JP4388463B2 - Fireproof coated steel structure - Google Patents
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本発明は、火災時の梁の伸び出し量を低減可能な無耐火被覆鉄骨構造物に関するものである。 The present invention relates to a fireproof coated steel structure that can reduce the amount of beam extension during a fire.
鉄骨構造物が火災を受けた場合には、火災階の梁が熱膨張して、柱を押し出すことにより、柱に大きな部材角が生じ層崩壊に至る可能性がある。このため、平成１２年建設省告示第１４３３号として告示された「耐火性能検証法」において、柱の部材角δ／ｈ（ここで、δは梁の伸び出し量の総和、ｈは階の高さ）を１／５０以下にするために、火災区画の床面積Ｓの規模（火災区画の加熱梁の総延長Ｌ≒√Ｓ）に応じた温度制限を設けている。
また、欧州鋼構造協会（ＥＣＣＳ）が１９８０年に公表した「標準火災加熱に対する鋼構造耐力部材の耐火設計ヨーロッパ基準」や、特許文献１の例では、柱の部材角δ／ｈを１／３０以下とすることが開示されている。梁の伸び出し量を低減できる構造としては、例えば、特許文献２には、梁継手に形状記憶合金を用いて梁の伸び出しをキャンセルすることのできる熱変形吸収構造に関する発明が開示されている。また、特許文献３には、ブレース構面骨組の梁を長期曲げモーメントが小さくなる位置で分割し、この分割梁の分割側の端部を水平方向に摺動自在に接続するスライド継手を設けて梁の伸び出し量を低減させる構造に関する発明が開示されている。
In addition, in the example of “Fireproof design European standard of steel structural bearing members against standard fire heating” published by the European Steel Structure Association (ECCS) in 1980 and the example of Patent Document 1, the member angle δ / h of the column is 1/30. The following is disclosed. As a structure capable of reducing the extension amount of the beam, for example, Patent Document 2 discloses an invention relating to a thermal deformation absorption structure that can cancel the extension of the beam by using a shape memory alloy for the beam joint. . Further, Patent Document 3 is provided with a slide joint that divides a beam of a brace structure frame at a position where the long-term bending moment becomes small, and connects the ends of the divided beams in a slidable manner in the horizontal direction. An invention relating to a structure for reducing the extension amount of a beam is disclosed.
しかしながら、上記特許文献２に記載の発明の構造では、数十ｍｍ以上に達する梁の伸び出し量を吸収させることは困難であり、かつ、高価ということに加えて、梁上部の床スラブに拘束される場合では、熱変形吸収効果が十分に発揮されないなどの問題がある。
また、上記特許文献３に記載の発明の構造においても、対象がブレース構面骨組および分割梁構造に限定され、かつ特殊なスライド継手の採用によるコスト高に加えて、梁上部の床スラブに拘束される場合には、スライド継手の効果が十分に発揮されないなどの問題がある。このため、火災時の梁の伸び出し量を効果的に低減でき、高温強度および高温ヤング係数の高い無耐火被覆構造の鉄骨構造物の実現が課題となっていた。
However, in the structure of the invention described in Patent Document 2, it is difficult to absorb the extension amount of the beam reaching several tens of mm or more, and in addition to being expensive, the structure is restrained by the floor slab above the beam. In such a case, there is a problem that the thermal deformation absorption effect is not sufficiently exhibited.
Also in the structure of the invention described in Patent Document 3, the object is limited to the brace frame and the split beam structure, and in addition to the high cost due to the use of a special slide joint, it is restrained to the floor slab above the beam. In such a case, there is a problem that the effect of the slide joint is not sufficiently exhibited. For this reason, the extension amount of the beam at the time of a fire can be reduced effectively, and realization of the steel structure of a fireproof covering structure with high temperature strength and high temperature Young's modulus was a subject.
そこで、本発明は、火災時に高温にさらされる鉄骨部材を無耐火被覆とする鉄骨構造物において、高温強度および高温ヤング係数が高い鋼材を柱部材に用いることにより、特殊な梁継手や骨組構造を用いることなく、火災時の梁の伸び出し量を低減して、すなわち、柱部材角（δ／ｈ）を最終的に１／５０以下に抑制可能にして層崩壊を有利に防止できる、無耐火被覆鉄骨構造物を提供することを目的とするものである。 Therefore, the present invention is a steel structure in which a steel member exposed to a high temperature in the event of a fire has a fireproof coating, and a steel member having a high temperature strength and a high temperature Young's modulus is used for the column member, so that a special beam joint or a frame structure can be obtained. Without using it, the amount of extension of the beam during a fire can be reduced, that is, the column member angle (δ / h) can be finally reduced to 1/50 or less, and the layer collapse can be advantageously prevented. The object is to provide a coated steel structure.
本発明は、以下の（１）〜（３）を要旨とするものである。
（１）火災時に火炎を受けて高温にさらされる鉄骨部材を無耐火被覆とする鉄骨構造物であって、該鉄骨構造物を構成する無耐火被覆の柱を、常温時の降伏強度により高温時の降伏強度を無次元化した高温降伏強度比ｐ（高温降伏強度／常温降伏強度）が、鋼材温度Ｔ（℃）が６００℃以上８００℃以下の範囲で、ｐ≧−０．００２９×Ｔ＋２．４８を満足し、かつ、常温時のヤング係数により高温時のヤング係数を無次元化した高温ヤング係数比ｒ（高温ヤング係数／常温ヤング係数）が、鋼材温度Ｔ（℃）が６００℃以上８００℃以下の範囲で、ｒ≧−０．００１７×Ｔ＋１．７７を満足する、高温強度および高温ヤング係数が高い鋼材で形成し、該柱と接合する梁を、該柱形成用の鋼材の高温強度および高温ヤング係数未満の従来鋼材で形成したことを特徴とする、無耐火被覆鉄骨構造物。
（２）前記梁の高温ヤング係数比をｒｂとし、前記柱の高温ヤング係数比をｒｃとするときのこれらの比ｒｂ／ｒｃが、鋼材温度Ｔ（℃）が６００℃以上８００℃以下の範囲で、ある温度を境界にして、ｒｂ／ｒｃ＜０．０５を満足することを特徴とする、請求項１に記載の無耐火被覆鉄骨構造物。
（３）前記梁を床スラブと一体化させた合成梁とするとともに、該床スラブに耐火補強筋を配したことを特徴とする、請求項１または２に記載の無耐火被覆鉄骨構造物。
The gist of the present invention is the following (1) to (3).
(1) A steel structure having a non-fireproof coating on a steel member that is exposed to a high temperature by receiving a flame in the event of a fire, and the pillar of the fireproof coating that constitutes the steel structure is heated at a high temperature by the yield strength at normal temperature. The high-temperature yield strength ratio p (high-temperature yield strength / room-temperature yield strength) obtained by making the yield strength of the steel dimensionless is in the range where the steel material temperature T (° C.) is 600 ° C. or higher and 800 ° C. or lower, and p ≧ −0.0029 × T + 2. 48, and the high temperature Young's modulus ratio r (high temperature Young's modulus / room temperature Young's modulus) obtained by making the Young's modulus at high temperatures dimensionless by the Young's modulus at normal temperature is a steel material temperature T (° C) of 600 ° C or higher and 800 ° C. A beam formed of a steel material having a high temperature strength and a high temperature Young's modulus satisfying r ≧ −0.0017 × T + 1.77 within a range of ℃ or less, and a beam to be joined to the column is a high temperature strength of the steel material for forming the column. And conventional steel with a high temperature Young's modulus less than A fire-resistant coated steel structure characterized by being formed.
(2) When the high temperature Young's modulus ratio of the beam is rb and the high temperature Young's modulus ratio of the column is rc, the ratio rb / rc is a range in which the steel material temperature T (° C) is 600 ° C or higher and 800 ° C or lower. The refractory-coated steel frame structure according to claim 1 , wherein rb / rc <0.05 is satisfied at a certain temperature as a boundary .
(3) The fire-resistant coated steel structure according to claim 1 or 2, wherein the beam is a composite beam integrated with a floor slab, and a fireproof reinforcing bar is disposed on the floor slab.
本発明は、火災を受ける可能性のある鉄骨構造物において、柱を６００〜８００℃で十分な高温強度と高温ヤング係数を有する鋼材で形成して、梁を柱より高温強度、高温ヤング係数の低い鋼材、例えば従来鋼で形成することにより、特殊な梁継手や骨組構造を用いることなく火災時の梁の伸び出し量を低減して、柱部材角を最終的に１／５０以下に抑えることができ、火災による６００〜８００℃高温時においても層崩壊を生じない、無耐火被覆構造の鉄骨構造物を安定的に実現することができる。 The present invention provides a steel structure having a possibility of receiving a fire, in which a column is formed of a steel material having a sufficiently high temperature strength and a high temperature Young's modulus at 600 to 800 ° C., and the beam has a higher temperature strength and a higher temperature Young's modulus than the column. By using low steel, for example, conventional steel, the amount of beam extension during a fire is reduced without using special beam joints or frame structures, and the column member angle is finally reduced to 1/50 or less. It is possible to stably realize a steel structure having a fire-resistant covering structure that does not cause layer collapse even at a high temperature of 600 to 800 ° C. due to a fire.
