JP5574330B2 - Seismic isolation structure - Google Patents
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Description
本発明は建物等の構造物を対象とする免震構造、特に既存の免震構造建物に対して応答低減機構を付加することによって地震時の応答変位を大幅に低減させ得る免震構造に関する。 The present invention relates to a seismic isolation structure intended for a structure such as a building, and more particularly to a seismic isolation structure that can significantly reduce response displacement during an earthquake by adding a response reduction mechanism to an existing base isolation structure.
周知のように免震構造は1980年代から案件適用が始まり、1995年の阪神大震災の後に普及した構法である。一方、地震動については1990年代後半から長周期地震動に対する検討が行われるようになったものの、それ以前には観測波と建設地での模擬波だけで設計されることが多かった。
免震構造は長周期化と減衰の付与によって地震時の応答低減を図るものであるので、従来の設計用地震力のように短周期成分が卓越していて長周期化していくと入力が小さくなる場合には問題ないが、長周期地震動のように長周期化しても入力が低下しない場合には大きな変位が生じる可能性がある。
そのため、2000年以前に建設された免震建物では、設計当時の想定を超えた長周期地震動により応答変位が免震クリアランス（地盤に一体化された擁壁等と免震構造体との間の隙間）に納まらずに躯体が擁壁に衝突してしまうことも想定され、そのような既存の免震建物に長周期地震動が作用しても過大な応答変位が生じないようにするための対策が求められている。
As is well known, the seismic isolation structure has been applied since the 1980s, and has become popular since the 1995 Great Hanshin Earthquake. On the other hand, with regard to ground motion, long-period ground motion has been studied since the latter half of the 1990s, but before that, it was often designed with only observation waves and simulated waves at construction sites.
Since the seismic isolation structure is designed to reduce the response during an earthquake by increasing the period and damping, the input becomes smaller as the period increases and the period increases, as in the conventional design seismic force. However, there is a possibility that a large displacement occurs if the input does not decrease even if the period is increased as in the case of long-period ground motion.
For this reason, in seismic isolation buildings constructed before 2000, the response displacement due to long-period ground motion exceeding the assumptions at the time of design is reduced by the seismic isolation clearance (between the retaining wall integrated into the ground and the seismic isolation structure). Measures to prevent excessive response displacement from occurring even if long-period ground motions act on such existing base-isolated buildings, where it is assumed that the housing will collide with the retaining wall without being within the gap. Is required.
免震構造において変位を抑制するための対策としては、以下の手法が知られている。
（ａ）免震層のバネ剛性を増大する。
この手法では応答変位は小さくなるが、短周期化してしまい免震効果が大幅に低下（応答加速度が大幅に増大）してしまい、有効ではない。
（ｂ）免震層に減衰を付加する。
免震層にオイルダンパー等の減衰装置を付加することで短周期化せずに応答変位を低減できるが、応答加速度が増大するデメリットがある。また、高振動数域（短周期領域）では応答変位がほぼ地動変位となることから、加速度の増大を抑制しながら大幅に変位を低減することは難しい。
The following methods are known as measures for suppressing displacement in a base-isolated structure.
(A) Increase the spring stiffness of the seismic isolation layer.
Although this method reduces the response displacement, it shortens the cycle and significantly reduces the seismic isolation effect (response acceleration increases significantly), which is not effective.
(B) Add attenuation to the seismic isolation layer.
By adding a damping device such as an oil damper to the seismic isolation layer, the response displacement can be reduced without shortening the period, but there is a demerit that the response acceleration increases. In addition, since the response displacement is almost a ground motion displacement in the high frequency range (short cycle range), it is difficult to significantly reduce the displacement while suppressing an increase in acceleration.
（ｃ）免震層に慣性質量ダンパーを付加する。
図１１に示すモデルのように、構造体バネ２と構造体減衰３により免震支持されている質量mの構造体（既存免震建物）１に対し、免震層の水平剛性（すなわち構造体バネ２のバネ剛性k1）と並列に慣性質量ダンパー４による慣性質量ψ1を付与することにより、長周期化しつつ応答変位を低減できる。
しかし、高振動数域において応答変位はm/(m+ψ1)倍に低減されるものの、応答加速度はψ1/(m+ψ1)倍までしか低減されず、高振動数域においては慣性質量ダンパーを設置することで応答加速度が増大するという問題がある。
(C) An inertia mass damper is added to the seismic isolation layer.
As in the model shown in FIG. 11, the horizontal stiffness of the seismic isolation layer (that is, the structural body) with respect to the structural body (existing base-isolated building) 1 having a mass m supported by the structural spring 2 and the structural damping 3. By providing the inertial mass ψ 1 by the inertial mass damper 4 in parallel with the spring stiffness k 1 ) of the spring 2, the response displacement can be reduced while increasing the period.
