JP4537621B2 - Steel tube column base and method for strengthening steel tube column base - Google Patents

Steel tube column base and method for strengthening steel tube column base Download PDF

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Publication number
JP4537621B2
JP4537621B2 JP2001184435A JP2001184435A JP4537621B2 JP 4537621 B2 JP4537621 B2 JP 4537621B2 JP 2001184435 A JP2001184435 A JP 2001184435A JP 2001184435 A JP2001184435 A JP 2001184435A JP 4537621 B2 JP4537621 B2 JP 4537621B2
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Prior art keywords
steel pipe
rib
pipe column
base
column base
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JP2003001476A (en
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雅一 杉本
知徳 冨永
哲己 近藤
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Nippon Steel Corp
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Nippon Steel Corp
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Description

【０００１】
【発明の属する技術分野】
本発明は、例えば道路照明用ポールや道路標識用ポール等の鋼管柱を、道路等の躯体に固定するための鋼管柱基部及び鋼管柱基部の強化方法に関するものである。
【０００２】
【従来の技術】
道路照明用ポールや道路標識用ポール等の鋼管柱をコンクリート等からなる躯体に固定するための鋼管柱基部としては、図７に示すように鋼管柱１０の下端部にベースプレート１１を溶接するとともに、鋼管柱１０とベースプレート１１との間を複数のリブ１２により補強した構造が一般的である。各リブ１２は上端部が斜めになった平板状の三角リブであり、各リブ１２は鋼管柱１０にＴ字溶接されている。そしてベースプレート１１をアンカーボルト１３を用いて躯体に固定することにより、鋼管柱１０を垂直に支持している。
【０００３】
しかし上記のような従来の鋼管柱基部は、風や交通振動などを受けて鋼管柱１０に曲げモーメントが作用したとき、リブ１２の上端部１４である溶接止端部付近に大きい応力集中が生じ、繰返し応力によりこの部分の強度が低下するおそれがあった。また、リブ１２の上端部１４の回し溶接部が溶接熱による引張り残留応力と熱影響部材質劣化との重複により構造欠陥となりやすく、耐力や疲労特性が低下するという問題があった。
【０００４】
このような問題は構造部材に補強用のリブをＴ字溶接した構造体に共通するものであって、日本鋼構造協会「鋼構造物の疲労設計指針・同解説」でも、ガセットをすみ肉溶接した継手が鋼部材の耐力や疲労特性を低下させるので、設計に配慮するように指摘されている。
【０００５】
本発明は上記した従来の問題点を解決し、鋼管柱に繰返し曲げモーメントが作用した場合においても、リブの溶接止端部の強度低下を抑制することができ、またリブの上端部の回し溶接部の耐力や疲労性能の低下を防止することができる鋼管柱基部及び鋼管柱基部の強化方法を提供するためになされたものである。
【０００６】
【課題を解決するための手段】
上記の課題を解決するためになされた本発明の鋼管柱基部は、鋼管柱の基部をＴ字溶接されたリブにより補強した鋼管柱基部であって、前記のリブは上端部が屈曲された逆Ｕ字状または逆Ｖ字状のリブであり、かつリブの溶接止端部に超音波により棒状工具を軸方向に振動させ、その先端を処理対象となる金属表面にあてがうことによって表面を窪ませる超音波振動によるピーニング処理が施されたものであることを特徴とするものである。また本発明の鋼管柱基部の強化方法は、鋼管柱の基部に上端部が屈曲された逆Ｕ字状または逆Ｖ字状のリブをＴ字溶接したのち、各リブの溶接止端部に超音波により棒状工具を軸方向に振動させ、その先端を処理対象となる金属表面にあてがうことによって表面を窪ませる超音波振動によるピーニング処理を施すことを特徴とすることを特徴とするものである。
【０００７】
