JP5648568B2 - CFT column design method - Google Patents

CFT column design method Download PDF

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JP5648568B2
JP5648568B2 JP2011096740A JP2011096740A JP5648568B2 JP 5648568 B2 JP5648568 B2 JP 5648568B2 JP 2011096740 A JP2011096740 A JP 2011096740A JP 2011096740 A JP2011096740 A JP 2011096740A JP 5648568 B2 JP5648568 B2 JP 5648568B2
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concrete
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難波　隆行
隆行 難波
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JFE Steel Corp
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Description

本発明は、土木建築構造物に用いられるＣＦＴ（Ｃｏｎｃｒｅｔｅ Ｆｉｌｌｅｄ Ｓｔｅｅｌ Ｔｕｂｅの略）柱の設計方法に関し、特にＣＦＴ柱として要求される性能を満足させる鋼管の選定方法に関する。   The present invention relates to a design method for CFT (Concrete Filled Steel Tube) columns used in civil engineering structures, and more particularly to a method for selecting a steel pipe that satisfies the performance required for CFT columns.

鋼管の内部にコンクリートを充填したコンクリート充填鋼管構造（ＣＦＴ（Ｃｏｎｃｒｅｔｅ Ｆｉｌｌｅｄ Ｓｔｅｅｌ Ｔｕｂｅの略）柱構造とも言う）は、コンクリートの特徴（圧縮力に強いが、引張り力に弱い特性）と鋼管の特徴（引張り力に強いが、圧縮力により座屈する特性）を組合わせることによって、それぞれの欠点を解消したもので変形性能に優れ、地震に強く、また耐火性も備えた構造である。   Concrete filled steel pipe structure filled with concrete inside the steel pipe (also called CFT (Concrete Filled Steel Tube) column structure) is characterized by concrete (characteristics strong against compressive force but weak against tensile force) and steel pipe ( It is a structure that is superior in deformation performance, strong against earthquakes, and also has fire resistance.

ＣＦＴ柱構造は、変形させると、鋼管・コンクリートの降伏後も変形が進むにつれ耐力（曲げモーメントへの抵抗力）が上昇し、コンクリート耐力と鋼管耐力の単純和を上回る耐力の得られることが知られている。ＣＦＴ柱構造の耐力評価には非特許文献１、２などで提案されている、Ｍ−Ｎインタラクションカーブが用いられる。   It is known that when the CFT column structure is deformed, the yield strength (resistance to bending moment) increases as the deformation progresses after the yield of steel pipe / concrete, and the yield strength exceeds the simple sum of concrete strength and steel pipe strength. It has been. The MN interaction curve proposed in Non-Patent Documents 1 and 2 is used for the strength evaluation of the CFT column structure.

図１２は非特許文献２に記載された短期許容耐力評価方法（単純累加強度）によるＭ−Ｎインタラクションカーブの一例を示し、正の軸方向力はコンクリートが負担し、コンクリートが負担しきれない分は鉄骨が負担するものとして計算される。一方、負の軸方向力は鉄骨が負担するものとして計算される。短期許容耐力は設計上考慮される、塑性変形が生じない最大変形時の耐力である。   FIG. 12 shows an example of an MN interaction curve according to the short-term allowable yield strength evaluation method (simple cumulative strength) described in Non-Patent Document 2, in which the positive axial force is borne by the concrete and cannot be fully borne by the concrete. Is calculated as the burden of the steel frame. On the other hand, the negative axial force is calculated assuming that the steel frame bears. The short-term allowable yield strength is the maximum yield strength that does not cause plastic deformation.

