surface of the steel plate, and (c) is upward to both ends of the steel plate of (a). Sectional drawing explaining the situation where tensile stress was generated in the vicinity of the back surface of the steel sheet due to the bending load of (b), (d) is a fatigue crack further developed by repeated bending loads shown in (b) and (c) The perspective view explaining the situation is shown. 一実施形態における疲労き裂補修構造及び補修方法の効果を模式的に説明する説明図であって、（ａ）は疲労き裂補修が完了した状況を説明する斜視図、（ｂ）は（ａ）の鋼板の両端に下向きの曲げ荷重が作用して鋼板の表面側のき裂接触面に作用する圧縮残留応力が減少している状況を説明する断面図、（ｃ）は（ａ）の鋼板の両端に上向きの曲げ荷重が作用して鋼板の裏面側のき裂接触面に作用する圧縮残留応力が減少している状況を説明する断面図、（ｄ）は（ｂ）及び（ｃ）に示した曲げ荷重が繰返し載荷されても疲労き裂が進展していない状況を説明する斜視図を示している。It is explanatory drawing which illustrates typically the effect of the fatigue crack repair structure and repair method in one Embodiment, (a) is a perspective view explaining the condition where fatigue crack repair was completed, (b) is (a) Sectional drawing explaining the situation where the downward bending load acts on both ends of the steel plate of) and the compressive residual stress acting on the crack contact surface on the surface side of the steel plate is reduced, (c) is the steel plate of (a) Sectional drawing explaining the situation where the compressive residual stress which acts on the crack contact surface of the back surface side of a steel plate is reducing by the upward bending load acting on both ends of (b) and (c) The perspective view explaining the condition where the fatigue crack has not progressed even if the shown bending load is loaded repeatedly is shown. 一般的な構造用鋼材の応力−ひずみ曲線である。It is a stress-strain curve of a general structural steel material. 板曲げ疲労試験機の側面図である。It is a side view of a plate bending fatigue testing machine. 実施例１における面外ガセット溶接継手試験体の構造を説明する斜視図である。It is a perspective view explaining the structure of the out-of-plane gusset welded joint test body in Example 1. 実施例１による延命化効果を説明するＳ−Ｎ線図である。It is a SN diagram explaining the life extension effect by Example 1. FIG. 実施例１における面外ガセット溶接継手試験体の疲労き裂補修順序を説明する斜視図である。It is a perspective view explaining the fatigue crack repair order of the out-of-plane gusset welded joint specimen in Example 1. 実施例２及び３におけるＴ形溶接継手試験体の構造を説明する斜視図である。It is a perspective view explaining the structure of the T-shaped welded joint test body in Examples 2 and 3. 実施例２及び３による延命化効果を説明するＳ−Ｎ線図である。It is a SN diagram explaining the life extension effect by Example 2 and 3. FIG. 実施例２及び３におけるＴ形溶接継手試験体の疲労き裂補修順序を説明する斜視図である。It is a perspective view explaining the fatigue crack repair order of the T-shaped welded joint specimen in Examples 2 and 3. 実施例４におけるＴ形溶接継手試験体のピーニング処理中のひずみの発生状況を説明するグラフである。It is a graph explaining the generation | occurrence | production condition of the distortion in the peening process of the T-shaped welded joint test body in Example 4. 面外ガセット溶接継手のまわし溶接部における溶接止端に発生した疲労き裂がその周辺の鋼板部に進展していく状況を説明する斜視図であって、（ａ）は疲労き裂が発生していない状況、（ｂ）はまわし溶接部の溶接止端に疲労き裂が発生した状況、（ｃ）はまわし溶接部の溶接止端に発生した疲労き裂が進展して溶接止端から離れ始めた状況、（ｄ）は疲労き裂が鋼板部に１０ｍｍ進展した状況、（ｅ）は疲労き裂が鋼板部に３０ｍｍ進展した状況、（ｆ）は疲労き裂が鋼板部に６０ｍｍ進展した状況を示している。It is a perspective view explaining the situation where the fatigue crack generated at the weld toe in the turn welded portion of the out-of-plane gusset weld joint propagates to the surrounding steel plate portion, where (a) shows the fatigue crack generated. (B) is a situation where a fatigue crack has occurred at the weld toe of the rotary weld, (c) is a situation where the fatigue crack generated at the weld toe of the rotary weld is advancing away from the weld toe (D) is a situation where the fatigue crack has propagated to the steel plate portion by 10 mm, (e) is a situation where the fatigue crack has propagated to the steel plate portion by 30 mm, and (f) is a situation where the fatigue crack has propagated to the steel plate portion by 60 mm. Indicates the situation. 図１４の（ｂ）〜（ｆ）に示した面外ガセット溶接継手を疲労き裂に沿って切断した断面図である。It is sectional drawing which cut | disconnected the out-of-plane gusset welded joint shown to (b)-(f) of FIG. 14 along the fatigue crack.

以下、本発明の鋼構造物の疲労き裂補修構造及び補修方法を具体化した一実施形態について図面を参照しつつ具体的に説明する。   Hereinafter, an embodiment embodying a fatigue crack repair structure and repair method for a steel structure according to the present invention will be described in detail with reference to the drawings.

（１）疲労き裂補修構造及び補修方法
図１に本実施形態の疲労き裂補修方法を説明する斜視図を示す。図１（ａ）は鋼板の表面に疲労き裂が発生した状況、図１（ｂ）は鋼板の表面から裏面まで疲労き裂が進展した状況、図１（ｃ）は鋼板の表面に疲労き裂周辺ピーニング工程を実施している状況、図１（ｄ）は鋼板の表面に疲労き裂直上ピーニング工程を実施している状況、図１（ｅ）は鋼板の裏面に疲労き裂周辺ピーニング工程を実施している状況、図１（ｆ）は鋼板の裏面に疲労き裂直上ピーニング工程を実施している状況を示している。 (1) Fatigue crack repair structure and repair method FIG. 1 is a perspective view illustrating a fatigue crack repair method according to the present embodiment. FIG. 1 (a) shows a situation in which a fatigue crack has occurred on the surface of the steel sheet, FIG. 1 (b) shows a situation in which the fatigue crack has progressed from the front surface to the back surface of the steel sheet, and FIG. Fig. 1 (d) shows the situation where the fatigue crack peening process is performed on the surface of the steel sheet, and Fig. 1 (e) shows the situation where the fatigue crack peening process is performed on the back surface of the steel sheet. FIG. 1 (f) shows a situation in which a fatigue crack directly above peening process is carried out on the back surface of the steel sheet.

鋼板１に外力が繰返し作用すると、金属疲労によって、図１（ａ）に示すように鋼板１の表面１ａに疲労き裂２が発生する。この疲労き裂２を放置すると、疲労き裂２は、厚さ方向（深さ方向）と面方向（横方向）に半だ円状にき裂断面が拡大しながら進展し、やがてき裂断面が鋼板１の裏面１ｂまで到達して、図１（ｂ）に示すように鋼板１の表面１ａから裏面１ｂまで貫通した疲労き裂２となる。この貫通した疲労き裂２の進展を防止するために、図１（ｃ）〜（ｆ）に示す補修が行われる。   When an external force is repeatedly applied to the steel plate 1, a fatigue crack 2 is generated on the surface 1a of the steel plate 1 due to metal fatigue, as shown in FIG. If this fatigue crack 2 is left as it is, the fatigue crack 2 propagates while the crack cross section expands in a semi-circular shape in the thickness direction (depth direction) and in the plane direction (lateral direction), and eventually cracks. The cross-section reaches the back surface 1b of the steel plate 1 and becomes a fatigue crack 2 penetrating from the front surface 1a to the back surface 1b of the steel plate 1 as shown in FIG. In order to prevent the fatigue crack 2 from penetrating, the repairs shown in FIGS. 1C to 1F are performed.

図１（ｃ）に示すように、まず鋼板１の表面１ａ側の疲労き裂２と平行に疲労き裂２の両側に２本のピーニング軌道Ｌａ１及びＬａ２を設定する。ここで、疲労き裂２からピーニング軌道Ｌａ１及び疲労き裂２からピーニング軌道Ｌａ２までの間隔は同一間隔とし、後述するチッパー３ａの先端と鋼板１とのピーニング時の接触面が疲労き裂２の直上に重ならない間隔を確保する。 As shown in FIG. 1C, first, two peening tracks La 1 and La 2 are set on both sides of the fatigue crack 2 in parallel with the fatigue crack 2 on the surface 1a side of the steel plate 1. Here, the intervals from the fatigue crack 2 to the peening trajectory La 1 and from the fatigue crack 2 to the peening trajectory La 2 are the same, and the contact surface at the time of peening between the tip of the chipper 3a and the steel plate 1 described later is the fatigue crack. Secure an interval that does not overlap directly above 2.

次にピーニング軌道Ｌａ１、Ｌａ２の順にピーニングを行って鋼板１の表面１ａに塑性変形を付与し、疲労き裂２の開口部を閉じて表面側き裂接触面２ａを形成する。この工程を疲労き裂周辺ピーニング工程と呼ぶ。なお、表面側き裂接触面２ａは疲労き裂２の最上方付近のみに形成されており、表面側き裂接触面２ａより下方では疲労き裂２の対向する内側面同士が接触していない。 Next, peening is performed in the order of peening trajectories La 1 and La 2 to impart plastic deformation to the surface 1a of the steel sheet 1, and the opening of the fatigue crack 2 is closed to form the surface side crack contact surface 2a. This process is called a fatigue crack peripheral peening process. In addition, the surface side crack contact surface 2a is formed only near the uppermost part of the fatigue crack 2, and the inner side surfaces where the fatigue crack 2 faces are not in contact below the surface side crack contact surface 2a. .

ピーニングには先端にチッパー３ａが取り付けられた市販の手持ち可能なピーニング器具３を使用する。ピーニング器具３はコンプレッサー（図示せず）の空気圧を利用して、チッパー３ａを高速振動するエアーハンマーであり、このピーニング器具３を使用したピーニングをエアーハンマーピーニングと呼ぶ。   For peening, a commercially available hand-held peening instrument 3 having a tip 3a attached to the tip is used. The peening device 3 is an air hammer that vibrates the chipper 3a at high speed using the air pressure of a compressor (not shown), and peening using the peening device 3 is called air hammer peening.

チッパー３ａの先端形状は、４ｍｍ×５ｍｍ程度の平坦な矩形形状であり、少し角が丸く面取りされている。この先端形状は、いくつかの先端形状のチッパー３ａを試して、鋼板１の表面に塑性変形を付与し易いものとして決定しているが、コンプレッサーの空気圧や使用するピーニング器具３の性能によってチッパー３ａの最適な先端形状は異なるものと考えられる。   The tip shape of the chipper 3a is a flat rectangular shape of about 4 mm × 5 mm, and its corners are chamfered slightly rounded. This tip shape is determined by trying several tip-shaped chippers 3a so as to easily impart plastic deformation to the surface of the steel plate 1. The tipper 3a depends on the air pressure of the compressor and the performance of the peening device 3 to be used. The optimum tip shape is considered to be different.