However, although the response displacement is reduced by m / (m + ψ 1 ) times in the high frequency range, the response acceleration is reduced only to ψ 1 / (m + ψ 1 ) times, and in the high frequency range, There is a problem that the response acceleration is increased by installing the inertia mass damper.
（ｄ）免震層に慣性質量ダンパーと付加バネを直列に接続した応答低減機構を付加する。
図１２に示すモデルのように、特許文献１に開示されているような応答低減機構、すなわち慣性質量ダンパー４と付加バネ５とを直列に接続した応答低減機構を免震層の水平剛性と並列に設置する。この場合、慣性質量ダンパー４には第１の付加減衰６（図では付加減衰１と記している）を並列に接続するか、あるいは慣性質量ダンパー４として第１の付加減衰６を並列に組み込んだものを用いる。また、付加バネ５には第２の付加減衰７（同、付加減衰２）を並列に接続する。なお、第１の付加減衰６あるいは第２の付加減衰７のいずれかを省略する場合もある。
そして、その応答低減機構の固有周期T’を、慣性質量ダンパー４による慣性質量ψ2と付加バネ５のバネ剛性k2に基づいて図中に示すような関係に設定して構造体１の固有周期と同調させることにより、共振時の応答を大幅に改善することが可能である。
(D) A response reduction mechanism in which an inertia mass damper and an additional spring are connected in series is added to the seismic isolation layer.
As in the model shown in FIG. 12, the response reduction mechanism disclosed in Patent Document 1, that is, the response reduction mechanism in which the inertia mass damper 4 and the additional spring 5 are connected in series is parallel to the horizontal rigidity of the seismic isolation layer. Install in. In this case, a first additional attenuation 6 (denoted as additional attenuation 1 in the figure) is connected in parallel to the inertial mass damper 4, or the first additional attenuation 6 is incorporated in parallel as the inertial mass damper 4. Use things. The additional spring 5 is connected in parallel with a second additional attenuation 7 (the same additional attenuation 2). In some cases, either the first additional attenuation 6 or the second additional attenuation 7 is omitted.
Then, the natural period T ′ of the response reduction mechanism is set to a relationship as shown in the drawing based on the inertia mass ψ 2 of the inertia mass damper 4 and the spring stiffness k 2 of the additional spring 5, so By tuning with the period, the response at resonance can be greatly improved.
上記（ｄ）に示した応答低減機構によれば、第２の付加減衰７が比較的小さくても、同調により当該部の変位が拡大して大きなエネルギー吸収を図れる特徴があるが、第２の付加減衰７の変位が大きくなるためストロークの大きな減衰装置が必要となり、その第２の付加減衰としてストロークが500〜600mmもの大ストロークの免震用オイルダンパーを用いなければならず、その点では改善の余地を残している。 According to the response reduction mechanism shown in (d) above, even if the second additional attenuation 7 is relatively small, there is a feature that the displacement of the part can be enlarged by tuning and large energy absorption can be achieved. Since the displacement of the additional damping 7 is large, a damping device with a large stroke is required, and as a second additional damping, a large stroke seismic isolation oil damper with a stroke of 500 to 600 mm must be used, which is an improvement. Leaving room for.
上記事情に鑑み、本発明は上記従来の応答低減機構をさらに改良して、変位を抑制しつつ免震効果を充分に発揮し得る有効適切な免震構造を提供することを目的とする。 In view of the above circumstances, an object of the present invention is to further improve the conventional response reduction mechanism and provide an effective and appropriate seismic isolation structure that can sufficiently exhibit the seismic isolation effect while suppressing displacement.
本発明は、構造体を構造体バネと構造体減衰を介して固定端に接続するとともに、前記構造体の地震動入力に対する応答変位を低減させるための応答低減機構を前記構造体バネと並列に設置してなる免震構造であって、前記応答低減機構を、慣性質量ダンパーと、該慣性質量ダンパーに対して直列に接続した付加減衰と、該付加減衰に対して並列に接続した復元バネとにより構成し、前記復元バネのバネ剛性k2、および前記付加減衰の減衰係数Cd2を、前記構造体バネのバネ剛性k1、前記構造体の質量m、前記慣性質量ダンパーの慣性質量ψ2に基づき、次の関係を満足するように設定してなることを特徴とする。 In the present invention, the structure is connected to the fixed end via the structure spring and the structure damping, and a response reduction mechanism for reducing the response displacement of the structure to the seismic motion input is installed in parallel with the structure spring. The response reducing mechanism includes an inertial mass damper, an additional damping connected in series to the inertial mass damper, and a restoring spring connected in parallel to the additional damping. The spring stiffness k 2 of the restoring spring and the damping coefficient C d2 of the additional damping are set to the spring stiffness k 1 of the structure spring, the mass m of the structure, and the inertia mass ψ 2 of the inertia mass damper. Based on this, the following relationship is set.