なお、処理区間の母材に鋼管軸方向の引張応力が作用するような荷重を鋼管柱の基部に与えた状態で、超音波振動によるピーニング処理を施すことにより、さらに強化効果を高めることができる。超音波振動によるピーニング処理の好ましい条件は、振幅２０〜５０μｍ、振動数１０〜５０ｋＨｚの範囲である。
【０００８】
上記のように本発明では、溶接止端部となる上端部が屈曲された逆Ｕ字状または逆Ｖ字状のリブを使用することにより、リブ上端部を鋼管柱の主応力方向から直角方向になるまで逃がし、リブ上端部の剛性を低下させている。この結果、鋼管柱に曲げ応力が作用した場合に溶接止端部に生じる応力集中が大幅に緩和され、また溶接熱による引張り残留応力をも大幅に緩和することができる。
【０００９】
さらに本発明では、リブの溶接止端部に超音波振動によるピーニング処理を施した。この処理は超音波により棒状工具を軸方向に振動させ、その先端を処理対象となる金属表面にあてがうことによって表面を窪ませる方法である。この結果、溶接止端部に高密度のエネルギが与えられて塑性変形が生じ、圧縮残留応力が付与される。このため鋼管柱基部の弱点であった溶接止端部がさらに強化され、鋼管柱に繰返し曲げモーメントが作用した場合においても、リブの溶接止端部の強度低下を抑制することができるとともに、リブの上端部の回し溶接部の耐力や疲労性能の低下を防止することができる。
【００１０】
【発明の実施の形態】
以下に本発明の好ましい実施形態を示す。
図１において、１０は道路照明用ポールや道路標識用ポール等として用いられる鋼管柱、１１はこの鋼管柱１０の下端部に溶接されたベースプレート、１２は鋼管柱１０とベースプレート１１との間を補強するためにＴ字溶接された複数枚のリブである。この実施形態ではリブ１２は逆Ｕ字状であるが、図２に示す他の実施形態のように逆Ｖ字状のリブ１２としてもよい。ベースプレート１１はアンカーボルト１３により道路等の躯体に固定され、鋼管柱１０を垂直に保持している。
【００１１】
鋼管柱１０の主応力方向は上下方向であり、リブ１２も全体としては鋼管柱１０の主応力方向に延びている。しかしリブ１２の上部は円弧状に緩和屈曲され、溶接止端部となるリブ１２の上端部１４は鋼管柱１０の主応力方向に対して直角になるまで屈曲されている。
【００１２】
このようにリブ１２の上端部１４を鋼管柱１０の主応力方向から逃げる方向に緩和屈曲させることにより、リブ１２の上端部１４を低剛性構造とすることができる。その結果、リブ１２の上端部１４における応力集中が緩和されるとともに、溶接部の溶接残留熱応力も大幅に緩和され、溶接構造体としての耐力や疲労性能が大幅に向上する。
【００１３】
このような効果を十分に発揮させるためには、リブ１２の上端部１４の曲率半径をリブ１２の肉厚の３倍以上としておくことが好ましい。曲率半径がこれよりも小さくなると、リブ１２を屈曲させる際に材質劣化が生じ易くなり、また剛性を低下させる効果も小さくなる。
【００１４】
参考のために、図１に示す鋼管柱基部と図７に示す従来の鋼管柱基部とをＦＥＭ解析した応力集中図を、図３、図４として示す。これらの図は、鋼管柱１０の上端に等しい水平荷重を与えたときのリブ１２の周辺の発生応力分布を等高線によって示したものであり、図中の単位はＭＰａである。図３と図４を対比すれば明らかなように、リブ１２の上端部１４を屈曲させることにより、集中応力の最大値は従来構造に比較して半減することが分かる。
【００１５】
しかも本発明においては、屈曲されたリブ１２の溶接止端部にさらに超音波振動によるピーニング処理が施される。ピーニング処理部２０は図１中に拡大して示したように、リブ１２の中心線の両側の中心角αの領域であり、一般的には３０°≦α≦６０°の範囲とすればよい。図１ではαはほぼ４５°である。
【００１６】
この超音波振動によるピーニング処理は、図５に示されるように超音波打撃装置２１の棒状工具２２の先端を処理対象となる金属表面に当てて軸方向に超音波振動させ、処理対象部分に打撃を与え表面を窪ませる方法である。棒状工具２２の先端は一般的に断面円形であり、その直径は１〜６ｍｍ程度が好ましい。直径が１ｍｍ未満では強度が不足して十分な打撃を与えることができず、直径が６ｍｍを超えると質量が大きくなるために超音波振動を行なわせ難くなるためである。
【００１７】
棒状工具２２の振動数は１０〜５０ｋＨｚ、振幅は２０〜５０μｍが望ましい。これは、鋼材に与えられる打撃のエネルギーがこの周波数の領域で効率よく大きくなることによる。また振幅が２０μｍ未満では十分な打撃を与えることができない一方、振幅が５０μｍを超えると、鋼材に入る塑性変形が大きくなり過ぎることがあり、好ましくない。
【００１８】
上記のような条件で処理された金属表面は、高密度のエネルギにより塑性変形を生じて０．１〜０．５ｍｍ程度の深さに凹み、表層から１０ｍｍ以上の深さまで圧縮応力を導入することができる。また表層から１００μｍ程度の深さまで金属組織に大きな変化を生じてホワイトレイヤーと呼ばれる組織層が形成され、良好な耐食性、耐磨耗性、摩擦抵抗の低減を図ることができる。
【００１９】
