JP2004036130A

JP2004036130A - Bridge falling preventive device

Info

Publication number: JP2004036130A
Application number: JP2002192049A
Authority: JP
Inventors: Hiroyuki Sakurai; 桜井　弘幸
Original assignee: Toyo Tire and Rubber Co Ltd
Current assignee: Toyo Tire Corp
Priority date: 2002-07-01
Filing date: 2002-07-01
Publication date: 2004-02-05

Abstract

<P>PROBLEM TO BE SOLVED: To stably maintain high absorbing performance against an impactive compressive load such as a big earthquake while simplifying and miniaturizing the whole structure and reducing weight and costs by remarkably increasing the allowable bearing stress by enhancing the material strength of an elastic cushioning material itself. <P>SOLUTION: This bridge falling preventive device is constituted as a structure for laminating a plurality of short fiber reinforced rubber 4A formed in a sheet shape by kneading a plurality of short fibers 4b in a rubber elastic body 4a by mutually applying an orientation angle so that the orientation angle of the fibers 4b of the respective short fiber reinforced rubber 4A is equally spaced in the peripheral direction, and is used as the elastic cushioning material 4 fixed to and held by a load receiving plate 3 of a bracket 1 fixed to an end part vicinal side wall surface of a bridge beam. <P>COPYRIGHT: (C)2004,JPO