本発明は、概念的には、火災を受ける可能性のある鉄骨構造物において、柱を６００〜８００℃での高温強度および高温ヤング係数の高い鋼材で形成して無耐火被覆構造を可能にするとともに、この柱と接合する梁を、上記柱形成用の鋼材の高温強度および高温ヤング係数未満の従来鋼材で形成して、火災時に伸びる梁の端部を高温剛性の大きい柱によって拘束して梁を撓ませることにより、梁の伸び出しによる柱の強制変形を抑制し、柱部材角（δ／ｈ）を最終的に１／５０以下に抑制して層崩壊を防止するものである。
本発明者らは、本発明に至る事前検討において、火災により高温に加熱された場合でも無耐火被覆構造で十分に耐えられる鉄骨構造物を実現するためには、６００〜８００℃での高温強度および高温ヤング係数が高い鋼材が必要であるが、このような鋼材を柱と梁に同時に使用した場合には、火災時の梁の伸び出しによって、柱に大きな押出力が作用して柱が強制変形を受け、柱部材角（δ／ｈ）が１／５０以上、条件によってはさらに１／３０以上になって、層崩壊が生じやすくなるという知見を得た。
The present invention conceptually enables pillars to be formed of steel materials having a high temperature strength at 600 to 800 ° C. and a high temperature Young's modulus in a steel structure that is likely to receive a fire, thereby enabling a fireproof coating structure. At the same time, the beam to be joined to this column is made of a conventional steel material having a high temperature strength and a Young's modulus less than that of the above-mentioned steel for forming the column. Is to suppress the forced deformation of the column due to the extension of the beam, and finally suppress the column member angle (δ / h) to 1/50 or less to prevent layer collapse.
In the preliminary study leading to the present invention, the present inventors have developed a high-temperature strength at 600 to 800 ° C. in order to realize a steel structure that can sufficiently withstand a fire-resistant coating structure even when heated to a high temperature by a fire. Steel materials with high Young's modulus at high temperatures are required. However, when such steel materials are used at the same time for the columns and beams, the columns are forced by a large pushing force acting on the columns due to the extension of the beams in the event of a fire. As a result of deformation, the column member angle (δ / h) was 1/50 or more, and further 1/30 or more depending on the conditions, and it was found that layer collapse tends to occur.
本発明は、上記の知見に基づいてなされたものであり、より具体的には、以下の（１）〜（３）を要旨とするものである。
（１） 請求項１に記載の本発明では、鉄骨構造物を構成する無耐火被覆の柱を、常温時の降伏強度により高温時の降伏強度を無次元化した高温降伏強度比ｐ（高温降伏強度／常温降伏強度）が、鋼材温度Ｔ（℃）が６００℃以上８００℃以下の範囲で、ｐ≧−０．００２９×Ｔ＋２．４８を満足し、かつ、常温時のヤング係数により高温時のヤング係数を無次元化した高温ヤング係数比ｒ（高温ヤング係数／常温ヤング係数）が、鋼材温度Ｔ（℃）が６００℃以上８００℃以下の範囲で、ｒ≧−０．００１７×Ｔ＋１．７７を満足する高温強度および高温ヤング係数が高い鋼材（以下、上記高温降伏強度比ｐおよび高温ヤング係数比ｒの条件を満たす本発明に適合した鋼材を、単に「（６００〜８００℃での）高温強度および高温ヤング係数が高い鋼材」とも言う。）で形成し、この柱と接合する梁を、柱形成用の鋼材の高温強度および高温ヤング係数未満の従来鋼材、例えばＳＭ４９０Ａ（ＪＩＳ Ｇ ３１０６）、ＳＮ４９０Ｂ（ＪＩＳ Ｇ ３１３６）などの従来鋼材で形成することにより、火災時に伸びる梁の端部を柱によって拘束して梁を撓ませることにより、梁の伸び出し量を低減して、梁の伸び出しによる柱の強制変形を抑制し、柱部材角（δ／ｈ）を最終的に１／５０以下に抑制する。
ここで、ｐ≧−０．００２９×Ｔ＋２．４８、および、ｒ≧−０．００１７×Ｔ＋１．７７の条件は、火災により６００〜８００℃へ加熱された高温時でも十分な降伏強度および高温剛性を確保して無耐火被覆構造を実現する重要な条件となるものである。
This invention is made | formed based on said knowledge, More specifically, it makes the following (1)-(3) a summary.
(1) In the present invention according to claim 1, a high temperature yield strength ratio p (high temperature yield strength) is obtained by making the yield strength at high temperature non-dimensional with the yield strength at normal temperature of the pillar of the fireproof coating constituting the steel structure. (Strength / room temperature yield strength) satisfying p ≧ −0.0029 × T + 2.48 when the steel material temperature T (° C.) is in the range of 600 ° C. to 800 ° C., and the Young's modulus at room temperature Non-dimensional Young's modulus high temperature Young's modulus ratio r (high temperature Young's modulus / room temperature Young's modulus) is r ≧ −0.0017 × T + 1.77 when the steel material temperature T (° C.) is in the range of 600 ° C. to 800 ° C. A steel material having a high temperature strength and a high high temperature Young's modulus satisfying the above (hereinafter referred to as a steel material suitable for the present invention that satisfies the conditions of the high temperature yield strength ratio p and the high temperature Young's modulus ratio r is simply “high temperature (at 600 to 800 ° C.) Strength and high temperature Young's modulus Also referred to as high steel ".) In forming, the beam to be joined to the pillar, the conventional steel under high-temperature strength and high temperature Young's modulus of the steel for pillaring include, for example SM490A (JIS G 3106), SN490B (JIS G 3136) By using conventional steel materials such as the above, the end of the beam that is extended in the event of a fire is restrained by the column and the beam is bent, thereby reducing the amount of beam extension and forcibly deforming the column due to the beam extension. The column member angle (δ / h) is finally suppressed to 1/50 or less.
Here, the conditions of p ≧ −0.0029 × T + 2.48 and r ≧ −0.0017 × T + 1.77 are sufficient yield strength and high temperature rigidity even at a high temperature heated to 600 to 800 ° C. by a fire. This is an important condition for ensuring a fire-resistant coating structure.
この柱に接合する梁の条件としては、柱を上記の条件を満足する鋼材で形成した場合において、火災時の梁の伸び出しが、柱部材角（δ／ｈ）が最終的に１／５０以下になるように端部が柱で拘束される（梁が伸びても撓むことにより伸び出し量が低減する）必要があることから、梁は柱形成用の鋼材の高温強度および高温ヤング係数未満の従来鋼材で形成することが重要な条件になる。
なお、本発明で対象となる柱は、角形または円形の鋼管（溶接管を含む）やＨ形鋼などで構成され、また、梁は、Ｈ形鋼で構成される。この柱と梁の接合は、通常の場合、接合金物やダイアフラムを使用したボルト接合や、溶接接合またはボルト接合と溶接接合の併用により行われるが、いずれを組み合わせた場合にも本発明の適用は可能である。
As a condition of the beam to be joined to the column, when the column is formed of a steel material that satisfies the above-described conditions, the beam extends in the event of a fire, and the column member angle (δ / h) is finally 1/50. since there (elongation out amount is reduced by flexing even elongation beams) should end is constrained by the pillar to be less than, the high-temperature strength and high temperature Young's modulus of the steel for beam pillaring It becomes an important condition to form with less conventional steel materials.
In addition, the column used as object in this invention is comprised with a square or circular steel pipe (a welding pipe is included), H-section steel, etc., and a beam is comprised with H-section steel. In general, the column and beam are joined by a bolt joint using a joint metal or a diaphragm, or a weld joint or a combination of a bolt joint and a weld joint. Is possible.
（２） さらに、請求項２に記載の本発明では、梁を、柱の高温ヤング係数比ｒｃにより梁の高温ヤング係数比ｒｂを除したｒｂ／ｒｃが、鋼材温度Ｔ（℃）が６００℃以上８００℃以下の範囲で、ｒｂ／ｒｃ＜０．０５となる温度域を有する（６００〜８００℃の範囲の、ある温度を境界にして、ｒｂ／ｒｃ≧０．０５からｒｂ／ｒｃ＜０．０５へ切り替わる）、柱形成用の鋼材より常に高温強度および高温ヤング係数が低い鋼材で形成することにより、火災時の梁の伸び出し量が、梁が自由膨張した場合の１割程度まで低減できる構造とすることができる。 (2) Further, in the present invention according to claim 2, rb / rc obtained by dividing the high temperature Young's modulus ratio rb of the beam by the high temperature Young's modulus ratio rc of the column has a steel material temperature T (° C) of 600 ° C. It has a temperature range where rb / rc <0.05 in the range of 800 ° C. or less (between a certain temperature in the range of 600 to 800 ° C., rb / rc ≧ 0.05 to rb / rc <0 .05)) By forming with steel material that always has lower high-temperature strength and high-temperature Young's modulus than steel for column formation, the extension amount of the beam during a fire is reduced to about 10% when the beam expands freely. The structure can be made.