本発明ではこのような超音波振動によるピーニング処理部２０を、図１、図２に示されるように各リブ１２の溶接止端部に形成する。この結果、溶接止端部の応力集中が緩和されるとともに、溶接止端部に圧縮応力が導入され、疲労強度が飛躍的に向上する。また前記したようにリブ１２の溶接止端部は溶接熱による引張り残留応力と熱影響部材質劣化との重複により構造欠陥となり易い部分であるが、超音波振動によるピーニング処理により組織変化を生じさせることによって、微細なクラックなどの構造欠陥をも修復することができる効果がある。
【００２０】
このように本発明の方法の鋼管柱基部は、上端部１４が屈曲された逆Ｕ字状または逆Ｖ字状のリブ１２の溶接止端部に超音波振動によるピーニング処理を施したものであるから、それぞれの構成による効果が組み合わされる。その結果、風や振動などによって鋼管柱１０に曲げモーメントが作用したときにリブ１２の溶接止端部付近に生ずる応力集中を大幅に緩和することができ、また後記する実施例のデータに示されるように、この部分の疲労強度を著しく向上させることができる。しかも本発明は超音波打撃装置２１以外の付帯設備を必要とせず、現場においても容易に施工できる利点がある。
【００２１】
なお、通常は鋼管柱１０の基部に溶接された各リブ１２の溶接止端部に超音波打撃装置２１の棒状工具２２の先端を当ててピーニング処理を施せばよいが、処理区間の母材に鋼管軸方向の引張応力が作用するような荷重（例えば曲げ荷重）を鋼管柱基部に与えた状態で、超音波振動によるピーニング処理を施すこともできる。このように外力を加えて引張応力を作用させた状態でピーニング処理を施して溶接止端部に圧縮応力を与えれば、外力を取り除くとさらに大きい圧縮応力を溶接止端部１４に残留させることが可能となる。このため一段と優れた補強効果を得ることができるようになる。
【００２２】
以上の説明では各リブ１２の溶接止端部のみに超音波振動によるピーニング処理を施したが、その他の溶接部にもピーニング処理を施しても差し支えないことはもちろんである。しかしリブ１２の下方部分等は鋼管柱基部の疲労強度を直接左右する部分ではないため、あまり実益はないと考えられる。
【００２３】
【実施例】
図１に示す本発明の鋼管柱基部に試験機により繰返し曲げ応力を加え、疲労強度試験を行なった。使用した材料は鋼管、リブともにＳＭ４９０である。また比較のために、図７に示す構造の鋼管基部リブ廻りの部分試験片に繰返し引張り応力を加える疲労強度試験を行なった。その結果、図６に黒丸で示すように図７に示す従来構造の疲労特性は、鉄道橋設計示方書の設計寿命曲線のＥ等級〜Ｄ等級に相当するものであった。これに対して本発明品の疲労特性は、白丸で示すように設計寿命曲線のＡ等級にまで大幅に上昇した。なお、先端工具の振幅は４０μｍであり、振動数は３０ｋＨｚとした。
【００２４】
さらに引張応力が作用する荷重を鋼管柱基部に与えた状態で、超音波振動によるピーニング処理を施した場合には、その疲労特性は白三角で示すように設計寿命曲線のＡ等級以上にまで上昇した。なお、図６中に示される右上向きの矢印は、その時点で試験体に変化が見られなかったので、載荷を終了したことを意味するものである。ここで本試験に使用した従来構造の部分試験片の溶接品質は非常にグレードの高いものであり、通常の工業製品レベルでは疲労寿命が若干低くなるはずである。
【００２５】
【発明の効果】
以上に説明したように、本発明によれば上端部が屈曲された逆Ｕ字状または逆Ｖ字状のリブの溶接止端部に超音波振動によるピーニング処理を施すことにより、リブ上端の回し溶接部の耐力や疲労性能の低下を大幅に防止することができる。その結果、鋼管柱に繰返し曲げモーメントが作用した場合においてもリブの溶接止端部付近の強度低下がなく、長期間にわたり使用しても安全上の問題がない。しかも本発明は鋼管柱基部の構造を変える必要がないため、既存の設備に対しても容易に適用できる利点がある。
【図面の簡単な説明】
【図１】本発明の第１の実施形態を示す正面図である。
【図２】本発明の第２の実施形態を示す斜視図である。
【図３】逆Ｕ字状のリブを用いた鋼管柱基部をＦＥＭ解析した応力集中図である。
【図４】従来構造の鋼管柱基部をＦＥＭ解析した応力集中図である。
【図５】超音波打撃装置の側面図である。
【図６】実施例における疲労強度試験の結果を示すＳ-Ｎ曲線である。
【図７】従来例を示す斜視図である。
【符号の説明】
１０ 鋼管柱
１１ ベースプレート
１２ リブ
１３ アンカーボルト
１４ 上端部
２０ ピーニング処理部
２１ 超音波打撃装置
２２ 棒状工具[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a steel pipe column base for fixing a steel pipe column such as a road lighting pole or a road sign pole to a housing such as a road and a method for strengthening the steel pipe column base.