ピーニング方法としては、本実施形態のエアーハンマーピーニングの他、鋼球を投射することによる衝撃を利用するショットピーニングや、超音波振動による衝撃を利用する超音波ピーニングなどがあるが、鋼材表面に塑性変形を効率よく付与することが可能な衝撃エネルギーと、様々な施工条件に対応可能な作業性を考慮すると、手持ち可能なエアーハンマーピーニングが本実施形態を実施する上で最も適していると考えられる。   The peening method includes air peening of this embodiment, shot peening that uses the impact of projecting a steel ball, and ultrasonic peening that uses the impact of ultrasonic vibration. Considering the impact energy that can efficiently apply deformation and workability that can handle various construction conditions, it is considered that hand-held air hammer peening is the most suitable for carrying out this embodiment. .

図２にピーニング軌道Ｌａ１の疲労き裂周辺ピーニング工程を実施している状況を示す。疲労き裂２は面方向に直線的に進展することから、例えば、木製の角材をピーニングを行う際のガイド４（定規）として使用することができる。ガイド４の長手方向がピーニング軌道Ｌａ１と平行になるように鋼板１の表面１ａ上に設置して、クランプ等のガイド固定治具５を用いて、鋼板１とガイド４とを一緒に挟み込むことによって固定する。ここで、鋼板１がクランプ等で挟み込めない構造である場合には、マグネットを用いて鋼板１にガイド４を固定することもできる。 FIG. 2 shows a situation where the fatigue crack peripheral peening process of the peening trajectory La 1 is performed. Since the fatigue crack 2 propagates linearly in the plane direction, it can be used as, for example, a guide 4 (ruler) when peening a wooden square. Install on the surface 1a of the steel plate 1 so that the longitudinal direction of the guide 4 is parallel to the peening track La 1 and sandwich the steel plate 1 and the guide 4 together using a guide fixing jig 5 such as a clamp. Fixed by. Here, when the steel plate 1 has a structure that cannot be sandwiched by a clamp or the like, the guide 4 can be fixed to the steel plate 1 using a magnet.

続いて図１（ｄ）に示すように、鋼板１の表面１ａ側の疲労き裂２の直上にピーニング軌道Ｌａ３を設定する。そして、ピーニング軌道Ｌａ３に沿ってピーニングを行うことによって、表面側き裂接触面２ａの接触面積や接触圧力を増加させる。このピーニング軌道Ｌａ３に沿ってピーニングを行う工程を疲労き裂直上ピーニング工程と呼ぶ。 Subsequently, as shown in FIG. 1 (d), a peening trajectory La 3 is set immediately above the fatigue crack 2 on the surface 1 a side of the steel plate 1. Then, by performing peening along a peening trajectory La 3, to increase the contact area and contact pressure-out surface side Cracks contact surface 2a. A step of performing peening along the peening trajectory La 3 is referred to as fatigue裂直on peening.

なお、疲労き裂周辺ピーニング工程によって形成された表面側き裂接触面２ａが疲労き裂直上ピーニング工程によって再度開口することがないように、疲労き裂直上ピーニング工程で使用するピーニング器具３のチッパー３ａの先端幅は、図１（ｂ）の疲労き裂２の開口幅よりも大きく設定されていることは言うまでもない。   In addition, the chipper of the peening apparatus 3 used in the fatigue crack directly above peening process so that the surface side crack contact surface 2a formed by the fatigue crack periphery peening process does not open again by the fatigue crack directly above peening process. Needless to say, the tip width of 3a is set larger than the opening width of the fatigue crack 2 in FIG.

続いて図１（ｅ）に示すように、鋼板１の裏面１ｂ側の疲労き裂２と平行に疲労き裂２の両側に２本のピーニング軌道Ｌｂ１及びＬｂ２を設定して、上述した鋼板１の表面１ａ側のピーニング軌道Ｌａ１及びＬａ２に対するピーニング処理と同様の方法で、ピーニング軌道Ｌｂ１及びＬｂ２に対して疲労き裂周辺ピーニング工程を実施する。これにより、疲労き裂２の開口部が閉じられて裏面側き裂接触面２ｂが形成される。 Subsequently, as shown in FIG. 1 (e), by setting the two peening trajectory Lb 1 and Lb 2 on both sides of the fatigue crack 2-out parallel fatigue cracks 2 on the back surface 1b side of the steel plate 1, described above A fatigue crack peripheral peening process is performed on the peening tracks Lb 1 and Lb 2 in the same manner as the peening process on the peening tracks La 1 and La 2 on the surface 1a side of the steel plate 1. Thereby, the opening part of the fatigue crack 2 is closed and the back surface side crack contact surface 2b is formed.

続いて図１（ｆ）に示すように、鋼板１の裏面１ｂ側の疲労き裂２の直上にピーニング軌道Ｌｂ３を設定して、上述した鋼板１の表面１ａ側のピーニング軌道Ｌａ３に対するピーニング処理と同様の方法で、ピーニング軌道Ｌｂ３に対して疲労き裂直上ピーニング工程を実施する。これにより、裏面側き裂接触面２ｂの接触面積や接触圧力が増加する。 Subsequently, as shown in FIG. 1 (f), a peening trajectory Lb 3 is set immediately above the fatigue crack 2 on the back surface 1 b side of the steel plate 1, and the peening for the peening trajectory La 3 on the surface 1 a side of the steel plate 1 described above. A peening process immediately above the fatigue crack is performed on the peening trajectory Lb 3 by the same method as the processing. Thereby, the contact area and the contact pressure of the back side crack contact surface 2b increase.

本実施形態の疲労き裂補修方法を実施する上での留意点として、本実施形態の疲労き裂補修方法は、鋼板１の表面１ａから裏面１ｂまで貫通した疲労き裂２を補修の対象としているが、疲労き裂２がかなり進展してき裂開口幅が大きくなり、ピーニングにより鋼板１に塑性変形を加えることでき裂接触面２ａ及び２ｂを形成することができたとしても、この塑性変形量が大きくて鋼板１の断面性能等に悪影響を及ぼす場合においては適用の対象外とする。   As a point to keep in mind when carrying out the fatigue crack repair method of the present embodiment, the fatigue crack repair method of the present embodiment uses the fatigue crack 2 penetrating from the front surface 1a to the back surface 1b of the steel plate 1 as the object of repair. However, even if the fatigue crack 2 progresses considerably and the crack opening width becomes large and plastic deformation can be applied to the steel plate 1 by peening and the crack contact surfaces 2a and 2b can be formed, the amount of plastic deformation is If it is large and adversely affects the cross-sectional performance of the steel sheet 1, it is not applicable.

また、疲労き裂２が面方向に進展して、鋼板１が疲労き裂２で分断された場合においては、本実施形態の疲労き裂補修方法を適用することができない。疲労き裂２の開口部を閉じるためには、力のつり合い上、疲労き裂２の面方向の先端よりも先の部分の鋼板１に疲労き裂２が発生していない領域１ｃ（図２参照）が必要である。   In addition, when the fatigue crack 2 propagates in the plane direction and the steel plate 1 is divided by the fatigue crack 2, the fatigue crack repair method of the present embodiment cannot be applied. In order to close the opening of the fatigue crack 2, a region 1 c where the fatigue crack 2 is not generated in the steel plate 1 beyond the front end in the surface direction of the fatigue crack 2 in view of balance of force (FIG. 2). Reference) is required.

また、疲労き裂２の開口部の全域を確実に閉じるためには、疲労き裂２の面方向の先端よりも先の部分までピーニング処理を施すのが望ましい。例えば、図２に示すように、ピーニング軌道Ｌａ１、Ｌａ２、Ｌａ３、Ｌｂ１、Ｌｂ２及びＬｂ３の長さを、疲労き裂２の面方向の進展長さよりも１０ｍｍ以上長く設定しておくとよい。ここで、図２に示すように、鋼板１の表面１ａ側の疲労き裂２の進展長さと裏面１ｂ側の疲労き裂２の進展長さとが大きく異なる場合には、少なくとも疲労き裂２の進展長さが長い側のピーニング軌道の長さを、疲労き裂２の面方向の進展長さよりも１０ｍｍ以上長く設定しておくとよい。ピーニング軌道の長さは疲労き裂２のき裂開口幅の開き具合に応じて適宜設定することが可能であり、疲労き裂２のき裂開口幅が小さい場合には、疲労き裂２の面方向の進展長さとピーニング軌道の長さを同程度の長さとしてもよい。 Moreover, in order to close the whole region of the opening portion of the fatigue crack 2 with certainty, it is desirable to perform a peening process to a portion ahead of the tip in the surface direction of the fatigue crack 2. For example, as shown in FIG. 2, the lengths of the peening trajectories La 1 , La 2 , La 3 , Lb 1 , Lb 2 and Lb 3 are set to be 10 mm or more longer than the length of the fatigue crack 2 in the surface direction. It is good to keep. Here, as shown in FIG. 2, when the progress length of the fatigue crack 2 on the front surface 1a side of the steel plate 1 and the progress length of the fatigue crack 2 on the back surface 1b side are greatly different, at least the fatigue crack 2 It is preferable to set the length of the peening track on the side with the longer propagation length to be longer than the progress length in the surface direction of the fatigue crack 2 by 10 mm or more. The length of the peening trajectory can be appropriately set according to the degree of opening of the crack opening width of the fatigue crack 2, and when the crack opening width of the fatigue crack 2 is small, the fatigue crack 2 The length in the surface direction and the length of the peening trajectory may be the same length.

本実施形態によれば、鋼板１の表面１ａ及び裏面１ｂの疲労き裂２の開口部が閉じて、き裂の対向する内側面同士が接触したき裂接触面２ａ及び２ｂが形成され、き裂接触面２ａ及び２ｂには少なからず圧縮残留応力が導入さている。したがって、外力による引張応力と圧縮残留応力とが相殺されることによって、鋼板１の表面１ａ及び裏面１ｂの疲労き裂２が開口しにくくなる、あるいはき裂開口幅が広がりにくくなる。これにより、疲労き裂２の面方向への進展を止める、あるいは疲労き裂２の面方向への進展を遅延させて鋼構造物の疲労寿命の延命化を図ることができる。   According to this embodiment, the opening portions of the fatigue crack 2 on the front surface 1a and the back surface 1b of the steel plate 1 are closed, and crack contact surfaces 2a and 2b are formed in which the inner surfaces facing each other are in contact with each other. Compressive residual stress is introduced into the crack contact surfaces 2a and 2b. Therefore, the tensile stress and the compressive residual stress due to the external force are offset, so that the fatigue crack 2 on the front surface 1a and the back surface 1b of the steel plate 1 is difficult to open or the crack opening width is difficult to expand. As a result, it is possible to extend the fatigue life of the steel structure by stopping the progress of the fatigue crack 2 in the plane direction or delaying the progress of the fatigue crack 2 in the plane direction.