なお、本発明では前記付加減衰にリリーフ機構を付加することが好ましい。また、付加減衰にリリーフ機構を付加することに代えて、もしくはそれに加えて、前記慣性質量ダンパーに過負荷防止機構を付加することも好ましい。 In the present invention, it is preferable to add a relief mechanism to the additional attenuation. It is also preferable to add an overload prevention mechanism to the inertial mass damper instead of or in addition to adding a relief mechanism to the additional damping.
本発明によれば、固定端に対して免震支持される構造体に対して、慣性質量ダンパーと付加減衰と復元バネとによる応答低減機構を設置し、復元バネおよび付加減衰の諸元を適正に設定することにより、構造体の加速度を制御しつつ変位を大幅に低減することができる。
特に、本発明によれば、長周期地震動のように長周期成分が卓越する場合でも免震層の過大な変位が防止され、したがって過去の基準により設計された既存免震建物に対して本発明の応答低減機構を付加することで、設計当時の想定を超える長周期地震動による応答変位を免震クリアランスの範囲に納まるように低減させることができ、躯体が擁壁に衝突してしまうといった事態を未然に防止することができる。
According to the present invention, a response reduction mechanism using an inertial mass damper, additional damping, and a restoring spring is installed on a structure that is seismically isolated from the fixed end, and the specifications of the restoring spring and the additional damping are set appropriately. By setting to, the displacement can be greatly reduced while controlling the acceleration of the structure.
In particular, according to the present invention, excessive displacement of the seismic isolation layer is prevented even when long-period components are dominant, such as long-period ground motion, and therefore the present invention is applied to existing base-isolated buildings designed according to past standards. By adding the response reduction mechanism, it is possible to reduce the response displacement due to long-period ground motion exceeding the assumption at the time of design so that it falls within the range of the seismic isolation clearance, and the case where the frame collides with the retaining wall. It can be prevented in advance.
図１は本発明の免震構造の実施形態をモデルとして示すものである。これは（ａ）に示すような既存の免震建物に対して（ｂ）に示すように応答低減機構を付加することで構造体の応答変位を大きく抑制するようにしたものである。なお、上述した従来の免震構造と共通する要素については同一符号を付してある。
本実施形態の応答低減機構は、慣性質量ダンパー４と直列に主たる減衰要素としての付加減衰７（以下ではこれを上述の応答低減機構の場合と同様に第２の付加減衰７という。但し図１では付加減衰２と記す）を接続し、その第２の付加減衰７と並列に復元バネ５’を接続した構成としている。
慣性質量ダンパー４には第１の付加減衰６（図１では付加減衰１）を並列に接続するか、あるいは慣性質量ダンパー４として第１の付加減衰６を並列に組み込んだものを用いれば良いが、この第１の付加減衰６の効果は小さいので省略することも可能であり、その場合は、慣性質量ダンパー４と第２の付加減衰７と復元バネ５’とにより応答低減機構が構成されることになる。
FIG. 1 shows an embodiment of the seismic isolation structure of the present invention as a model. This is to largely suppress the response displacement of the structure by adding a response reduction mechanism as shown in (b) to the existing base-isolated building as shown in (a). In addition, the same code | symbol is attached | subjected about the element which is common in the conventional seismic isolation structure mentioned above.
The response reduction mechanism of the present embodiment is an additional attenuation 7 as a main attenuation element in series with the inertial mass damper 4 (hereinafter, this is referred to as a second additional attenuation 7 as in the case of the above-described response reduction mechanism. However, FIG. In this case, the additional spring 2 'is connected, and a restoring spring 5' is connected in parallel with the second additional damper 7.
The inertial mass damper 4 may be connected to the first additional attenuation 6 (additional attenuation 1 in FIG. 1) in parallel, or the inertial mass damper 4 incorporating the first additional attenuation 6 in parallel may be used. The effect of the first additional damping 6 is small and can be omitted. In this case, the inertia mass damper 4, the second additional damping 7, and the restoring spring 5 'constitute a response reducing mechanism. It will be.
本発明における上記の応答低減機構は、図１２に示した従来の応答低減機構と同様に、慣性質量ダンパー４と第２の付加減衰７を直列に接続した応答低減機構を免震層の剛性（構造体バネk1）と並列に付加するものであるが、従来のものが慣性質量ψ2と付加バネ５のバネ剛性k2とによる同調機構であるのに対し、本発明ではそのような同調を行うものではなく、従来における同調用の付加バネ５に代えて残留変形を防止するための単なる復元バネ５’を設置するに留めており、したがってその復元バネ５’のバネ剛性k2は次式により従来における付加バネ５のバネ剛性k2に比較して充分に小さく設定することができる。
そして本発明では、復元バネ５’のバネ剛性k2を、構造体バネ２のバネ剛性k1、構造体１の質量m、慣性質量ダンパー４の慣性質量ψ2に基づき、次の関係を満足するように設定する。
The response reduction mechanism of the present invention is similar to the conventional response reduction mechanism shown in FIG. 12 except that the response reduction mechanism in which the inertia mass damper 4 and the second additional damping 7 are connected in series is the rigidity of the seismic isolation layer ( Although it is added in parallel to the structure spring k 1 ), the conventional one is a tuning mechanism based on the inertia mass ψ 2 and the spring stiffness k 2 of the additional spring 5, whereas in the present invention, such tuning is performed. not performing, the spring stiffness k 2 'of which bear in installing, hence its restoring spring 5' merely restoring spring 5 to prevent residual deformation instead of adding the spring 5 for tuning in a conventional next According to the equation, the spring stiffness k 2 of the conventional additional spring 5 can be set sufficiently small.