[0002]
[Prior art]
As a steel pipe column base for fixing a steel pipe column such as a road lighting pole or a road sign pole to a frame made of concrete or the like, a base plate 11 is welded to the lower end of the steel pipe column 10 as shown in FIG. A structure in which the space between the steel pipe column 10 and the base plate 11 is reinforced by a plurality of ribs 12 is common. Each rib 12 is a flat triangular rib whose upper end is inclined, and each rib 12 is T-welded to the steel pipe column 10. And the steel pipe column 10 is supported vertically by fixing the base plate 11 to the housing using the anchor bolts 13.
[0003]
However, in the conventional steel pipe column base as described above, when a bending moment is applied to the steel pipe column 10 due to wind or traffic vibration, a large stress concentration occurs in the vicinity of the weld toe, which is the upper end portion 14 of the rib 12. Further, there is a possibility that the strength of this portion is lowered due to repeated stress. Further, there is a problem in that the turning welded portion of the upper end portion 14 of the rib 12 is likely to be a structural defect due to the overlap between the tensile residual stress due to the welding heat and the deterioration of the heat-affected member material, and the proof stress and fatigue characteristics are lowered.
[0004]
Such a problem is common to structures in which reinforcing ribs are T-welded to structural members, and gusset is fillet welded by the Japan Steel Structure Association's “Fatigue Design Guidelines for Steel Structures”. It has been pointed out that the designed joints give consideration to the design, because the joints reduce the yield strength and fatigue properties of steel members.
[0005]
The present invention solves the above-described conventional problems, and even when a bending moment is repeatedly applied to a steel pipe column, it is possible to suppress a decrease in strength of the weld toe portion of the rib, and to turn weld the upper end portion of the rib. It is made in order to provide the reinforcement method of the steel pipe column base and the steel pipe column base which can prevent the yield strength of a part and the fall of fatigue performance.
[0006]
[Means for Solving the Problems]
The steel pipe column base of the present invention made to solve the above problems is a steel tube column base reinforced by a T-welded rib at the base of the steel tube column, and the rib is the reverse of the bent upper end portion. It is a U-shaped or inverted V-shaped rib, and a bar-shaped tool is vibrated in the axial direction by ultrasonic waves at the weld toe end of the rib, and the surface is recessed by applying the tip to the metal surface to be processed. It is characterized by being subjected to peening treatment by ultrasonic vibration. Also, the steel pipe column base strengthening method of the present invention is such that a reverse U-shaped or reverse V-shaped rib whose upper end is bent is welded to the base of the steel tube column, and then the weld toe of each rib is super welded. The bar-shaped tool is vibrated in the axial direction by sound waves, and a peening process is performed by ultrasonic vibration that dents the surface by applying the tip to a metal surface to be treated.
[0007]
In addition, the reinforcing effect can be further enhanced by performing a peening process by ultrasonic vibration in a state where a load that causes a tensile stress in the axial direction of the steel pipe acts on the base material of the processing section is applied to the base of the steel pipe column. . Preferred conditions for the peening treatment by ultrasonic vibration are an amplitude of 20 to 50 μm and a frequency of 10 to 50 kHz.