Description

【０００１】
【発明の属する技術分野】
本発明は、地震等の外力が加わった場合に橋桁が橋脚や橋台等の下部構造物から落下することを防止するように構成されている落橋防止装置に関するものである。
【０００２】
【従来の技術】
この種の落橋防止装置として従来より次のような構成のものが知られている。その一つは、図４及び図５に示すように、橋脚や橋台等の下部構造物２１上に載架された鉄鋼製、鉄筋コンクリート製あるいはプレストレスコンクリート製の橋桁２２Ａの端部近傍の側壁面に固定されたブラケット１と、このブラケット１の前面側に固定された二つ割り形式のケーブルガイド２と、このケーブルガイド２の背面側に位置するブラケット１の荷重受け板３に固定保持された弾性緩衝材４と、この弾性緩衝材４、ブラケット１の荷重受け板３及びケーブルガイド２の中央部を貫通して隣接する橋桁２２Ｂの端部近傍の側壁面側に固定のブラケット１間に亘り架設されたＰＣ鋼等の連結ケーブル５と、この連結ケーブル５の端部に固定されたストッパー６と弾性緩衝材４の間に介在されたスプリング７等とを具備してなり、上記弾性緩衝材４は、クロロプレンゴムなどの弾性ゴム単体から構成されている。
【０００３】
上記構成の落橋防止装置２０においては、橋桁２２Ａ，２２Ｂの温度変化に伴う伸縮及び地震等の外力が作用した場合の橋桁２２Ａ，２２Ｂの相対移動をスプリング７の圧縮変位によって吸収する一方、大地震等によって橋桁２２Ａ，２２Ｂが大きく移動することに伴いスプリング７が最大限にまで弾性的に縮小され剛体化された状態で連結ケーブル５を介してブラケット１の荷重受け板３に作用する衝撃的な圧縮荷重を弾性緩衝材４の圧縮変形により吸収する。これによって、衝撃荷重がブラケット１や連結ケーブル５に加わることを緩和し、落橋しようとする橋桁２２Ａ，２２Ｂを連結ケーブル５で連結支持して下部構造物２１からの脱落を防止する。
【０００４】
他の一つは、例えば特開平１１−６１７４０号公報、特開平１０−１３１１２３号公報、特開２０００−２２０１１１号公報等に開示されているように、上記の図５に示す落橋防止装置２０と同様な構成要素を備えたものを基本構成とし、これに加えて、弾性ゴム単体からなる弾性緩衝材をブラケットに固定されたシリンダ（筒状部材）内に収容させるとともに、そのシリンダ内にスプリングを介して作用する圧縮荷重を弾性緩衝材に伝達するピストン状の支圧板を摺動自在に嵌合保持させて弾性緩衝材をシリンダ及び支圧板により密閉するように構成したものであり、このような構成の落橋防止装置の場合は、衝撃的な圧縮荷重を受けたとき、弾性緩衝材が支圧板で密閉されることで、この弾性緩衝材の許容支圧応力を高めて小さな断面積の弾性緩衝材で衝撃的な圧縮荷重を支持して所定の落橋防止機能を発揮する。
【０００５】
【発明が解決しようとする課題】
上記した従来の落橋防止装置のうち、図５に示したような構成を有する前者のものでは、弾性緩衝材４を構成する弾性ゴム単体の材料強度が連結ケーブル５に比べて非常に小さく、この弾性緩衝材４で連結ケーブル５と同等な強度を負担させるためには弾性緩衝材４の受圧面積を大きく設定する必要があり、その結果、弾性緩衝材４自体が大径化するのみならず、周辺部材、例えば弾性緩衝材４を固定保持する荷重受け板３を有するブラケット１等も大きくしなければならないことから、落橋防止装置２０全体が大型化、重量化して、該装置２０の施工作業を複雑化するとともに、コストが嵩み、さらに、大地震等による衝撃的な圧縮荷重の負担によって弾性緩衝材４が永久変形して塑性化され、以降の衝撃的圧縮荷重に対して高い吸収性能を安定よく発揮させることができないという問題がある。
【０００６】
一方、シリンダ及び支圧板を付加した構成を有する後者のものでは、大きな衝撃的圧縮荷重を受けたとき、弾性緩衝材を密閉することで、この弾性緩衝材の許容支圧応力を高めることが可能であり、その分だけ弾性緩衝材の断面積を縮小して前者のものに比べて落橋装置全体の小型化、軽量化が図れ、かつ、施工作業の容易化及びコストダウンが図れるという利点を有している。しかしながら、この後者の落橋防止装置においても、弾性緩衝材はあくまでもクロロプレンゴム等の弾性ゴム単体であるから、弾性緩衝材自体の材料強度が小さく、それに伴い許容支圧応力も低い。そのため、衝撃的な圧縮荷重が作用したときの弾性緩衝材の密閉化による許容支圧応力の増大を見込んだとしても、この弾性緩衝材の断面積の縮小度合は僅かであり、また、弾性緩衝材の他にシリンダ及び支圧板等を付加する必要があることも相俟って、装置全体の構造が複雑になるとともに、小型化、軽量化並びにコストダウンにも自ずと限界があった。
