JP3950284B2

JP3950284B2 - Method for reinforcing concrete slabs

Info

Publication number: JP3950284B2
Application number: JP2000188999A
Authority: JP
Inventors: 俊昭太田
Original assignee: Japan Science and Technology Agency; National Institute of Japan Science and Technology Agency
Current assignee: Japan Science and Technology Agency; National Institute of Japan Science and Technology Agency
Priority date: 2000-06-23
Filing date: 2000-06-23
Publication date: 2007-07-25
Anticipated expiration: 2020-06-23
Also published as: JP2002004226A

Description

【０００１】
【産業上の利用分野】
本発明は、既設の橋梁の鉄筋コンクリート床版の補強方法に関する。
【０００２】
【従来技術及び問題点】
現在、我が国では総延長約７５００ｋｍの道路橋があり、その適切な維持管理が重要な課題となっている。特に車両の重量が大型化されたことに伴って、許容応力度の引き上げが行われ、補修・補強を必要とするコンクリート床版が急増している。コンクリート床版の補修・補強方法としては、鋼板接着工法，上面又は下面での床版増厚工法，床版の打ち換え工法，縦桁増設工法等がある。例えば縦桁増設工法では、図１のように橋梁１の既設の縦桁２に隣接させて新たにコンクリート製の縦桁５を増設するもので、耐荷力を増大させ作用応力度を低減するのに効果があるが、死荷重が増加するうえ、工事に交通規制を必要とし、工期も長い。他の従来法もそれぞれ一長一短があり、何れも工事中に少なくとも片側の通行を遮断する必要がある。
【０００３】
【課題を解決するための手段】
本発明は、このような問題を解消すべく案出されたものであり、道路橋の通行を遮断することなく、短工期でかつ安価に橋梁を補修することを目的とする。
本発明のコンクリート床版の補強方法では、既設主桁 (4) に両端部が支持された仮設横桁 (13) を設け、仮設横桁 (13) に載置されたジャッキ (13a) により床版 (3) を押上げた状態で緊張ケーブル (11) を張設し、床版 (3) の下面に接着された新設縦桁 (10) に前記緊張ケーブル (11) によって揚力を付与した後、ジャッキ及び仮設横桁を撤去する。軽量でかつ十分な強度を得るためには、非硬化型連続炭素繊維製又はガラス繊維強化プラスチック製の緊張用ケーブルを用いることが好ましい。新設縦桁を非硬化型連続炭素繊維製又はガラス繊維強化プラスチック製にすると、死荷重が更に低減し、耐久性が向上する。
【０００４】
【作用】
床版３の劣化は、橋梁１を通過する車両等の重量により床版３に撓み変形が繰り返し発生することに起因する。そこで本発明では縦桁を増設して床版３を下から押上げ撓み変形を軽減することによって経時的な劣化の進行を抑制する。
本発明に従ったコンクリート床版の補強方法は、たとえば図２に示すように橋軸方向に伸びた縦桁２，２をもつ橋梁１に適用される。既設縦桁２，２はＩ型鋼等の既設主桁４，４を介して橋脚（図示せず）に支えられている。
まず断面Ｉ字状の新設縦桁１０を補強される既設橋梁１の縦桁２，２の中央で橋軸方向に床版３の下面に当接するように配置する。次に緊張ケーブル１１が既設縦桁２又は既設の主桁４の上部から、新設縦桁１０の下部に設けたケーブルサドル１２を経由して他方の既設縦桁２又は既設主桁４の上部に差渡される。緊張ケーブル１１は橋軸方向に所定の間隔で多数差渡される。緊張ケーブル１１は強い張力が掛けられた状態で張設されるため、新設縦桁１０が上方に持ち上げられる。その結果、橋梁１を通過する車両等の重量に対して床版３の撓み応力が軽減され、撓み変形の繰り返しによる床版の劣化が抑えられる。
【０００５】
本発明に従ったコンクリート床版の補強方法には、新設縦桁１０及び緊張ケーブル１１の材料として、好ましくは構造用新材料である炭素繊維やアラミド繊維，ガラス繊維素材等が用いられる。これら新材料は従来の土木構造材料に比べ、非常に軽量で強度もあるため、これら新材料を用いることにより、補強工事による死荷重の増大が抑制され、構造物自体の小型化や長大化、また施工の省人化・省力化等のさまざまな効果が期待される。また耐久性・耐食性も高いため、施工時にコンクリートの巻立て等の防錆処理が不要になり、施工後も維持管理が楽になる。具体的には、非硬化型連続炭素繊維（ＵＣＣＦ；Unresin Continuous Carbon Fibers）やガラス繊維強化プラスチック（ＧＦＲＰ；Glass Fiber Reinforced Plastic）が用いられる。ＵＣＣＦには、強度・弾性率が高く比重が小さい，耐食性・耐薬品性に優れる，可撓性のため輸送に有利である等の特長がある。ＧＦＲＰには、耐熱性が高く不燃性である，電気絶縁性が高い，色材を自由に選べる等の特長がある。
【０００６】
【実施の形態】
本発明に従ったコンクリート床版の補強方法の一例として、幅１２．６ｍ，全長２２ｍ，Ｉ型鋼製の既設縦桁２の高さ１．２ｍ，既設縦桁数６本，既設縦桁間隔２．１ｍである橋梁１を補強する場合を説明する（図３）。
補強材の新設縦桁１０には、高さ６５ｃｍ，長さ２２．２ｍ，断面積２２０ｃｍ²のＧＦＲＰ製Ｉ型縦桁（一本当り重量８８０ｋｇ）が５本用いられる。新設縦桁１０は床版３の下面にエポキシモルタルで接着され、対傾構の位置ではＬ型金具（図示せず）を用いてボルト接合する。緊張ケーブル１１は断面積１ｃｍ²のＵＣＣＦ製とし、一端を既設主桁４の上部にアンカ１４により固定し、新設縦桁１０下面に設けたケーブルサドル１２を経由して他端を他方の既設主桁４の上部にアンカ１４により固定し、一定の張力を掛けた状態で張設する（図４）。アンカ１４は、たとえば鋼製のラッパ状のパイプが用いられる。このアンカ１４を既設主桁４のウェブ上部にあけた穴に挿通し、緊張ケーブル１１をアンカ１４に挿通した後、緊張ケーブル１１の端部に結びコブをつくることで完全に緊張ケーブル１１はウェブに固定される。緊張ケーブル１１は直接既設主桁４のウェブに接触しないので損傷することなく耐久性が向上する。好ましくは挿通した緊張ケーブル１１とアンカ１４との間にエポキシ樹脂等を充填する。
緊張ケーブル１１の張設に際しては、床板３を押上げた状態にしておくことが好ましい。たとえば、図５のように既設主桁４の下部に支持された仮設横桁１３を設置し、仮設横桁１３の上に載置したジャッキ１３ａにより床版３を押上げることができる。また、緊張ケーブル１１の途中にターンバックルを設けて張力を調整することもできる。緊張ケーブル１１が張設された後、ジャッキ１３ａは揚力を緩めて撤去される。これにより、緊張ケーブル１１には床版３を押上げる適度の張力が掛けられる。仮設横桁１３は補強工事終了後に撤去される。
緊張ケーブル１１の張設間隔は、要求強度，荷重等を考慮して決められる。この例の場合には十分な強度を得るために、新設縦桁１０一本当り橋軸方向に６５ｃｍの間隔で３３本張設される。３３本の各緊張ケーブル１１は新設縦桁１０の下端に設けられたケーブルサドル１２により緊張ケーブル１１一本当り１００ｋｇｆ程度の張力が掛かり、新設縦桁１０一本には３３本の各緊張ケーブル１１の合計で１７００ｋｇｆ程度の揚力が与えられる。これにより、新設縦桁１０一本の自重８８０ｋｇｆを差し引いても８２０ｋｇｆ程度の揚力が床版３に与えられ、補強工事後の床版３の劣化を抑制することができる。
【０００７】
新設縦桁１０にコストの低いＩ形鋼も採用できる。この場合でも新設縦桁１０の自重１３００ｋｇｆを差し引いて４００ｋｇ程度の揚力が床版３に与えられ、補強工事後の床版３の劣化を抑制することができる。しかし、ＵＣＣＦやＧＦＲＰ等の新材料製の新設縦桁１０を用いるほうが耐食性の観点から好ましい。
【０００８】
【発明の効果】
以上に説明したように、本発明のコンクリート床版の補強方法は、既設縦桁の間に新設縦桁を設け、新設縦桁の下部を両側の既設縦桁に固定した緊張材で引上げている。このため、死荷重の増加を抑制しながら床版の補強をし、劣化を防止することができる。補強工事は簡単な構造で全て橋の下で行なえるので通行規制をする必要もなく、新たにコンクリートを打設する必要もないので工期も短縮できる。