（３） 請求項３に記載の本発明では、梁が、床スラブと合成梁｛コンクリートからなる床スラブと鉄骨梁とを頭付きスタッド（ＪＩＳ Ｂ １１９８）などの剪断ずれ止めで接合することにより、梁と床スラブが一体となって曲げに抵抗する構造（日本建築学会：各種合成構造設計指針・同解説、１９８５年）を有する梁を意味し、以下これを「合成梁」という。｝を形成する場合に、床スラブのコンクリートの熱容量により、梁の伸び出し量をさらに低減できる。さらに、床スラブに耐火補強筋を配して上階床に対する耐荷力を増すことにより、高温時に梁が強度喪失しても水平防火区画としての床の機能を損なわないようにして、伸び出し量をさらに低減できる構造とするものである。 (3) In the present invention according to claim 3, the beam is formed by joining a floor slab and a composite beam {a floor slab made of concrete and a steel beam with a shearing detent such as a headed stud (JIS B 1198). This means a beam having a structure in which the beam and the floor slab are integrated to resist bending (the Architectural Institute of Japan: various composite structural design guidelines and explanations, 1985), and this is hereinafter referred to as a “composite beam”. }, The extension amount of the beam can be further reduced by the heat capacity of the concrete of the floor slab. In addition, by placing fire reinforcement reinforcement on the floor slab to increase the load bearing capacity against the upper floor, even if the beam loses strength at high temperatures, the function of the floor as a horizontal fire protection compartment is not impaired, and the amount of extension It is set as the structure which can further reduce.
なお、本発明の柱を形成する鋼材としては、一般的な火災で想定される１時間程度の比較的短時間の６００〜８００℃の高温暴露において、上記（１）に記載される高温降伏強度比ｐおよび高温ヤング係数比ｒの範囲を満足する鋼材を用いる必要がある。このような鋼材としては、例えば、国際特許公開ＷＯ０３／０８７４１４号公報記載の発明のような、「質量％で、Ｃ：０．００５％以上０．０８％未満、Ｓｉ：０．５％以下、Ｍｎ：０．１〜１．６％、Ｐ：０．０２％以下、Ｓ：０．０１％以下、Ｍｏ：０．１〜１．５％、Ｎｂ：０．０３〜０．３％、Ｔｉ：０．０２５％以下、Ｂ：０．０００５〜０．００３％、Ａｌ：０．０６％以下、Ｎ：０．００６％以下を含有し、さらに必要に応じて特定量のＣｕ、Ｎｉ、Ｃｒ、Ｖ、Ｃａ、ＲＥＭ、Ｍｇ等の強化元素を含有し、かつ、残部がＦｅおよび不可避的不純物からなる鋼材」が、溶接性、コスト上昇回避の観点から適性が高いものである。 In addition, as a steel material which forms the column of the present invention, the high temperature yield strength described in the above (1) in a high temperature exposure of 600 to 800 ° C. for a relatively short time of about 1 hour assumed in a general fire. It is necessary to use a steel material that satisfies the range of the ratio p and the high temperature Young's modulus ratio r. As such a steel material, for example, as in the invention described in International Patent Publication No. WO03 / 087414, “in mass%, C: 0.005% or more and less than 0.08%, Si: 0.5% or less, Mn: 0.1 to 1.6%, P: 0.02% or less, S: 0.01% or less, Mo: 0.1 to 1.5%, Nb: 0.03 to 0.3%, Ti : 0.025% or less, B: 0.0005 to 0.003%, Al: 0.06% or less, N: 0.006% or less, and, if necessary, specific amounts of Cu, Ni, Cr Steel materials that contain reinforcing elements such as V, Ca, REM, Mg, etc., and the balance consisting of Fe and inevitable impurities ”are highly suitable from the viewpoints of weldability and cost increase avoidance.
しかし、必ずしもこのような鋼材に限定される訳ではなく、溶接性、コスト上昇がそれほど問題とならない場合には、例えば、オーステナイト系耐熱鋼であるＳＵＨ６６０（ＪＩＳ Ｇ ４３１２）のような、「質量％で、Ｃ：０．０８％以下、Ｓｉ：１．００％以下、Ｍｎ：２．００％以下、Ｐ：０．０４０％以下、Ｓ：０．０３０％以下、Ｎｉ：２４．００〜２７．００％、Ｍｏ：１．００〜１．５０％、Ｔｉ：１．９０〜２．３５％、Ｖ：０．１０〜０．５０％、Ａｌ：０．３５％以下、Ｂ：０．００１〜０．０１０％を含有し、残部がＦｅおよび不可避的不純物からなる鋼材」を用いることも可能である。このＳＵＨ６６０規格の鋼材は、例えば特開昭６０−２２１５５６号公報ないし特開平７−２３８３４９号公報に記載の発明を参照すれば、本発明で規定する６００〜８００℃での高温降伏強度比ｐの範囲を満足するものであり、また、文献「ステンレス鋼便覧」（長谷川正義監修：日本工業新聞社、１９７３年、図２．１２）を参照すれば、本発明で規定する６００〜８００℃での高温ヤング係数比ｒの範囲を満足するものであることが分かる。 However, the present invention is not necessarily limited to such a steel material, and when the weldability and cost increase are not so serious, for example, “mass%” such as SUH660 (JIS G 4312) which is an austenitic heat resistant steel. C: 0.08% or less, Si: 1.00% or less, Mn: 2.00% or less, P: 0.040% or less, S: 0.030% or less, Ni: 24.00-27. 00%, Mo: 1.00-1.50%, Ti: 1.90-2.35%, V: 0.10-0.50%, Al: 0.35% or less, B: 0.001- It is also possible to use a “steel material containing 0.010%, the balance being Fe and inevitable impurities”. For example, referring to the invention described in JP-A-60-221556 or JP-A-7-238349, the SUH660 standard steel material has a high-temperature yield strength ratio p at 600 to 800 ° C. specified in the present invention. It satisfies the range, and with reference to the document “Stainless Steel Handbook” (supervised by Masayoshi Hasegawa: Nihon Kogyo Shimbun, 1973, FIG. 2.12), it is 600 to 800 ° C. as defined in the present invention. It can be seen that the high temperature Young's modulus ratio r is satisfied.
従来、６００℃以上での高温強度を有する鋼材は、一般に耐火鋼と呼称されており、例えば、特開平２−７７５２３号公報に記載の発明では、６００℃で常温降伏強度の２／３以上（約７０％）の高温強度を有する耐火鋼が提案されている。その他の耐火鋼に関する発明の例でも、６００℃での降伏強度を常温降伏強度の２／３以上とすることが一般的となっている。
しかしながら、７００℃の耐火鋼、８００℃の耐火鋼は、現時点では高温強度の設定（常温降伏強度との比率）に一般則が見られない。例えば、特開平１０−６８０４４号公報に記載の発明では、所定量のＭｏとＮｂを添加した鋼材でミクロ組織をベイナイトとすることにより、７００℃での降伏強度を、常温降伏強度の５６％以上にするものであるが、８００℃での降伏強度は示されていない。
Conventionally, a steel material having a high-temperature strength at 600 ° C. or higher is generally called a refractory steel. For example, in the invention described in Japanese Patent Application Laid-Open No. 2-77523, the normal temperature yield strength at 600 ° C. is 2/3 or more ( A refractory steel having a high temperature strength of about 70% has been proposed. In other examples of the invention relating to refractory steel, it is common that the yield strength at 600 ° C. is 2/3 or more of the room temperature yield strength.
However, 700 ° C. refractory steel and 800 ° C. refractory steel do not show a general rule in the setting of high-temperature strength (ratio to room-temperature yield strength) at present. For example, in the invention described in Japanese Patent Application Laid-Open No. 10-68044, the yield strength at 700 ° C. is 56% or more of the normal temperature yield strength by using a steel material to which a predetermined amount of Mo and Nb is added and the microstructure is bainite. The yield strength at 800 ° C. is not shown.
すなわち、これらの例のように６００℃程度の高温強度を確保した鋼材は既に市場でも使用されており、７００℃程度の高温強度を確保する鋼材の発明もなされているが、火災時の梁の伸び出し量を低減し無耐火被覆構造を可能とすることを前提として、７００℃、８００℃での高温強度を確保した鋼材を用いた鉄骨構造物は従来なかったといえる。
耐火設計においては、火災継続時間内（１時間程度）で高い強度を維持すればよく、従来の耐熱鋼のように長時間の高温強度を維持する必要はなく、比較的短時間の高温強度を維持すればよい。例えば、８００℃での保持時間が３０分程度の短時間、降伏強度が確保できれば、本発明でいう８００℃耐火鋼として十分利用できる。
That is, steel materials having a high temperature strength of about 600 ° C. have already been used in the market as in these examples, and steel materials that have a high temperature strength of about 700 ° C. have been invented. It can be said that there has never been a steel structure using a steel material that secures high-temperature strength at 700 ° C. and 800 ° C. on the premise that the extension amount is reduced to enable a fire-resistant coating structure.
