JP4479138B2 - Column base structure and seismic reinforcement method - Google Patents

Column base structure and seismic reinforcement method Download PDF

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Publication number
JP4479138B2
JP4479138B2 JP2001271302A JP2001271302A JP4479138B2 JP 4479138 B2 JP4479138 B2 JP 4479138B2 JP 2001271302 A JP2001271302 A JP 2001271302A JP 2001271302 A JP2001271302 A JP 2001271302A JP 4479138 B2 JP4479138 B2 JP 4479138B2
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column
base structure
diagonal
column base
hysteresis damping
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JP2003074019A (en
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素之 岡野
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Obayashi Corp
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Obayashi Corp
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Description

【0001】
【発明の属する技術分野】
本発明は、耐震性が要求される柱脚構造、特に道路、鉄道等に供される高架橋の橋脚に適用される柱脚構造及び耐震補強方法に関する。
【0002】
【従来の技術】
道路、鉄道等の橋梁には、河川、海峡等を横断する狭義の橋梁のほかに市街地において連続的に建設される、いわゆる高架橋がある。かかる高架橋は、効率的な土地利用の観点から、道路上、鉄道上あるいは河川上の空間に連続して建設されるものであり、道路と道路あるいは道路と鉄道とが平面で交差する場合にそれらのいずれかを高架橋とすることにより、交通渋滞を解消することも可能となる。
【0003】
【発明が解決しようとする課題】
かかる高架橋を構築するにあたっては、鉄筋コンクリート(RC)からなる橋脚で下部構造を構築するのが一般的であるが、最近では、RCとダンパーブレースとを組み合わせた下部構造が研究開発されており、耐震性を向上させることができるという点で今後多いに期待されているものである。
【0004】
一方、RCだけで構成する従来型の下部構造の場合、ダンパーブレースを併用した場合よりも降伏剛性が低くなり、地震時の応答変位が大きくなる傾向にある。
【0005】
そのため、橋脚断面を大きくして応答変位を抑えるとともに終局耐力を大きくする必要が生じ、その結果、橋脚自体はもちろんのこと、該橋脚を支持するフーチング、さらには該フーチングに作用する鉛直荷重を支持層まで伝達する杭などの規模が大きくなり、高架橋の下部構造を構築するにあたってコスト高となるのを余儀なくされていた。
【0006】
本発明は、上述した事情を考慮してなされたもので、橋脚を大断面とせずとも耐震性を向上させることが可能な柱脚構造を提供することを目的とする。
【0007】
また、本発明は、既設のコンクリート柱の耐震性を向上させることが可能な耐震補強方法を提供することを目的とする。
【0008】
【課題を解決するための手段】
上記目的を達成するため、本発明に係る柱脚構造は請求項1に記載したように、履歴減衰特性を有する斜材をその一端がフーチングに他端が該フーチングに立設されたコンクリート柱にそれぞれ接合されるように前記コンクリート柱の脚部側方に方杖状に配置したものである。
【0009】
また、本発明に係る耐震補強方法は請求項2に記載したように、履歴減衰特性を有する斜材をその一端がフーチングに他端が該フーチングに立設されたコンクリート柱にそれぞれ接合されるように前記コンクリート柱の脚部側方に方杖状に配置するものである。
【0010】