図１０は非特許文献１に記載されたＣＦＴ柱の終局耐力評価方法（一般化累加強度）を示し、角形鋼管および円形鋼管で幅高さ比が４を超え１２以下で軸力・変形が小さい場合は、コンクリートは圧縮強度ｃσｃｂ、鋼管は降伏応力Ｆｙから算出されるＭ−Ｎインタラクションカーブ上の任意の軸耐力、曲げ耐力を加算し、そのうち最大耐力となるものをＣＦＴ柱の耐力としている。   FIG. 10 shows the ultimate strength evaluation method (generalized cumulative strength) of the CFT column described in Non-Patent Document 1, and the axial force / deformation is small when the width-to-height ratio is more than 4 and less than 12 for square steel pipes and circular steel pipes. In this case, the concrete is added with the compressive strength cσcb, and the steel pipe is added with arbitrary axial strength and bending strength on the MN interaction curve calculated from the yield stress Fy, and the maximum strength is the strength of the CFT column.

図１１は非特許文献２に記載されたＣＦＴ柱の終局耐力評価方法（一般化累加強度）を示し、幅高さ比が６以下の場合、コンクリートは圧縮強度Ｆｃに鉄骨の径厚比・強度に応じたコンファインド効果分を加算した応力、鉄骨は一軸降伏応力ｓσｙに周方向力を加味して算出されるＭ−Ｎインタラクションカーブ上の任意の軸耐力、曲げ耐力を加算し、そのうち最大耐力となるものをＣＦＴ柱の耐力としている。   FIG. 11 shows the ultimate strength evaluation method (generalized cumulative strength) of the CFT column described in Non-Patent Document 2. When the width-height ratio is 6 or less, the concrete has a compressive strength Fc and a diameter-thickness ratio / strength of the steel frame. Add the confining effect according to the stress, and the steel frame adds the arbitrary axial strength and bending strength on the MN interaction curve calculated by adding the circumferential force to the uniaxial yield stress sσy, of which the maximum strength This is the strength of the CFT pillar.

このようにＣＦＴ柱構造ではコンクリート耐力と鋼管耐力の単純和を上回る耐力が得られるが、非特許文献１の耐力評価法は、鋼管部分の耐力を降伏応力ベースで決定するもので、ＣＦＴ柱構造とともに変形する鋼管における強度特性の変化は反映されていない。   Thus, in the CFT column structure, a yield strength exceeding the simple sum of the concrete yield strength and the steel pipe yield strength can be obtained. However, the strength evaluation method of Non-Patent Document 1 determines the yield strength of the steel pipe portion on the basis of the yield stress. The change of the strength characteristics in the steel pipe which deforms with it is not reflected.

鋼管における強度特性の変化は、例えば、図９（非特許文献３より引用）のひずみ硬化で示され、ひずみ硬化により、最大耐力は降伏応力×塑性断面係数で算出した曲げ耐力を上回るようになるので、ＣＦＴ柱構造の耐力を精度良く求めるためにはひずみ硬化分を反映させることが必要である。 The change in the strength characteristics of the steel pipe is shown by, for example, strain hardening in FIG. 9 (cited from Non-Patent Document 3) . With strain hardening, the maximum yield strength exceeds the bending strength calculated by yield stress x plastic section modulus. Therefore, in order to accurately obtain the proof stress of the CFT column structure, it is necessary to reflect the strain hardening.

尚、非特許文献２の終局耐力評価法の場合、ＣＦＴ柱の降伏後耐力上昇を考慮し、コンクリート強度を割り増している。しかし、非特許文献２は４００〜５９０Ｎ／ｍｍ２級鋼と圧縮強度が９０Ｎ／ｍｍ２以下のコンクリートを用いるＣＦＴ柱を対象とするもので、より高強度のコンクリートと鋼管を用いるＣＦＴ柱の場合において合理的な設計方法を示唆するものではない。 In the case of the ultimate strength evaluation method of Non-Patent Document 2, the concrete strength is increased in consideration of the increase in yield strength after yielding of the CFT column. However, Non-Patent Document 2 is intended for CFT columns using 400 to 590 N / mm grade 2 steel and concrete having a compressive strength of 90 N / mm 2 or less. In the case of CFT columns using higher strength concrete and steel pipes It does not suggest a rational design method.