In fire-resistant design, it is only necessary to maintain high strength within the fire duration (about 1 hour), and it is not necessary to maintain high-temperature strength for a long time unlike conventional heat-resistant steel. Just keep it. For example, if the yield strength can be ensured for a short time of about 30 minutes at 800 ° C., it can be sufficiently used as 800 ° C. refractory steel in the present invention.
従来の６００℃耐火鋼では、高温降伏強度が常温時の２／３以上となるように性能を定めていたが、鉄骨構造物の実設計範囲が、常温降伏強度下限の０．２〜０．４倍程度であることを勘案すれば、常温時の降伏強度から高温時の降伏強度を無次元化した高温降伏強度比ｐ（高温降伏強度／常温時降伏強度）が、鋼材温度Ｔ（℃）が６００℃以上８００℃以下の範囲でｐ≧−０．００２９×Ｔ＋２．４８を満足することが必要となる（後述する図６参照。）。言い換えると、実績の高温降伏強度比（ｐ）が、上式に基づけば、６００℃でｐ≧０．７４、７００℃でｐ≧０．４５、８００℃でｐ≧０．１６を満足すればよい。
また、高温降伏強度比ｐと、常温時のヤング係数から高温時のヤング係数を無次元化した高温ヤング係数比ｒ（高温ヤング係数／常温ヤング係数）を比較すると、同一温度ではｐよりｒの方が低下の割合が緩やか、すなわちｐ＜ｒの関係にあることが知られている。本発明では、ｒが６００℃でｐ≒ｒとし、さらにｐの降下勾配（０．００２９）とｒの降下勾配の比が３／５程度となるように仮定すると、ｒが、鋼材温度Ｔ℃が６００℃以上８００℃以下の範囲でｒ≧−０．００１７×Ｔ＋１．７７を満足することが必要となる（後述する図７参照。）。言い換えると、実績の高温ヤング係数比（ｒ）が、上式に基づけば、６００℃でｒ≧０．７５、７００℃でｒ≧０．５８、８００℃でｒ≧０．４１を満足すればよい。
In the conventional 600 ° C. refractory steel, the performance was determined so that the high-temperature yield strength was 2/3 or more at room temperature, but the actual design range of the steel structure was 0.2 to 0. Considering that it is about 4 times, the high-temperature yield strength ratio p (high-temperature yield strength / room-temperature yield strength), which is dimensionless from the yield strength at normal temperature to the yield strength at high temperature, is the steel temperature T (° C). However, it is necessary to satisfy p ≧ −0.0029 × T + 2.48 in the range of 600 ° C. to 800 ° C. (see FIG. 6 described later). In other words, if the actual high temperature yield strength ratio (p) satisfies p ≧ 0.74 at 600 ° C., p ≧ 0.45 at 700 ° C., and p ≧ 0.16 at 800 ° C. Good.
Further, when the high temperature yield strength ratio p is compared with the high temperature Young's modulus ratio r (high temperature Young's modulus / room temperature Young's modulus) obtained by making the Young's modulus at high temperature non-dimensional from the Young's modulus at normal temperature, r is higher than p at the same temperature. It is known that the rate of decrease is moderate, that is, p <r. In the present invention, assuming that r is 600 ° C. and p≈r, and that the ratio of the descending slope of p (0.0029) to the descending slope of r is about 3/5, r is the steel temperature T ° C. However, it is necessary to satisfy r ≧ −0.0017 × T + 1.77 in the range of 600 ° C. to 800 ° C. (see FIG. 7 described later). In other words, if the actual high temperature Young's modulus ratio (r) satisfies r ≧ 0.75 at 600 ° C., r ≧ 0.58 at 700 ° C., and r ≧ 0.41 at 800 ° C. Good.
本発明では、柱に６００〜８００℃での高温強度および高温ヤング係数が高い鋼材を用いる一方で、梁には前記鋼材の高温強度および高温ヤング係数未満の鋼材、例えばＳＭ４９０Ａ（ＪＩＳ Ｇ ３１０６）、ＳＮ４９０Ｂ（ＪＩＳ Ｇ ３１３６）などの従来鋼、ないしユーロコード３（１９９３年）「鉄骨造建築物の設計」の「耐火構造設計」中の「一般鋼」（以下、これらを総称して単に従来鋼とも言う。）を用いることも主要な発明特定事項である。例えば、柱、梁ともに６００〜８００℃での高温強度および高温ヤング係数が高い鋼材を用いた場合、梁が相対的に強く高温時の剛性も高くなるため、却って梁の伸び出し量が大きくなってしまい、火災による昇温過程の比較的早い段階で柱の部材角制限（例えば１／５０）を超過して層崩壊に至る懸念が大となる。また、柱に６００〜８００℃での高温強度および高温ヤング係数が高い鋼材を用い、梁に従来鋼を通常の被覆厚で耐火被覆して用いた場合でも、耐火被覆により梁鋼材温度の上昇が遅延することに伴い上記無耐火被覆の例以上に梁が強くなってしまう一方で、梁鋼材温度の上昇を全く回避できる訳ではないので梁の伸び出し問題を回避できない。この場合、梁の耐火被覆厚さを通常の被覆厚さよりさらに吹き増して梁の温度上昇に伴う伸び出しを抑制するなどの対策を施さざるを得ない。
そこで、本発明では、柱を６００〜８００℃での高温強度および高温ヤング係数が高い鋼材で形成し、梁を柱形成鋼材より高温強度および高温ヤング係数未満、例えばＳＭ４９０Ａ、ＳＮ４９０Ｂや、ユーロコード３の一般鋼などの従来鋼材で形成し、特殊な梁継手や骨組構造を用いることなく、火災時の梁の伸び出し量を低減できる構造を、無耐火被覆構造として新たに提供するものである。
In the present invention, a steel material having a high temperature strength at 600 to 800 ° C. and a high Young's modulus is used for the column, while a steel material having a high temperature strength and a high temperature Young's modulus less than that of the steel material, for example, SM490A (JIS G 3106), Conventional steel such as SN490B (JIS G 3136), or “general steel” in “fireproof structure design” of “design of steel structure” in Eurocode 3 (1993) (hereinafter collectively referred to simply as conventional steel) It is also a major invention specific matter. For example, when steel materials with a high temperature strength at 600 to 800 ° C. and a high temperature Young's modulus are used for both the column and the beam, the beam is relatively strong and the rigidity at high temperature is increased, so that the amount of extension of the beam is increased. Therefore, there is a great concern that the column member angle limit (for example, 1/50) is exceeded at a relatively early stage of the temperature rising process due to a fire and the layer collapses. Moreover, even when a steel material having a high temperature strength at 600 to 800 ° C. and a high temperature Young's modulus is used for the column and the conventional steel is fire-coated with a normal coating thickness for the beam, the temperature of the beam steel material is increased by the fire-resistant coating. With the delay, the beam becomes stronger than the above example of the non-refractory coating. On the other hand, the increase in beam steel temperature cannot be avoided at all, so the problem of beam extension cannot be avoided. In this case, it is unavoidable to take measures such as increasing the thickness of the fireproof coating of the beam further than the normal coating thickness to suppress the expansion due to the temperature rise of the beam.
Therefore, in the present invention, the column is formed of a steel material having a high temperature strength at 600 to 800 ° C. and a high temperature Young's modulus, and the beam is less than the column forming steel material at a high temperature strength and a high temperature Young's modulus, such as SM490A, SN490B, Eurocode 3 A structure that is made of conventional steel such as ordinary steel and that can reduce the amount of beam extension in the event of a fire without using a special beam joint or frame structure is newly provided as a fireproof coating structure.
本発明が適用可能な火災時の室内雰囲気温度（火災温度）の上限は、鋼製柱に６００〜８００℃での高温強度および高温ヤング係数が高い鋼材を用い、かつ、鋼材の裸使用（無耐火被覆）であっても、鋼材の熱容量を考慮すれば、８００℃を大きく超える９５０℃程度とすることができる。さらに、仕上げボード材の熱遮蔽効果を期待できる場合の火災温度の上限は、鋼材の熱容量を考慮した火災温度適用範囲の拡大効果と相まって、１１５０℃程度とすることができる。なお、ここでの適用可能な火災温度の上限は、具体的な事例に即した部材実験や熱伝導解析等により確認することができる。
以下に、本発明の技術的思想についてさらに詳述する。
The upper limit of the indoor atmospheric temperature (fire temperature) to which the present invention can be applied is that the steel column is made of steel having a high temperature strength at 600 to 800 ° C. and a high high temperature Young's modulus, and the steel is barely used (no Even in the case of fireproof coating, if the heat capacity of the steel material is taken into consideration, it can be set to about 950 ° C., which greatly exceeds 800 ° C. Furthermore, the upper limit of the fire temperature when the heat shielding effect of the finished board material can be expected can be set to about 1150 ° C. in combination with the effect of expanding the fire temperature application range in consideration of the heat capacity of the steel material. In addition, the upper limit of the applicable fire temperature here can be confirmed by a member experiment based on a specific example, a heat conduction analysis, or the like.
The technical idea of the present invention will be described in detail below.