また、単に疲労き裂２の直上のみをピーニングするだけでは、疲労き裂２の開口部付近の対向する内側面を近づける方向に塑性変形を付与しにくいため、効率よくき裂接触面２ａ及び２ｂを形成することができない。本実施形態においては、疲労き裂周辺ピーニング工程によって疲労き裂２の開口部付近の対向する内側面を近づける方向に塑性変形を付与することができるため、効率よくき裂接触面２ａ及び２ｂを形成することができる。   In addition, simply peening just above the fatigue crack 2 makes it difficult to impart plastic deformation in the direction in which the opposing inner surfaces near the opening of the fatigue crack 2 are brought closer, so the crack contact surfaces 2a and 2b are efficiently provided. Can not form. In the present embodiment, since the plastic deformation can be imparted in the direction in which the opposing inner surfaces near the opening of the fatigue crack 2 are brought closer by the fatigue crack peripheral peening process, the crack contact surfaces 2a and 2b are efficiently formed. Can be formed.

また、疲労き裂周辺ピーニング工程によってき裂接触面２ａ及び２ｂを形成した後に、疲労き裂直上ピーニング工程を施すことによって、き裂接触面２ａ及び２ｂの接触面積や接触圧力が増加する。これにより、き裂接触面２ａ及び２ｂの広い範囲で高い圧縮残留応力を導入することができるため、疲労き裂２を開口しようとする引張応力に抵抗する効果はさらに高くなる。   Further, after forming the crack contact surfaces 2a and 2b by the fatigue crack peripheral peening process, the contact area and the contact pressure of the crack contact surfaces 2a and 2b are increased by performing the fatigue crack direct peening process. Thereby, since a high compressive residual stress can be introduced in a wide range of the crack contact surfaces 2a and 2b, the effect of resisting the tensile stress that attempts to open the fatigue crack 2 is further enhanced.

また、市販の手持ち可能なピーニング器具３を使用してピーニングを行うという簡易な方法で疲労き裂２の補修を行うため、簡便かつ安価に疲労き裂２を補修することができる。また、鋼板１の表面１ａ及び裏面１ｂのみに加工を施すため、鋼板１への削孔等は不要であり、疲労き裂２の発生部位の構造や疲労き裂２の進展具合を配慮することなく適用することが可能である。   Further, since the fatigue crack 2 is repaired by a simple method of peening using a commercially available hand-held peening instrument 3, the fatigue crack 2 can be repaired easily and inexpensively. Further, since only the front surface 1a and the back surface 1b of the steel plate 1 are processed, there is no need to drill holes in the steel plate 1, and the structure of the fatigue crack 2 occurrence site and the progress of the fatigue crack 2 should be taken into consideration. It is possible to apply without.

また、疲労き裂２に沿って設置したガイド４によりピーニングの軌道を案内するため、疲労き裂２に平行して正確な軌道でピーニングを行うことができる。したがって、ピーニングによって鋼板１に付与する塑性変形の精度を確保することができる。   Further, since the peening trajectory is guided by the guide 4 installed along the fatigue crack 2, the peening can be performed with an accurate trajectory parallel to the fatigue crack 2. Therefore, the precision of the plastic deformation given to the steel plate 1 by peening can be ensured.

（２）閉口させた疲労き裂の力学的な考え方
上述した本実施形態の疲労き裂補修構造は、疲労き裂２が開口する方向に働く引張応力に対して、き裂接触面２ａ及び２ｂに導入した圧縮残留応力が抵抗することによって、鋼板１の表面１ａ及び裏面１ｂの疲労き裂２が開口しにくくなる、あるいはき裂開口幅が広がりにくくなる。 (2) Mechanical concept of closed fatigue crack In the fatigue crack repair structure of the present embodiment described above, the crack contact surfaces 2a and 2b against the tensile stress acting in the direction in which the fatigue crack 2 opens. By resisting the compressive residual stress introduced into the surface, the fatigue cracks 2 on the front surface 1a and the back surface 1b of the steel plate 1 are difficult to open or the crack opening width is difficult to expand.

図３は疲労き裂補修を行わない場合の疲労き裂の進展状況を模式的に説明する説明図である。疲労き裂補修を行っていない図３（ａ）に示す鋼板１は、き裂接触面２ａ及び２ｂが形成されていないため、図３（ｂ）に示すように、鋼板１の両端に下向きの曲げ荷重が作用すると鋼板１の表面１ａ付近に引張応力が発生して表面１ａ側の疲労き裂２のき裂開口幅が広がる。同様に、図３（ｃ）に示すように、鋼板１の両端に上向きの曲げ荷重が作用すると鋼板１の裏面１ｂ付近に引張応力が発生して裏面１ｂ側の疲労き裂２のき裂開口幅が広がる。鋼板１に図３（ｂ）及び（ｃ）に示す外力が繰返し載荷されると、図３（ｄ）に示すように、金属疲労によって疲労き裂２が面方向に進展していく。   FIG. 3 is an explanatory diagram schematically illustrating the progress of fatigue cracks when fatigue crack repair is not performed. The steel plate 1 shown in FIG. 3 (a) that has not undergone fatigue crack repair has no crack contact surfaces 2a and 2b, so that the steel plate 1 faces downward at both ends of the steel plate 1 as shown in FIG. 3 (b). When a bending load is applied, tensile stress is generated in the vicinity of the surface 1a of the steel sheet 1, and the crack opening width of the fatigue crack 2 on the surface 1a side is widened. Similarly, as shown in FIG. 3C, when an upward bending load is applied to both ends of the steel plate 1, tensile stress is generated in the vicinity of the back surface 1b of the steel plate 1, and the crack opening of the fatigue crack 2 on the back surface 1b side is generated. The width expands. When the external force shown in FIGS. 3B and 3C is repeatedly loaded on the steel plate 1, as shown in FIG. 3D, the fatigue crack 2 propagates in the plane direction due to metal fatigue.

一方、図４は本実施形態の疲労き裂補修方法により疲労き裂補修を行った場合の疲労き裂の進展を抑制する効果について模式的に説明する説明図である。図４（ａ）の鋼板１には疲労き裂２の開口部が閉じてき裂接触面２ａ及び２ｂが形成されており、このき裂接触面２ａ及び２ｂには圧縮残留応力が導入されている。   On the other hand, FIG. 4 is an explanatory view schematically illustrating the effect of suppressing the progress of fatigue cracks when the fatigue crack repair is performed by the fatigue crack repair method of the present embodiment. In the steel plate 1 in FIG. 4A, the opening of the fatigue crack 2 is closed and crack contact surfaces 2a and 2b are formed, and compressive residual stress is introduced into the crack contact surfaces 2a and 2b. .

この状態で、図４（ｂ）に示すように、鋼板１の両端に下向きの曲げ荷重が作用すると鋼板１の表面１ａ付近に引張応力が発生し、この引張応力が疲労き裂２を開口させる方向に働く。ところが、表面側き裂接触面２ａに導入した圧縮残留応力が引張応力よりも大きければ、引張応力と圧縮残留応力とが相殺されることにより圧縮残留応力が小さくなるものの疲労き裂２が開口することはない。同様に、図４（ｃ）に示すように、鋼板１の両端に上向きの曲げ荷重が作用すると鋼板１の裏面１ｂ付近に引張応力が発生し、裏面側き裂接触面２ｂに導入した圧縮残留応力が小さくなるものの疲労き裂２が開口することはない。   In this state, as shown in FIG. 4B, when a downward bending load is applied to both ends of the steel plate 1, tensile stress is generated near the surface 1 a of the steel plate 1, and this tensile stress opens the fatigue crack 2. Work in the direction. However, if the compressive residual stress introduced into the surface side crack contact surface 2a is larger than the tensile stress, the fatigue crack 2 opens although the compressive residual stress is reduced by canceling out the tensile stress and the compressive residual stress. There is nothing. Similarly, as shown in FIG. 4 (c), when an upward bending load acts on both ends of the steel plate 1, tensile stress is generated in the vicinity of the back surface 1b of the steel plate 1, and the compressive residual introduced into the back side crack contact surface 2b. Although the stress is reduced, the fatigue crack 2 does not open.

このように図４（ｂ）及び（ｃ）に示す外力が繰返し載荷されたとしても、疲労き裂２が開口することがないため、図４（ｄ）に示すように、疲労き裂２が面方向に進展することはない。したがって、外力の繰返し載荷に対して、疲労き裂２の進展を止める、あるいは疲労き裂２の進展を遅延することができる。   Thus, even if the external force shown in FIGS. 4B and 4C is repeatedly loaded, the fatigue crack 2 does not open. There is no progress in the plane direction. Therefore, it is possible to stop the growth of the fatigue crack 2 or delay the development of the fatigue crack 2 with respect to repeated loading of external force.

なお、図４（ｂ）及び（ｃ）においては、鋼板１の両端に作用する外力として曲げ荷重を想定したが、本実施形態の疲労き裂補修構造は、鋼板１の両端に引張荷重が作用する場合であっても効果を奏する。鋼板１の両端に引張荷重が作用することによって鋼板１の表面１ａ付近及び裏面１ｂ付近に引張応力が発生した場合、き裂接触面２ａ及び２ｂに導入した圧縮残留応力がこの引張応力よりも大きければ、疲労き裂２が面方向に進展することはない。   4B and 4C, a bending load is assumed as an external force acting on both ends of the steel plate 1. However, in the fatigue crack repair structure of this embodiment, a tensile load acts on both ends of the steel plate 1. Even if you do it, it is effective. When tensile stress is generated near the front surface 1a and the back surface 1b of the steel plate 1 due to the tensile load acting on both ends of the steel plate 1, the compressive residual stress introduced into the crack contact surfaces 2a and 2b is larger than this tensile stress. In this case, the fatigue crack 2 does not propagate in the surface direction.

以上より、鋼板を貫通する疲労き裂の開口部を閉口させることは、疲労き裂の面方向への進展を止める、あるいは疲労き裂の面方向への進展を遅延させて、鋼構造物の疲労寿命の延命化を図る上で効果的であることがわかる。   From the above, closing the opening of the fatigue crack that penetrates the steel plate stops the progress of the fatigue crack in the plane direction or delays the progress of the fatigue crack in the plane direction of the steel structure. It can be seen that this is effective in extending the fatigue life.