ところで、コンクリート単体の変形性能は高強度になるほど低下するため、ＣＦＴ構造においても充填コンクリートの高強度化により変形性能が低下する傾向がある。   By the way, since the deformation performance of a concrete single body falls, so that it becomes high strength, also in CFT structure, there exists a tendency for a deformation performance to fall by the high intensity | strength of filling concrete.

図８は、充填コンクリートの強度が低い場合のＣＦＴ構造の特性を説明する模式図で、充填コンクリートの強度が低い場合は、鋼管・コンクリートで最大耐力が発揮される変形量が異なっても、その後の耐力低下がなだらかなため、ＣＦＴ柱の最大耐力に与える影響は小さい。   FIG. 8 is a schematic diagram for explaining the characteristics of the CFT structure when the strength of the filled concrete is low. When the strength of the filled concrete is low, even if the deformation amount at which the maximum strength is exhibited in the steel pipe / concrete is different, Since the decrease in the proof stress is gentle, the effect on the maximum proof strength of the CFT column is small.

一方、コンクリートに高強度材料を用いた場合は、コンクリートの破壊が脆性的となるため、鋼管とコンクリートで最大強度が発揮される変形量が相違すると両者の性能が十分に生かされない（図７）。   On the other hand, when high-strength material is used for concrete, fracture of the concrete becomes brittle, so if the amount of deformation at which the maximum strength is exhibited differs between steel pipe and concrete, the performance of both is not fully utilized (Fig. 7). .

すなわち、ＣＦＴ柱において、鋼管部分とコンクリート部分がそれぞれの最大耐力を発揮する変形量が大きく異なると、鋼管部分のひずみ硬化による耐力上昇をCFT柱の耐力向上に十分に反映できない可能性がある。また、鋼管の変形性能がＣＦＴ柱の（コンクリートの耐力低下により決まる）変形性能と比較して過剰となり、合理的なＣＦＴ構造とはいい難い。   That is, in the CFT column, if the deformation amount at which the steel pipe portion and the concrete portion exhibit the maximum proof stress is greatly different, the increase in the proof stress due to strain hardening of the steel pipe portion may not be sufficiently reflected in the improvement in the proof strength of the CFT column. Further, the deformation performance of the steel pipe becomes excessive compared with the deformation performance of the CFT column (determined by the decrease in the yield strength of the concrete), and it is difficult to say that a rational CFT structure is used.

そこで、本発明は、耐力と安全性に優れる、高強度コンクリートを用いたＣＦＴ柱を製造する際、適切な鋼管を選定することが可能なＣＦＴ柱の設計方法を提供することを目的とする。   Then, this invention aims at providing the design method of the CFT pillar which can select an appropriate steel pipe, when manufacturing the CFT pillar using the high strength concrete which is excellent in yield strength and safety | security.

本発明の課題は以下の手段で達成可能である。
１．鋼管内に充填するコンクリートとして高強度コンクリートを用いるＣＦＴ柱の設計方法であって、前記鋼管として、ＣＦＴ柱において最大耐力が得られる柱変形角に安全率を乗じた柱変形角以上で破断が生じ、且つ前記柱変形角において最も耐力が大きい鋼管を所望の降伏強度・最大強度を有する候補鋼管のうちから選定することを特徴とするＣＦＴ柱の設計方法。
２．前記柱変形角において最も耐力が大きい鋼管としてひずみ硬化による耐力上昇が最も大きい鋼管を所望の降伏強度・最大強度を有する候補鋼管のうちから選定することを特徴とする１記載のＣＦＴ柱の設計方法。 The object of the present invention can be achieved by the following means.
1. A CFT column design method using high-strength concrete as concrete to be filled in a steel pipe, wherein the steel pipe breaks at a column deformation angle greater than the column deformation angle obtained by multiplying the column deformation angle at which the maximum strength is obtained in the CFT column by a safety factor. A method for designing a CFT column, wherein a steel pipe having the greatest yield strength at the column deformation angle is selected from candidate steel pipes having desired yield strength and maximum strength.
2. 2. The method of designing a CFT column according to 1, wherein a steel pipe having the largest yield strength increase by strain hardening is selected from candidate steel pipes having desired yield strength and maximum strength as the steel pipe having the greatest yield strength at the column deformation angle. .