【０００７】
本発明は上記のような実情に鑑みてなされたもので、弾性緩衝材自体の材料強度を高めることで許容支圧応力の著しい増大を図り、全体構造を簡単にし、かつ、小型化、軽量化並びにコストダウンを実現しながら、大地震等による衝撃的な圧縮荷重に対して高い吸収性能、ひいては落橋防止機能を常に安定よく維持することができる落橋防止装置を提供することを目的としている。
【０００８】
【課題を解決するための手段】
上記目的を達成するために、本発明に係る落橋防止装置は、橋桁の端部近傍の側壁面に固定されたブラケットと、このブラケットの荷重受け板に固定保持された弾性緩衝材と、この弾性緩衝材及びブラケットの荷重受け板の中央部を貫通して隣接する橋桁側に固定のブラケット間に亘り架設された連結ケーブルと、この連結ケーブルの端部に固定されたストッパーと弾性緩衝材の間に介在されたスプリングとを具備してなる落橋防止装置であって、
上記弾性緩衝材は、ゴム弾性体中に短繊維を混練してシート状に形成された短繊維補強ゴムの複数枚を、各短繊維補強ゴムの繊維の配向方向が周方向で等分配置されるように互いに配向角度を付けて積層した構造に構成されていることを特徴とするものである。
【０００９】
上記構成の本発明によれば、複数枚の短繊維補強ゴムが積層された構造の弾性緩衝材を使用することにより、弾性ゴム単体のものに比べて弾性緩衝材の材料強度（耐力）が高められて圧縮荷重に対するエネルギー吸収能力の向上が図れるとともに、シリンダ及び支圧板等を付加しなくても弾性緩衝材自体の許容支圧応力の増大を図ることが可能となる。これによって、連結ケーブルと同等な強度を負担させるために必要な弾性緩衝材の受圧面積が小さくてすみ、その分だけ弾性緩衝材の断面積を縮小することが可能で、落橋装置全体の構造の簡単化と共に小型化、軽量化が図れ、それに伴って施工作業の容易化及びコストダウンも図れる。また、弾性緩衝材を構成する複数枚の短繊維補強ゴムが、それらの繊維の配向方向が周方向で等分配置されるように互いに配向角度を付けて積層された構造であるから、大地震等による衝撃的な圧縮荷重の負担によって弾性緩衝材が永久変形して塑性化されたり、繊維の破損により降伏点に達したりすることがなく、予想される最大圧縮荷重のもとでも極めて高い耐力を維持するだけでなく、弾性緩衝材が全体的にほぼ均等に圧縮変形して偏り変形や局部的な歪みの発生がなく、常に一定の支圧面積を確保することが可能となり、これによって、地震等のように繰り返し作用する衝撃圧縮荷重に対しても常に高いエネルギー吸収性能、ひいては落橋防止機能を安定よく発揮させることが可能である。
【００１０】
上記構成の落橋防止装置において、上記積層構造の弾性緩衝材を構成する複数枚の短繊維補強ゴムの配向角度は、該弾性緩衝材の積層加工面（製造面）を考慮すると、請求項２に記載のように、上下に隣接する短繊維補強ゴム間で９０°もしくは４５°に設定されていることが好ましいが、エネルギー吸収性能の保持面から考慮すると、複数枚の短繊維補強ゴムをそれらの繊維の配向方向が放射状に等分配置されるように、｛３６０／Ｎ（短繊維補強ゴムの積層数）｝の角度単位でずらせて積層することが特に好ましい。
【００１１】
また、本発明において、請求項３に記載のように、積層構造の弾性緩衝材の露出面全体を耐候性ゴムで被覆することによって、長年月に亘り風雨に晒され、かつ、激しい温度変化に見舞われる条件下で設置使用される弾性緩衝材、特にゴムの劣化等を防いで長年月経過後においても所定の落橋防止機能を確実に発揮させることができる。
【００１２】
