JP2019109095A - Cross sectional reduction rate estimation method and load resistance force estimation method - Google Patents
Cross sectional reduction rate estimation method and load resistance force estimation method Download PDFInfo
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本発明は、鉄筋の断面減少率を推定する技術および鉄筋の耐荷力を推定する技術に関する。 The present invention relates to a technology for estimating the cross-sectional reduction rate of reinforcing bars and a technology for estimating the load resistance of reinforcing bars.
ＲＣ（Reinforced Concrete）造やＳＲＣ（Steel Reinforced Concrete）造などの構造物において、鉄筋腐食は構造物の構造性能を大きく低下させる。主に鉄筋は部材に生じる引張応力を負担し、健全な鉄筋の場合は断面積すべてが有効となるが、腐食した場合は鉄が腐食生成物に変わるために腐食部分は力学的に有効とはならず、その分だけ断面減少が生じることになる。 In structures such as reinforced concrete (RC) and steel reinforced concrete (SRC), rebar corrosion greatly reduces the structural performance of the structure. Reinforcing bars mainly bear the tensile stress generated in the members, and in the case of healthy rebars, the entire cross-sectional area is effective, but when corroded, the corroded portion is mechanically effective because iron is converted to a corrosion product. In addition, the cross-sectional reduction will occur by that much.
例えば、非特許文献１には、鉄筋が腐食することで断面積が減少し、鉄筋断面減少率の増加にともなって、構造物としての“はり”の耐荷性能が低下することが示されている。すなわち、鉄筋の断面減少率が分かれば、腐食劣化した構造物の現時点での耐荷性能が評価できる。 For example, Non-Patent Document 1 shows that corrosion of rebar reduces the cross-sectional area, and the load-bearing performance of the “beam” as a structure decreases with an increase in the rebar reduction rate. . That is, if the reduction rate of the cross section of the reinforcing bar is known, the load resistance performance of the corrosion deteriorated structure can be evaluated.
鉄筋の断面減少率を計測する方法としては、非特許文献２のように、大気中において鉄筋の腐食前と腐食後の腐食部分を取り除いた外形を計測し、断面積の差を断面減少率としているが、この方法では現存するコンクリート構造物中で鉄筋の腐食による断面減少率を測定することはできない。したがって、腐食過程におけるコンクリート中の鉄筋の断面減少率を、鉄筋を取り出さずに推定することができれば、実構造物の耐荷性能を評価することが可能となる。例えば、はりの耐荷力を推定するには、非特許文献１のように鉄筋断面減少率と耐荷力の関係を用いれば良い。 As a method of measuring the reduction in area of rebar, as in Non-Patent Document 2, measure the outer shape of the rebar from which the corroded portions before and after corrosion are removed in the atmosphere, and the difference in cross-sectional area is taken as the reduction in area However, with this method, it is not possible to measure the reduction in area due to the corrosion of reinforcing bars in existing concrete structures. Therefore, if it is possible to estimate the cross-sectional reduction rate of the reinforcing bars in concrete in the corrosion process without taking out the reinforcing bars, it is possible to evaluate the load resistance performance of the actual structure. For example, in order to estimate the load carrying capacity of a beam, the relationship between the reinforcing bar cross-sectional reduction rate and the load carrying capacity may be used as in Non-Patent Document 1.
また、特許文献１では鉄筋の腐食を光ファイバセンサにより検知する方法が開示されている。 Further, Patent Document 1 discloses a method of detecting corrosion of a reinforcing bar by an optical fiber sensor.
鉄筋の断面減少率は、次の式で求められる。
（（腐食前の鉄筋の断面積）−（腐食部分を取り除いた鉄筋の断面積））／（腐食前の鉄筋の断面積）×１００（％）
The reduction rate of the cross section of the reinforcing bar can be obtained by the following equation.
((Cross-sectional area of rebar before corrosion)-(Cross-sectional area of rebar from which a corroded part has been removed)) / (Cross-sectional area of rebar before corrosion) × 100 (%)
しかしながら、上記の鉄筋の断面減少率は、これらの非特許文献では腐食後にコンクリート中から鉄筋を取り出して、腐食生成物を取り除いてから外形を測定して断面積を算出する必要があるため、実構造物においての計測、さらには連続的に計測するのは困難である。 However, in these non-patent documents, it is necessary to take out the reinforcing steel from the concrete after corrosion, remove the corrosion products, and then measure the external shape to calculate the cross-sectional area. It is difficult to measure in a structure or even continuously.
また、特許文献１では、非破壊で鉄筋腐食を検知できるものの定量的に鉄筋の断面減少率を推定できるものではない。 Moreover, in patent document 1, although what can detect reinforcement corrosion nondestructively can not estimate the cross-section reduction rate of reinforcement quantitatively quantitatively.
本発明は、このような事情に鑑みてなされたものであり、実構造物の鉄筋の腐食にともなう膨張ひずみの挙動に基づいて、コンクリート中の鉄筋の断面減少率を非破壊で定量的に把握することができる断面減少率推定方法および耐荷力推定方法を提供することを目的とする。 This invention is made in view of such a situation, and based on the behavior of the expansion strain accompanying corrosion of the reinforcing bar of a real structure, grasps the section reduction rate of the reinforcing bar in concrete nondestructively quantitatively. It is an object of the present invention to provide a cross section reduction rate estimation method and load resistance estimation method that can be performed.