本発明に係る柱脚構造においては、履歴減衰特性を有する斜材をコンクリート柱の脚部側方に方杖状に配置してある。
【0011】
このようにすると、柱脚構造全体の復元力特性は、斜材の剛性が加わる分だけ、コンクリート柱だけの場合よりも初期剛性が大きくなり、入力地震に対する応答変位が低減する。
【0012】
また、斜材の履歴減衰特性による減衰作用により、入力地震に対する応答変位はさらに抑制されるとともに、柱脚構造に生じる部材力も低減する。
【0013】
したがって、設計上要求される許容変位及び許容応力度が同じである場合、コンクリート柱の断面を小さくすることができる。すなわち、コンクリート柱の断面を小さくすると、その分、コンクリート柱の剛性及び降伏強度が小さくなるが、剛性の低減分については斜材で補うことができるとともに、降伏強度が小さくなっても、上述したように斜材による履歴減衰特性の減衰作用により、入力地震動によって生じる部材力自体が低減するため、そもそもコンクリート柱に従来と同様の降伏強度をもたせる必要がなくなる。また、斜材の履歴減衰作用により、コンクリート柱の振動も速やかに収斂する。
【0014】
また、本発明に係る耐震補強方法においては、履歴減衰特性を有する斜材を既設のコンクリート柱の脚部側方に方杖状に配置する。
【0015】
このようにすると、柱脚構造全体の復元力特性は、斜材の剛性が加わる分だけ、コンクリート柱だけの場合よりも初期剛性が大きくなり、入力地震に対する応答変位が低減する。
【0016】
また、斜材の履歴減衰特性による減衰作用により、入力地震に対する応答変位はさらに抑制されるとともに、柱脚構造に生じる部材力も低減する。
【0017】
したがって、同じ規模の地震波が入力した場合、斜材を設けたことによって剛性が高くなる分だけ、既設のコンクリート柱に生じる応答変位は大幅に減少するとともに、斜材によって履歴減衰特性が発揮される分だけ、既設のコンクリート柱の応答変位がさらに抑制されるとともに、該コンクリート柱の振動もすみやかに収斂する。
【0018】
斜材は、一端がフーチングに他端が該フーチングに立設されたコンクリート柱に接合されていればよく、接合形式については、剛接合、ピン接合など、任意の接合形式を選択すればよい。
【0019】
また、斜材は、コンクリート柱の脚部側方に方杖状に配置されていればよく、コンクリート柱の周囲にいくつ配置するかは任意である。すなわち、単体の斜材をコンクリート柱の脚部側方に配置するほか、例えば互いに背中合わせとなるように対でコンクリート柱の脚部両側方に配置してもよいし、かかる一対の斜材を別の直交構面に別途配置するようにしてもよいし、所望の角度ごとにコンクリート柱の側方周囲に複数配置するようにしてもよい。特に、ラーメン架構を構成する一対のコンクリート柱の脚部に設ける場合には、単体の斜材をラーメン架構の外側位置又は内側位置に配置され全体として対称となるように各コンクリート柱に配置することが考えられる。
【0020】
コンクリート柱は、コンクリートを主体として構成された柱という意味であって、RC柱はもちろんのこと、鋼管内にコンクリートが充填されたいわゆるCFT柱やPC柱をも含む概念である。
【0021】
斜材は、履歴減衰特性を有するものであればいかなる構造のものでもよく、例えば極軟鋼やスリット入り薄鋼板を軸方向変形に対して履歴減衰を発揮するように斜材の中間位置に設けたり、同様の材料を曲げ変形に対して履歴減衰を発揮するように斜材の中間位置に設けたり、やはり同様の材料をせん断変形に対して履歴減衰を発揮するように斜材のコンクリート柱側端部に設けたりすることが考えられる。
【0022】
なお、本発明の柱脚構造及び耐震補強方法は、主として高架橋の下部構造に適用することを想定しているが、かかる用途に限定されるものではなく、建築土木を問わず、あらゆる柱脚に適用することができることは言うまでもない。
【0023】
【発明の実施の形態】
以下、本発明に係る柱脚構造及び耐震補強方法の実施の形態について、添付図面を参照して説明する。なお、従来技術と実質的に同一の部品等については同一の符号を付してその説明を省略する。
【0024】
(第1実施形態)
【0025】
本実施形態に係る柱脚構造は高架橋の下部構造に適用したものであって、図1は、該下部構造を橋軸方向から見た正面図である。同図でわかるように、本実施形態に係る柱脚構造11は、一対の斜材12,12を背中合わせとなるようにRC柱2の脚部両側方に方杖状に配置してある。
【0026】