さらに、本発明において、弾性緩衝材は、請求項４に記載のように、少なくとも三枚以上の短繊維補強ゴムの積層構造に構成されていることが望ましい。これは短繊維補強ゴムが二枚以下の場合は、この短繊維補強ゴムに反り等が発生して受圧面積が微妙に変化して性能が低下する可能性があるが、三枚以上の積層構造とすることによって、反り等の発生を防いで性能を長期間に亘り安定よく保持することが可能である。
【００１３】
【発明の実施の形態】
以下、本発明の実施の形態を図面にもとづいて説明する。
図１は本発明に係る落橋防止装置の要部の縦断面図であり、同図において、１〜３及び５〜７の符号を付した構成要素は、図５に示した従来の落橋防止装置における構成要素と全く同一のものであるため、それら構成要素についての詳しい説明は省略する。また、図１に示す落橋防止装置１０の使用態様も図４と同様であるため、ここでは図示を省略する。
【００１４】
本発明に係る落橋防止装置１０における弾性緩衝材４は、図２に明示するように、天然ゴムからなるゴム弾性体４ａ中に、例えばポリエステルやナイロンなど長さが３〜３０ｍｍ程度、好ましくは３〜１５ｍｍの合成短繊維４ｂ…を混練して厚さｔが３〜２０ｍｍ程度、好ましくは５〜１０ｍｍのシート状に形成された短繊維補強ゴム４Ａの複数枚（図面上では、９枚で示すが、３枚以上であればよい）を、各短繊維補強ゴム４Ａの短繊維４ｂ…の配向方向が周方向で等分に配置されるように、上下に隣接する短繊維補強ゴム４Ａ，４Ａ間で９０°もしくは４５°の配向角度を付けて積層した構造に構成されている。
【００１５】
上記積層構造の弾性緩衝材４の露出面全体、すなわち、積層方向の上下面、外周面及び連結ケーブル５が貫通する中央の貫通孔４Ｂの内周面は、クロロプレンゴム等の耐候性に優れたカバーゴム８で被覆されている。
【００１６】
上記のような短繊維補強ゴム４Ａの積層構造から構成された弾性緩衝材４を使用してなる本発明に係る落橋防止装置１０においては、弾性緩衝材４自体の材料強度（耐力）が弾性ゴム単体のものに比べて高められて圧縮荷重に対するエネルギー吸収能力が向上するとともに、シリンダ及び支圧板等を用いなくても弾性緩衝材４自体の許容支圧応力を増大することが可能である。これによって、連結ケーブル５と同等な強度を負担させるために必要となる弾性緩衝材４の受圧面積が小さくてすみ、その分だけ弾性緩衝材４の断面積を縮小することが可能となり、落橋装置１０全体の構造の簡単化と共に小型化、軽量化が図れ、それに伴って施工作業の容易化及びコストダウンも図れる。
【００１７】
また、弾性緩衝材４を構成する複数枚の短繊維補強ゴム４Ａが、各繊維４ｂ…の配向方向が周方向で等分に配置されるように互いに配向角度を付けて積層された構造であるから、大地震等によって衝撃的な圧縮荷重を負担したとしても弾性緩衝材４の短繊維補強ゴム４Ａが永久変形して塑性化されたり、短繊維４ｂ…の破損により降伏点に達したりすることがなく、予想される最大圧縮荷重のもとでも極めて高い破壊強度（耐力）を維持するとともに、弾性緩衝材４が全体的にほぼ均等に圧縮変形して偏り変形や局部的な歪みの発生もなく、常に一定の支圧面積を確保する。これによって、地震等のように繰り返し作用する衝撃圧縮荷重に対しても常に高いエネルギー吸収性能、ひいては落橋防止機能を安定よく発揮させることが可能である。
【００１８】
さらに、本発明に係る落橋防止装置１０では、弾性緩衝材４の露出面全体が耐候性ゴム８で被覆されているので、長年月に亘り風雨に晒され、かつ、激しい温度変化に見舞われる条件下での設置使用に際しても、弾性緩衝材４の特にゴム弾性体４ａの劣化等を防いで長年月経過後に地震等により大きな圧縮荷重が衝撃的に作用した場合も高いエネルギー吸収性能を発揮させて所定の落橋防止機能を確保することができる。
【００１９】
【実験例】
図５に示すように、弾性ゴム単体からなる弾性緩衝材を用いた従来品に対応する比較例と、図２に示すように、短繊維補強ゴムの複数枚を上下に隣接する短繊維補強ゴム間で繊維配向方向に９０°の角度を付けて積層した構造の弾性緩衝材を用いた本発明品に対応する実施例１，２とを試作し、これら各弾性緩衝材の設計値諸元を表１に示すように設定した上で、比較例及び実施例１，２それぞれの弾性緩衝材の性能試験を行った。
【００２０】
【表１】