【図面の簡単な説明】
【図１】従来工法の一例を示すモデル図
【図２】本発明に従った補強工事を説明する橋軸直角方向断面図
【図３】本発明に従った補強工事の一例を説明する斜視断面図
【図４】ケーブル端部を既設縦桁に固定する構造例
【図５】補強工事の施工中の状態
【符号の説明】
１：橋梁２：既設縦桁３：床版４：既設主桁５：縦桁１０：新設縦桁１１：緊張ケーブル１２：ケーブルサドル１３：仮設横桁１３ａ：ジャッキ[0001]
[Industrial application fields]
The present invention relates to a method for reinforcing an existing bridge reinforced concrete slab.
[0002]
[Prior art and problems]
Currently, there is a road bridge with a total length of about 7500 km in Japan, and its proper maintenance is an important issue. In particular, with the increase in the weight of vehicles, the allowable stress level has been raised, and concrete slabs that require repair and reinforcement are rapidly increasing. As concrete floor slab repair / reinforcement methods, there are a steel plate bonding method, a floor slab thickening method on the upper or lower surface, a floor slab replacement method, a stringer expansion method, and the like. For example, in the method of expanding a girder, a concrete girder 5 is newly added adjacent to the existing girder 2 of the bridge 1 as shown in FIG. 1 to increase the load carrying capacity and reduce the acting stress. Although it is effective, the dead load increases, traffic regulation is required for construction, and the construction period is long. Each of the other conventional methods has advantages and disadvantages, and it is necessary to block traffic on at least one side during construction.
[0003]
[Means for Solving the Problems]
The present invention has been devised to solve such a problem, and an object thereof is to repair a bridge in a short construction period and at a low cost without blocking the passage of a road bridge.
In the method for reinforcing a concrete floor slab of the present invention, a temporary cross girder (13) having both ends supported on an existing main girder (4 ) is provided, and the floor is placed by a jack (13a) placed on the temporary cross girder (13). After tension plate (11) is stretched in the state where plate (3) is pushed up, lift is applied to the newly installed stringer (10) bonded to the lower surface of floor slab (3 ) by means of tension cable (11) . Remove jacks and temporary cross beams. In order to obtain light weight and sufficient strength, it is preferable to use a tension cable made of non-curing continuous carbon fiber or glass fiber reinforced plastic. When the newly installed stringer is made of non-curing continuous carbon fiber or glass fiber reinforced plastic, the dead load is further reduced and the durability is improved.
[0004]
[Action]
The deterioration of the floor slab 3 is caused by repeated deformation of the floor slab 3 due to the weight of a vehicle or the like passing through the bridge 1. Therefore, in the present invention, the progress of deterioration over time is suppressed by increasing the stringers and reducing the bending deformation by pushing up the floor slab 3 from below.
The concrete slab reinforcing method according to the present invention is applied to a bridge 1 having longitudinal girders 2 and 2 extending in the direction of the bridge axis as shown in FIG. 2, for example. The existing stringers 2 and 2 are supported by bridge piers (not shown) via existing main girders 4 and 4 such as I-shaped steel.