以上で説明した一実施形態において、表面側き裂接触面２ａ及び裏面側き裂接触面２ｂに作用する圧縮残留応力は設計引張応力以上であることが好ましい。き裂接触面２ａ及び２ｂに作用する圧縮残留応力が、設計荷重によって発生する引張応力（設計引張応力）以上であれば、設計荷重に対して疲労き裂２が開口することがない。したがって、疲労き裂２の進展を止める、あるいは疲労き裂２の進展を遅延させて鋼構造物の疲労寿命の延命化を図る効果を十分に得ることができる。   In the embodiment described above, the compressive residual stress acting on the front side crack contact surface 2a and the rear side crack contact surface 2b is preferably equal to or greater than the design tensile stress. If the compressive residual stress acting on the crack contact surfaces 2a and 2b is equal to or greater than the tensile stress generated by the design load (design tensile stress), the fatigue crack 2 does not open to the design load. Therefore, it is possible to sufficiently obtain the effect of stopping the fatigue crack 2 from progressing or delaying the fatigue crack 2 from extending the fatigue life of the steel structure.

さらに好ましくは、表面側き裂接触面２ａ及び裏面側き裂接触面２ｂに作用する圧縮残留応力が降伏応力と同程度又はそれ以上であるとよい。許容応力度法で設計された既設の鋼構造物は、設計引張応力が鋼材の許容引張応力以内に収まるように設計されている。設計では許容引張応力を降伏応力の１／１．７程度としており、実際に作用する引張応力は許容引張応力のさらに１／２程度と考えられている。したがって、圧縮残留応力が降伏応力と同程度又はそれ以上となっていれば、疲労き裂２の進展を確実に防ぐことが可能である。   More preferably, the compressive residual stress acting on the front side crack contact surface 2a and the rear side crack contact surface 2b is equal to or higher than the yield stress. Existing steel structures designed by the allowable stress method are designed so that the design tensile stress is within the allowable tensile stress of the steel material. In the design, the allowable tensile stress is set to about 1 / 1.7 of the yield stress, and the actually applied tensile stress is considered to be about 1/2 of the allowable tensile stress. Therefore, if the compressive residual stress is equal to or higher than the yield stress, the fatigue crack 2 can be reliably prevented from progressing.

このように、き裂接触面２ａ及び２ｂに大きな圧縮残留応力を発生させるためには、ピーニングによって疲労き裂２周辺の鋼板の表面及び裏面に塑性変形を付与して疲労き裂２の開口部を閉口してき裂接触面２ａ及び２ｂを形成するとともに、さらなる塑性変形を加えて、き裂接触面２ａ及び２ｂの接触圧力を大きくする必要がある。   Thus, in order to generate a large compressive residual stress on the crack contact surfaces 2a and 2b, plastic deformation is applied to the front and back surfaces of the steel plate around the fatigue crack 2 by peening, and the opening of the fatigue crack 2 is formed. Is closed to form the crack contact surfaces 2a and 2b, and further plastic deformation is required to increase the contact pressure of the crack contact surfaces 2a and 2b.

鋼材に圧縮応力が作用すると、圧縮応力が作用した方向（圧縮方向）に鋼材が縮み、圧縮方向の直角方向に膨らもうとする性質がある。したがって、疲労き裂周辺ピーニング工程によって鋼板の表面及び裏面にピーニングの衝撃を加えれば、ピーニングの衝撃荷重が作用した方向（荷重方向）には鋼板が縮み、荷重方向の直角方向に膨らもうとする。すなわち、疲労き裂２が閉じる方向に変形しようとする。疲労き裂２が閉じてき裂接触面２ａ及び２ｂが形成された時点で、この変形が塑性変形領域まで到達していれば、き裂接触面２ａ及び２ｂが保持され、き裂接触面２ａ及び２ｂに圧縮残留応力を発生させることができる。   When compressive stress acts on a steel material, the steel material shrinks in the direction in which the compressive stress is applied (compression direction) and tends to swell in a direction perpendicular to the compression direction. Therefore, if a peening impact is applied to the front and back surfaces of the steel sheet by the fatigue crack peripheral peening process, the steel sheet will shrink in the direction (load direction) in which the impact load of the peening has acted and swell in a direction perpendicular to the load direction. To do. That is, the fatigue crack 2 tends to deform in the closing direction. If the deformation has reached the plastic deformation region when the fatigue crack 2 is closed and the crack contact surfaces 2a and 2b are formed, the crack contact surfaces 2a and 2b are held, and the crack contact surfaces 2a and 2b Compressive residual stress can be generated in 2b.

図５に一般的な構造用鋼材の応力−ひずみ曲線を示す。この応力−ひずみ曲線は引張試験によって得られた鋼材の引張特性であるが、鋼材の引張特性と圧縮特性は類似していることから、鋼材の圧縮特性として代用することもできる。ここでは、図５を圧縮特性として代用して鋼材表面に付与する塑性変形（塑性ひずみ）について説明する。   FIG. 5 shows a stress-strain curve of a general structural steel material. This stress-strain curve is the tensile property of the steel material obtained by the tensile test. However, since the tensile property and the compression property of the steel material are similar, they can be substituted as the compression property of the steel material. Here, the plastic deformation (plastic strain) imparted to the steel material surface by using FIG. 5 as a compression characteristic will be described.

図５において、ｐ１は比例限界、ｐ２は弾性限界、ｐ３は上降伏点、ｐ４は下降伏点、ｐ６は引張強度、ｐ７は破断点であり、０−ｐ１間は応力−ひずみが直線的な比例関係にある比例範囲、０−ｐ２間は除荷することでひずみεが０に戻る弾性範囲、下降伏点ｐ４以降は除荷してもひずみεが０に戻らずに残留ひずみが蓄積する塑性範囲と呼ばれており、鋼材に塑性変形を付与するということは、鋼材に残留ひずみを付与することである。 In FIG. 5, p 1 is the proportional limit, p 2 is the elastic limit, p 3 is the upper yield point, p 4 is the lower yield point, p 6 is the tensile strength, p 7 is the breaking point, and between 0 and p 1 stress - proportional range distortion is in linear proportional relationship, 0-p 2 between the elastic range back to strain epsilon 0 by unloading, is below the yield point p 4 since distortion be unloaded epsilon 0 It is called a plastic range in which residual strain accumulates without returning to the point, and imparting plastic deformation to a steel material is to impart residual strain to the steel material.

例えば、鋼材に作用する圧縮応力を徐々に大きくしていけば、やがて応力−ひずみ曲線上のｐＡに到達する。ここで、圧縮応力を除荷すれば、ｐＡからｐＢに向かって弾性的にひずみεが減少し、０−ｐＢ間に相当する残留ひずみが蓄積する。 For example, if the compressive stress acting on the steel material is gradually increased, it eventually reaches p A on the stress-strain curve. Here, if the compressive stress is unloaded, the strain ε is elastically decreased from p A to p B , and a residual strain corresponding to 0-p B is accumulated.

鋼板の表面及び裏面にピーニングによる衝撃荷重を繰返し加えれば、ピーニングの衝撃荷重が作用した方向（荷重方向）には鋼板が縮み、荷重方向の直角方向に膨らもうとする。しかし、き裂接触面２ａ及び２ｂが形成された以降は、荷重方向の直角方向の変形が拘束されるため、ピーニングの衝撃荷重により鋼板が縮むほど、き裂接触面２ａ及び２ｂの接触圧力が大きくなり、ここでピーニングを終了しても塑性変形した鋼材表面の形状は保持され、き裂接触面２ａ及び２ｂの接触圧力も保持される。   If an impact load due to peening is repeatedly applied to the front and back surfaces of the steel sheet, the steel sheet shrinks in the direction (load direction) in which the peening impact load is applied, and tends to swell in a direction perpendicular to the load direction. However, after the crack contact surfaces 2a and 2b are formed, the deformation in the direction perpendicular to the load direction is restrained, so that the contact pressure of the crack contact surfaces 2a and 2b increases as the steel sheet shrinks due to the impact load of peening. Even when peening is finished, the shape of the surface of the steel material plastically deformed is maintained, and the contact pressure of the crack contact surfaces 2a and 2b is also maintained.

以上詳述したことから明らかなように、本実施形態の鋼構造物の疲労き裂補修構造及び補修方法によれば、鋼板の表面から裏面まで貫通した疲労き裂を簡便かつ安価に補修することが可能であり、疲労き裂の進展を止める、あるいは疲労き裂の進展を遅延させて鋼構造物の疲労寿命の延命化を図ることができる。   As is clear from the above detailed description, according to the fatigue crack repair structure and repair method of the steel structure of the present embodiment, the fatigue crack penetrating from the front surface to the back surface of the steel sheet can be repaired easily and inexpensively. It is possible to extend the fatigue life of the steel structure by stopping the progress of the fatigue crack or delaying the progress of the fatigue crack.

（３）その他の実施形態
なお、本発明は上述した実施の形態に限定されるものではなく、本発明の主旨を逸脱しない範囲で種々の変更を施すことが可能であることは言うまでもない。 (3) Other Embodiments The present invention is not limited to the above-described embodiments, and it goes without saying that various modifications can be made without departing from the gist of the present invention.

例えば、図１に示す表面側き裂接触面２ａ及び裏面側き裂接触面２ｂは、疲労き裂２の最上方付近及び最下方付近のみに形成されており、表面側き裂接触面２ａより下方かつ裏面側き裂接触面２ｂより上方では疲労き裂２の対向する内側面同士が接触してはいない。しかし、疲労き裂２の最上方から最下方までの全域にわたってき裂接触面が形成されていてもよい。   For example, the surface side crack contact surface 2a and the back surface side crack contact surface 2b shown in FIG. 1 are formed only near the uppermost part and the lowermost part of the fatigue crack 2, and from the surface side crack contact surface 2a. The lower inner surface and the upper surface of the back side crack contact surface 2b are not in contact with the opposing inner side surfaces of the fatigue crack 2. However, a crack contact surface may be formed over the entire region from the top to the bottom of the fatigue crack 2.