【００２１】
性能試験は、最大荷重２０００ｋＮの２軸試験機を用いての圧縮試験であり、圧縮変形量は３０ｍｍ、加振周波数は０．０５Ｈｚとする。この圧縮試験による結果、比較例及び実施例１，２それぞれのばね定数及び耐力は表２に示すとおりであり、また、比較例及び実施例１，２それぞれの荷重−変位特性は、図３に示すとおりであった。
【００２２】
【表２】

【００２３】
表２及び図３からも明らかなように、実施例１は、変形量が２９ｍｍに至るまでは比較例よりも高い荷重を示し、３０ｍｍの変形量では比較例の荷重が実施例１よりも上まわることが確認された。実施例２は、変形量が３０ｍｍに至るまで比較例に比べて若干高い荷重を示すが、比較例に近い荷重−変位特性を有することが確認された。
また、実施例１，２共に耐力は３３０ｋＮ以上であり、連結ケーブルの引張荷重の（２／３）以上の耐力を有し、かつ、繊維の破損を原因とする降伏点は３０ｍｍの変形量に達するまで確認されない。
【００２４】
以上の実験結果から、短繊維補強ゴムの積層構造を用いた実施例１，２の弾性緩衝材では、連結ケーブルの引張荷重の（２／３）以上で比較例と同等の耐力を有しつつも、比較例の許容支圧応力１８．０Ｎ／ｍｍ２　に対して１０Ｎ／ｍｍ２（１５５％）増大した許容支圧応力を２８．０Ｎ／ｍｍ２　とでき、比較例に比べて弾性緩衝材を約６５％程度の小径化が可能であることを確認できた。
【００２５】
【発明の効果】
以上要するに、本発明は、複数枚の短繊維補強ゴムの積層構造の弾性緩衝材を使用することにより、弾性緩衝材の材料強度（耐力）を高めて弾性ゴム単体のものに比べて弾性緩衝材自体の許容支圧応力の著しい増大を図ることができ、これによって、連結ケーブルと同等な強度を負担させるために必要な弾性緩衝材の受圧面積、ひいては断面積の縮小を可能にして、落橋装置全体の構造の簡単化と共に小型化、軽量化並びに施工作業の容易化及びコストダウンを実現することができる。それでいて、弾性緩衝材を構成する複数枚の短繊維補強ゴムをそれらの繊維の配向方向が周方向で等分配置されるように互いに配向角度を付けて積層した構造としているので、大地震等による衝撃的な圧縮荷重の負担によっても弾性緩衝材が永久変形して塑性化したり、繊維の破損により降伏点に達したりすることがなく、予想される最大圧縮荷重のもとでも極めて高い耐力を維持するだけでなく、弾性緩衝材が全体的にほぼ均等に圧縮変形して偏り変形や局部的な歪みの発生もなく、常に一定の支圧面積を確保させて地震等のような繰り返し衝撃圧縮荷重に対しても常に高いエネルギー吸収性能、ひいては落橋防止機能を安定よく発揮させることができるという効果を奏する。
【００２６】
特に、請求項３のように、積層構造の弾性緩衝材の露出面全体を耐候性ゴムで被覆する構成を採用することによって、長年月に亘り風雨に晒され、かつ、激しい温度変化に見舞われる条件下で設置使用される弾性緩衝材のゴムの劣化等を防いで長年月経過後においても所定の落橋防止機能を確実に発揮させることができる。
【図面の簡単な説明】
【図１】本発明に係る落橋防止装置の要部の縦断面図である。
【図２】同上落橋防止装置における弾性緩衝材の拡大縦断面図である。
【図３】圧縮性能試験結果の一つである荷重−変位特性図である。
【図４】落橋防止装置の施工状態を説明する部分断面図である。
【図５】従来の落橋防止装置の要部の縦断面図である。
【符号の説明】
１　ブラケット
３　荷重受け板
４　弾性緩衝材
４ａ　ゴム弾性体
４ｂ　短繊維
４Ａ　短繊維補強ゴム
５　連結ケーブル
６　ストッパー
７　スプリング
８　耐候性カバーゴム
１０　落橋防止装置[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a fall prevention device configured to prevent a bridge girder from falling from a substructure such as a pier or an abutment when an external force such as an earthquake is applied.
[0002]
[Prior art]
The following configuration is conventionally known as this kind of bridge prevention device. One of them is, as shown in FIGS. 4 and 5, a side wall surface near an end of a bridge girder 22A made of steel, reinforced concrete or prestressed concrete mounted on a lower structure 21 such as a pier or an abutment. , A split-type cable guide 2 fixed to the front side of the bracket 1, and an elastic buffer fixed and held to a load receiving plate 3 of the bracket 1 located on the rear side of the cable guide 2. Material 4 and the elastic cushioning material 4, the load receiving plate 3 of the bracket 1, and the central portion of the cable guide 2, and the bridge portion 22B is bridged between the fixed brackets 1 on the side wall surface near the end portion of the adjacent bridge girder 22B. A connecting cable 5 made of PC steel or the like, a stopper 6 fixed to an end of the connecting cable 5 and a spring 7 interposed between the elastic cushioning members 4 and the like. Buffer material 4 is made of an elastic rubber alone such as chloroprene rubber.
[0003]
In the fall prevention device 20 having the above configuration, the relative displacement of the