［１．梁の伸び出し量低減の考え方］
（１ａ）梁の伸び出しと高温時ヤング係数
火災時に建築物が層崩壊することは許容できないから、少なくとも柱の熱応力による損傷は極力回避する必要がある。そこで、本発明では、柱に許容できない強制変形が起こる以前に、梁に局部破壊を生じさせて柱の熱応力を緩和すればよいという耐火設計の考え方を採用する。
すなわち、火災時には、梁に対して柱が拘束を与えると考えられるので、柱の剛性を高めて梁の材端拘束度を大にして、梁を意図的に早期に局部破壊させて熱応力の緩和を図り、柱が外側に大きく押し出されるような強制変形を防止することが建築物の層崩壊を回避するうえで有効である。なお、この場合、望ましくは床スラブに耐火補強筋などを配しておき、梁の局部破壊後も、上階床に対する耐荷力を維持し、水平防火区画としての床の機能を損なわないようにする。このようにすれば、梁が高温時に強度喪失しても、床の荷重は柱に直接伝達されるため、床崩壊を回避することが可能となる。
[1. Concept of reducing beam extension]
(1a) Beam extension and Young's modulus at high temperature Since it is unacceptable for a building to undergo layer collapse during a fire, it is necessary to avoid at least damage to the column due to thermal stress. In view of this, the present invention adopts the concept of fireproof design in which a local fracture is caused in the beam to relieve the thermal stress of the column before unacceptable forced deformation occurs in the column.
In other words, in the event of a fire, the column is considered to constrain the beam, so the rigidity of the column is increased to increase the degree of material end restraint of the beam, and the beam is intentionally destroyed at an early stage to cause thermal stress. It is effective in avoiding the layer collapse of the building to ease the deformation and prevent the forced deformation that the column is pushed out greatly. In this case, it is desirable to place fire reinforcement reinforcements on the floor slab, so that the load resistance against the upper floor is maintained even after the local destruction of the beam, so that the function of the floor as a horizontal fire protection section is not impaired. To do. In this way, even if the beam loses its strength when the temperature is high, the floor load is directly transmitted to the column, so that the floor collapse can be avoided.
図１（ａ）、（ｂ）に梁の材端拘束度と熱変形の関係を示す。まず、図１（ａ）は、柱に６００〜８００℃での高温強度および高温ヤング係数が高い鋼材を用い、梁に前記鋼材の高温強度および高温ヤング係数未満の従来鋼材を用いた場合を示す。同図より、柱による梁の材端拘束度を大きくして梁の伸び出しを小さくすることによって、柱の強制変形を小さくし柱部材角δ／ｈを１／５０以下に小さくして層崩壊を防止できることが分かる。
一方、図１（ｂ）は、柱と梁に同レベルの高温強度および高温ヤング係数が高い鋼材を用いた場合を示す。この場合、柱による梁の材端拘束度が小さく、梁の伸び出しが大きくなり、柱の強制変形が大きくなることによって、柱部材角δ／ｈが１／５０より大幅に大きくなり、層崩壊が生じやすくなることが分かる。このような現象の発生を回避する必要があることは言うまでもない。
FIGS. 1A and 1B show the relationship between the degree of material end restraint of a beam and thermal deformation. First, FIG. 1A shows a case where a steel material having a high temperature strength at 600 to 800 ° C. and a high high temperature Young's modulus is used for the column, and a conventional steel material having a high temperature strength and a high temperature Young's modulus less than that of the steel material is used for the beam. . From the figure, by increasing the material end restraint of the beam by the column and reducing the extension of the beam, the forced deformation of the column is reduced and the column member angle δ / h is reduced to 1/50 or less, and the layer collapses. It can be seen that this can be prevented.
On the other hand, FIG.1 (b) shows the case where the steel material with the same high temperature strength and high temperature Young's modulus is used for a column and a beam. In this case, the material end restraint degree of the beam by the column is small, the extension of the beam is large, and the forced deformation of the column is large, so that the column member angle δ / h becomes significantly larger than 1/50 and the layer collapses. It turns out that it becomes easy to occur. Needless to say, it is necessary to avoid the occurrence of such a phenomenon.
（１ｂ）梁の伸び出し量の算定方法
火災時の加熱により梁温度が均等にＴ℃まで上昇して、熱応力σｔを生じたとすると、この時の梁の歪εｔ、熱膨張による梁の見掛け上の伸び率ａの相互には下記式の関係が成り立つ。
σｔ＝Ｅｔｂ×εｔ （１）
ａ＝ｂ×Ｔ−εｔ （２）
ここに、σｔ：高温時の梁の熱応力（Ｎ／ｍｍ２）
εｔ：高温時の梁の歪
Ｅｔｂ：高温時の梁のヤング係数（＝ｒｂ×Ｅｂ）（Ｎ／ｍｍ２）
Ｅｂ：常温時のヤング係数（Ｎ／ｍｍ２）
ｒｂ：高温時の梁の高温ヤング係数比（ただし０＜ｒｂ≦１）
ａ：梁の見掛け上の伸び率
ｂ：線膨張係数（＝１．２×１０−５）
Ｔ：高温時の鋼材温度（℃）
(1b) Calculation method for the amount of extension of the beam If the beam temperature rises to T ° C evenly due to heating during a fire and thermal stress σt is generated, the strain εt of the beam at this time and the appearance of the beam due to thermal expansion The relationship of the following formula is established between the above elongation percentages a.
σt = Etb × εt (1)
a = b × T−εt (2)
Where σt: thermal stress of the beam at high temperature (N / mm 2 )
εt: strain of the beam at high temperature Etb: Young's modulus of the beam at high temperature (= rb × Eb) (N / mm 2 )
Eb: Young's modulus at normal temperature (N / mm 2 )
rb: High temperature Young's modulus ratio of the beam at high temperature (where 0 <rb ≦ 1)
a: Apparent elongation of the beam
b: Linear expansion coefficient (= 1.2 × 10 −5 )
T: Steel material temperature at high temperature (° C)
一方、高温時の梁の材端弾性固定係数（バネ定数）をｋとすると、梁の熱応力σｔは、次式で表される。
σｔ＝ｋ×ｌ／Ａｂ×ａ （３）
ここに、 ｋ：高温時の梁の材端弾性固定係数（バネ定数）（Ｎ／ｍｍ）
Ａｂ：梁の断面積（ｍｍ２）
ｌ：梁の長さ（ｍｍ）
ただし、ｋは、図２に示す火災時変形のモデルを基に式（４）で求める。なお、柱は高温時においても長期荷重に対して十分な軸耐力を有するものとする。
ｋ＝１／（１／ｋｕ＋１／ｋｄ）＝２４×Ｅｃ×Ｉｃ
×｛ｒｃ／（１＋ｒｃ）｝／［（ｈ−ｄｂ）×｛（ｈ−ｄｂ）２
＋１０．４×ｄｃ２｝］ （４）
ここに、ｋｕ：火災階の上階柱（常温）による梁の材端拘束度（Ｎ／ｍｍ）
１／ｋｕ＝（ｈ−ｄｂ）３／（２４×Ｅｃ×Ｉｃ）
＋（ｈ−ｄｂ）／（Ｇｃ×Ａｃ）
＝（ｈ−ｄｂ）×｛（ｈ−ｄｂ）２＋１０．４×ｄｃ２｝
／（２４×Ｅｃ×Ｉｃ）
ｈ：階の高さ（ｍｍ）
ｄｂ：梁のせい（梁の上下フランジの中心間距離）（ｍｍ）
Ｅｃ：常温時の柱のヤング係数（Ｎ／ｍｍ２）
Ｉｃ：柱の断面二次モーメント（＝Ａｃ×ｄｃ２／６）（ｍｍ４）
Ｇｃ：常温時の柱の剪断弾性係数（＝Ｅｃ／２．６）（ｍｍ３）
Ａｃ：柱の断面積（ｍｍ２）
ｄｃ：柱のせい（柱の左右フランジの中心間距離）（ｍｍ）
ｋｄ：火災階の柱（高温）による梁の材端拘束度（Ｎ／ｍｍ）
１／ｋｄ＝（ｈ−ｄｂ）
×｛（ｈ−ｄｂ）２＋１０．４×ｄｃ２｝
／（２４×Ｅｔｃ×Ｉｃ）
Ｅｔｃ：高温時の柱のヤング係数（＝ｒｃ×Ｅｃ）（Ｎ／ｍｍ２）
ｒｃ：高温時の柱の高温ヤング係数比（ただし０＜ｒｃ≦１）
On the other hand, assuming that the material end elastic fixation coefficient (spring constant) of the beam at high temperature is k, the thermal stress σt of the beam is expressed by the following equation.