In the present invention, the following relationship is satisfied based on the spring stiffness k 2 of the restoring spring 5 ′ based on the spring stiffness k 1 of the structure spring 2, the mass m of the structure 1 , and the inertia mass ψ 2 of the inertia mass damper 4. Set to
また、本発明においては第２の付加減衰７が慣性質量ダンパー４と直列に配置された主たる減衰要素であり、その第２の付加減衰７の減衰係数Cd2を第１の付加減衰６の減衰係数Cd1よりも充分に大きくし（Cd2≫Cd1）、かつ次式により過減衰（減衰定数hd2>1.0）となるように第２の減衰係数Cd2を充分に大きく設定する必要がある。
すなわち、本発明では第２の付加減衰７の減衰係数Cd2を、構造体バネ２のバネ剛性k1、構造体１の質量m、慣性質量ダンパー４の慣性質量ψ2に基づき、次の関係を満足するように設定する。
In the present invention, the second additional attenuation 7 is a main attenuation element arranged in series with the inertial mass damper 4, and the attenuation coefficient C d2 of the second additional attenuation 7 is set to the attenuation of the first additional attenuation 6. It is necessary to set the second attenuation coefficient C d2 sufficiently large so that it is sufficiently larger than the coefficient C d1 (C d2 >> C d1 ) and over-damping (attenuation constant h d2 > 1.0) according to the following equation: is there.
That is, in the present invention, the damping coefficient C d2 of the second additional damping 7 is based on the spring stiffness k 1 of the structure spring 2, the mass m of the structure 1 , and the inertia mass ψ 2 of the inertia mass damper 4. Set to satisfy.
なお、本発明において使用する慣性質量ダンパー４としては、特許文献１にも開示されているようにたとえばボールねじ機構とフライホイール（回転錘）とを組み合わせたものが好適に採用可能であり、それによれば回転錘の実際の質量の数百倍以上もの大きな質量効果が得られるものである。
そして、本発明では慣性質量ダンパー４に過負荷防止機構を付加することが好ましい。すなわち、たとえば上記のようなボールねじ機構とフライホイールとによる慣性質量ダンパー４の場合には，回転錘をボールねじ機構に対して摩擦材を介して接合することにより回転錘からの伝達トルクを頭打ちにした過負荷防止機構（フェールセーフ機構）とすることができ、それにより慣性質量ダンパー４が所望の相対加速度α以上で摩擦材が滑ってトルクを頭打ちとすることができる。
この場合、構造体１の質量mに対する慣性質量ψ2の比が大きいほど変位抑制効果があるが、その比が過度に大きいと加速度が増加するので、次式の範囲で設定することが好ましい。
As the inertia mass damper 4 used in the present invention, as disclosed in Patent Document 1, for example, a combination of a ball screw mechanism and a flywheel (rotating weight) can be suitably employed. According to this, a large mass effect of several hundred times or more the actual mass of the rotary weight can be obtained.
In the present invention, it is preferable to add an overload prevention mechanism to the inertial mass damper 4. That is, for example, in the case of the inertial mass damper 4 using the ball screw mechanism and the flywheel as described above, the torque transmitted from the rotating weight is peaked by joining the rotating weight to the ball screw mechanism via a friction material. Thus, the overload prevention mechanism (fail-safe mechanism) can be provided, whereby the friction mass slides at the inertial mass damper 4 at a desired relative acceleration α or more, and the torque reaches a peak.
In this case, the larger the ratio of the inertial mass ψ 2 to the mass m of the structure 1 is, the more effective the displacement is suppressed. However, if the ratio is excessively large, the acceleration increases.