First, the new vertical girder 10 having an I-shaped cross section is arranged at the center of the vertical beams 2 and 2 of the existing bridge 1 to be reinforced so as to contact the lower surface of the floor slab 3 in the bridge axis direction. Next, the tension cable 11 passes from the upper part of the existing stringer 2 or the existing main beam 4 to the upper part of the other existing stringer 2 or the existing main beam 4 via the cable saddle 12 provided in the lower part of the newly installed stringer 10. Passed over. A number of tension cables 11 are passed at predetermined intervals in the bridge axis direction. Since the tension cable 11 is stretched in a state where a strong tension is applied, the new stringer 10 is lifted upward. As a result, the bending stress of the floor slab 3 is reduced with respect to the weight of the vehicle or the like passing through the bridge 1, and deterioration of the floor slab due to repeated bending deformation is suppressed.
[0005]
In the method for reinforcing a concrete floor slab according to the present invention, carbon fiber, aramid fiber, glass fiber material or the like, which is preferably a new structural material, is used as a material for the newly installed stringer 10 and the tension cable 11. Since these new materials are extremely light and strong compared to conventional civil engineering structural materials, the use of these new materials suppresses the increase in dead load due to reinforcement work, and makes the structures themselves smaller and longer, In addition, various effects such as labor saving and labor saving of construction are expected. In addition, because it has high durability and corrosion resistance, rust prevention treatment such as winding concrete is unnecessary during construction, and maintenance is easy after construction. Specifically, uncured continuous carbon fibers (UCCF) and glass fiber reinforced plastics (GFRP) are used. UCCF has features such as high strength and elastic modulus, low specific gravity, excellent corrosion resistance and chemical resistance, and flexibility for transportation. GFRP has features such as high heat resistance and nonflammability, high electrical insulation, and the ability to freely select color materials.
[0006]
[Embodiment]
As an example of a method for reinforcing a concrete floor slab according to the present invention, a width of 12.6 m, a total length of 22 m, a height of an existing stringer 2 made of I-type steel of 1.2 m, an existing stringer number of six, an existing stringer interval The case where the bridge 1 which is 2.1 m is reinforced is demonstrated (FIG. 3).
Five new GFRP I-type beams (weight 880 kg each) having a height of 65 cm, a length of 22.2 m, and a cross-sectional area of 220 cm ² are used for the new stringer 10 of the reinforcing material. The newly installed stringer 10 is bonded to the lower surface of the floor slab 3 with epoxy mortar, and is bolted using an L-shaped bracket (not shown) at the position of the tilted structure. The tension cable 11 is made of UCCF having a cross-sectional area of 1 cm ² , one end is fixed to the upper part of the existing main girder 4 by an anchor 14, and the other end is connected to the other existing main via a cable saddle 12 provided on the lower surface of the newly installed vertical girder 10. It fixes to the upper part of the girder 4 with the anchor 14, and it tensions in the state which applied fixed tension (FIG. 4). As the anchor 14, for example, a steel trumpet pipe is used. The anchor cable 14 is inserted into the hole formed in the upper part of the web of the existing main girder 4, the tension cable 11 is inserted into the anchor 14, and then the end of the tension cable 11 is tied to form a hump so that the tension cable 11 is completely connected to the web. Fixed to. Since the tension cable 11 does not directly contact the web of the existing main girder 4, durability is improved without being damaged. Preferably, an epoxy resin or the like is filled between the inserted tension cable 11 and the anchor 14.