本発明によれば、耐力と安全性に優れる、充填コンクリートとして高強度コンクリートを用いるＣＦＴ柱を設計する際に、コンクリートを充填する鋼管を適切に選定することが可能で、産業上極めて有用である。   According to the present invention, when designing a CFT column that uses high-strength concrete as filling concrete, which is excellent in yield strength and safety, it is possible to appropriately select a steel pipe filled with concrete, which is extremely useful industrially. .

応力ーひずみ線図が異なる角形鋼管（その１）に高強度コンクリートを充填したＣＦＴ柱の鋼管部分の荷重（鋼管端部モーメント）−変形（柱変形角＝柱の水平変形／柱高さ）関係を用いて、本発明における鋼管の選定基準を説明する図。Load (steel tube end moment) -deformation (column deformation angle = horizontal deformation of the column / column height) of CFT columns filled with high-strength concrete in square steel tubes with different stress-strain diagrams (Part 1) The figure explaining the selection criteria of the steel pipe in this invention using FIG. 応力ーひずみ線図が異なる角形鋼管（その２）に高強度コンクリートを充填したＣＦＴ柱の鋼管部分の荷重（鋼管端部モーメント）−変形（柱変形角＝柱の水平変形／柱高さ）関係を用いて、本発明における鋼管の選定基準を説明する図。Load (steel pipe end moment) -deformation (column deformation angle = horizontal deformation of the column / column height) of CFT columns filled with high-strength concrete in square steel tubes (part 2) with different stress-strain diagrams The figure explaining the selection criteria of the steel pipe in this invention using FIG. 図１の角形鋼管（その１）の応力ーひずみ線図の模式図。The schematic diagram of the stress-strain diagram of the square steel pipe (the 1) of FIG. 図２の角形鋼管（その２）の応力ーひずみ線図の模式図。The schematic diagram of the stress-strain diagram of the square steel pipe (the 2) of FIG. 修正補エネルギーを説明する図。The figure explaining correction supplementary energy. 本発明の効果を説明する図。The figure explaining the effect of this invention. 充填コンクリートの強度がＣＦＴ構造の特性に及ぼす影響を説明する模式図で、コンクリートが低強度の場合。This is a schematic diagram illustrating the effect of the strength of filled concrete on the properties of the CFT structure, when the concrete is of low strength. 充填コンクリートの強度がＣＦＴ構造の特性に及ぼす影響を説明する模式図で、コンクリートが高強度の場合。This is a schematic diagram illustrating the effect of the strength of filled concrete on the properties of the CFT structure, when the concrete is of high strength. 中空鋼管の計算耐力と履歴曲線の比較図。Comparison of calculated yield strength and hysteresis curve of hollow steel pipe. Ｍ−ＮインタラクションカーブによるＣＦＴ柱の終局耐力評価方法（一般化累加強度）の一例を示す図。The figure which shows an example of the ultimate strength evaluation method (generalized progressive strength) of the CFT pillar by a MN interaction curve. Ｍ−ＮインタラクションカーブによるＣＦＴ柱の終局耐力評価方法（一般化累加強度）の他の例を示す図。The figure which shows the other example of the ultimate strength evaluation method (generalized progressive strength) of the CFT pillar by a MN interaction curve. Ｍ−ＮインタラクションカーブによるＣＦＴ柱の耐力評価方法で短期許容耐力評価方法（単純累加強度）を示す図。The figure which shows the short-term allowable strength evaluation method (simple cumulative strength) by the strength evaluation method of the CFT column by the MN interaction curve.