[0008]
As described above, in the present invention, by using an inverted U-shaped or inverted V-shaped rib having a bent upper end serving as a weld toe, the upper end of the rib is perpendicular to the main stress direction of the steel pipe column. The rigidity of the upper end of the rib is reduced. As a result, when a bending stress is applied to the steel pipe column, the stress concentration generated at the weld toe is remarkably relieved, and the tensile residual stress due to welding heat can be remarkably relieved.
[0009]
Furthermore, in this invention, the peening process by the ultrasonic vibration was performed to the weld toe part of the rib. This treatment is a method in which a bar-shaped tool is vibrated in the axial direction by ultrasonic waves, and the tip is applied to a metal surface to be treated to dent the surface. As a result, high-density energy is applied to the weld toe portion, plastic deformation occurs, and compressive residual stress is applied. For this reason, the weld toe which was a weak point of the steel pipe column base is further strengthened, and even when a bending moment is repeatedly applied to the steel pipe column, it is possible to suppress a decrease in strength of the weld toe of the rib and It is possible to prevent a decrease in yield strength and fatigue performance of the rotating welded portion of the upper end portion of the steel plate.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Preferred embodiments of the present invention are shown below.
In FIG. 1, 10 is a steel pipe column used as a road lighting pole or a road sign pole, 11 is a base plate welded to the lower end of the steel pipe column 10, and 12 is a reinforcement between the steel pipe column 10 and the base plate 11. In order to do this, it is a plurality of ribs which are T-welded. In this embodiment, the rib 12 has an inverted U-shape, but may be an inverted V-shaped rib 12 as in another embodiment shown in FIG. The base plate 11 is fixed to a frame such as a road by anchor bolts 13 and holds the steel pipe column 10 vertically.
[0011]
The main stress direction of the steel pipe column 10 is the vertical direction, and the ribs 12 also extend in the main stress direction of the steel pipe column 10 as a whole. However, the upper portion of the rib 12 is gently bent in an arc shape, and the upper end portion 14 of the rib 12 serving as the weld toe portion is bent until it is perpendicular to the main stress direction of the steel pipe column 10.
[0012]
Thus, the upper end portion 14 of the rib 12 can be made to have a low-rigidity structure by gently bending the upper end portion 14 of the rib 12 in a direction to escape from the main stress direction of the steel pipe column 10. As a result, the stress concentration at the upper end portion 14 of the rib 12 is alleviated, and the welding residual thermal stress of the welded portion is also remarkably reduced, so that the yield strength and fatigue performance as a welded structure are greatly improved.
[0013]
In order to sufficiently exhibit such an effect, it is preferable to set the radius of curvature of the upper end portion 14 of the rib 12 to be three times or more the thickness of the rib 12. When the radius of curvature is smaller than this, material deterioration is liable to occur when the rib 12 is bent, and the effect of lowering rigidity is also reduced.
[0014]
For reference, FIG. 3 and FIG. 4 show stress concentration diagrams obtained by FEM analysis of the steel pipe column base shown in FIG. 1 and the conventional steel pipe column base shown in FIG. In these drawings, the generated stress distribution around the rib 12 when a horizontal load equal to the upper end of the steel pipe column 10 is applied is shown by contour lines, and the unit in the figure is MPa. As apparent from a comparison between FIG. 3 and FIG. 4, it can be seen that by bending the upper end portion 14 of the rib 12, the maximum value of the concentrated stress is halved compared to the conventional structure.
[0015]
In addition, in the present invention, the weld toe portion of the bent rib 12 is further subjected to peening by ultrasonic vibration. As shown in an enlarged view in FIG. 1, the peening processing unit 20 is a region having a central angle α on both sides of the center line of the rib 12 and generally has a range of 30 ° ≦ α ≦ 60 °. . In FIG. 1, α is approximately 45 °.
[0016]
In this peening process by ultrasonic vibration, as shown in FIG. 5, the tip of the bar-shaped tool 22 of the ultrasonic impacting device 21 is applied to the metal surface to be processed and ultrasonically vibrated in the axial direction to hit the processing target part. It is a method to give the surface and dent. The tip of the rod-shaped tool 22 is generally circular in cross section, and its diameter is preferably about 1 to 6 mm. This is because if the diameter is less than 1 mm, the strength is insufficient and sufficient impact cannot be applied, and if the diameter exceeds 6 mm, the mass increases, making it difficult to perform ultrasonic vibration.