なお、RC柱2は、互いに対向する位置にて立設された一対のRC柱2,2となるよう、杭7を打ち込んだ上でその上に設けられたフーチング8にそれぞれ立設してあり、該RC柱の頂部に架け渡された梁3とともに高架橋の下部構造であるRCラーメン架構4を構成している。
【0027】
ここで、斜材12は図2の詳細図に示すように、履歴減衰特性を有する極軟鋼等の履歴減衰材料13をロッド材14,14の間に介在させてなり、軸方向変形に対して履歴減衰を発揮することができるようになっている。
【0028】
また、斜材12は、その一端をフーチング8に他端を該フーチングに立設されたRC柱2にそれぞれピン接合してあり、RC柱2が地震時水平荷重によって振動しているときにも軸力だけが伝達されるようになっている。
【0029】
本実施形態に係る柱脚構造11においては、履歴減衰特性を有する一対の斜材12,12をRC柱2の脚部両側方に方杖状に配置してある。
【0030】
このようにすると、柱脚構造全体の復元力特性は、斜材12の剛性が加わる分だけ、RC柱2だけの場合よりも初期剛性が大きくなり、入力地震に対する応答変位が低減する。
【0031】
また、斜材12の履歴減衰特性による減衰作用により、入力地震に対する応答変位はさらに抑制されるとともに、柱脚構造11に生じる部材力も低減する。
【0032】
図3(a)、(b)は、柱脚構造11の復元力特性及びRC柱2だけで構成された従来の柱脚構造における復元力特性をそれぞれ示したものであり、図4(a)、(b)は、中小地震が入力した場合のそれぞれの履歴性状を、図5(a)、(b)は大地震が入力した場合のそれぞれの履歴性状を示した図である。
【0033】
なお、柱脚構造11は、最終強度とそのときの水平変位とを従来の柱脚構造と一致させてあり、RC柱2は、斜材12によって増加する剛性及び強度の分だけ、その断面を低減させてある。
【0034】
これらの図でわかるように、中小地震の場合(図4)、従来の柱脚構造では、RC柱が弾性範囲にとどまるため、履歴減衰は全く期待することができず、そのため、水平応答変位はδ2まで進行するとともに、それに伴って応答部材力もH2と大きくなる。
【0035】
それに対し、本実施形態の柱脚構造11では、斜材12による履歴減衰が発揮されるため、水平応答変位はδ1に、応答部材力はH1にそれぞれ抑制される。
【0036】
また、大地震の場合(図5)、従来の柱脚構造では、RC柱が塑性化して履歴減衰が若干期待できるものの、水平応答変位はδ2′と非常に大きくなるとともに、それに伴って応答部材力も終局強度Hとなる。
【0037】
それに対し、本実施形態の柱脚構造11では、斜材12による履歴減衰が発揮されるため、水平応答変位はδ1′に、応答部材力はH1′にそれぞれ抑制される。
【0038】
以上説明したように、本実施形態に係る柱脚構造11によれば、斜材12による履歴減衰作用により、地震時応答変位及び地震時応答部材力を従来よりも大幅に低減させることができる。
【0039】
また、斜材12に水平剛性を負担させることができるため、RC柱2の断面を小さくすることが可能となり、RC柱2の規模、ひいてはフーチング8や杭7の規模を小さくすることが可能となり、例えばかかる柱脚構造11を高架橋の下部構造に適用したならば、該下部構造の構築コストを大幅に低減することが可能となる。
【0040】
本実施形態では、履歴減衰特性を有する極軟鋼等の履歴減衰材料13をロッド材14,14の間に介在させてなる斜材12で本発明の斜材を構成したが、これに代えて図6に示す斜材を用いるようにしてもよい。
【0041】
ここで、図6(a)に示す斜材12aは、実施形態と同様、履歴減衰特性を有する極軟鋼等の履歴減衰材料13をロッド材14,14の間に介在させてなるが、該履歴減衰材料は、曲げ変形に対して履歴減衰を発揮するように構成してある。
【0042】
図6(b)に示す斜材12bは、ロッド材14の柱接合端に極軟鋼等の履歴減衰材料13を介在させてなり、該履歴減衰材料をせん断変形に対して履歴減衰を発揮するように構成してある。
【0043】
また、本実施形態では、斜材12をフーチング8とRC柱2にピン接合するようにしたが、斜材の接合形式はピン接合に限定されるものではなく、これに代えて剛接合としてもかまわない。
【0044】
また、本実施形態では、一対の斜材12,12をRC柱2の脚部両側方に背中合わせとなるように配置したが、必ずしも対で配置する必要はなく、単体の斜材12をRC柱2の脚部側方に配置するようにしてもよいし、RC柱2を取り囲むように複数配置してもかまわない。
【0045】