bridge girders

22A and 22B when an external force such as expansion and contraction and an earthquake due to a temperature change of the

bridge girders

22A and 22B acts is absorbed by the compression displacement of the spring 7, while a large earthquake occurs. As the

bridge girders

22A and 22B move largely due to, for example, the spring 7 is elastically reduced to the maximum and rigidized, and the impact acting on the load receiving plate 3 of the bracket 1 via the connecting cable 5 in a state of being rigid. The compression load is absorbed by the compression deformation of the elastic cushioning material 4. This alleviates the impact load from being applied to the bracket 1 and the connecting cable 5, and connects and supports the

bridge girders

22A and 22B to be dropped by the connecting cable 5 to prevent the bridge girders from dropping off from the lower structure 21.
[0004]
The other one is, as disclosed in, for example, JP-A-11-61740, JP-A-10-131123, JP-A-2000-220111, and the like, as shown in FIG. The basic configuration is the one provided with similar components. In addition to this, an elastic cushioning material made of elastic rubber alone is accommodated in a cylinder (cylindrical member) fixed to the bracket, and a spring is mounted in the cylinder. A piston-like supporting plate that transmits a compressive load acting on the elastic buffer to the elastic buffer is slidably fitted and held, and the elastic buffer is sealed by the cylinder and the supporting plate. In the case of a bridge fall prevention device with a structure, when an impact compressive load is applied, the elastic bearing material is hermetically sealed by the bearing plate to increase the allowable bearing stress of the elastic buffer material and reduce the cross-sectional area. In favor of shocking compressive load of an elastic cushioning material exhibits a predetermined girder prevention function.
[0005]
[Problems to be solved by the invention]
Among the above-mentioned conventional fall prevention devices, in the former device having the configuration as shown in FIG. 5, the material strength of the elastic rubber alone constituting the elastic cushioning material 4 is much smaller than that of the connection cable 5, In order for the elastic cushioning member 4 to bear the same strength as that of the connecting cable 5, it is necessary to set a large pressure receiving area of the elastic cushioning member 4. As a result, not only the elastic cushioning member 4 itself increases in diameter, but also Peripheral members, for example, the bracket 1 having the load receiving plate 3 for fixing and holding the elastic cushioning member 4 also need to be made large, so that the entire anti-falling bridge device 20 becomes larger and heavier, and the construction work of the device 20 is reduced. In addition to the complexity, the cost increases, and the elastic shock-absorbing material 4 is permanently deformed and plasticized due to the impact of a compressive load caused by a large earthquake or the like. There is a problem that can not be stabilized well exhibited.
[0006]
On the other hand, in the case of the latter having a configuration in which a cylinder and a supporting plate are added, it is possible to increase the allowable bearing stress of the elastic cushioning material by sealing the elastic cushioning material when receiving a large impact compressive load. Therefore, the cross-sectional area of the elastic cushioning material is reduced by that much, so that the whole bridge-falling device can be reduced in size and weight compared to the former, and the construction work can be facilitated and the cost can be reduced. are doing. However, also in the latter bridge-fall prevention device, since the elastic cushioning material is a single elastic rubber such as chloroprene rubber, the material strength of the elastic cushioning material itself is small, and accordingly the allowable bearing stress is also low. Therefore, even if it is anticipated that the allowable bearing stress will increase due to the sealing of the elastic cushioning material when a shocking compressive load is applied, the degree of reduction in the cross-sectional area of the elastic cushioning material is small, and In addition to the necessity of adding a cylinder and a supporting plate in addition to the material, the structure of the entire apparatus becomes complicated, and there is naturally a limit in reducing the size, weight, and cost.
[0007]
SUMMARY OF THE INVENTION The present invention has been made in view of the above-described circumstances. By increasing the material strength of the elastic cushioning material itself, the allowable bearing stress is significantly increased, the overall structure is simplified, and the size and weight are reduced. It is another object of the present invention to provide a device for preventing a bridge from falling, which can maintain a high absorption performance against a shocking compressive load due to a large earthquake or the like and, moreover, a function for preventing a bridge from falling at all times while realizing cost reduction.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, a bridge fall prevention device according to the present invention includes a bracket fixed to a side wall surface near an end of a bridge girder, an elastic cushioning material fixed and held on a load receiving plate of the bracket, A connecting cable extending between brackets fixed to the bridge girder adjacent to the bridge girder penetrating the center portion of the cushioning member and the load receiving plate of the bracket, and between a stopper fixed to an end of the connecting cable and the elastic cushioning material. Bridge prevention device comprising a spring interposed in the
The above-mentioned elastic cushioning material is obtained by kneading short fibers into a rubber elastic body and arranging a plurality of sheets of short fiber reinforced rubber formed in a sheet shape, in which the orientation directions of the fibers of each short fiber reinforced rubber are equally divided in the circumferential direction. Thus, they are configured to be laminated with an orientation angle with each other.
[0009]
According to the present invention having the above configuration, by using the elastic cushioning material having a structure in which a plurality of short fiber reinforced rubbers are laminated, the material strength (proof strength) of the elastic cushioning material is increased as compared with a single elastic rubber. As a result, the energy absorbing ability against the compressive load can be improved, and the allowable bearing stress of the elastic cushioning material itself can be increased without adding a cylinder and a bearing plate. As a result, the pressure receiving area of the elastic cushioning material necessary to bear the same strength as that of the connecting cable can be reduced, and the cross-sectional area of the elastic cushioning material can be reduced by that much, and the overall structure of the drop bridge device can be reduced. With simplification, downsizing and weight reduction can be achieved, and accordingly, simplification of construction work and cost reduction can be achieved. In addition, since a plurality of short fiber reinforced rubbers constituting the elastic cushioning material are stacked at an orientation angle to each other so that the orientation directions of the fibers are equally spaced in the circumferential direction, a large earthquake occurs. The elastic shock absorbing material is not permanently deformed and plasticized due to the impact of the compressive load due to the impact of the fiber, and the yield point is not reached due to fiber breakage. In addition, the elastic cushioning material is almost uniformly compressed and deformed as a whole, so that there is no uneven deformation or local distortion, and it is possible to always secure a constant bearing area. It is possible to constantly exhibit a high energy absorption performance and a stable fall prevention function even for impact compression loads that repeatedly act like an earthquake.
[0010]
In the bridge-fall prevention device having the above structure, the orientation angle of the plurality of short fiber reinforced rubbers constituting the elastic cushioning material having the laminated structure is defined by claim 2 in consideration of the lamination processing surface (production surface) of the elastic cushioning material. As described, it is preferable that the angle is set to 90 ° or 45 ° between vertically adjacent short fiber reinforced rubbers. However, in view of holding energy absorbing performance, a plurality of short fiber reinforced rubbers are used. It is particularly preferable to stack the fibers by shifting them by an angle unit of {360 / N (number of laminated short fiber reinforced rubbers)} so that the orientation directions of the fibers are evenly arranged radially.
[0011]
Further, in the present invention, by covering the entire exposed surface of the elastic cushioning material of the laminated structure with the weather-resistant rubber as described in claim 3, it is exposed to wind and rain for many months, and is subjected to severe temperature change. It is possible to prevent the deterioration of the elastic cushioning material, particularly rubber, which is installed and used under the conditions encountered, and to reliably exhibit the predetermined bridge prevention function even after many months have passed.
[0012]
Further, in the present invention, it is desirable that the elastic cushioning material has a laminated structure of at least three or more short fiber reinforced rubbers. This is because if the number of short fiber reinforced rubbers is two or less, the short fiber reinforced rubber may warp and the pressure receiving area may slightly change to lower the performance. By doing so, it is possible to prevent the occurrence of warpage or the like and maintain the performance stably over a long period of time.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a longitudinal sectional view of a main part of an apparatus for preventing a bridge from falling according to the present invention, in which components denoted by reference numerals 1 to 3 and 5 to 7 are conventional devices for preventing a bridge from falling as shown in FIG. Since these are exactly the same as the components in the above, detailed description of those components will be omitted. The usage mode of the fallen bridge prevention device 10 shown in FIG. 1 is the same as that of FIG.
[0014]
As shown in FIG. 2, the elastic cushioning material 4 in the bridge-fall prevention device 10 according to the present invention has a length of, for example, about 3 to 30 mm, preferably 3 to 30 mm, such as polyester or nylon, in a rubber elastic body 4 a made of natural rubber. A plurality of short fiber reinforced rubbers 4A formed into a sheet having a thickness t of about 3 to 20 mm, preferably 5 to 10 mm by kneading synthetic short fibers 4b of about 15 mm (in the drawing, 9 sheets are shown). However, three or more short fiber reinforced