本発明に係るＣＦＴ柱の設計方法は複数の候補鋼管の中から、１．ＣＦＴ柱に用いる鋼管の耐破断性能（破断時の変形の大きさ）に関する選定基準（１）、２．ＣＦＴ柱の最大耐力を大きくするための鋼管特性への選定基準（２）を満足するように鋼管を選定することを特徴とする。候補鋼管は所望の引張強度を有する鋼管でＣＦＴ柱用として経済性に優れるものを指す。以下、具体的に説明する。   A method for designing a CFT column according to the present invention is as follows. Selection criteria (1) for fracture resistance (size of deformation at fracture) of steel pipes used for CFT columns. The steel pipe is selected so as to satisfy the selection criteria (2) for steel pipe characteristics for increasing the maximum proof stress of the CFT column. Candidate steel pipe refers to a steel pipe having a desired tensile strength and excellent in economic efficiency for CFT columns. This will be specifically described below.

図１、２を用いて１％ひずみ時の応力が異なる計８種の角形鋼管モデルを対象として、鋼材の引張破断で決まる角形鋼管の変形性能、所定の変形時における耐力上昇率について検討する。図３、４に上記８種類の角形鋼管の鋼管材のＳＳカーブを示す。
図１、２は応力ーひずみ線図（ＳＳカーブと言う場合がある）が異なる鋼管材（角形鋼管の母材）を用いた８種類の、径７００ｍｍ、長さ４０００ｍｍの角形鋼管に高強度コンクリートを充填したＣＦＴ柱を上下端の回転を拘束された状態で上端を水平方向に変形させたときの鋼管部分の荷重（鋼管端部モーメント）−変形（柱変形角＝柱の水平変形／柱高さ）関係を計算で求めた結果を示す。ただし、ＣＦＴ柱において、コンクリートのみが軸方向力を負担する場合を想定し、鋼管が負担する軸方向力を０とする。 With reference to FIGS. 1 and 2, the deformation performance of a square steel pipe determined by tensile fracture of the steel material and the rate of increase in yield strength at a predetermined deformation are examined for a total of eight types of square steel pipe models with different stresses at 1% strain. FIGS. 3 and 4 show the SS curves of the above eight types of square steel pipes.
Figures 1 and 2 show high-strength concrete in eight types of square steel pipes with a diameter of 700 mm and a length of 4000 mm using steel pipe materials (base materials of square steel pipes) with different stress-strain diagrams (sometimes referred to as SS curves). Steel tube part load (steel tube end moment)-deformation (column deformation angle = horizontal deformation of the column / column height) when the upper end of the CFT column filled with is deformed in the horizontal direction with the rotation of the upper and lower ends restricted A) The result of calculating the relationship is shown. However, assuming that only the concrete bears the axial force in the CFT column, the axial force that the steel pipe bears is zero.

図３は降伏応力４４０Ｎ／ｍｍ２、引張強度５９０Ｎ／ｍｍ２の鋼材の場合のＳＳカーブで、降伏比は約７５％、図４は降伏応力５００Ｎ／ｍｍ２、引張強度５９０Ｎ／ｍｍ２の鋼材のＳＳカーブで、降伏比は約８５％の鋼材である。鋼材の一様伸び（引張強度発現時のひずみ）は８％とするが、柱材端接合部のひずみ集中係数を２と仮定し、平面保持仮定時の材端断面縁歪が４％となった時点で引張により破断するものとみなす。ただし、図３、４では４％ひずみ時にほぼ引張強度を発現しているものとして扱う。 Figure 3 is the yield stress 440 N / mm 2, in SS curve in the case of the tensile strength 590N / mm 2 steel, about 75% yield ratio, FIG. 4 is yield stress 500 N / mm 2, a tensile strength of 590N / mm 2 steel This is a steel material with a yield ratio of about 85%. The uniform elongation of steel (strain at the time of developing tensile strength) is 8%, but assuming that the strain concentration factor of the column end joint is 2 and the end edge strain at the end of the plane is 4%. It is considered that it will break when pulled. However, in FIGS. 3 and 4, it is assumed that the tensile strength is almost expressed at 4% strain.