また、本発明における第２の付加減衰７の変位は小さいので一般的な小ストロークの制震用オイルダンパーを使用できるが、その第２の付加減衰７にはリリーフ機構を付加することが好ましい。たとえば、第２の付加減衰７としてオイルダンパーを使用する場合には、そのオイルダンパーのシリンダー内圧が一定以上になった際に逃がし弁を開いて内圧を所定以内にするようなリリーフ機構を付加することにより、第２の付加減衰７の負担力を頭打ちにすることができる。 Further, since the displacement of the second additional damping 7 in the present invention is small, a general small stroke damping oil damper can be used. However, it is preferable to add a relief mechanism to the second additional damping 7. For example, when an oil damper is used as the second additional damping 7, a relief mechanism is added that opens the relief valve and keeps the internal pressure within a predetermined range when the cylinder internal pressure of the oil damper exceeds a certain level. As a result, the load of the second additional attenuation 7 can reach its peak.
以下、本発明の具体的な設計例とその効果について説明する。
・設計例１
既存の免震建物としての構造体１の諸元を以下とする。
構造体１の質量m＝10000ton、免震層の水平剛性（構造体バネ）k1＝35.5kN/mm、固有振動数f＝0.3Hz、固有周期T＝3.33sec、免震層の減衰定数h＝0.2として構造体減衰C1＝75.4kN/kine。
上記の免震建物に付加する応答低減機構の諸元を以下とする。
慣性質量ダンパー４には過負荷防止機構を付加せず、その慣性質量ψ2＝10000ton、したがってψ2/m＝1.0とする。復元バネk2＝11.8kN/mm（構造体バネk1の1/3に設定。したがって同調しない）、第１の付加減衰Cd1＝155kN/kine、第２の付加減衰（オイルダンパー）Cd2＝3020kN/kine、減衰定数hd2＝8.0>1.0（過減衰）とする。第２の付加減衰には相対速度0.025m/sで作動するリリーフ機構を付加し、リリーフ後の減衰係数はリリーフ前の0.02倍とする。
Hereinafter, specific design examples and effects of the present invention will be described.
・ Design example 1
The specifications of the structure 1 as an existing seismic isolation building are as follows.
Mass of structure 1 m = 10000ton, horizontal stiffness of base isolation layer (structure spring) k 1 = 35.5kN / mm, natural frequency f = 0.3Hz, natural period T = 3.33sec, damping constant h of base isolation layer Assuming = 0.2, the structure damping C 1 = 75.4 kN / kine.
The specifications of the response reduction mechanism added to the above seismic isolated building are as follows.
The inertial mass damper 4 is not provided with an overload prevention mechanism, and its inertial mass ψ 2 = 10000 tons, and therefore ψ 2 /m=1.0. Restoration spring k 2 = 11.8 kN / mm (set to 1/3 of structure spring k 1 and therefore not synchronized), first additional damping C d1 = 155 kN / kine, second additional damping (oil damper) C d2 = 3020 kN / kine, attenuation constant h d2 = 8.0> 1.0 (overdamped). A relief mechanism that operates at a relative speed of 0.025 m / s is added to the second additional damping, and the damping coefficient after relief is 0.02 times that before relief.
構造体１の固有角振動数ω0、地震動の加振角振動数ωとした場合の応答倍率を図２に示す。第２の付加減衰についてはリリーフ機構が作動する前と後で大きく特性が変化するので、減衰係数をリリーフ前の線形時とリリーフ後の非線形特性時（1/10に低減するものと設定）の２ケースで求めた。なお、応答倍率とは加振振幅に対する応答振幅の比率を表したものである。
図２より、既存免震建物に本発明の応答低減機構を付加することで、高振動数域での加速度はやや増加する傾向があるが、免震層変位は大幅に低減することがわかる。特に、長周期地震動のように低振動数領域での加振成分が大きな地震動の場合、加振振動数比ξ（免震建物の１次固有振動数に対する比率）が２以下の長周期域の振動特性が重要になるが、本発明ではそのような長周期域で充分な変位抑制効果が見られる。
なお、従来のように免震層に単にオイルダンパー等の粘性減衰だけを付加する場合には、高振動数域で応答倍率が１に収斂する特性しかできないので、本発明のような大幅な変位抑制効果は期待できない。
また、本発明によれば、加振振動数比ξが大きいいわゆる短周期領域の卓越する地震動に対しては、既存免震建物よりも応答加速度がやや増大することになるが、第２の付加減衰７のリリーフ荷重を適切に設定することで加速度応答を制御することができる。
FIG. 2 shows the response magnification when the natural angular frequency ω 0 of the structure 1 and the excitation angular frequency ω of the ground motion are set. Since the characteristics of the second additional damping change greatly before and after the relief mechanism is activated, the damping coefficient is linear before relief and nonlinear characteristics after relief (set to 1/10). Obtained in 2 cases. The response magnification represents a ratio of the response amplitude to the excitation amplitude.
From FIG. 2, it can be seen that by adding the response reduction mechanism of the present invention to an existing base-isolated building, the acceleration in the high frequency range tends to increase slightly, but the base-isolated layer displacement is greatly reduced. In particular, in the case of ground motion with a large excitation component in the low frequency region, such as long-period ground motion, the vibration frequency ratio ξ (ratio to the primary natural frequency of the base-isolated building) is 2 or less. Although vibration characteristics are important, in the present invention, a sufficient displacement suppression effect is observed in such a long period region.