[0017]
The bar-shaped tool 22 preferably has a frequency of 10 to 50 kHz and an amplitude of 20 to 50 μm. This is because the energy of impact given to the steel material is efficiently increased in this frequency range. On the other hand, if the amplitude is less than 20 μm, a sufficient impact cannot be given. On the other hand, if the amplitude exceeds 50 μm, plastic deformation entering the steel material may become too large, which is not preferable.
[0018]
The metal surface treated under the conditions as described above is plastically deformed by high-density energy and is recessed to a depth of about 0.1 to 0.5 mm, and compressive stress is introduced from the surface layer to a depth of 10 mm or more. Can do. In addition, a large change is caused in the metal structure from the surface layer to a depth of about 100 μm, and a structure layer called a white layer is formed, and good corrosion resistance, wear resistance, and reduction in frictional resistance can be achieved.
[0019]
In the present invention, the peening processing part 20 by such ultrasonic vibration is formed at the weld toe part of each rib 12 as shown in FIGS. As a result, the stress concentration at the weld toe is alleviated, and a compressive stress is introduced into the weld toe, and the fatigue strength is dramatically improved. Further, as described above, the weld toe portion of the rib 12 is a portion that tends to become a structural defect due to the overlap of the tensile residual stress due to welding heat and the deterioration of the heat-affected material, but it causes a structural change by peening treatment by ultrasonic vibration. As a result, it is possible to repair structural defects such as fine cracks.
[0020]
Thus, the steel pipe column base portion of the method of the present invention is obtained by subjecting the weld toe end of the inverted U-shaped or inverted V-shaped rib 12 with the upper end portion 14 bent to a peening process by ultrasonic vibration. Therefore, the effects of the respective configurations are combined. As a result, the stress concentration generated near the weld toe portion of the rib 12 when a bending moment acts on the steel pipe column 10 due to wind or vibration can be relieved significantly, and is shown in the data of the examples described later. Thus, the fatigue strength of this part can be remarkably improved. Moreover, the present invention does not require ancillary equipment other than the ultrasonic hitting device 21 and has an advantage that it can be easily constructed on site.
[0021]
Normally, the peening process may be performed by applying the tip of the rod-like tool 22 of the ultrasonic striking device 21 to the weld toe end of each rib 12 welded to the base of the steel pipe column 10, but the base material of the processing section Peening treatment by ultrasonic vibration can be performed in a state where a load (for example, bending load) on which a tensile stress in the axial direction of the steel pipe acts is applied to the steel pipe column base. In this way, if a peening process is performed in a state where an external force is applied and a tensile stress is applied to apply a compressive stress to the weld toe, a larger compressive stress may remain in the weld toe 14 when the external force is removed. It becomes possible. For this reason, it becomes possible to obtain a further excellent reinforcing effect.
[0022]
In the above description, only the weld toe portion of each rib 12 has been subjected to peening treatment by ultrasonic vibration, but it goes without saying that other weld portions may be subjected to peening treatment. However, the lower portion of the rib 12 is not a portion that directly affects the fatigue strength of the steel pipe column base portion, so it is considered that there is not much profit.
[0023]
【Example】
A fatigue strength test was performed by repeatedly applying bending stress to the steel pipe column base of the present invention shown in FIG. The material used is SM490 for both steel pipe and rib. For comparison, a fatigue strength test was performed in which tensile stress was repeatedly applied to partial test pieces around the steel pipe base rib having the structure shown in FIG. As a result, as indicated by black circles in FIG. 6, the fatigue characteristics of the conventional structure shown in FIG. 7 corresponded to E grade to D grade of the design life curve of the railway bridge design specification. On the other hand, the fatigue characteristics of the product of the present invention greatly increased to the A grade of the design life curve as shown by white circles. The amplitude of the tip tool was 40 μm, and the frequency was 30 kHz.
[0024]
In addition, when peening treatment by ultrasonic vibration is applied with a tensile stress acting on the steel tube column base, its fatigue characteristics rise to A grade or higher of the design life curve as shown by white triangles. did. Note that the arrow pointing upward in FIG. 6 means that loading has ended because no change was seen in the specimen at that time. Here, the weld quality of the partial test piece of the conventional structure used in this test is very high grade, and the fatigue life should be slightly lower at the level of normal industrial products.