上記選定基準１（ＣＦＴ柱に用いる鋼管の耐破断性能（破断時の変形の大きさ）に関する要求）を満足させるため、鋼管として、ＣＦＴ柱の最大柱変形角（設計目標値として設定する）に安全率を乗じた柱変形角以上で破断するものを選定する。   In order to satisfy the above selection criteria 1 (requirements regarding the fracture resistance of steel pipes used for CFT columns (the magnitude of deformation at the time of fracture)), the maximum column deformation angle of CFT columns (set as a design target value) as a steel pipe Select those that break at a column deformation angle multiplied by the safety factor.

ＣＦＴ柱としての変形性能が０．０１（ｒａｄ）で、鋼管の破断に対する安全率を２とする場合、鋼管の破断で決まる変形性能は０．０２（ｒａｄ）以上必要である。この条件を満たすのはＹＲ７５％の場合ｃａｓｅ−１、２、３のＳＳカーブを有する鋼管、ＹＲ８５％の場合ｃａｓｅ−５のＳＳカーブを有する鋼管である。   When the deformation performance as a CFT column is 0.01 (rad) and the safety factor against breakage of the steel pipe is 2, the deformation performance determined by the breakage of the steel pipe must be 0.02 (rad) or more. This condition satisfies steel pipes having an SS curve of cases-1, 2 and 3 when YR is 75%, and steel pipes having an SS curve of case-5 when YR is 85%.

上記選定基準２（ＣＦＴ柱の最大耐力を大きくするための鋼管特性への要求）を満足させるため、鋼管として前記最大柱変形角において最もひずみ硬化が大きいものを選定する。ＣＦＴ柱におけるコンクリートの最大耐力発揮変形が０．０１（ｒａｄ）である場合、同じ変形における鋼管の耐力上昇率が最も高いのはｃａｓｅ−１、２、３の鋼管の中ではｃａｓｅ−３の鋼管である。従って、前記の条件における最適なＳＳカーブはＹＲ７５％の場合ｃａｓｅ−３の鋼管となる。ＹＲ８５％の場合は最適な鋼管はＳＳカーブがｃａｓｅ−５と６の中間程度となる鋼管である。   In order to satisfy the above selection criterion 2 (requirement for steel pipe characteristics for increasing the maximum proof stress of the CFT column), a steel pipe having the largest strain hardening at the maximum column deformation angle is selected. When the deformation of the maximum strength of concrete in the CFT column is 0.01 (rad), the rate of increase in the yield strength of the steel pipe in the same deformation is the highest in the steel pipes of case-1, 2, 3 It is. Therefore, the optimum SS curve under the above conditions is a case-3 steel pipe when YR is 75%. In the case of YR85%, the optimum steel pipe is a steel pipe whose SS curve is about halfway between cases-5 and 6.

本発明は、鋼管として、ひずみ硬化が早期に現れ（ラウンドハウス化したＳＳカーブを有することで可能となる）、それに伴い鋼管自体の引張側の破断により決まる変形能力（柱変形角）は低下するが、ＣＦＴ柱の変形性能（柱変形角）に安全率を乗じた値以上の変形性能（柱変形角）を備えたものを候補鋼管より選定することで、ＣＦＴ柱の安全性を損なうことなく、高い耐力を発揮させるものである。   In the present invention, strain hardening appears early as a steel pipe (which is possible by having a round housed SS curve), and the deformation capacity (column deformation angle) determined by the fracture on the tensile side of the steel pipe itself decreases accordingly. However, by selecting from the candidate steel pipes that have a deformation performance (column deformation angle) equal to or greater than the value obtained by multiplying the deformation performance (column deformation angle) of the CFT column by a safety factor, the safety of the CFT column is not impaired. , To demonstrate high proof stress.