rubbers

4A, 4A are vertically arranged such that the orientation direction of the short fibers 4b of each short fiber reinforced rubber 4A is equally spaced in the circumferential direction. The structure is such that the layers are stacked with an orientation angle of 90 ° or 45 ° between them.
[0015]
The entire exposed surface of the elastic cushioning material 4 having the laminated structure, that is, the upper and lower surfaces, the outer peripheral surface in the laminating direction, and the inner peripheral surface of the central through hole 4B through which the connecting cable 5 passes are excellent in weather resistance such as chloroprene rubber. It is covered with a cover rubber 8.
[0016]
In the bridge-fall prevention device 10 according to the present invention using the elastic cushioning member 4 having the laminated structure of the short fiber reinforced rubber 4A as described above, the material strength (proof strength) of the elastic cushioning member 4 itself is the elastic rubber. It is possible to increase the energy absorbing ability against a compressive load by increasing compared to a single unit, and to increase the allowable bearing stress of the elastic cushioning material 4 itself without using a cylinder and a bearing plate. As a result, the pressure receiving area of the elastic cushioning material 4 required to bear the same strength as that of the connection cable 5 can be reduced, and the cross-sectional area of the elastic cushioning material 4 can be reduced by that much, and the drop bridge device can be reduced. It is possible to reduce the size and weight as well as to simplify the structure of the entire structure 10, thereby facilitating the construction work and reducing the cost.
[0017]
Further, the structure is such that a plurality of short fiber reinforced rubbers 4A constituting the elastic cushioning member 4 are laminated at an orientation angle so that the orientation directions of the fibers 4b are equally spaced in the circumferential direction. Therefore, even if a shocking compressive load is borne by a large earthquake or the like, the short fiber reinforced rubber 4A of the elastic cushioning material 4 is permanently deformed and plasticized, or the short fiber 4b... In addition to maintaining the extremely high breaking strength (proof strength) even under the expected maximum compressive load, the elastic cushioning material 4 is almost uniformly compressed and deformed as a whole, causing uneven deformation and local distortion. Instead, always maintain a constant bearing area. As a result, it is possible to stably exhibit a high energy absorption performance and a stable bridge prevention function even for an impact compression load that repeatedly acts such as an earthquake.
[0018]
Furthermore, in the bridge-fall prevention device 10 according to the present invention, since the entire exposed surface of the elastic cushioning material 4 is covered with the weather-resistant rubber 8, it is exposed to wind and rain for many months and is subjected to severe temperature changes. Even when installed and used below, the elastic cushioning material 4, especially the rubber elastic body 4a, is prevented from deteriorating, etc., and even if a large compressive load is applied by impact due to an earthquake or the like after many months, a high energy absorbing performance is exhibited. A predetermined bridge prevention function can be secured.
[0019]
[Experimental example]
As shown in FIG. 5, a comparative example corresponding to a conventional product using an elastic cushioning material consisting of an elastic rubber alone, and as shown in FIG. Examples 1 and 2 corresponding to the present invention using an elastic cushioning material having a structure in which fibers are laminated at an angle of 90 ° in the fiber orientation direction were prototyped, and design values of these elastic cushioning materials were obtained. After setting as shown in Table 1, the performance test of the elastic cushioning material of each of Comparative Example, Examples 1 and 2, was performed.
[0020]
[Table 1]

[0021]
The performance test is a compression test using a biaxial testing machine with a maximum load of 2000 kN. The amount of compression deformation is 30 mm, and the vibration frequency is 0.05 Hz. As a result of this compression test, the spring constant and the proof stress of each of Comparative Example and Examples 1 and 2 are as shown in Table 2, and the load-displacement characteristics of each of Comparative Example and Examples 1 and 2 are shown in FIG. It was as shown.
[0022]
[Table 2]