[0025]
【The invention's effect】
As described above, according to the present invention, by applying a peening process by ultrasonic vibration to the weld toe of the inverted U-shaped or inverted V-shaped rib whose upper end is bent, the rotation of the upper end of the rib is performed. It is possible to greatly prevent a decrease in yield strength and fatigue performance of the welded portion. As a result, even when a bending moment is repeatedly applied to the steel pipe column, there is no decrease in strength near the weld toe portion of the rib, and there is no safety problem even if it is used for a long period of time. And since this invention does not need to change the structure of a steel pipe pillar base, there exists an advantage which can be easily applied also to the existing installation.
[Brief description of the drawings]
FIG. 1 is a front view showing a first embodiment of the present invention.
FIG. 2 is a perspective view showing a second embodiment of the present invention.
FIG. 3 is a stress concentration diagram obtained by FEM analysis of a steel pipe column base portion using inverted U-shaped ribs.
FIG. 4 is a stress concentration diagram obtained by FEM analysis of a steel pipe column base portion having a conventional structure.
FIG. 5 is a side view of the ultrasonic striking device.
FIG. 6 is a SN curve showing the results of fatigue strength tests in Examples.
FIG. 7 is a perspective view showing a conventional example.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Steel pipe pillar 11 Base plate 12 Rib 13 Anchor bolt 14 Upper end part 20 Peening process part 21 Ultrasonic hitting device 22 Bar-shaped tool

Claims (4)

鋼管柱の基部をＴ字溶接されたリブにより補強した鋼管柱基部であって、前記のリブは上端部が屈曲された逆Ｕ字状または逆Ｖ字状のリブであり、かつリブの溶接止端部に超音波により棒状工具を軸方向に振動させ、その先端を処理対象となる金属表面にあてがうことによって表面を窪ませる超音波振動によるピーニング処理が施されたものであることを特徴とする鋼管柱基部。A steel pipe column base portion in which a base portion of a steel pipe column is reinforced by a rib welded to a T-shape, wherein the rib is an inverted U-shaped or inverted V-shaped rib having a bent upper end portion, and welding of the rib is stopped. It is characterized in that a bar-shaped tool is vibrated in the axial direction by ultrasonic waves at the end , and subjected to peening treatment by ultrasonic vibration that dents the surface by applying the tip to the metal surface to be treated. Steel pipe column base. 鋼管柱の基部に上端部が屈曲された逆Ｕ字状または逆Ｖ字状のリブをＴ字溶接したのち、各リブの溶接止端部に超音波により棒状工具を軸方向に振動させ、その先端を処理対象となる金属表面にあてがうことによって表面を窪ませる超音波振動によるピーニング処理を施すことを特徴とする鋼管柱基部の強化方法。After T-welding an inverted U-shaped or inverted V-shaped rib whose upper end is bent at the base of the steel tube column, a rod-shaped tool is vibrated in the axial direction by ultrasonic waves at the weld toe of each rib. A method for strengthening a steel pipe column base, characterized by performing a peening process by ultrasonic vibration that dents a surface by applying a tip to a metal surface to be processed. 処理区間の母材に鋼管軸方向の引張応力が作用するような荷重を鋼管柱の基部に与えた状態で、超音波振動によるピーニング処理を施すことを特徴とする鋼管柱基部の強化方法。  A method for strengthening a steel pipe column base, comprising performing a peening process by ultrasonic vibration in a state where a load that causes a tensile stress in the axial direction of the steel pipe acts on a base material in a processing section is applied to the base of the steel pipe column. 振幅２０〜５０μｍ、振動数１０〜５０ｋＨｚの条件下で超音波振動によるピーニング処理を施すことを特徴とする請求項２または３に記載の鋼管柱基部の強化方法。  The steel pipe column base strengthening method according to claim 2 or 3, wherein peening treatment by ultrasonic vibration is performed under conditions of an amplitude of 20 to 50 µm and a frequency of 10 to 50 kHz.
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JP4537649B2 (en) 2002-10-08 2010-09-01 新日本製鐵株式会社 Rotating welded joint, manufacturing method of Rotated welded joint, and welded structure
TWI273157B (en) * 2003-07-22 2007-02-11 Nippon Steel Corp Joining structure
JP4695355B2 (en) * 2004-07-15 2011-06-08 新日本製鐵株式会社 Boom / arm member for construction machine with excellent weld fatigue strength and method for manufacturing the same
JP4757697B2 (en) * 2006-04-18 2011-08-24 新日本製鐵株式会社 Method for improving fatigue performance of fillet welds
KR100939406B1 (en) 2007-10-31 2010-01-28 구희정 Reinforce rib
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