なお、上記選定基準１である鋼管への耐破断性能（変形性能：破断時の変形の大きさ）は修正補エネルギー（図５参照）の降伏応力に対する大きさの比に左右される（例えば、非特許文献４〜６）。修正補エネルギーを大きくするには、１．ＹＲを低くする、２．塑性化後の比較的早い段階での応力上昇を抑える、３．最大応力時のひずみを大きくすることのいずれも有効であるが、ＹＲの低下、最大応力時のひずみの増大には限界があるので、塑性化直後の応力上昇（ひずみ硬化）を抑えることが経済的に有効である。   Note that the fracture resistance performance (deformation performance: the magnitude of deformation at the time of fracture) to the steel pipe, which is the above selection criterion 1, depends on the ratio of the magnitude of the corrected supplemental energy (see FIG. 5) to the yield stress (for example, Non-patent documents 4 to 6). To increase the corrected supplemental energy: 1. Lower YR 2. Suppress stress rise at a relatively early stage after plasticization. Increasing the strain at the maximum stress is effective, but there is a limit to the decrease in YR and the increase in strain at the maximum stress, so it is economical to suppress the stress increase (strain hardening) immediately after plasticization Effective.

一方、上記選定基準２ではＣＦＴ柱の最大柱変形角を大きくするために、鋼管として前記最大柱変形角において最もひずみ硬化が大きいものを選定する。ＣＦＴ柱は、充填されるコンクリートが負担する荷重が最大となる柱変形が、鋼管単体の柱と比較して小さい場合が多く、鋼管のひずみ硬化による応力上昇が遅い場合にはＣＦＴ柱として鋼管とコンクリートの両方の耐荷重性能を最大限に利用できない。従って、鋼管のひずみ硬化が、ひずみが比較的小さい段階で起こる材料が望ましい。   On the other hand, in the above selection criterion 2, in order to increase the maximum column deformation angle of the CFT column, a steel pipe having the largest strain hardening at the maximum column deformation angle is selected. CFT columns are often smaller in deformation than the column of a single steel pipe, and the stress increase due to strain hardening of the steel pipe is slow. The load bearing performance of both concrete cannot be used to the maximum. Therefore, a material in which strain hardening of a steel pipe occurs at a stage where the strain is relatively small is desirable.

本発明において鋼管に対する上記選定基準１、２は相反するが、選定基準１に関しては、鋼管耐破断性能はコンクリート変形性能以上であれば良く、その範囲内で選定基準２を満足するＳＳカーブを備えた鋼管を選定するのが良い。ただし、鋼管の破断による耐力低下は急激に起こることから、選定基準１を満足させるよう鋼管を選定する場合は一定の安全率を有することが望ましい。選定基準１、２に関する具体的な検討は、ＦＥＭ解析によるか、非特許文献７に記載されたＣＤＣ法により行うことが出来る。   In the present invention, the above selection criteria 1 and 2 for steel pipes are contradictory, but with respect to selection criteria 1, the steel pipe fracture resistance is only required to be greater than the concrete deformation performance, and the SS curve satisfying the selection criteria 2 is provided within that range. It is recommended to select a steel pipe. However, since the proof stress drop due to the breakage of the steel pipe occurs abruptly, it is desirable to have a certain safety factor when selecting the steel pipe to satisfy the selection criterion 1. Specific examination regarding the selection criteria 1 and 2 can be performed by FEM analysis or by the CDC method described in Non-Patent Document 7.

本発明によればＣＦＴ柱構造が変形する際、比較的早期に鋼管の耐力が上昇するため、当該ＣＦＴ柱を用いた構造物は地震外力を受けた際に従来構造と比較して変形が小さく抑えられるか、倒壊を避けることができる（図６）。   According to the present invention, when the CFT column structure is deformed, the proof stress of the steel pipe is increased relatively early. Therefore, the structure using the CFT column is less deformed than the conventional structure when subjected to an earthquake external force. It can be suppressed or collapse can be avoided (FIG. 6).

早期にひずみ硬化する鋼管は、一般に鋼材の引張側の破断により決まる変形性能が低下するが、ＣＦＴ柱としての変形性能としての変形性能に安全率を乗じた以上の鋼管としての変形性能を確保するため、構造性能を低下させることは無い。   Steel pipes that are strain-hardened at an early stage generally have a deformation performance that is determined by the fracture on the tensile side of the steel material. However, the deformation performance as a CFT column is ensured to be more than the product obtained by multiplying the deformation performance by the safety factor. Therefore, the structural performance is not deteriorated.