図7は、単体の斜材12をRCラーメン架構4の外側位置にくるように各RC柱2に方杖状に配置してなる柱脚構造11aを示したものであり、図8は、同じく単体の斜材12をRCラーメン架構4の内側位置にくるように各RC柱2に方杖状に配置してなる柱脚構造11bを示したものである。
【0046】
かかる構成において、前者、すなわちRCラーメン架構4の外側位置にくるように単体の斜材12を配置した場合には、該RCラーメン架構4の内側を道路や線路などのスペースとして利用する場合に適しており、後者、すなわちRCラーメン架構4の内側位置にくるように単体の斜材12を配置した場合には、RCラーメン架構4の外側が道路や河川に隣接している場合に適する。
【0047】
(第2実施形態)
【0048】
次に、第2実施形態に係る耐震補強方法について説明する。なお、第1実施形態と実質的に同一の部品等については同一の符号を付してその説明を省略する。
【0049】
本実施形態に係る耐震補強方法においては、一対の斜材12,12をそれらの一端がフーチング8に他端が該フーチングに立設されたコンクリート柱である既設のRC柱2にそれぞれピン接合されるように該RC柱の脚部両側方に方杖状に配置する(図1参照)。
【0050】
このようにすると、柱脚構造全体の復元力特性は、斜材12の剛性が加わる分だけ、RC柱2だけの場合よりも初期剛性が大きくなり、入力地震に対する応答変位が低減する。
【0051】
また、斜材12の履歴減衰特性による減衰作用により、入力地震に対する応答変位はさらに抑制されるとともに、柱脚構造に生じる部材力も低減する。
【0052】
以上説明したように、本実施形態に係る耐震補強方法によれば、同じ規模の地震波が入力した場合、一対の斜材12,12を設けたことによって剛性が高くなる分だけ、既設のRC柱2に生じる応答変位は大幅に減少するとともに、一対の斜材12,12によって履歴減衰特性が発揮される分だけ、既設のRC柱2の応答変位がさらに抑制されるとともに、応答部材力も低減する。また、RC柱2の振動もすみやかに収斂させることができる。
【0053】
本実施形態では、履歴減衰特性を有する極軟鋼等の履歴減衰材料13をロッド材14,14の間に介在させてなる斜材12で本発明の斜材を構成したが、第1実施形態と同様、これに代えて図6に示す斜材を用いるようにしてもよい。
【0054】
また、本実施形態では、斜材12をフーチング8とRC柱2にピン接合するようにしたが、第1実施形態と同様、やはりピン接合に代えて剛接合としてもかまわない。
【0055】
斜材12の配置数あるいは配置形態についても第1実施形態と同様であり、必ずしも対で配置する必要はなく、単体の斜材12をRC柱2の脚部側方に配置するようにしてもよいし、RC柱2を取り囲むように複数配置してもかまわない。
【0056】
【発明の効果】
以上述べたように、本発明に係る柱脚構造及び耐震補強方法によれば、斜材による履歴減衰作用により、地震時応答変位及び地震時応答部材力を従来よりも大幅に低減させることができる。また、斜材に水平剛性を負担させることができるため、コンクリート柱の断面を小さくすることが可能となり、コンクリート柱の規模、ひいてはフーチングや杭の規模を小さくすることが可能となり、例えばかかる柱脚構造を高架橋の下部構造に適用したならば、該下部構造の構築コストを大幅に低減することが可能となる。
【0057】
【図面の簡単な説明】
【図1】本実施形態に係る柱脚構造が適用される高架橋の下部構造を橋軸方向から見た正面図。
【図2】本実施形態に係る柱脚構造の詳細図。
【図3】本実施形態に係る柱脚構造の作用を示した図。
【図4】同じく本実施形態に係る柱脚構造の作用を示した図。
【図5】同じく本実施形態に係る柱脚構造の作用を示した図。
【図6】変形例に係る斜材の詳細図。
【図7】変形例に係る柱脚構造が適用される高架橋の下部構造を橋軸方向から見た正面図。
【図8】別の変形例に係る柱脚構造が適用される高架橋の下部構造を橋軸方向から見た正面図。
【符号の説明】
2 RC柱(コンクリート柱)
8 フーチング
11、11a、11b 柱脚構造
12、12a、12b 斜材
[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a column base structure that requires earthquake resistance, and more particularly to a column base structure and a seismic reinforcement method applied to a viaduct pier used for roads, railways, and the like.