また、表面側き裂接触面２ａの接触面積と接触圧力を掛け合わせた合力として、疲労き裂２を開口しようとする引張応力に抵抗することができれば本発明の鋼構造物の疲労寿命の延命化を図る効果が得られることから、表面側き裂接触面２ａは必ずしも疲労き裂２の最上方付近に形成されている必要はなく、疲労き裂２の最上方の対向する内側面同士が接触していなくてもよい。ただし、一般に鋼板１の表面１ａにおいて最も大きな引張応力が発生することを勘案すれば、表面側き裂接触面２ａの接触面積と接触圧力が一定の場合には、表面側き裂接触面２ａの形成位置が疲労き裂２の上方に近いほど本発明の鋼構造物の疲労寿命の延命化を図る効果が高くなる。同様に、裏面側き裂接触面２ｂについても必ずしも疲労き裂２の最下方付近に形成されている必要はない。   Further, if the tensile stress that attempts to open the fatigue crack 2 can be resisted as a resultant force obtained by multiplying the contact area of the surface side crack contact surface 2a and the contact pressure, the life of the steel structure of the present invention can be extended. Therefore, the surface side crack contact surface 2a is not necessarily formed in the vicinity of the uppermost part of the fatigue crack 2, and the inner surfaces facing each other at the uppermost part of the fatigue crack 2 are formed. It may not be in contact. However, considering that generally the largest tensile stress is generated on the surface 1a of the steel plate 1, when the contact area and the contact pressure of the surface side crack contact surface 2a are constant, the surface side crack contact surface 2a The closer the formation position is to above the fatigue crack 2, the higher the effect of extending the fatigue life of the steel structure of the present invention. Similarly, the back side crack contact surface 2b is not necessarily formed near the lowermost part of the fatigue crack 2.

また、図１では鋼板１の表面１ａ側を先行してピーニング処理を施しているが、ピーニング処理は、表面１ａ側及び裏面１ｂ側のうちのいずれの側を先行して行ってもよい。   In FIG. 1, the peening process is performed in advance on the front surface 1a side of the steel sheet 1. However, the peening process may be performed on either the front surface 1a side or the back surface 1b side.

また、図１（ｃ）及び（ｅ）に示す疲労き裂周辺ピーニング工程において、疲労き裂２と平行に疲労き裂２の両側に２本のピーニング軌道を設定したが、疲労き裂２を挟んだ両側のうち少なくとも一側に複数本のピーニング軌道を設定してもよい。き裂接触面２ａ及び２ｂの形成が可能であれば、疲労き裂２を挟んだ両側のうち一側のみにピーニング軌道を設定してもよい。   In the fatigue crack peripheral peening process shown in FIGS. 1 (c) and 1 (e), two peening trajectories are set on both sides of the fatigue crack 2 in parallel to the fatigue crack 2. A plurality of peening trajectories may be set on at least one of the sandwiched sides. If the crack contact surfaces 2a and 2b can be formed, the peening trajectory may be set only on one side of both sides of the fatigue crack 2.

また、図１（ｃ）及び（ｅ）に示す疲労き裂周辺ピーニング工程において、き裂接触面２ａ及び２ｂの接触面積及び接触圧力が、疲労き裂２を開口しようとする引張応力に抵抗可能な値となる場合には、図１（ｄ）及び（ｆ）に示す疲労き裂直上ピーニング工程を省略してもよい。   Further, in the fatigue crack peripheral peening process shown in FIGS. 1C and 1E, the contact area and contact pressure of the crack contact surfaces 2a and 2b can resist the tensile stress that attempts to open the fatigue crack 2. In the case of a low value, the peening process immediately above the fatigue crack shown in FIGS. 1 (d) and (f) may be omitted.

また、本実施形態におけるピーニング器具３のチッパー３ａの先端形状は、平坦な矩形形状としているが、平坦に限らず部分的に凹凸を有していてもよい。また、矩形に限らず円形であってもよい。また、疲労き裂周辺ピーニング工程と疲労き裂直上ピーニング工程で、それぞれ異なる形状のチッパー３ａを使用してもよい。   Moreover, although the front-end | tip shape of the chipper 3a of the peening instrument 3 in this embodiment is made into the flat rectangular shape, you may have unevenness | corrugation partially not only in flatness. Moreover, not only a rectangle but circular may be sufficient. Moreover, you may use the chipper 3a of a respectively different shape in a fatigue crack periphery peening process and a fatigue crack direct peening process.

また、図１及び２において、ピーニング器具３のチッパー３ａを鋼板１に対してほぼ直角に立ててピーニングを行っているが、鋼板１に対して斜めからピーニングを行ってもよい。   1 and 2, peening is performed with the chipper 3a of the peening device 3 standing substantially at right angles to the steel plate 1, but peening may be performed on the steel plate 1 obliquely.

また、本実施形態の疲労き裂補修によって、疲労き裂２の進展を止める、あるいは疲労き裂２の進展を遅延させて鋼構造物の疲労寿命を耐用年数まで延命化することができれば、恒久的な疲労き裂補修対策となるが、仮に耐用年数まで延命化することができずに、補修後に更に疲労き裂が大きく進展した場合には、本実施形態の疲労き裂補修を再度実施して延命化を図ることも可能であるし、従来の補修方法を施すことも可能である。   Moreover, if the fatigue crack repair of this embodiment can stop the progress of the fatigue crack 2 or delay the progress of the fatigue crack 2 to extend the fatigue life of the steel structure to the service life, it will be permanent. However, if the fatigue crack is not able to be extended to the end of its useful life and the fatigue crack has further increased after the repair, the fatigue crack repair of this embodiment is performed again. It is possible to extend the lifespan and apply the conventional repair method.

前述のとおり、鋼板の表面から裏面まで貫通した疲労き裂の開口部を閉口させることによって、疲労き裂の進展を止める、あるいは疲労き裂の進展を遅延させて、鋼構造物の疲労寿命の延命化を図ることが可能な点については、力学的に説明できる。   As described above, by closing the opening of the fatigue crack that penetrates from the surface to the back of the steel plate, the fatigue life of the steel structure is reduced by stopping the growth of the fatigue crack or delaying the progress of the fatigue crack. The points that can extend the life can be explained dynamically.

ここでは、鋼橋における代表的な溶接継手である面外ガセット溶接継手及びＴ形溶接継手について試験体を作成し、この試験体の鋼板部分に鋼板を貫通した疲労き裂を発生させて、この疲労き裂の補修を行ったものと、補修を行っていないものとで疲労寿命の比較を行った。   Here, specimens were prepared for out-of-plane gusset weld joints and T-type weld joints, which are typical weld joints in steel bridges, and fatigue cracks that penetrated the steel sheets were generated in the steel sheet portions of the test specimens. Fatigue life was compared between those with and without fatigue crack repair.

（実施例１）
本実施例は、鋼板を貫通した疲労き裂が発生した面外ガセット溶接継手を補修の対象とし、疲労寿命の延命化効果を実験により検証したものである。実験には図６に示す板曲げ疲労試験機１０を使用した。板曲げ疲労試験機１０は、面外ガセット溶接継手試験体２０の一端側をボルト固定して、他端側に加振器１１により繰返し載荷を行う装置である。 Example 1
In this example, an out-of-plane gusset welded joint in which a fatigue crack that penetrates through a steel plate has been repaired, and the effect of prolonging the fatigue life has been verified by experiments. A plate bending fatigue testing machine 10 shown in FIG. 6 was used for the experiment. The plate bending fatigue testing machine 10 is a device that fixes one end of an out-of-plane gusset welded joint specimen 20 with bolts and repeatedly loads the other end with a vibrator 11.

図７に実施例１における面外ガセット溶接継手試験体２０の構造を説明する斜視図を示す。面外ガセット溶接継手試験体２０は、幅３００ｍｍ、長さ７００ｍｍ、厚さ１２ｍｍの鋼板１（材質ＳＭ４９０）の表面１ａと直角方向に、高さ３００ｍｍ、長さ３４０ｍｍ、厚さ１２ｍｍのガセットプレート２１（材質ＳＭ４９０）を等脚長６ｍｍのすみ肉溶接で接合した構造からなる。   The perspective view explaining the structure of the out-of-plane gusset welded joint test body 20 in Example 1 in FIG. 7 is shown. The out-of-plane gusset welded joint specimen 20 has a gusset plate 21 having a height of 300 mm, a length of 340 mm, and a thickness of 12 mm in a direction perpendicular to the surface 1a of the steel plate 1 (material SM490) having a width of 300 mm, a length of 700 mm, and a thickness of 12 mm. It consists of a structure in which (material SM490) is joined by fillet welding with an equal leg length of 6 mm.

この面外ガセット溶接継手試験体２０を板曲げ疲労試験機１０にセットして、応力制御の条件で繰返し載荷による疲労試験を行った。面外ガセット溶接継手試験体２０の固定位置は長さ方向の端部から２４０ｍｍの範囲、繰返し荷重の載荷位置は固定位置と反対側の端部から１１５ｍｍの位置とした。   This out-of-plane gusset welded joint specimen 20 was set in a plate bending fatigue testing machine 10 and a fatigue test by repeated loading was performed under the condition of stress control. The fixing position of the out-of-plane gusset welded joint specimen 20 was in a range of 240 mm from the end in the length direction, and the loading position of the repeated load was set at 115 mm from the end opposite to the fixing position.

ここで、面外ガセット溶接継手試験体２０に作用する応力の検出にはひずみゲージ１２を使用し、ひずみゲージ１２の貼り付け位置は、面外ガセット溶接継手試験体２０の表面１ａの長さ方向の中心線から載荷方向に１２ｍｍ離れ、幅方向の中心線上及び中心線から両側に７５ｍｍ離れた位置の３箇所とした。   Here, the strain gauge 12 is used to detect the stress acting on the out-of-plane gusset welded joint specimen 20, and the position where the strain gauge 12 is attached is the length direction of the surface 1a of the out-of-plane gusset weld joint specimen 20. The center line was 12 mm away from the center line in the loading direction, and three places on the center line in the width direction and 75 mm away from the center line on both sides.

図８に実施例１の延命化効果を説明するＳ−Ｎ線図を示す。Ｓ−Ｎ線図は横軸を繰返し載荷の繰返し数Ｎ、縦軸を応力範囲Δσとして、試験体が破断に至った点をプロットしたグラフであって、日本鋼構造協会（ＪＳＳＣ）ではＳ−Ｎ線図に破線で示すＪＳＳＣ−Ａ〜Ｈの８段階の等級を定めて鋼構造物の継手構造の疲労破壊に対する耐久性を評価している。ここで、ＪＳＳＣ−Ｅ（８０）という表記はΔσ＝８０ＭＰａで２００万回の繰返し荷重が載荷されると破断に至ることを示している。   FIG. 8 shows an SN diagram for explaining the life extension effect of the first embodiment. The SN diagram is a graph in which the horizontal axis is the number of repeated loadings N and the vertical axis is the stress range Δσ, and plots the points at which the specimen has broken. Eight grades of JSSC-A to H indicated by broken lines in the N diagram are determined, and the durability against fatigue failure of the joint structure of the steel structure is evaluated. Here, the notation of JSSC-E (80) indicates that fracture occurs when a repeated load of 2 million times is loaded at Δσ = 80 MPa.