[0023]
As is clear from Table 2 and FIG. 3, Example 1 shows a higher load than the comparative example until the deformation amount reaches 29 mm, and the load of the comparative example is higher than that of Example 1 at a deformation amount of 30 mm. It was confirmed that it turned. Example 2 showed a slightly higher load than the comparative example until the deformation amount reached 30 mm, but it was confirmed that it had a load-displacement characteristic close to that of the comparative example.
In addition, the proof stress of each of Examples 1 and 2 is 330 kN or more, the proof stress is equal to or more than (2/3) of the tensile load of the connection cable, and the yield point due to fiber breakage is 30 mm. Not confirmed until reached.
[0024]
From the above experimental results, the elastic cushioning materials of Examples 1 and 2 using the laminated structure of the short fiber reinforced rubber have the same proof stress as the comparative example at (2/3) or more of the tensile load of the connecting cable. Also, the allowable bearing stress increased by 10 N / mm2 (155%) from the allowable bearing stress of 18.0 N / mm2 of the comparative example can be set to 28.0 N / mm2, and the elastic cushioning material is about 65 times larger than that of the comparative example. It was confirmed that the diameter could be reduced by about%.
[0025]
【The invention's effect】
In short, the present invention increases the material strength (proof strength) of an elastic cushioning material by using an elastic cushioning material having a laminated structure of a plurality of short fiber reinforced rubbers, thereby improving the elastic cushioning material as compared with a single elastic rubber. It is possible to significantly increase the allowable bearing stress of itself, thereby reducing the pressure receiving area of the elastic cushioning material required to bear the same strength as the connecting cable, and consequently the cross-sectional area can be reduced. It is possible to realize a reduction in size and weight, simplification of construction work, and cost reduction as well as simplification of the entire structure. Nevertheless, the structure is such that a plurality of short fiber reinforced rubbers constituting the elastic cushioning material are laminated at an orientation angle to each other so that the orientation directions of the fibers are equally spaced in the circumferential direction. The elastic cushioning material is not permanently deformed and plasticized even under the impact of an impressive compressive load, nor does it reach the yield point due to fiber breakage, maintaining extremely high proof stress even under the expected maximum compressive load In addition to this, the elastic cushioning material compresses and deforms almost evenly as a whole, and does not generate uneven deformation or local distortion. This has the effect of always exhibiting a high energy absorption performance and, consequently, a function of preventing a bridge from falling.
[0026]
In particular, by adopting a configuration in which the entire exposed surface of the elastic cushioning material of the laminated structure is covered with weather-resistant rubber as in claim 3, it is exposed to wind and rain for many months and suffers a severe temperature change. By preventing deterioration of the rubber of the elastic cushioning material installed and used under the conditions, a predetermined bridge prevention function can be reliably exerted even after many months have passed.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view of a main part of a bridge prevention device according to the present invention.
FIG. 2 is an enlarged vertical sectional view of an elastic cushioning material in the falling bridge prevention device.
FIG. 3 is a load-displacement characteristic diagram which is one of the compression performance test results.
FIG. 4 is a partial cross-sectional view illustrating a construction state of the fall prevention device.
FIG. 5 is a longitudinal sectional view of a main part of a conventional bridge fall prevention device.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Bracket 3 Load receiving plate 4 Elastic cushioning material 4a Rubber elastic body 4b Short fiber 4A Short fiber reinforced rubber 5 Connecting cable 6 Stopper 7 Spring 8 Weatherproof cover rubber 10 Falling bridge prevention device

Claims

橋桁の端部近傍の側壁面に固定されたブラケットと、このブラケットの荷重受け板に固定保持された弾性緩衝材と、この弾性緩衝材及びブラケットの荷重受け板の中央部を貫通して隣接する橋桁側に固定のブラケット間に亘り架設された連結ケーブルと、この連結ケーブルの端部に固定されたストッパーと弾性緩衝材の間に介在されたスプリングとを具備してなる落橋防止装置であって、
上記弾性緩衝材は、ゴム弾性体中に短繊維を混練してシート状に形成された短繊維補強ゴムの複数枚を、各短繊維補強ゴムの繊維の配向方向が周方向で等分配置されるように互いに配向角度を付けて積層した構造に構成されていることを特徴とする落橋防止装置。A bracket fixed to the side wall surface near the end of the bridge girder, an elastic cushioning material fixedly held on a load receiving plate of the bracket, and a central portion of the elastic cushioning material and the load receiving plate of the bracket penetrating and adjacent to the bracket. What is claimed is: 1. A fall prevention device comprising: a connecting cable erected between brackets fixed on a bridge girder side; and a stopper fixed to an end of the connecting cable and a spring interposed between elastic cushioning materials. ,
The above-mentioned elastic cushioning material is obtained by kneading short fibers into a rubber elastic body and arranging a plurality of sheets of short fiber reinforced rubber formed in a sheet shape, in which the orientation directions of the fibers of each short fiber reinforced rubber are equally divided in the circumferential direction. A bridge-preventing device characterized in that it is constructed in such a manner that it is laminated with an orientation angle with respect to each other.

上記積層構造の弾性緩衝材を構成する複数枚の短繊維補強ゴムの配向角度が、上下に隣接する短繊維補強ゴム間で９０°もしくは４５°に設定されている請求項１に記載の落橋防止装置。2. The bridge prevention device according to claim 1, wherein the orientation angle of the plurality of short fiber reinforced rubbers constituting the elastic cushioning material of the laminated structure is set to 90 ° or 45 ° between vertically adjacent short fiber reinforced rubbers. 3. apparatus.

上記積層構造の弾性緩衝材の露出面全体が、耐候性ゴムで被覆されている請求項１または２に記載の落橋防止装置。The fall prevention device according to claim 1 or 2, wherein the entire exposed surface of the elastic cushioning material of the laminated structure is covered with weather resistant rubber.

上記弾性緩衝材は、少なくとも三枚以上の短繊維補強ゴムの積層構造に構成されている請求項１ないし３のいずれかに記載の落橋防止装置。The fall prevention device according to any one of claims 1 to 3, wherein the elastic cushioning material has a laminated structure of at least three or more short fiber reinforced rubbers.