[0002]
[Prior art]
Bridges such as roads and railroads include so-called viaducts that are continuously built in urban areas, in addition to narrowly-defined bridges that cross rivers and straits. Such viaducts are constructed continuously in space on roads, railroads or rivers from the viewpoint of efficient land use, and when roads and roads or roads and railroads intersect on a plane, By making either of these viaducts, it is possible to eliminate traffic congestion.
[0003]
[Problems to be solved by the invention]
In constructing such a viaduct, it is common to construct the substructure with piers made of reinforced concrete (RC), but recently, a substructure combining RC and damper brace has been researched and developed, It is expected in the future that it can improve the performance.
[0004]
On the other hand, in the case of a conventional substructure composed only of RC, the yield rigidity is lower than when a damper brace is used in combination, and the response displacement during an earthquake tends to increase.
[0005]
Therefore, it is necessary to increase the cross section of the pier to suppress the response displacement and increase the ultimate proof stress.As a result, not only the pier itself but also the footing that supports the pier, and the vertical load that acts on the footing are supported. The scales of piles that transmit to the layers have increased, and it has been unavoidable that the cost of building the viaduct substructure has increased.
[0006]
The present invention has been made in consideration of the above-described circumstances, and an object of the present invention is to provide a column base structure capable of improving the earthquake resistance without having a large cross section of the pier.
[0007]
Moreover, an object of this invention is to provide the earthquake-proof reinforcement method which can improve the earthquake resistance of the existing concrete pillar.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, the column base structure according to the present invention is a concrete column in which a diagonal material having a hysteresis damping characteristic is provided on one end of the footing and the other end is erected on the footing. They are arranged like a cane on the side of the leg of the concrete column so as to be joined.
[0009]
The seismic reinforcement method according to the present invention, as described in claim 2, is such that a diagonal member having hysteresis damping characteristics is joined to a concrete column having one end thereof and the other end standing on the footing. In addition, it is arranged like a cane on the side of the leg portion of the concrete pillar.
[0010]
In the column base structure according to the present invention, diagonal members having hysteresis damping characteristics are arranged in a cane shape on the side of the leg portion of the concrete column.
[0011]
If it does in this way, the restoring force characteristic of the whole column base structure will have initial rigidity larger than the case of only a concrete column, and the response displacement with respect to an input earthquake will reduce by the part which added the rigidity of diagonal.
[0012]
In addition, the response due to the input earthquake is further suppressed by the damping action due to the hysteresis damping characteristics of the diagonal members, and the member force generated in the column base structure is also reduced.
[0013]
Therefore, when the allowable displacement and the allowable stress required in design are the same, the cross section of the concrete column can be reduced. In other words, when the cross section of the concrete column is reduced, the rigidity and yield strength of the concrete column are reduced accordingly, but the reduced amount of rigidity can be supplemented with diagonal materials, and even if the yield strength is reduced, the above-mentioned Thus, since the member force itself generated by the input earthquake motion is reduced by the damping action of the hysteresis damping characteristic by the diagonal member, it is not necessary to give the concrete column the same yield strength in the first place. Moreover, the vibration of the concrete column is quickly converged by the hysteresis damping action of the diagonal material.
[0014]
Moreover, in the seismic reinforcement method according to the present invention, the diagonal member having the hysteresis damping characteristic is arranged in a cane shape on the side of the leg portion of the existing concrete column.
[0015]
If it does in this way, the restoring force characteristic of the whole column base structure will have initial rigidity larger than the case of only a concrete column, and the response displacement with respect to an input earthquake will reduce by the part which added the rigidity of diagonal.
[0016]
In addition, the response due to the input earthquake is further suppressed by the damping action due to the hysteresis damping characteristics of the diagonal members, and the member force generated in the column base structure is also reduced.
[0017]
Therefore, when seismic waves of the same scale are input, the response displacement generated in the existing concrete column is greatly reduced by the increase in rigidity due to the provision of the diagonal material, and the hysteresis damping characteristic is exhibited by the diagonal material. Accordingly, the response displacement of the existing concrete column is further suppressed, and the vibration of the concrete column is quickly converged.
[0018]
The diagonal member is only required to be joined to a concrete column with one end being footed and the other end being erected on the footing, and any joining type such as rigid joining or pin joining may be selected.