σt = k × l / Ab × a (3)
Where, k: elastic end modulus of the beam at high temperature (spring constant) (N / mm)
Ab: Cross-sectional area of the beam (mm 2 )
l: Length of beam (mm)
However, k is calculated | required by Formula (4) based on the model of the deformation | transformation at the time of a fire shown in FIG. Note that the column has sufficient axial strength against long-term load even at high temperatures.
k = 1 / (1 / ku + 1 / kd) = 24 × Ec × Ic
× {rc / (1 + rc)} / [(h−db) × {(h−db) 2
+ 10.4 × dc 2 }] (4)
Here, ku: Beam end restraint degree (N / mm) of the upper floor pillar (room temperature) of the fire floor
1 / ku = (h−db) 3 / (24 × Ec × Ic)
+ (H-db) / (Gc × Ac)
= (H-db) × {(h-db) 2 + 10.4 × dc 2 }
/ (24 × Ec × Ic)
h: Floor height (mm)
db: Because of the beam (distance between the centers of the upper and lower flanges of the beam) (mm)
Ec: Young's modulus of the column at normal temperature (N / mm 2 )
Ic: the pillars of the second moment (= Ac × dc 2/6 ) (mm 4)
Gc: Shear elastic modulus of the column at normal temperature (= Ec / 2.6) (mm 3 )
Ac: Column cross-sectional area (mm 2 )
dc: Pillar fault (distance between the centers of the left and right flanges of the pillar) (mm)
kd: Beam end restraint (N / mm) due to pillars (high temperature) on fire floor
1 / kd = (h−db)
× {(h-db) 2 + 10.4 × dc 2 }
/ (24 x Etc x Ic)
Etc: Young's modulus of the column at high temperature (= rc × Ec) (N / mm 2 )
rc: High temperature Young's modulus ratio of the column at high temperature (where 0 <rc ≦ 1)
式（１）に式（２）〜（４）を代入して、火災時の梁の見掛け上の伸び率ａが求まる。
ａ＝ｂ×Ｔ／｛１＋ｋ×（ｌ／Ａｂ）／Ｅｔｂ｝
＝ｂ×Ｔ／（１＋２４×Ｉｃ×ＬＡＢ×ＲＣＢ／ＨＤＣ） （５）
ここに、Ｅｃ／Ｅｄ＝１．０
また、式表現の簡略化のために、次のＬＡＢ、ＲＣＢ、ＨＤＣの符号を用いた。
ＬＡＢ＝ｌ／Ａｂ
ＲＣＢ＝ｒｃ／｛（１＋ｒｃ）×ｒｂ｝
ＨＤＣ＝（ｈ−ｄｂ）×｛（ｈ−ｄｂ）２＋１０．４×ｄｃ２｝
式（５）は、１スパン分であるから、ｎスパンの伸び率ａｎは次のようになる。
ａｎ＝ｂ×Ｔ／（１＋２４×ｎ×Ｉｃ×ＬＡＢ×ＲＣＢ／ＨＤＣ）
ここで、ａｎ：ｎスパンの梁の見掛け上の伸び率である。
ｎ：火災区画の梁のスパン数（ここでは各梁の長さはすべて同一とする。）
よって、火災時の梁の伸び出し量の総和δが、次のように求められる。
δ＝ａｎ×Ｌ
＝ｂ×Ｔ×Ｌ／（１＋２４×ｎ×Ｉｃ×ＬＡＢ×ＲＣＢ／ＨＤＣ） （６）
ここに、Ｌ：火災区画の梁の総延長（＝ｎ×ｌ）（ｍｍ）
By substituting the equations (2) to (4) into the equation (1), the apparent elongation rate a of the beam at the time of fire is obtained.
a = b × T / {1 + k × (l / Ab) / Etb}
= B * T / (1 + 24 * Ic * LAB * RCB / HDC) (5)
Here, Ec / Ed = 1.0
In order to simplify the expression, the following LAB, RCB, and HDC codes were used.
LAB = 1 / Ab
RCB = rc / {(1 + rc) × rb}
HDC = (h−db) × {(h−db) 2 + 10.4 × dc 2 }
Since Equation (5) is for one span, the elongation ratio an of n spans is as follows.
an = b × T / (1 + 24 × n × Ic × LAB × RCB / HDC)
Here, an is the apparent elongation of the n-span beam.
n: Number of spans of the fire compartment beams (here, the length of each beam is the same)
Therefore, the sum δ of the amount of extension of the beam at the time of a fire is obtained as follows.
δ = a n × L
= B * T * L / (1 + 24 * n * Ic * LAB * RCB / HDC) (6)
Where L: total extension of the fire compartment beam (= n × l) (mm)
例えば、柱、梁ともに従来鋼を用いた場合、柱：□−４００×１９、梁：Ｈ−６００×２００×１１×１７、階の高さ（ｈ）：４ｍ、各梁の長さ（ｌ）１２ｍ、火災区画の加熱梁の総延長（Ｌ）：２４ｍとすれば、ｄ＝３８．１ｃｍ、ｄｂ：５８．３ｃｍ、Ａｂ＝１３１．７ｃｍ２、Ｉｃ＝６６，６００ｃｍ４、ＬＡＢ＝９．１１／ｃｍ、ＨＤＣ＝４５，１００，０００ｃｍ３であり、５５０℃でｒｃ＝ｒｂ＝０．３２５（表１参照）であるから、ＲＣＢ＝０．７５となる。
よって、温度（Ｔ）が５５０℃の時点で梁の伸び出し量の総和δは、δ＝１０．６ｃｍとなり柱部材角１／５０（δ＝８．０ｃｍ）を大きく超えてしまう。
ちなみに、柱に高温強度および高温ヤング係数の高い鋼材、梁に従来鋼を用いた場合は、同じ５５０℃でｒｃ＝０．８３５、ｒｂ＝０．３２５（表１参照）であるから、ＲＣＢ＝１．４となる。この結果、梁の伸び出し量の総和δは、δ＝８．３ｃｍとなり柱部材角１／５０を僅かに超える程度となる。
For example, when conventional steel is used for both columns and beams, columns: □ -400 × 19, beams: H-600 × 200 × 11 × 17, floor height (h): 4 m, length of each beam (l ) Total length of heated beams in fire compartment (L): 24 m, d = 38.1 cm, db: 58.3 cm, Ab = 131.7 cm 2 , Ic = 66,600 cm 4 , LAB = 9. Since 11 / cm, HDC = 45,100,000 cm 3 and rc = rb = 0.325 (see Table 1) at 550 ° C., RCB = 0.75.
Therefore, when the temperature (T) is 550 ° C., the total extension δ of the beams is δ = 10.6 cm, which greatly exceeds the column member angle 1/50 (δ = 8.0 cm).
By the way, when steel material with high strength and high temperature Young's modulus is used for the column and conventional steel is used for the beam, rc = 0.835 and rb = 0.325 (see Table 1) at the same 550 ° C. Therefore, RCB = 1.4. As a result, the total sum δ of the extending amount of the beam is δ = 8.3 cm, which is slightly over the column member angle 1/50.
これらのことは、以下のように説明できる。
式（６）の分子は、梁の自由膨張による伸び出し量を示す一方、分母は、１＋０．６４６×ＲＣＢとなる。このとき、次の２通りに分けて考える。
（ｉ）高温時にｒｃ＝ｒｂの場合（高温時に柱と梁のヤング係数が同じ場合）
ＲＣＢ＝１／（１＋ｒｃ）となり、０＜ｒｃ≦１であることから、０．５≦ＲＣＢ＜１．０となる。よって式（６）の分母は、１．３３≦分母＜１．６５となるため、梁の伸び出し量の総和δは、梁が自由膨張した場合の０．６１〜０．７５倍程度の低減（最大でも６割程度の低減）に留まる。
（ｉｉ）高温時にｒｃ＞ｒｂの場合（高温時に柱より常に梁のヤング係数が低い場合）
ＲＣＢ＝｛１／（１＋ｒｃ）｝／（ｒｂ／ｒｃ）となり、上記（ｉ）の場合をさらに、ｒｂ／ｒｃで除している点が異なる。このｒｂとｒｃとの比（ｒｂ／ｒｃ）は、一般に数％程度になると無視できるほど小さい値であると見なせることから、本発明ではこの判断境界を５％未満に設定することとする。そこで、高温時において、ｒｂ／ｒｃ＜０．０５となる温度域が存在する（ある温度を境界にして、ｒｂ／ｒｃ≧０．０５からｒｂ／ｒｃ＜０．０５へ切り替わる）とすれば、上記（ｉ）より０．５≦１／（１＋ｒｃ）＜１．０であることから、１０．０＜ＲＣＢ＜２０．０となる。よって式（６）の分母は、７．４６＜分母＜１３．９となるため、梁の伸び出し量の総和δは、梁が自由膨張した場合の０．０７〜０．１３倍程度（１割程度）まで低減されることになる。
このことは、柱を６００〜８００℃での高温強度および高温ヤング係数が高い鋼材で形成し、この柱と接合する梁を、柱形成用の鋼材より常に高温強度および高温ヤング係数の低い鋼材、ここでは６００〜８００℃の範囲でｒｂ／ｒｃ＜０．０５となる温度域を有する（６００〜８００℃の範囲のある温度を境界にして、ｒｂ／ｒｃ≧０．０５からｒｂ／ｒｃ＜０．０５へ切り替わる）鋼材で形成することにより、火災時の梁の伸び出し量が、梁が自由膨張した場合の１割程度まで低減できることを示している。
These can be explained as follows.
The numerator of equation (6) indicates the amount of extension due to free expansion of the beam, while the denominator is 1 + 0.646 × RCB. At this time, the following two methods are considered.