図８にプロットした黒塗り丸印は、実施例１の比較例として実施した疲労試験の試験結果（比較例１〜６）を示している。比較例１〜６は、様々な応力範囲において、疲労き裂２の補修を行わずに破断に至るまで試験を続けた試験結果である。ここで、まわし溶接部２２ａの溶接止端に発生した疲労き裂２が進展してすみ肉溶接金属２２の溶接止端から離れて鋼板１に３０ｍｍ進展した時点（Ｎ３０）、又は疲労き裂２が鋼板１の裏面１ｂまで貫通した時点を破断（Ｎｆ）と定義した。図８に示すとおり、比較例１〜６の面外ガセット溶接継手試験体２０は、ＪＳＳＣ−Ｅ等級程度の疲労破壊に対する耐久性を有している。 The black circles plotted in FIG. 8 indicate the test results (Comparative Examples 1 to 6) of the fatigue test performed as a comparative example of Example 1. Comparative Examples 1 to 6 are test results in which the test was continued until fracture occurred without repairing the fatigue crack 2 in various stress ranges. Here, when the fatigue crack 2 generated at the weld toe of the turn welded portion 22a has progressed and has moved away from the weld toe of the fillet weld metal 22 to the steel plate 1 (N 30 ), or the fatigue crack The time when 2 penetrated to the back surface 1b of the steel plate 1 was defined as the fracture (N f ). As shown in FIG. 8, the out-of-plane gusset welded joint specimens 20 of Comparative Examples 1 to 6 have durability against fatigue fracture of about JSSC-E grade.

図８にプロットした白塗り四角印は、実施例１の疲労試験の試験結果を示している。実施例１においては、応力範囲９７ＭＰａの応力制御の条件で繰返し載荷による疲労試験を実施して、繰返し数１４９万回で鋼板１の表面１ａの疲労き裂２がＮ３０の段階まで進展した。この時、疲労き裂２は鋼板１の裏面１ｂまで貫通していた。この状態で疲労試験を一時中断して、本発明の疲労き裂補修方法により疲労き裂２の補修を行った。 The white squares plotted in FIG. 8 indicate the test results of the fatigue test of Example 1. In Example 1, by carrying out fatigue tests by cyclic loading in conditions of stress control of stress range 97 MPa, the fatigue crack second surface 1a of the steel sheet 1 has progressed to the stage of the N 30 at repeated several 1.49 million times. At this time, the fatigue crack 2 penetrated to the back surface 1 b of the steel plate 1. In this state, the fatigue test was temporarily suspended, and the fatigue crack 2 was repaired by the fatigue crack repair method of the present invention.

図９に実施例１における面外ガセット溶接継手試験体２０の疲労き裂２の補修順序を説明する斜視図を示す。初めに表面１ａ側の疲労き裂２の開口部を閉口し、続いて面外ガセット溶接継手試験体２０の上下方向を反転して裏面１ｂ側の疲労き裂２の開口部を閉口した。表面１ａ側のピーニングは、図９の（１）〜（８）の順序で実施した。ここで、（７）及び（８）は、まわし溶接部２２ａの溶接止端に発生した疲労き裂２をピーニングする処理であるが、まわし溶接部２２ａまわりの曲線状のピーニング軌道を連続してピーニングすることは困難であるため、（７）及び（８）に二分割して処理を行った。裏面１ｂ側の疲労き裂２の補修手順は、図１（ｅ）及び（ｆ）で示した手順と同様とした。   FIG. 9 is a perspective view for explaining the repair order of the fatigue crack 2 of the out-of-plane gusset welded joint specimen 20 in Example 1. FIG. First, the opening portion of the fatigue crack 2 on the front surface 1a side was closed, and then the opening portion of the fatigue crack 2 on the back surface 1b side was closed by reversing the vertical direction of the out-of-plane gusset welded joint specimen 20. The peening on the surface 1a side was performed in the order of (1) to (8) in FIG. Here, (7) and (8) are processes for peening the fatigue crack 2 generated at the weld toe of the turn welded portion 22a, and the curved peening trajectory around the turn welded portion 22a is continuously performed. Since peening is difficult, the process was divided into (7) and (8). The repair procedure of the fatigue crack 2 on the back surface 1b side was the same as the procedure shown in FIGS. 1 (e) and (f).

ピーニング処理に用いたピーニング器具は、打撃数９０Ｈｚ、ピンストローク１６ｍｍ、消費空気量０．１４ｍ３/ｍｉｎの市販のエアーハンマーである。また、チッパーは、市販のタガネの先端を、角が丸みをおびた４ｍｍ×５ｍｍ程度の平坦な面になるように加工したものである。ピーニング器具へのエアーの供給には、タンク容量１０リットルの小型のエアーコンプレッサーを用いた。ピーニング処理中のエアーコンプレッサーの空気圧力は０．５〜０．６ＭＰａであった。 The peening instrument used for the peening treatment is a commercially available air hammer having a hit frequency of 90 Hz, a pin stroke of 16 mm, and an air consumption of 0.14 m 3 / min. The chipper is obtained by processing the tip of a commercially available chisel so that it has a flat surface of about 4 mm × 5 mm with rounded corners. A small air compressor having a tank capacity of 10 liters was used to supply air to the peening apparatus. The air pressure of the air compressor during the peening process was 0.5 to 0.6 MPa.

ピーニング処理によって疲労き裂２の開口部を閉口した後に、応力範囲１００ＭＰａの応力制御の条件で繰返し載荷による疲労試験を再度行った結果、疲労き裂２の開口部を閉口した後の繰返し数が８８１万回に達しても疲労き裂２が再度開口及び進展することはなかった。   After the opening of the fatigue crack 2 was closed by the peening process, the fatigue test by repeated loading was performed again under the stress control conditions of the stress range of 100 MPa. As a result, the number of repetitions after the opening of the fatigue crack 2 was closed was Even after reaching 8.81 million times, fatigue crack 2 did not open and propagate again.

すなわち疲労き裂２がＮ３０の段階まで進展した時点で疲労き裂２の補修を行った場合の面外ガセット溶接継手試験体２０は、少なくともＪＳＳＣ−Ｄ等級に相当する疲労破壊に対する耐久性を有しているものと見なせる。 That plane gusset welded joint specimens 20 in the case of performing repairs of the fatigue crack 2 when the fatigue crack 2 is developed to the stage of N 30 is the resistance to the corresponding fatigue fracture at least JSSC-D grade It can be regarded as having.

このように、鋼板を貫通した疲労き裂が発生した面外ガセット溶接継手に本発明の疲労き裂補修方法を適用することによって、疲労き裂の進展を止める、あるいは疲労き裂の進展を遅延させて、疲労破壊に対する耐久性を格段に向上させることができる。これにより、鋼構造物の疲労寿命の延命化を図ることができる。   In this way, by applying the fatigue crack repair method of the present invention to an out-of-plane gusset welded joint in which a fatigue crack has penetrated the steel plate, the fatigue crack growth is stopped or the fatigue crack propagation is delayed. Thus, the durability against fatigue failure can be remarkably improved. Thereby, the life extension of the fatigue life of the steel structure can be achieved.

（実施例２及び３）
本実施例は、鋼板を貫通した疲労き裂が発生したＴ形溶接継手を補修の対象とし、疲労寿命の延命化効果を実験により検証したものである。実験には実施例１と同様に図６に示した板曲げ疲労試験機１０を使用した。 (Examples 2 and 3)
In this example, a T-type welded joint in which a fatigue crack that penetrates through a steel plate occurred was subjected to repair, and the effect of extending the fatigue life was verified by experiments. In the experiment, the plate bending fatigue tester 10 shown in FIG.

図１０に実施例２及び３におけるＴ形溶接継手試験体３０の構造を説明する斜視図を示す。Ｔ形溶接継手試験体３０は、幅３３４ｍｍ、長さ６００ｍｍ、厚さ１２ｍｍの鋼板１（材質ＳＭ４００）の幅方向の両端面に、鋼板１の面方向と直角方向に、高さ１００ｍｍ、長さ２００ｍｍ、厚さ１２ｍｍのフランジ部材３１（材質ＳＭ４００）を等脚長６ｍｍのすみ肉溶接で接合した構造からなる。   FIG. 10 is a perspective view for explaining the structure of the T-shaped welded joint test body 30 in Examples 2 and 3. FIG. The T-shaped welded joint specimen 30 has a height of 100 mm and a length in the direction perpendicular to the surface direction of the steel plate 1 on both end faces in the width direction of the steel plate 1 (material SM400) having a width of 334 mm, a length of 600 mm and a thickness of 12 mm. The flange member 31 (material SM400) having a thickness of 200 mm and a thickness of 12 mm is joined by fillet welding with an equal leg length of 6 mm.

このＴ形溶接継手試験体３０を板曲げ疲労試験機１０にセットして、応力制御の条件で繰返し載荷による疲労試験を行った。Ｔ形溶接継手試験体３０の固定位置は長さ方向の端部から２４０ｍｍの範囲、繰返し荷重の載荷位置は固定位置と反対側の端部から１２０ｍｍの位置とした。   This T-shaped welded joint specimen 30 was set in the plate bending fatigue testing machine 10 and a fatigue test by repeated loading was performed under the condition of stress control. The fixed position of the T-shaped welded joint specimen 30 was in the range of 240 mm from the end in the length direction, and the loading position of the repeated load was 120 mm from the end opposite to the fixed position.

ここで、Ｔ形溶接継手試験体３０に作用する応力の検出にはひずみゲージ１２を使用し、ひずみゲージ１２の貼り付け位置は、Ｔ形溶接継手試験体３０の表面１ａのまわし溶接部３２ａの溶接止端から載荷方向に５ｍｍ離れ、幅方向の両端から７５ｍｍ離れた位置の２箇所とした。   Here, the strain gauge 12 is used to detect the stress acting on the T-shaped welded joint specimen 30, and the strain gauge 12 is attached at the position of the turn welded portion 32a of the surface 1a of the T-shaped welded joint specimen 30. Two locations were located 5 mm away from the weld toe in the loading direction and 75 mm away from both ends in the width direction.