Note that when only viscous damping such as an oil damper is added to the seismic isolation layer as in the prior art, only the characteristic that the response magnification is converged to 1 in the high frequency range can be obtained. The inhibitory effect cannot be expected.
In addition, according to the present invention, the response acceleration is slightly higher than that of the existing base-isolated building for the seismic motion that excels in the so-called short period region where the excitation frequency ratio ξ is large. The acceleration response can be controlled by appropriately setting the relief load of the attenuation 7.
次に、上記設計例１の免震建物に対する時刻歴応答解析を行い、本発明の効果を検証する。既存免震建物の諸元およびそれに付加する応答低減機構の諸元は上記設計例１の場合と同じとする。
長周期成分の多い地震動として、下記の３波で検討する。
(1)想定東海地震（名古屋三の丸）ＥＷ 最大加速度186gal
(2)想定南海地震（大阪湾岸WOS）ＮＳ 最大加速度84.9gal
(3)建築センター波 Level-2 最大加速度356gal
Next, a time history response analysis is performed on the base-isolated building of the design example 1 to verify the effect of the present invention. The specifications of the existing seismic isolation building and the specifications of the response reduction mechanism added thereto are the same as in the case of the above design example 1.
The following three waves are considered as earthquake motions with many long-period components.
(1) Assumed Tokai earthquake (Nagoya Sannomaru) EW Maximum acceleration 186gal
(2) Assumed Nankai earthquake (Osaka Wangan WOS) NS Maximum acceleration 84.9gal
(3) Architectural Center Wave Level-2 Maximum acceleration 356gal
上記の地震動に対して応答解析を行い、上記免震建物の加速度と変位を検討する。
さらに、第２の付加減衰７としてのオイルダンパーのストロークを検討するために最大応答変位を追記する。
また、付加したダンパーを含め建物全体に入力される地震エネルギーを求め、既存免震建物に入力されるエネルギーとの比較を行う。なお、地震入力エネルギー（総エネルギー入力）Eは次式で求められる。
Response analysis is performed for the above-mentioned ground motion, and the acceleration and displacement of the base-isolated building are examined.
Furthermore, in order to examine the stroke of the oil damper as the second additional damping 7, the maximum response displacement is added.
In addition, the seismic energy input to the entire building including the added damper is obtained and compared with the energy input to the existing base-isolated building. The seismic input energy (total energy input) E is obtained by the following equation.
図３〜図５に各地震動の入力波形、応答スペクトルを、加速度、速度、変位について示す。また、入力加速度の振動数成分の分布をみるためフーリエスペクトルも付記する。
図６〜図８に各地震動に対する解析結果を示し、その結果を図９にまとめて示す。
図６から、想定東海地震の場合には加速度、変位とも大幅に低減されることがわかる。この場合の第２の付加減衰７の変位は13mm、総エネルギー入力は0.3倍に低減した。
図７から、想定南海地震の場合には加速度は大差ないが変位は大幅に低減されることがわかる。この場合の第２の付加減衰７の変位は6.2mm、総エネルギー入力は0.85倍に低減した。
図８から、建築センター波の場合には、加速度は微増するが変位は大幅に低減されることがわかる。この場合の第２の付加減衰７の変位は89mm、総エネルギー入力は0.81倍に低減した。
3 to 5 show the input waveform and response spectrum of each seismic motion in terms of acceleration, velocity, and displacement. A Fourier spectrum is also added to see the distribution of frequency components of input acceleration.
The analysis results for each earthquake motion are shown in FIGS. 6 to 8, and the results are summarized in FIG.
FIG. 6 shows that both acceleration and displacement are significantly reduced in the case of the assumed Tokai earthquake. In this case, the displacement of the second additional attenuation 7 was 13 mm, and the total energy input was reduced 0.3 times.
From FIG. 7, it can be seen that in the case of the assumed Nankai earthquake, the acceleration is not much different, but the displacement is greatly reduced. In this case, the displacement of the second additional attenuation 7 was 6.2 mm, and the total energy input was reduced to 0.85 times.
FIG. 8 shows that in the case of a building center wave, the acceleration slightly increases but the displacement is greatly reduced. In this case, the displacement of the second additional attenuation 7 was 89 mm, and the total energy input was reduced to 0.81 times.
・設計例２
上記の設計例１とは非線形特性のみを変更した場合について検討を行う。
慣性質量ダンパー４の慣性質量ψ2を設計例１と同様にψ2＝10000tonとするが、過負荷防止機構により相対加速度α＝0.3m/s2以上で0.02倍となるように設定する。
第２の付加減衰７は設計例１と同様にCd2＝3020kN/kineのオイルダンパーとし、ここではリリーフ機構を付加しない。
・ Design example 2
With respect to the above design example 1, a case where only the nonlinear characteristic is changed will be examined.