(I) When rc = rb at high temperature (when the Young's modulus of the column and beam is the same at high temperature)
RCB = 1 / (1 + rc). Since 0 <rc ≦ 1, 0.5 ≦ RCB <1.0. Therefore, since the denominator of the equation (6) is 1.33 ≦ denominator <1.65, the total δ of the extension amount of the beam is reduced by about 0.61 to 0.75 times when the beam is freely expanded. (Reduction of about 60% at the maximum).
(Ii) When rc> rb at a high temperature (when the Young's modulus of the beam is always lower than the column at a high temperature)
RCB = {1 / (1 + rc)} / (rb / rc), which is different in that the case (i) is further divided by rb / rc. Since the ratio of rb to rc (rb / rc) is generally considered to be negligibly small when it is about several percent, in the present invention, this judgment boundary is set to less than 5%. Therefore, if there is a temperature range where rb / rc <0.05 at high temperatures (switching from rb / rc ≧ 0.05 to rb / rc <0.05 with a certain temperature as a boundary), From the above (i), since 0.5 ≦ 1 / (1 + rc) <1.0, 10.0 <RCB <20.0. Therefore, since the denominator of the formula (6) is 7.46 <denominator <13.9, the total sum δ of the extension amount of the beam is about 0.07 to 0.13 times (1 Will be reduced to about 10%).
This means that a column is formed of a steel material having a high temperature strength at 600 to 800 ° C. and a high temperature Young's modulus, and a beam to be joined to the column is always a steel material having a low temperature strength and a high temperature Young's modulus lower than the steel material for column formation, Here, it has a temperature range where rb / rc <0.05 in the range of 600 to 800 ° C. (with a certain temperature in the range of 600 to 800 ° C. as a boundary, rb / rc ≧ 0.05 to rb / rc <0. It is shown that the extension amount of the beam at the time of fire can be reduced to about 10% when the beam expands freely.
［２．合成梁による梁の伸び出し量の考え方］
梁を合成梁とした場合、床スラブのコンクリートの熱容量により、コンクリートの上昇温度は鉄骨梁より小さくなり、梁の伸び出し量は前述した場合より低減される。文献「ＦＲ鋼の耐熱性能とこれを用いた合成梁の耐火性能」（窪田伸ほか：日本建築学会大会学術講演梗概集、１９９９．９、ｐｐ．４３〜４６）より転載した、合成梁試験体の梁温度と床スラブ上面（スラブ裏面）温度の例を図３（ａ）に示す。図３（ｂ）は、ここで用いた合成梁試験体と加熱実験装置例を示すものである。図３（ａ）に示すように、梁（ここではＨ−４００×２００×８×１３）の下フランジおよびウエブの温度が約６００℃の場合でも床スラブ上面は約５０℃に留まっている。
[2. Concept of beam extension by composite beams]
When the beam is a composite beam, due to the heat capacity of the concrete of the floor slab, the temperature of the concrete rises lower than that of the steel beam, and the extension amount of the beam is reduced as compared with the case described above. Composite beam specimens reprinted from the document "Heat resistance performance of FR steel and fire resistance performance of composite beams using this steel" (Nobu Kubota et al .: Summary of Annual Conference of Architectural Institute of Japan, 19999.9, pp. 43-46) FIG. 3A shows an example of the beam temperature and the floor slab upper surface (slab back surface) temperature. FIG. 3B shows an example of a composite beam test body and a heating experimental apparatus used here. As shown in FIG. 3A, even when the temperature of the lower flange of the beam (here, H-400 × 200 × 8 × 13) and the web is about 600 ° C., the upper surface of the floor slab remains at about 50 ° C.
また、一般に梁では全断面一様の温度上昇を仮定するが、合成梁の場合、床スラブの熱容量のため、梁の下フランジから上フランジにかけて、梁断面の高さ方向に温度勾配が生じる。このため、梁に全断面一様の鋼材温度を仮定した場合に比べて、実際の梁の鋼材温度（平均値）は低くなり、梁の伸び出し量は前述した場合よりさらに低減される。
図３（ａ）から、載荷開始時の梁の最高温度は、ウエブおよび下フランジの約６００℃であるが、上フランジが約４５０℃のため、その平均値は約５５０℃となっており、最高温度から約１０％低くなっていることが分かる。
梁断面の高さ方向での温度勾配を考慮した場合、梁には熱たわみが生じるため、梁端部には、この熱たわみを拘束する曲げモーメントが生じ、これより梁端部は温度勾配を配慮しない場合に比べ早期に塑性化（局部座屈発生）する。このため、梁のたわみは大きくなり、同時に柱が受ける梁からの押し出し量は小さくなる。
In general, the beam is assumed to have a uniform temperature rise in the entire cross section, but in the case of a composite beam, due to the heat capacity of the floor slab, a temperature gradient occurs in the height direction of the beam cross section from the lower flange to the upper flange of the beam. For this reason, the steel material temperature (average value) of the actual beam is lower and the amount of extension of the beam is further reduced as compared with the case described above, compared to the case where the steel material temperature is assumed to be uniform throughout the beam.
From Fig. 3 (a), the maximum temperature of the beam at the start of loading is about 600 ° C for the web and the lower flange, but the upper flange is about 450 ° C, so the average value is about 550 ° C, It can be seen that the temperature is about 10% lower than the maximum temperature.
When considering the temperature gradient in the height direction of the beam cross section, the beam is subject to thermal deflection. Therefore, a bending moment constraining this thermal deflection is generated at the beam end, which causes the beam end to have a temperature gradient. Plasticization (local buckling) occurs earlier than when no consideration is given. For this reason, the deflection of the beam increases, and at the same time, the amount of extrusion from the beam received by the column decreases.
図４に、梁端部の座屈発生時の変形を示す。この図から局部座屈発生の結果、梁の伸び出し量は減少することが分かる。さらに梁温度が上昇すると、梁は大きく柱にぶら下がるような状態になり、一度外側に大きく押し出された柱は逆に内側に引き戻される。その後、温度を上昇させると、最終的に荷重を支えきれなくなり崩壊（３ヒンジ状態）に至る。図５に３ヒンジ形成時の変形を示す。この図から梁の伸び出し量がさらに減少することが分かる。 FIG. 4 shows deformation at the time of occurrence of buckling of the beam end. From this figure, it can be seen that the amount of extension of the beam decreases as a result of the occurrence of local buckling. When the beam temperature further rises, the beam is greatly hung from the column, and the column that has been greatly pushed outward is pulled back inward. Thereafter, when the temperature is raised, the load cannot be finally supported and collapse (three-hinge state) is reached. FIG. 5 shows the deformation when the three hinges are formed. From this figure, it can be seen that the amount of extension of the beam is further reduced.
本発明で柱形成用として適性が高いものとする６００〜８００℃での高温強度および高温ヤング係数が高い鋼材の一例として準備した０．０２％Ｃ−０．１％Ｓｉ−０．４％Ｍｎ−０．００４％Ｐ−０．００４％Ｓ−０．０１％Ａｌ−１．１％Ｍｏ−０．０５％Ｎｂ−０．０１％Ｔｉ−０．００１％Ｂ−０．００４％Ｎ、残部Ｆｅおよび不可避的不純物からなる鋼材に関して、ｐ（高温降伏強度／常温降伏強度）およびｒ（高温ヤング係数／常温ヤング係数）の測定例を図６、７に示す。なお、高温降伏強度はＪＩＳ Ｇ ０５６７−１９９８「金属材料および耐熱合金の高温引張試験方法」に、高温ヤング係数はＪＩＳ
Ｚ ２２８０−１９９３「金属材料の高温ヤング率試験方法」の押し当て式変位法によっている。
0.02% C-0.1% Si-0.4% Mn prepared as an example of a steel material having a high temperature strength at 600 to 800 ° C. and a high high temperature Young's modulus, which is highly suitable for column formation in the present invention. -0.004% P-0.004% S-0.01% Al-1.1% Mo-0.05% Nb-0.01% Ti-0.001% B-0.004% N, balance 6 and 7 show measurement examples of p (high temperature yield strength / room temperature yield strength) and r (high temperature Young's modulus / room temperature Young's modulus) regarding a steel material composed of Fe and inevitable impurities. The high-temperature yield strength is JIS G 0567-1998 “High-temperature tensile test method for metal materials and heat-resistant alloys”, and the high-temperature Young's modulus is JIS
Z 2280-1993 “Testing method for high-temperature Young's modulus of metal material” by the pressing displacement method.