図１１に実施例２及び３の延命化効果を説明するＳ−Ｎ線図を示す。図１１にプロットした黒塗り丸印は、実施例２及び３の比較例として実施した疲労試験の試験結果（比較例７〜１４）を示している。比較例７〜１４は、様々な応力範囲において、疲労き裂２の補修を行わずに破断に至るまで試験を続けた試験結果である。ここで、まわし溶接部３２ａの溶接止端に発生した疲労き裂２が進展してすみ肉溶接金属３２の溶接止端から離れて鋼板１に３０ｍｍ進展した時点（Ｎ３０）を破断（Ｎｆ）と定義した。図１１に示すとおり、比較例７〜１４のＴ形溶接継手試験体３０は、ＪＳＳＣ−Ｆ等級程度の疲労破壊に対する耐久性を有している。 FIG. 11 shows an SN diagram for explaining the life extension effect of the second and third embodiments. The black circles plotted in FIG. 11 indicate the test results (Comparative Examples 7 to 14) of the fatigue test performed as Comparative Examples of Examples 2 and 3. Comparative Examples 7 to 14 are test results obtained by continuing the test until the fracture occurred without repairing the fatigue crack 2 in various stress ranges. Here, when the fatigue crack 2 generated at the weld toe of the turn welded portion 32a progresses and is separated from the weld toe of the fillet weld metal 32 and progresses 30 mm to the steel plate 1 (N 30 ), the fracture (N f ) ). As shown in FIG. 11, the T-shaped welded joint specimens 30 of Comparative Examples 7 to 14 have durability against fatigue fracture of about JSSC-F grade.

図１１にプロットした白塗り四角印は、実施例２の疲労試験の試験結果を示している。実施例２においては、応力範囲４８ＭＰａの応力制御の条件で繰返し載荷による疲労試験を実施して、繰返し数６９０万回で鋼板１の表面１ａの疲労き裂２がＮ３０の段階まで進展した。この時、鋼板１の裏面１ｂの疲労き裂２もＮ３０の段階まで進展しており、鋼板１の内部で疲労き裂２が結合して鋼板１を貫通した疲労き裂２となっていた。この状態で疲労試験を一時中断して、本発明の疲労き裂補修方法により疲労き裂２の補修を行った。 The white squares plotted in FIG. 11 indicate the test results of the fatigue test of Example 2. In Example 2, was carried out fatigue tests by cyclic loading in conditions of stress control of stress range 48 MPa, the fatigue crack second surface 1a of the steel sheet 1 has progressed to the stage of the N 30 at repeated several 6.9 million times. At this time, fatigue cracks 2 on the back surface 1b of the steel plate 1 has also progressed to the stage of the N 30, it has been a fatigue crack 2 that fatigue crack 2 inside the steel plate 1 is passed through the steel sheet 1 bonded . In this state, the fatigue test was temporarily suspended, and the fatigue crack 2 was repaired by the fatigue crack repair method of the present invention.

図１２に実施例２におけるＴ形溶接継手試験体３０の疲労き裂２の補修順序を説明する斜視図を示す。初めに表面１ａ側の疲労き裂２の開口部を閉口し、続いてＴ形溶接継手試験体３０の上下方向を反転して裏面１ｂ側の疲労き裂２の開口部を閉口した。表面１ａ側のピーニングは、図１２の（１）〜（３）の順序で実施した。裏面１ｂ側の疲労き裂２の補修手順は表面１ａ側の補修手順と同様とした。また、ピーニング処理には実施例１と同様のピーニング器具を使用した。   FIG. 12 is a perspective view for explaining the repair order of the fatigue crack 2 of the T-shaped welded joint test body 30 in the second embodiment. First, the opening of the fatigue crack 2 on the front surface 1a side was closed, and then the opening of the fatigue crack 2 on the back surface 1b side was closed by reversing the vertical direction of the T-shaped welded joint specimen 30. The peening on the surface 1a side was performed in the order of (1) to (3) in FIG. The repair procedure of the fatigue crack 2 on the back surface 1b side was the same as the repair procedure on the front surface 1a side. Moreover, the peening apparatus similar to Example 1 was used for the peening process.

ピーニング処理によって疲労き裂２の開口部を閉口した後に、応力範囲１２６ＭＰａの応力制御の条件で繰返し載荷による疲労試験を再度行った結果、疲労き裂２の開口部を閉口した後の繰返し数が１１００万回に達した時点で疲労き裂２が再度開口して、鋼板１に３０ｍｍ進展した時点（Ｎ３０）の状態となった。 After the opening of the fatigue crack 2 was closed by the peening process, the fatigue test by repeated loading was performed again under the stress control conditions of the stress range of 126 MPa. As a result, the number of repetitions after the opening of the fatigue crack 2 was closed was The fatigue crack 2 reopened when reaching 11 million times, and reached a state (N 30 ) at which the steel plate 1 developed 30 mm.

図１１にプロットした白塗り三角印は、実施例３の疲労試験の試験結果を示している。実施例３においては、応力範囲５６ＭＰａの応力制御の条件で繰返し載荷による疲労試験を実施して、繰返し数４７０万回で鋼板１の表面１ａの疲労き裂２がＮ３０の段階まで進展した。その後、疲労試験を継続して、鋼板１の表面１ａから裏面１ｂまで貫通する疲労き裂２をＮ６０の段階まで進展させ、この状態で疲労試験を一時中断して、本発明の疲労き裂補修方法により疲労き裂２の補修を行った。疲労き裂２の補修順序は、実施例２と同様とした。 The white triangles plotted in FIG. 11 indicate the test results of the fatigue test of Example 3. In Example 3, was performed fatigue tests by cyclic loading in conditions of stress control of stress range 56 MPa, the fatigue crack second surface 1a of the steel sheet 1 has progressed to the stage of the N 30 at repeated several 4.7 million times. Thereafter, it continued fatigue test, to develop fatigue crack 2 that penetrates from the surface 1a of the steel plate 1 to the back surface 1b to the stage of the N 60, and suspended fatigue tested in this state, Fatigue of the present invention Crack The fatigue crack 2 was repaired by the repair method. The repair order of the fatigue crack 2 was the same as in Example 2.

ピーニング処理によって疲労き裂２の開口部を閉口した後に、応力範囲２０３ＭＰａの応力制御の条件で繰返し載荷による疲労試験を再度行った結果、疲労き裂２の開口部を閉口した後の繰返し数が２２１０万回に達しても疲労き裂２が再度開口及び進展することはなかった。再び疲労き裂２がＮ３０の段階まで進展することもなかった。 After the opening of the fatigue crack 2 was closed by the peening process, the fatigue test by repeated loading was performed again under the stress control conditions of the stress range of 203 MPa. As a result, the number of repetitions after the opening of the fatigue crack 2 was closed was Even after reaching 22.1 million times, the fatigue crack 2 did not open and propagate again. Did not have to progress to the stage of fatigue crack 2 N 30 again.

すなわち疲労き裂２がＮ３０又はＮ６０の段階まで進展した時点で疲労き裂２の補修を行った場合のＴ形溶接継手試験体３０は、少なくともＪＳＳＣ−Ｃ等級に相当する疲労破壊に対する耐久性を有しているものと見なせる。 That is, the T-shaped welded joint specimen 30 when the fatigue crack 2 is repaired when the fatigue crack 2 has progressed to the stage of N 30 or N 60 has at least durability against fatigue fracture corresponding to JSSC-C grade. It can be regarded as having sex.

このように、鋼板を貫通した疲労き裂が発生したＴ形溶接継手に本発明の疲労き裂補修方法を適用することによって、疲労き裂の進展を止める、あるいは疲労き裂の進展を遅延させて、疲労破壊に対する耐久性を格段に向上させることができる。これにより、鋼構造物の疲労寿命の延命化を図ることができる。   Thus, by applying the fatigue crack repair method of the present invention to a T-shaped welded joint in which a fatigue crack that penetrates the steel plate has occurred, the fatigue crack progress is stopped or the fatigue crack progress is delayed. Thus, the durability against fatigue failure can be significantly improved. Thereby, the life extension of the fatigue life of the steel structure can be achieved.

（実施例４）
本実施例は、鋼板を貫通した疲労き裂が発生したＴ形溶接継手に本発明の疲労き裂補修方法を適用した場合のピーニング処理中のひずみの発生状況を検証した実施例である。実験には実施例１と同様に図６に示した板曲げ疲労試験機１０を使用した。Ｔ形溶接継手試験体の構造は、図１０に示した実施例２及び３におけるＴ形溶接継手試験体３０と同様であるため説明を省略する。 Example 4
In this example, the state of occurrence of strain during the peening process in the case where the fatigue crack repair method of the present invention is applied to a T-shaped welded joint in which a fatigue crack that penetrates through a steel plate has occurred is verified. In the experiment, the plate bending fatigue tester 10 shown in FIG. The structure of the T-shaped welded joint specimen is the same as that of the T-shaped welded joint specimen 30 in Examples 2 and 3 shown in FIG.

図１３に実施例４におけるＴ形溶接継手試験体３０のピーニング処理中のひずみの発生状況を説明するグラフを示す。まずＴ形溶接継手試験体３０を板曲げ疲労試験機１０にセットして、応力制御の条件で繰返し載荷による疲労試験を行い、鋼板１の表面１ａから裏面１ｂまで貫通したＮ３０の段階の疲労き裂２を発生させた。 The graph explaining the generation | occurrence | production state of the distortion in the peening process of the T-shaped welded joint test body 30 in Example 4 in FIG. 13 is shown. First set the T-shaped welded joint specimens 30 to the plate bending fatigue tester 10 performs a fatigue test by repeated loading under conditions of stress control, fatigue stage N 30 which penetrate from the surface 1a of the steel plate 1 to the back surface 1b Crack 2 was generated.

次にＴ形溶接継手試験体３０を板曲げ疲労試験機１０から取り外して、Ｔ形溶接継手試験体３０の上下方向を反転して、鋼板１の裏面１ｂの疲労き裂２ａの開口部が完全に閉じるまで、実施例２と同様の補修手順で裏面１ｂ側のピーニング処理を行った。   Next, the T-shaped welded joint specimen 30 is removed from the plate bending fatigue testing machine 10, the vertical direction of the T-shaped welded joint specimen 30 is reversed, and the opening of the fatigue crack 2a on the back surface 1b of the steel plate 1 is completely formed. The peening treatment on the back surface 1b side was carried out by the same repair procedure as in Example 2 until it was closed.

その後、開口部が閉じた裏面１ｂ側の疲労き裂２の進展長さの中央でかつ疲労き裂２の直上に裏面側ひずみゲージ１２ｂを貼り付けた後、Ｔ形溶接継手試験体３０の上下方向を反転して、Ｔ形溶接継手試験体３０の表面１ａ側を上方に向けた。   Then, after attaching the back surface side strain gauge 12b in the center of the progress length of the fatigue crack 2 on the back surface 1b side where the opening is closed and immediately above the fatigue crack 2, the upper and lower sides of the T-shaped welded joint specimen 30 are The direction was reversed and the surface 1a side of the T-shaped welded joint specimen 30 was directed upward.