[0019]
In addition, it is sufficient that the diagonal members are arranged in a cane-like shape on the side of the leg portion of the concrete column, and how many are arranged around the concrete column is arbitrary. That is, in addition to arranging a single diagonal on the side of a concrete column leg, for example, it may be arranged on both sides of a concrete column in a pair so as to be back-to-back with each other. It may be arranged separately on the orthogonal composition plane, or may be arranged around the side of the concrete column for each desired angle. In particular, when it is provided on the legs of a pair of concrete columns that constitute a rigid frame, a single diagonal is placed on each concrete column so that it is symmetrical on the outside and inside of the rigid frame. Can be considered.
[0020]
The concrete column means a column mainly composed of concrete and includes not only the RC column but also a so-called CFT column or PC column in which concrete is filled in a steel pipe.
[0021]
The diagonal member may have any structure as long as it has a hysteresis damping characteristic. For example, an extremely mild steel or a slit steel sheet may be provided at an intermediate position of the diagonal member so as to exhibit hysteresis damping against axial deformation. The same material is provided in the middle of the diagonal so as to exhibit hysteresis damping against bending deformation, or the concrete material side edge of the diagonal is also used to exhibit hysteresis damping against shear deformation. It is conceivable to provide it in the section.
[0022]
The column base structure and seismic retrofitting method of the present invention are assumed to be mainly applied to the viaduct substructure, but are not limited to such applications, and are applicable to all column bases regardless of architectural civil engineering. It goes without saying that it can be applied.
[0023]
DETAILED DESCRIPTION OF THE INVENTION
DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of a column base structure and a seismic reinforcement method according to the present invention will be described with reference to the accompanying drawings. Note that components that are substantially the same as those of the prior art are assigned the same reference numerals, and descriptions thereof are omitted.
[0024]
(First embodiment)
[0025]
The column base structure according to the present embodiment is applied to a viaduct substructure, and FIG. 1 is a front view of the substructure viewed from the bridge axis direction. As can be seen from the figure, in the column base structure 11 according to the present embodiment, a pair of diagonal members 12, 12 are arranged like a cane on both sides of the leg of the RC column 2 so as to be back to back.
[0026]
The RC pillar 2 is erected on a footing 8 provided on the pile 7 after driving the pile 7 so as to be a pair of RC pillars 2 and 2 erected at positions facing each other. The RC frame 4 is a lower structure of the viaduct together with the beam 3 spanned on the top of the RC pillar.
[0027]
Here, as shown in the detailed view of FIG. 2, the diagonal member 12 is formed by interposing a hysteresis damping material 13 such as extremely mild steel having a hysteresis damping characteristic between the rod members 14 and 14 to prevent axial deformation. Hysteresis can be exhibited.
[0028]
Further, the diagonal member 12 is pin-joined at one end to the footing 8 and the other end to the RC column 2 standing on the footing, and the RC column 2 is also vibrated by a horizontal load during an earthquake. Only the axial force is transmitted.
[0029]
In the column base structure 11 according to the present embodiment, a pair of diagonal members 12 and 12 having a hysteresis damping characteristic are arranged in a cane shape on both sides of the leg portion of the RC column 2.
[0030]
If it does in this way, the restoring force characteristic of the whole column base structure will have initial rigidity larger than the case of only RC pillar 2 by the part which the rigidity of diagonal member 12 adds, and the response displacement with respect to an input earthquake will reduce.
[0031]
Moreover, the response displacement with respect to the input earthquake is further suppressed by the damping action due to the hysteresis damping characteristic of the diagonal member 12, and the member force generated in the column base structure 11 is also reduced.
[0032]
FIGS. 3 (a) and 3 (b) show the restoring force characteristic of the column base structure 11 and the restoring force characteristic in the conventional column base structure composed only of the RC column 2, respectively. FIGS. 5A and 5B show the respective history characteristics when a small and medium-sized earthquake is input, and FIGS. 5A and 5B show the respective history characteristics when a large earthquake is input.
[0033]
The column base structure 11 has the final strength and the horizontal displacement at that time matched to those of the conventional column base structure, and the RC column 2 has a cross section corresponding to the rigidity and strength increased by the diagonal member 12. Reduced.
[0034]
As can be seen from these figures, in the case of small and medium-sized earthquakes (Fig. 4), in the conventional column base structure, the RC column stays in the elastic range, so no hysteresis damping can be expected, so the horizontal response displacement is While proceeding to δ 2, the response member force is increased to H 2 accordingly .