図６より、本発明に適合する柱形成用鋼（図中●印）は、常温と高温の降伏強度比（ｐ）が、鋼材温度Ｔ（℃）が６００℃以上８００℃以下の範囲で、ｐ≧−０．００２９×Ｔ＋２．４８を満足している。一方、ユーロコード３（１９９３）に示される一般鋼（図中○印）は、同様にｐ≧−０．００１４×Ｔ＋１．０を満足しており、本発明に適合する柱形成用鋼は一般鋼より格段に高温降伏強度比が緩やかとなっていることが分かる。
図７より、本発明に適合する柱形成用鋼（図中●印）は、常温と高温のヤング係数比（ｒ）が、鋼材温度Ｔ（℃）が６００℃以上８００℃以下の範囲で、ｒ≧−０．００１７×Ｔ＋１．７７を満足している。一方、ユーロコード３（１９９３）に示される一般鋼（図中○印）は、同様にｒ≧−０．００１５×Ｔ＋１．１５を満足しており、本発明に適合する柱形成用鋼は一般鋼より格段に高温ヤング係数比が緩やかとなっていることが分かる。
以上のことは、本発明で柱形成用として適性が高いものとする鋼材が、高温強度が高く、かつ高温ヤング係数も高く、柱材として用いた場合に、火災時の梁の伸び出し量を低減し無耐火被覆構造とできることを示している。
From FIG. 6, the column forming steel suitable for the present invention (marked with ● in the figure) has a yield strength ratio (p) between normal temperature and high temperature, and the steel material temperature T (° C.) is in the range of 600 ° C. or higher and 800 ° C. or lower. p ≧ −0.0029 × T + 2.48 is satisfied. On the other hand, the general steel shown in Eurocode 3 (1993) (marked with a circle in the figure) similarly satisfies p ≧ −0.0014 × T + 1.0, and the column forming steel suitable for the present invention is general. It can be seen that the high-temperature yield strength ratio is much gentler than that of steel.
From FIG. 7, the column forming steel suitable for the present invention (marked with ● in the figure) has a Young's modulus ratio (r) between room temperature and high temperature, and the steel material temperature T (° C.) is in the range of 600 ° C. to 800 ° C. r ≧ −0.0017 × T + 1.77 is satisfied. On the other hand, the general steel shown in Eurocode 3 (1993) (marked with a circle in the figure) similarly satisfies r ≧ −0.0015 × T + 1.15, and the column forming steel suitable for the present invention is generally used. It can be seen that the high temperature Young's modulus ratio is much slower than steel.
The above is a steel material that has high suitability for column formation in the present invention, has a high temperature strength and a high temperature Young's modulus. It shows that it can be reduced and a fireproof coating structure can be obtained.
実施例１で示したような本発明で柱形成用として適性が高いものとする６００〜８００℃での高温強度および高温ヤング係数が高い鋼材と従来鋼を、柱、梁に用いた場合について、式（６）に基づく梁の伸び出し量δと鋼材温度（Ｔ℃）との関係を図８に示す。なお、ここでは、高温時の柱の高温降伏強度比ｐが０．２に達した時点で軸耐力の保持能力を喪失したとして計算をストップしている。
表１に、本発明例および比較例１、２で、柱と梁に使用した鋼材の高温降伏強度比ｐおよび高温ヤング係数比ｒを示す。なお、従来鋼のｐ、ｒは、ユーロコード３（１９９３）を参照して設定している。
About the case where the steel and the conventional steel having a high temperature strength at 600 to 800 ° C. and a high temperature Young's modulus, which are highly suitable for forming a column in the present invention as shown in Example 1, are used for columns and beams, FIG. 8 shows the relationship between the extension amount δ of the beam based on the formula (6) and the steel material temperature (T ° C.). Here, the calculation is stopped assuming that the holding capacity of the axial strength is lost when the high temperature yield strength ratio p of the column at high temperature reaches 0.2.
Table 1 shows the high temperature yield strength ratio p and the high temperature Young's modulus ratio r of the steel materials used for the columns and beams in the present invention example and Comparative Examples 1 and 2. In addition, p and r of conventional steel are set with reference to Eurocode 3 (1993).
図８は、柱：□−４００×１９、梁：Ｈ−６００×２００×１１×１７、階の高さ（ｈ）：４ｍ、各梁の長さ（ｌ）：１２ｍ、火災区画の加熱梁の総延長（Ｌ）：３６ｍの場合の鋼材温度と梁の伸び出し量δの関係を示すものである。図８より、柱、梁ともに従来鋼で形成した比較例１、柱、梁ともに６００〜８００℃での高温強度および高温ヤング係数が高い鋼材で形成した比較例２の場合いずれも、鋼材温度（Ｔ℃）が上昇するにつれて梁の伸び出し量δが増大して、温度が約３００℃で柱部材角が１／５０を、約５００℃で柱部材角が１／３０を超えることが分かる。 FIG. 8 shows a column: □ -400 × 19, a beam: H-600 × 200 × 11 × 17, a floor height (h): 4 m, a length (l) of each beam: 12 m, and a heating beam in a fire section. Total length (L): The relationship between the steel material temperature and the amount of extension δ of the beam in the case of 36 m. From FIG. 8, in both Comparative Example 1 in which both the column and the beam are made of conventional steel, and in Comparative Example 2 in which both the column and the beam are made of steel having a high temperature strength at 600 to 800 ° C. and a high temperature Young's modulus, It can be seen that the amount of extension δ of the beam increases as T ° increases, and that the column member angle exceeds 1/50 at a temperature of about 300 ° C. and the column member angle exceeds 1/30 at about 500 ° C.
一方、柱を６００〜８００℃での高温強度および高温ヤング係数が高い鋼材で形成し梁を従来鋼で形成した本発明例は、鋼材温度の上昇につれて梁の伸び出し量δが増大して、一旦、柱部材角が１／５０を超えるものの、５００℃でピークを迎えた後、梁の剛性低下が顕著になって梁の伸び出し量δが急激に減少して、最終的に柱部材角がほぼゼロとなることが分かる。
このことは、柱を６００〜８００℃での高温強度および高温ヤング係数が高い鋼材で形成し、火災時による高温に対して無耐火被覆構造を可能にするとともに、梁を柱形成鋼より高温強度および高温ヤング係数が低い鋼材で形成し、火災時の梁の伸び出しによる柱の強制変形を抑制することによって、柱部材角を最終的に１／５０以下に抑制することができ、火災時の層崩壊を防止できることを示している。
On the other hand, in the present invention example in which the column is formed of a steel material having a high temperature strength at 600 to 800 ° C. and a high temperature Young's modulus and the beam is formed of conventional steel, the amount of extension δ of the beam increases as the steel material temperature increases, Once the column member angle exceeds 1/50, after reaching a peak at 500 ° C., the beam stiffness decreases significantly, and the beam extension δ decreases sharply. Is almost zero.
This means that the column is made of steel material having a high temperature strength at 600 to 800 ° C. and a high temperature Young's modulus, making it possible to have a fireproof coating structure against the high temperature caused by a fire, and the beam has a higher strength than the column forming steel. In addition, by forming the steel material with a low high temperature Young's modulus and suppressing the forced deformation of the column due to the extension of the beam at the time of fire, the column member angle can be finally suppressed to 1/50 or less, and at the time of fire It shows that layer collapse can be prevented.
Claims (3)
該鉄骨構造物を構成する無耐火被覆の柱を、常温時の降伏強度により高温時の降伏強度を無次元化した高温降伏強度比ｐ（高温降伏強度／常温降伏強度）が、鋼材温度Ｔ（℃）が６００℃以上８００℃以下の範囲で、
ｐ≧−０．００２９×Ｔ＋２．４８
を満足し、かつ、常温時のヤング係数により高温時のヤング係数を無次元化した高温ヤング係数比ｒ（高温ヤング係数／常温ヤング係数）が、鋼材温度Ｔ（℃）が６００℃以上８００℃以下の範囲で、
ｒ≧−０．００１７×Ｔ＋１．７７
を満足する、高温強度および高温ヤング係数が高い鋼材で形成し、
該柱と接合する梁を、該柱形成用の鋼材の高温強度および高温ヤング係数未満の従来鋼材で形成したことを特徴とする、無耐火被覆鉄骨構造物。 A steel structure that has a fire-resistant coating on a steel member that is exposed to high temperatures in the event of a fire,
The high-temperature yield strength ratio p (high-temperature yield strength / room-temperature yield strength) obtained by making the yield strength at high temperatures dimensionless by the yield strength at room temperature is the steel material temperature T ( In the range of 600 ° C. or higher and 800 ° C. or lower,
p ≧ −0.0029 × T + 2.48
And the high temperature Young's modulus ratio r (high temperature Young's modulus / normal temperature Young's modulus) obtained by making the Young's modulus at high temperatures dimensionless by the Young's modulus at normal temperature has a steel material temperature T (° C) of 600 ° C to 800 ° C. In the following range:
r ≧ −0.0017 × T + 1.77
Which is made of steel with high temperature strength and high temperature Young's modulus,
A fire-resistant coated steel structure characterized in that a beam to be joined to the column is formed of a conventional steel material having a high-temperature strength and a high-temperature Young's modulus of the steel material for forming the column.
ｒｂ／ｒｃ＜０．０５
を満足することを特徴とする、請求項１に記載の無耐火被覆鉄骨構造物。 Hot Young's modulus ratio of the beam and rb, range these ratios rb / rc is steel temperature T (° C.) of 600 ° C. or higher 800 ° C. or less at the time of the high-temperature Young's modulus ratio of said post and rc, there With temperature as the boundary,
rb / rc <0.05
The fireproof coated steel structure according to claim 1, wherein:
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