その後、開口部が開いた状態の表面１ａ側の疲労き裂２の進展長さの中央でかつ疲労き裂２から５ｍｍ離れた位置に表面側ひずみゲージ１２ａを貼り付けた。すなわち表面側ひずみゲージ１２ａは、図１２の（２）で示されたピーニング処理領域の中央に貼り付けられている。その後、図１２の（１）で示されたピーニング処理領域のピーニングを実施した。   Then, the surface side strain gauge 12a was affixed in the center of the growth length of the fatigue crack 2 on the surface 1a side in the state where the opening was opened and at a position 5 mm away from the fatigue crack 2. That is, the surface-side strain gauge 12a is affixed to the center of the peening process region shown in (2) of FIG. Thereafter, peening was performed in the peening treatment region indicated by (1) in FIG.

図１３のグラフの横軸は、鋼板１の表面１ａ側のピーニングを開始してからの経過時間ｔであり、グラフ中に記載されている１往復目、２往復目、３往復目とは、図１２の（１）で示されたピーニング処理領域を疲労き裂２と平行にピーニング処理する際の往復回数を示している。また、グラフの縦軸は、表面側ひずみゲージ１２ａ及び裏面側ひずみゲージ１２ｂによって計測される鋼板１のひずみεである。ここで、ひずみεがマイナスの場合には鋼板１に圧縮ひずみが発生していることを示している。   The horizontal axis of the graph of FIG. 13 is the elapsed time t from the start of peening on the surface 1a side of the steel plate 1, and the first round trip, the second round trip, and the third round trip described in the graph are: 12 shows the number of reciprocations when the peening treatment region shown in (1) of FIG. 12 is peened in parallel with the fatigue crack 2. Moreover, the vertical axis | shaft of a graph is the distortion | strain (epsilon) of the steel plate 1 measured with the surface side strain gauge 12a and the back surface side strain gauge 12b. Here, when the strain ε is negative, it indicates that a compressive strain is generated in the steel plate 1.

図１３のグラフに示すように、鋼板１の表面１ａ側にピーニング処理を施すことによって、表面側ひずみゲージ１２ａのひずみεのマイナス値が増減を繰り返しながら徐々に大きくなる。すなわち鋼板１の表面１ａの圧縮残留ひずみが増加する。そして、表面側ひずみゲージ１２ａのひずみεのマイナス値が大きくなるのと連動して、裏面側ひずみゲージ１２ｂのひずみεのマイナス値も徐々に大きくなっている。すなわち鋼板１の裏面１ｂの圧縮残留ひずみも増加する。   As shown in the graph of FIG. 13, by performing the peening process on the surface 1a side of the steel plate 1, the negative value of the strain ε of the surface side strain gauge 12a gradually increases while repeatedly increasing and decreasing. That is, the compressive residual strain of the surface 1a of the steel plate 1 increases. In conjunction with the increase in the negative value of the strain ε of the front surface side strain gauge 12a, the negative value of the strain ε of the back surface side strain gauge 12b also gradually increases. That is, the compressive residual strain of the back surface 1b of the steel plate 1 also increases.

以上の実験結果から、鋼板１の表面１ａ側の疲労き裂２の周辺に圧縮残留ひずみを付与すれば、鋼板１の裏面１ｂ側の疲労き裂２の周辺にも圧縮残留ひずみが付与されることが明らかとなった。   From the above experimental results, if compressive residual strain is applied to the periphery of the fatigue crack 2 on the surface 1a side of the steel plate 1, the compressive residual strain is also applied to the periphery of the fatigue crack 2 on the back surface 1b side of the steel plate 1. It became clear.

これにより、発明者らが本発明の構想段階で抱いていた、鋼板を貫通した疲労き裂の表面側にピーニング処理を施して表面側にき裂接触面が形成された後に、裏面側のピーニング処理を施した場合、ピーニング時の衝撃荷重によって、せっかくき裂接触面が形成された表面側の疲労き裂が再度開いてしまうのではないかという懸念は払拭された。   Thus, the peening on the back side is performed after the peening process is performed on the surface side of the fatigue crack penetrating the steel plate, which the inventors had in the conception stage of the present invention, and the crack contact surface is formed on the surface side. When the treatment was applied, the concern that the fatigue crack on the surface side where the crack contact surface was formed would reopen due to the impact load during peening was eliminated.

Ｌａ１，Ｌａ２，Ｌａ３，Ｌｂ１，Ｌｂ２，Ｌｂ３ … ピーニング軌道
１ … 鋼板 １ａ … 表面
１ｂ … 裏面 ２ … 疲労き裂
２ａ … 表面側き裂接触面 ２ｂ … 裏面側き裂接触面
３ … ピーニング器具 ３ａ … チッパー
４ … ガイド ５ … ガイド固定治具
１０ … 板曲げ疲労試験機 １１ … 加振器
１２ … ひずみゲージ １２ａ… 表面ひずみゲージ
１２ｂ… 裏面ひずみゲージ ２０ … 面外ガセット溶接継手試験体
２１ … ガセットプレート ２２ … すみ肉溶接金属
２２ａ… まわし溶接部 ３０ … Ｔ形溶接継手試験体
３１ … フランジ部材 ３２ … すみ肉溶接金属
３２ａ… まわし溶接部 La 1 , La 2 , La 3 , Lb 1 , Lb 2 , Lb 3 ... Peening track 1 ... Steel plate 1a ... Surface 1b ... Back 2 ... Fatigue crack 2a ... Front side crack contact surface 2b ... Back side crack contact surface DESCRIPTION OF SYMBOLS 3 ... Peening instrument 3a ... Chipper 4 ... Guide 5 ... Guide fixing jig 10 ... Plate bending fatigue tester 11 ... Exciter 12 ... Strain gauge 12a ... Surface strain gauge 12b ... Back surface strain gauge 20 ... Out-of-plane gusset weld joint test Body 21 ... Gusset plate 22 ... Fillet weld metal 22a ... Turn weld part 30 ... T-shaped welded joint specimen 31 ... Flange member 32 ... Fillet weld metal 32a ... Turn weld part

Claims (6)

鋼板の表面から裏面まで貫通した疲労き裂の補修構造であって、
前記鋼板の表面の前記疲労き裂の開口部の周辺及び／又は直上を該疲労き裂と平行にピーニングすることにより該鋼板の表面に塑性変形が付与され、該鋼板の表面の該疲労き裂の開口部が閉じられてき裂接触面が形成されていると共に、
前記鋼板の裏面の前記疲労き裂の開口部の周辺及び／又は直上を該疲労き裂と平行にピーニングすることにより該鋼板の裏面に塑性変形が付与され、該鋼板の裏面の該疲労き裂の開口部が閉じられてき裂接触面が形成されていることを特徴とする鋼構造物の疲労き裂補修構造。 A repair structure for fatigue cracks penetrating from the front surface to the back surface of the steel plate,
Plastic deformation is imparted to the surface of the steel sheet by peening the periphery and / or directly above the opening of the fatigue crack on the surface of the steel sheet in parallel with the fatigue crack, and the fatigue crack on the surface of the steel sheet The opening is closed and a crack contact surface is formed,
Plastic deformation is imparted to the back surface of the steel plate by peening the periphery and / or directly above the opening of the fatigue crack on the back surface of the steel plate in parallel with the fatigue crack, and the fatigue crack on the back surface of the steel plate. A structure for repairing fatigue cracks in steel structures characterized in that the opening of the steel is closed and a crack contact surface is formed. 前記き裂接触面に作用する圧縮残留応力が設計引張応力以上であることを特徴とする請求項１に記載の鋼構造物の疲労き裂補修構造。   The fatigue crack repair structure for a steel structure according to claim 1, wherein a compressive residual stress acting on the crack contact surface is equal to or greater than a design tensile stress. 鋼板の表面から裏面まで貫通した疲労き裂を補修の対象とし、
前記鋼板の表面の前記疲労き裂を挟んだ両側のうち少なくとも一側を該疲労き裂と平行にピーニングすることにより該鋼板の表面に塑性変形を付与し、該鋼板の表面の該疲労き裂の開口部を閉じてき裂接触面を形成する疲労き裂周辺ピーニング工程と、
前記鋼板の裏面の前記疲労き裂を挟んだ両側のうち少なくとも一側を該疲労き裂と平行にピーニングすることにより該鋼板の裏面に塑性変形を付与し、該鋼板の裏面の該疲労き裂の開口部を閉じてき裂接触面を形成する疲労き裂周辺ピーニング工程と、を有することを特徴とする鋼構造物の疲労き裂補修方法。 Fatigue cracks that penetrate from the front to the back of the steel sheet are subject to repair.
Giving plastic deformation to the surface of the steel sheet by peening at least one side of both sides of the surface of the steel sheet sandwiching the fatigue crack in parallel with the fatigue crack, the fatigue crack on the surface of the steel sheet A peening process around a fatigue crack that closes the opening and forms a crack contact surface;
Giving plastic deformation to the back surface of the steel plate by peening at least one side of both sides of the back surface of the steel plate sandwiching the fatigue crack in parallel with the fatigue crack, the fatigue crack on the back surface of the steel plate A method for repairing a fatigue crack in a steel structure, comprising: a fatigue crack peripheral peening process that closes an opening of the steel and forms a crack contact surface. 前記鋼板の表面及び／又は裏面に対する前記疲労き裂周辺ピーニング工程の後工程として、前記疲労き裂の直上をピーニングすることにより前記鋼板の表面及び／又は裏面に塑性変形を付与し、前記き裂接触面の接触面積及び／又は接触圧力を増加する疲労き裂直上ピーニング工程を有することを特徴とする請求項３に記載の鋼構造物の疲労き裂補修方法。 As a post-process of the fatigue crack peripheral peening process for the front surface and / or the back surface of the steel plate, plastic deformation is imparted to the front surface and / or the back surface of the steel plate by peening immediately above the fatigue crack, and the crack The method for repairing a fatigue crack in a steel structure according to claim 3, further comprising a peening process immediately above the fatigue crack for increasing the contact area and / or the contact pressure of the contact surface. 前記疲労き裂と平行に設置したガイドにより前記ピーニングの軌道を案内しながら、該ピーニングを行うことを特徴とする請求項３又は４に記載の鋼構造物の疲労き裂補修方法。   The method of repairing a fatigue crack in a steel structure according to claim 3 or 4, wherein the peening is performed while guiding the peening trajectory with a guide installed in parallel with the fatigue crack. 前記き裂接触面に作用する圧縮残留応力が設計引張応力以上であることを特徴とする請求項３〜５のうちのいずれか一つに記載の鋼構造物の疲労き裂補修方法。   The method for repairing a fatigue crack in a steel structure according to any one of claims 3 to 5, wherein a compressive residual stress acting on the crack contact surface is equal to or greater than a design tensile stress.
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