[0035]
On the other hand, in the column base structure 11 of the present embodiment, since the hysteresis attenuation by the diagonal member 12 is exhibited, the horizontal response displacement is suppressed to δ 1 and the response member force is suppressed to H 1 .
[0036]
In the case of a large earthquake (Fig. 5), in the conventional column base structure, although the RC column is plasticized and a slight hysteresis attenuation can be expected, the horizontal response displacement becomes very large as δ 2 ′, and the response is accordingly accompanied. The member force also becomes the ultimate strength H.
[0037]
On the other hand, in the column base structure 11 of the present embodiment, the hysteresis damping due to the diagonal member 12 is exhibited, so that the horizontal response displacement is suppressed to δ 1 ′ and the response member force is suppressed to H 1 ′.
[0038]
As described above, according to the column base structure 11 according to this embodiment, the response displacement at the time of earthquake and the response member force at the time of earthquake can be significantly reduced by the hysteresis damping action by the diagonal member 12 as compared with the conventional case.
[0039]
Further, since the diagonal rigidity 12 can be loaded with the horizontal rigidity, the cross section of the RC pillar 2 can be reduced, and the scale of the RC pillar 2 and thus the scale of the footing 8 and the pile 7 can be reduced. For example, if such a column base structure 11 is applied to a viaduct substructure, the construction cost of the substructure can be greatly reduced.
[0040]
In the present embodiment, the diagonal member of the present invention is constituted by the diagonal member 12 in which the hysteresis damping material 13 such as extremely mild steel having the hysteresis damping characteristic is interposed between the rod members 14, 14. The diagonal material shown in FIG. 6 may be used.
[0041]
Here, the diagonal member 12a shown in FIG. 6 (a) is formed by interposing a hysteresis damping material 13 such as extremely mild steel having hysteresis damping characteristics between the rod members 14 and 14 as in the embodiment. The damping material is configured to exhibit hysteresis damping against bending deformation.
[0042]
The diagonal member 12b shown in FIG. 6 (b) is formed by interposing a hysteresis damping material 13 such as extra mild steel at the column joint end of the rod material 14 so that the hysteresis damping material exhibits hysteresis damping against shear deformation. It is configured.
[0043]
In the present embodiment, the diagonal member 12 is pin-joined to the footing 8 and the RC pillar 2. However, the oblique member joining type is not limited to pin joining, and instead of this, a rigid joint may be used. It doesn't matter.
[0044]
In the present embodiment, the pair of diagonal members 12, 12 are arranged so as to be back-to-back on both sides of the leg portion of the RC column 2, but it is not always necessary to arrange the pair of diagonal members 12 in pairs. 2 may be arranged on the side of the leg portion, or a plurality of the arrangement may be arranged so as to surround the RC pillar 2.
[0045]
FIG. 7 shows a column base structure 11a in which a single diagonal member 12 is arranged in a cane-like manner on each RC column 2 so as to be positioned outside the RC frame 4 and FIG. A column base structure 11b is shown in which a single diagonal member 12 is arranged in a cane-like manner on each RC column 2 so as to be positioned inside the RC rigid frame 4.
[0046]
In such a configuration, when the single diagonal member 12 is disposed so as to be located outside the RC frame 4 in the former case, it is suitable for the case where the inside of the RC frame 4 is used as a space such as a road or a track. In the latter case, that is, when the single diagonal member 12 is arranged so as to be located inside the RC rigid frame 4, it is suitable when the outside of the RC rigid frame 4 is adjacent to a road or a river.
[0047]
(Second Embodiment)
[0048]
Next, the seismic reinforcement method according to the second embodiment will be described. Note that components that are substantially the same as those of the first embodiment are denoted by the same reference numerals, and description thereof is omitted.
[0049]
In the seismic reinforcement method according to the present embodiment, a pair of diagonal members 12 and 12 are respectively pin-bonded to an existing RC column 2 which is a concrete column erected on the footing 8 at one end and on the footing at the other end. As shown in FIG. 1, the RC pillars are arranged in the shape of a cane on both sides of the leg part.
[0050]
If it does in this way, the restoring force characteristic of the whole column base structure will have initial rigidity larger than the case of only RC pillar 2 by the part which the rigidity of diagonal member 12 adds, and the response displacement with respect to an input earthquake will reduce.