The inertial mass ψ 2 of the inertial mass damper 4 is set to ψ 2 = 10000 tons as in Design Example 1, but is set to be 0.02 times the relative acceleration α = 0.3 m / s 2 or more by the overload prevention mechanism.
The second additional damping 7 is an oil damper of C d2 = 3020 kN / kine as in the first design example, and no relief mechanism is added here.
設計例２についての検討結果を図１０にまとめて示す。（ａ）は最大応答加速度および最大応答変位を示し、（ｂ）は第２の付加減衰７としてのオイルダンパーの変位と総エネルギー入力の低下率を示す。
図１０から明らかなように、第２の付加減衰７にリリーフ機構を付加せずに慣性質量ダンパー４に過負荷防止機構を付加することによっても、加速度をあまり増加させずに変位を充分に抑制する効果が得られることがわかる。
特に設計例２において上記の設計例１と大きく異なるのは、建築センター波でのオイルダンパー（第２の付加減衰７）の変位である。設計例２では慣性質量ダンパー４の負担力が頭打ちされることでオイルダンパーに作用する荷重も頭打ちされることから、ダンパー変位が設計例１の場合の89mmから11.5mmへと大幅に低下しており、したがってダンパーストロークが充分に小さくて済むことになる。
The examination result about the design example 2 is collectively shown in FIG. (A) shows the maximum response acceleration and the maximum response displacement, and (b) shows the displacement of the oil damper as the second additional damping 7 and the decrease rate of the total energy input.
As is clear from FIG. 10, the displacement can be sufficiently suppressed without increasing the acceleration by adding an overload prevention mechanism to the inertial mass damper 4 without adding a relief mechanism to the second additional damping 7. It turns out that the effect to do is acquired.
In particular, the design example 2 is greatly different from the design example 1 described above in the displacement of the oil damper (second additional attenuation 7) in the building center wave. In design example 2, the load acting on the oil damper is also peaked when the load of inertia mass damper 4 is peaked, so the damper displacement is greatly reduced from 89 mm in design example 1 to 11.5 mm. Therefore, the damper stroke can be made sufficiently small.
なお、上記設計例１では第２の付加減衰７にリリーフ機構を付加するのみとし、上記設計例２では慣性質量ダンパー４に過負荷防止機構を付加するのみとしたが、本発明においてはそれらの双方を付加する設計としても勿論良いし、双方がなくても良い。 In the above design example 1, only the relief mechanism is added to the second additional damping 7, and in the above design example 2, only the overload prevention mechanism is added to the inertial mass damper 4. Needless to say, both may be added, or both may be omitted.
本発明の効果を以下に列挙する。
（１）免震で支持される構造体の加速度を制御しつつ変位を大幅に低減することができる。従来のバネと減衰（オイルダンパー等）だけによる免震構造では変位と加速度を同時に抑制することは困難であるが、本発明により従来の手法では達成できなかった「加速度を増大させずに変位を低減する」ことが可能になる。
（２）慣性質量効果を用いることでやや長周期化するが、長周期地震動のように長周期成分が卓越する場合でも免震層の過大な変位が防止され、したがって過去の基準により設計された既存免震建物に対して適用すれば長周期地震動に対しても免震クリアランスの不足を解消することができる。
但し、本発明は既存免震建物に適用するのみならず、新築免震建物に対しても有効に適用できることは当然である。
The effects of the present invention are listed below.
(1) The displacement can be greatly reduced while controlling the acceleration of the structure supported by the seismic isolation. Although it is difficult to suppress displacement and acceleration at the same time with a conventional seismic isolation structure that uses only springs and damping (oil dampers, etc.), the present invention cannot achieve the displacement without increasing the acceleration. Can be reduced.
(2) The inertial mass effect is used to make the period somewhat longer, but even if the long-period component is dominant, such as long-period ground motion, excessive displacement of the seismic isolation layer is prevented, so it was designed based on past standards. If applied to existing base-isolated buildings, the shortage of base isolation clearance can be resolved even for long-period ground motion.
However, it goes without saying that the present invention can be applied not only to existing base-isolated buildings but also to newly built base-isolated buildings.