本発明は、ＣＦＴ柱としての変形性能を満足するように選定基準１、２によって鋼管を選定するが、ＣＦＴ柱自体の変形性能に替えてＣＦＴ柱を使用する構造物の層（複数階を有する構造物の床間）の変形性能としても良い。   In the present invention, the steel pipe is selected by the selection criteria 1 and 2 so as to satisfy the deformation performance as the CFT column, but the layer of the structure using the CFT column (having a plurality of floors) instead of the deformation performance of the CFT column itself. It may be the deformation performance between the floors of the structure.

コンクリート充填鋼管構造設計施工指針：日本建築学会Concrete filled steel pipe structure design and construction guidelines: Architectural Institute of Japan コンクリート充填鋼管（ＣＦＴ）造技術基準・同解説の運用及び計算例等：（社）新都市ハウジング協会Concrete Filled Steel Pipe (CFT) Construction Technical Standards, Operation and Calculation Examples, etc .: New City Housing Association ５９０Ｎ／ｍｍ２級角形鋼管の部材性能に関する実験的研究：下川 他、鋼構造年次論文報告集、巻：１６ 頁：１−６、２００８．１１Experimental study on member performance of 590N / mm2 class square steel pipe: Shimokawa et al., Annual Report of Steel Structure, Volume: 16 pages: 1-6, 2008.11 延性き裂発生を考慮した梁部材の塑性変形能力、 学術講演梗概集． Ｃ−１、 ２００３、 ｐｐ．８６３−８６４、Summary of academic lecture lectures on plastic deformation capacity of beam members considering ductile crack initiation. C-1, 2003, pp. 863-864, 歪・補エネルギーによる素材特性と部材変形性能に関する検討：小野 他、日本建築学会大会学術講演梗概集 Ｃ分冊、ｐ．１１３９、１９９３年Study on material properties and member deformation performance by strain and supplemental energy: Ono et al. 1139, 1993 金属系構造部材の局部座屈挙動における素材特性の影響（その３）：伊藤 他、日本建築学会大会学術講演梗概集 Ｃ−１分冊、ｐ．２６９、１９９６年Effect of material properties on local buckling behavior of metallic structural members (Part 3): Ito et al. 269, 1996 （財）日本建築センター：鉄骨梁端溶接接合部の脆性的破断防止ガイドライン・同解説Japan Building Center: Guidelines for Prevention of Brittle Fracture of Steel Beam End Welded Joints

Claims (2)

鋼管内に充填するコンクリートとして高強度コンクリートを用いるＣＦＴ柱の設計方法であって、前記鋼管として、ＣＦＴ柱において最大耐力が得られる柱変形角に安全率を乗じた柱変形角以上で破断が生じ、且つ前記安全率を乗じた柱変形角において最も耐力が大きい鋼管を所望の降伏強度・最大強度を有する候補鋼管のうちから選定することを特徴とするＣＦＴ柱の設計方法。   A CFT column design method using high-strength concrete as concrete to be filled in a steel pipe, wherein the steel pipe breaks at a column deformation angle greater than the column deformation angle obtained by multiplying the column deformation angle at which the maximum strength is obtained in the CFT column by a safety factor. And a method of designing a CFT column, wherein a steel pipe having the greatest yield strength at a column deformation angle multiplied by the safety factor is selected from candidate steel pipes having desired yield strength and maximum strength. 前記安全率を乗じた柱変形角において最も耐力が大きい鋼管としてひずみ硬化による耐力上昇が最も大きい鋼管を所望の降伏強度・最大強度を有する候補鋼管のうちから選定することを特徴とする請求項１記載のＣＦＴ柱の設計方法。   The steel pipe having the greatest increase in yield strength due to strain hardening is selected from candidate steel pipes having desired yield strength and maximum strength as the steel pipe having the greatest yield strength at the column deformation angle multiplied by the safety factor. The CFT pillar design method described.
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