[0051]
Further, due to the damping action of the diagonal member 12 due to the hysteresis damping characteristic, the response displacement to the input earthquake is further suppressed, and the member force generated in the column base structure is also reduced.
[0052]
As described above, according to the seismic reinforcement method according to the present embodiment, when seismic waves of the same scale are input, the existing RC pillars are increased by the amount of rigidity by providing the pair of diagonal members 12 and 12. 2 is greatly reduced, and the response displacement of the existing RC column 2 is further suppressed and the response member force is reduced by the amount that the hysteresis damping characteristic is exhibited by the pair of diagonal members 12, 12. . Further, the vibration of the RC pillar 2 can be quickly converged.
[0053]
In the present embodiment, the diagonal member of the present invention is configured by the diagonal member 12 in which the hysteresis damping material 13 such as extremely mild steel having a hysteresis damping characteristic is interposed between the rod members 14 and 14. Similarly, an oblique material shown in FIG. 6 may be used instead.
[0054]
Further, in the present embodiment, the diagonal member 12 is pin-joined to the footing 8 and the RC pillar 2, but, similarly to the first embodiment, a rigid joint may be used instead of the pin joint.
[0055]
The number or arrangement of the diagonal members 12 is the same as that of the first embodiment, and it is not always necessary to arrange the diagonal members 12 in pairs. The single diagonal members 12 may be arranged on the side of the leg portion of the RC pillar 2. Alternatively, a plurality may be arranged so as to surround the RC pillar 2.
[0056]
【The invention's effect】
As described above, according to the column base structure and the seismic reinforcement method according to the present invention, it is possible to significantly reduce the response displacement during earthquake and the response member force during earthquake due to the hysteresis damping action by the diagonal member. . In addition, since it is possible to impose horizontal rigidity on the diagonal members, it is possible to reduce the cross section of the concrete column, thereby reducing the size of the concrete column, and thus the size of the footing and piles. If the structure is applied to a viaduct substructure, the construction cost of the substructure can be greatly reduced.
[0057]
[Brief description of the drawings]
FIG. 1 is a front view of a viaduct substructure to which a column base structure according to the present embodiment is applied as viewed from a bridge axis direction.
FIG. 2 is a detailed view of a column base structure according to the present embodiment.
FIG. 3 is a view showing an operation of a column base structure according to the present embodiment.
FIG. 4 is a view showing the operation of the column base structure according to the present embodiment.
FIG. 5 is a view showing the operation of the column base structure according to the present embodiment.
FIG. 6 is a detailed view of a diagonal member according to a modified example.
FIG. 7 is a front view of a viaduct substructure to which a column base structure according to a modification is applied as viewed from the bridge axis direction.
FIG. 8 is a front view of a viaduct substructure to which a column base structure according to another modification is applied as viewed from the bridge axis direction.
[Explanation of symbols]
2 RC pillar (concrete pillar)
8 Footing 11, 11a, 11b Column base structure 12, 12a, 12b Diagonal material

Claims (2)

履歴減衰特性を有する斜材をその一端がフーチングに他端が該フーチングに立設されたコンクリート柱にそれぞれ接合されるように前記コンクリート柱の脚部側方に方杖状に配置したことを特徴とする柱脚構造。A diagonal member having a hysteresis damping characteristic is arranged in a cane-like manner on the side of the leg of the concrete column such that one end thereof is joined to the footing and the other end is joined to the concrete column standing on the footing. Column base structure. 履歴減衰特性を有する斜材をその一端がフーチングに他端が該フーチングに立設されたコンクリート柱にそれぞれ接合されるように前記コンクリート柱の脚部側方に方杖状に配置することを特徴とする耐震補強方法。A diagonal member having a hysteresis damping characteristic is arranged in a cane shape on the side of the leg of the concrete column such that one end thereof is joined to the footing and the other end is joined to the concrete column standing on the footing. Seismic reinforcement method.
JP2001271302A 2001-09-07 2001-09-07 Column base structure and seismic reinforcement method Expired - Fee Related JP4479138B2 (en)

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JP6645770B2 (en) * 2015-08-25 2020-02-14 東日本旅客鉄道株式会社 Seismic reinforcement structure
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