When the tension cable 11 is stretched, it is preferable to keep the floor plate 3 pushed up. For example, as shown in FIG. 5, a temporary horizontal girder 13 supported under the existing main girder 4 can be installed, and the floor slab 3 can be pushed up by a jack 13 a placed on the temporary horizontal girder 13. Further, a tension can be adjusted by providing a turnbuckle in the middle of the tension cable 11. After the tension cable 11 is stretched, the jack 13a is removed with the lift lifted. As a result, an appropriate tension for pushing up the floor slab 3 is applied to the tension cable 11. The temporary cross beam 13 is removed after the reinforcement work is completed.
The tension interval of the tension cable 11 is determined in consideration of required strength, load, and the like. In the case of this example, in order to obtain sufficient strength, 33 new stringers 10 are stretched at intervals of 65 cm in the bridge axis direction. Each of the 33 tension cables 11 is tensioned by about 100 kgf per tension cable 11 by a cable saddle 12 provided at the lower end of the newly installed stringer 10, and each of the 33 stringer cables 11 has 33 tension cables 11. A total lift of about 1700 kgf is given. Thereby, even if the own weight 880 kgf of the newly installed stringer 10 is subtracted, a lift of about 820 kgf is given to the floor slab 3, and deterioration of the floor slab 3 after the reinforcement work can be suppressed.
[0007]
Low cost I-shaped steel can be used for the newly installed stringer 10. Even in this case, the lift of about 400 kg is given to the floor slab 3 by subtracting the own weight 1300 kgf of the newly installed stringer 10, and the deterioration of the floor slab 3 after the reinforcement work can be suppressed. However, it is preferable from the viewpoint of corrosion resistance to use a new stringer 10 made of a new material such as UCCF or GFRP.
[0008]
【The invention's effect】
As described above, the method for reinforcing a concrete floor slab of the present invention is provided with a newly installed stringer between existing stringers, and the lower part of the newly installed stringer is pulled up by a tension material fixed to the existing stringers on both sides. . For this reason, it is possible to reinforce the floor slab while suppressing an increase in dead load and prevent deterioration. Reinforcement work can be performed under a bridge with a simple structure, so there is no need to restrict traffic and there is no need to place new concrete, so the construction period can be shortened.
[Brief description of the drawings]
FIG. 1 is a model diagram showing an example of a conventional construction method. FIG. 2 is a cross-sectional view perpendicular to a bridge axis explaining a reinforcement work according to the present invention. FIG. 3 is a perspective cross section explaining an example of a reinforcement work according to the present invention. Figure [Figure 4] Example of structure to fix cable end to existing stringer [Figure 5] State during reinforcement work [Explanation of symbols]
1: Bridge 2: Existing vertical girder 3: Floor slab 4: Existing main girder 5: Vertical girder 10: New vertical girder 11: Tension cable 12: Cable saddle 13: Temporary horizontal girder 13a: Jack

Claims

Existing main beam (4) to provide a temporary crossbeam having both ends supported (13), temporary crossbeam (13) placed the deck by a jack (13a) (3) non with push-up clogs state A new vertical cable made of curable continuous carbon fiber or glass fiber reinforced plastic tension cable (11) and bonded to the bottom surface of floor slab (3) made of non-cured continuous carbon fiber or glass fiber reinforced plastic. A method for reinforcing a concrete floor slab , characterized by removing a jack and a temporary horizontal girder after applying lift to the girder (10) by the tension cable (11) .