（３）過減衰となるような大きな減衰係数を持つ付加減衰（上記実施形態における第２の付加減衰。以下同じ）を慣性質量ダンパーと直列した構成であり、固有周期より短周期側の入力が小さい場合には総エネルギー入力が低減される。総エネルギー入力とは「ダンパーを含む構造物全体に入力されることにより構造物の損傷に関わる地震エネルギー」であって、これが大きいほどダンパーで吸収すべきエネルギーが大きくなり構造物の塑性化が進むことになるから、この値を小さくすることは損傷軽減に有効であり、ダンパーの疲労破壊を防止したり構造体の損傷を抑制することが可能である。
また、その付加減衰に対して並列に復元バネを設けることにより、慣性質量ダンパーや付加減衰の残留変形を防止することができる。
(3) A configuration in which additional attenuation (second additional attenuation in the above embodiment, the same applies hereinafter) having a large attenuation coefficient that causes over-attenuation is connected in series with an inertial mass damper. If it is small, the total energy input is reduced. The total energy input is “seismic energy related to damage to the structure when it is input to the entire structure including the damper”. The larger this is, the greater the energy that must be absorbed by the damper and the more plastic the structure is. Therefore, reducing this value is effective in reducing damage, and it is possible to prevent fatigue damage of the damper and to suppress damage to the structure.
Further, by providing a restoring spring in parallel with the additional damping, it is possible to prevent the inertia mass damper and the residual deformation of the additional damping.
（４）付加減衰に対してリリーフ機構を付加することにより、構造体に作用する制御力が過大にならないようにすることができる。構造体に作用する力は質量×加速度なので、制御力を低減することは加速度を低減する（頭打ちにする）ことに効果的である。 (4) By adding a relief mechanism to the additional damping, the control force acting on the structure can be prevented from becoming excessive. Since the force acting on the structure is mass × acceleration, reducing the control force is effective in reducing acceleration (heading out).
（５）慣性質量ダンパーに過負荷防止機構を設けることにより、付加減衰の変位（ストローク）が小さくて済み、免震層に設置する付加減衰として制震用の小ストロークのオイルダンパーを適用できる。制震用のオイルダンパーは免震用のオイルダンパーよりも減衰係数と負担力の大きい装置を安価に調達できるため、本発明の応答低減機構をローコストに構築できる。すなわち、一般的な免震用オイルダンパーのストロークは500〜600mm程度であるが、制震用オイルダンパーは80〜100mm程度であり、減衰係数は制震用の方が１桁大きいから、本発明によれば免震構造でありながらそのような特性の制震用オイダンパーを有効に活用できることになる。
（６）本発明の応答低減機構は免震層の下部構造と上部との間に設置するだけで良く、通常のオイルダンパーと同様に免震層上下の床梁間に設置できる。また、既存のダンパーよりも応答低減効果が大きいので、既存ダンパーの一部または全部を撤去して本発明の応答低減機構を設置することも可能である。
(5) By providing an overload prevention mechanism in the inertial mass damper, the displacement (stroke) of additional damping can be reduced, and a small stroke oil damper for damping can be applied as additional damping installed in the seismic isolation layer. Since the damping oil damper can procure a device having a larger damping coefficient and burden than the seismic isolation oil damper at a low cost, the response reduction mechanism of the present invention can be constructed at a low cost. That is, the stroke of a general seismic isolation oil damper is about 500 to 600 mm, but the damping oil damper is about 80 to 100 mm, and the damping coefficient is one digit larger than that of the seismic control. According to the present invention, it is possible to effectively use the seismic control oil damper having such a characteristic although it is a seismic isolation structure.
(6) The response reducing mechanism of the present invention only needs to be installed between the lower structure and the upper part of the base isolation layer, and can be installed between the floor beams above and below the base isolation layer in the same way as a normal oil damper. In addition, since the response reduction effect is greater than that of the existing damper, it is possible to remove part or all of the existing damper and install the response reduction mechanism of the present invention.
１ 構造体（既存免震建物）
２ 構造体バネ
３ 構造体減衰
４ 慣性質量ダンパー
５ 付加バネ
５’ 復元バネ
６ 第１の付加減衰
７ 第２の付加減衰（付加減衰）
1 structure (existing seismic isolation building)
2 Structural spring 3 Structural damping 4 Inertial mass damper 5 Additional spring 5 'Restoring spring 6 First additional damping 7 Second additional damping (additional damping)
Claims (3)
前記応答低減機構を、慣性質量ダンパーと、該慣性質量ダンパーに対して直列に接続した付加減衰と、該付加減衰に対して並列に接続した復元バネとにより構成し、
前記復元バネのバネ剛性k2、および前記付加減衰の減衰係数Cd2を、前記構造体バネのバネ剛性k1、前記構造体の質量m、前記慣性質量ダンパーの慣性質量ψ2に基づき、次の関係を満足するように設定してなることを特徴とする免震構造。
The response reduction mechanism comprises an inertial mass damper, an additional damping connected in series to the inertial mass damper, and a restoring spring connected in parallel to the additional damping,
Based on the spring stiffness k 2 of the restoring spring and the damping coefficient C d2 of the additional damping based on the spring stiffness k 1 of the structure spring, the mass m of the structure, and the inertia mass ψ 2 of the inertia mass damper, Seismic isolation structure characterized by being set up to satisfy the relationship.
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