（１）上記の目的を達成するため、本発明は、以下の手段を講じた。すなわち、本発明の断面減少率推定方法は、鋼材が腐食することによって減少した鋼材の断面の減少率を推定する断面減少率推定方法であって、前記鋼材の表面に光ファイバセンサを固定させる工程と、前記光ファイバセンサ中を伝搬する光波の特性変化を検出することによって、腐食生成物の発生による前記鋼材のひずみを検出する工程と、鋼材の断面減少率と鋼材の腐食膨張によるひずみとの関係を示す予め定められた関数を用いて、前記検出したひずみに対応する鋼材の断面減少率を推定する工程と、を含むことを特徴とする。 (1) In order to achieve the above object, the present invention takes the following measures. That is, the cross-section reduction rate estimation method of the present invention is a cross-section reduction rate estimation method for estimating a reduction rate of a cross section of a steel material reduced by corrosion of the steel material, and fixing an optical fiber sensor on the surface of the steel material. And detecting the distortion of the steel material due to the generation of a corrosion product by detecting the characteristic change of the light wave propagating in the optical fiber sensor, the reduction rate of the cross section of the steel material and the distortion due to the corrosion expansion of the steel material Estimating the cross-sectional reduction rate of the steel material corresponding to the detected strain using a predetermined function indicating a relationship.
このように、鋼材の断面減少率と鋼材の腐食膨張によるひずみとの関係を示す予め定められた関数に基づいて、検出したひずみに対応する鉄筋の断面減少率を推定するので、ひずみが検出することによって鉄筋の断面減少率を求めることが可能となる。これにより、鋼材が腐食した場合の断面減少率を非破壊で定量的に把握することが可能となる。 Thus, since the cross-sectional reduction rate of the rebar corresponding to the detected strain is estimated based on a predetermined function indicating the relationship between the cross-sectional reduction rate of the steel material and the strain due to the corrosion expansion of the steel material, the strain is detected This makes it possible to determine the reduction in area of the rebar. Thereby, it becomes possible to quantitatively grasp the cross-sectional reduction rate when the steel material is corroded nondestructively.
（２）また、本発明の断面減少率推定方法において、前記予め定められた関数は、コンクリート中で腐食した鋼材に巻き付けられた光ファイバセンサで検出したひずみと当該鋼材の断面減少率を実測して求められた値から特定された関数であることを特徴とする。 (2) Further, in the cross-sectional reduction rate estimation method of the present invention, the predetermined function measures the strain detected by the optical fiber sensor wound around the steel material corroded in concrete and the cross-sectional reduction rate of the steel material It is characterized in that it is a function specified from the value obtained by
このように、予め定められた関数は、実測値に基づくものであるので、正確に断面減少率を把握することが可能となる。 As described above, since the predetermined function is based on the actual measurement value, it is possible to accurately grasp the cross-sectional reduction rate.
（３）また、本発明の断面減少率推定方法において、前記鋼材は、実コンクリート構造中の鉄筋であることを特徴とする。 (3) Further, in the cross-sectional reduction rate estimation method of the present invention, the steel material is a reinforcing bar in an actual concrete structure.
このように、実コンクリート構造中の鉄筋に光ファイバセンサを巻き付けるので、非破壊で実構造物の鉄筋断面減少の状況を定量的に把握することが可能となる。 As described above, since the optical fiber sensor is wound around the reinforcing bars in the actual concrete structure, it is possible to nondestructively grasp the situation of the reduction in the reinforcing bar cross section of the actual structure quantitatively.
（４）また、本発明の耐荷力推定方法は、上記（１）から（３）のいずれかに記載の断面減少率推定方法により得られた鋼材の断面減少率を用いて、コンクリート構造物の耐荷力を推定することを特徴とする。 (4) In addition, according to the load carrying capacity estimation method of the present invention, the cross section reduction rate of the steel material obtained by the cross section reduction rate estimation method according to any one of (1) to (3) above is used to It is characterized by estimating load resistance.
この構成により、ここで得られた断面減少率を用いて、構造物モデルを作成してＦＥＭ等の解析を行なうことができる。その結果、腐食によって劣化したコンクリート部材としての耐荷力が推定でき、建設時に比べてどの程度耐荷性能が低下したかを把握することで、構造物の適切な維持管理に役立つことになる。 With this configuration, it is possible to create a structure model and analyze FEM or the like using the cross-sectional reduction rate obtained here. As a result, it is possible to estimate the load resistance as a concrete member that has deteriorated due to corrosion, and by grasping how much the load resistance performance is reduced compared to the time of construction, it is useful for appropriate maintenance and management of the structure.
本発明によれば、予め定められた関数に基づいて、検出したひずみに対応する腐食減少率を推定するので、ひずみが検出できれば腐食減少率を求めることが可能となる。これにより、鋼材の腐食した場合の腐食減少率を定量的に把握することが可能となる。 According to the present invention, since the corrosion reduction rate corresponding to the detected strain is estimated based on a predetermined function, if the strain can be detected, it is possible to obtain the corrosion reduction rate. This makes it possible to quantitatively grasp the rate of decrease in corrosion when the steel material corrodes.
本発明者らは、腐食による鋼材の腐食膨張と断面減少率との関係に着目し、鋼材に光ファイバセンサを固定し、コンクリート中の腐食環境下において光ファイバセンサのひずみから求めた鋼材の腐食膨張ひずみと鋼材の断面減少率との関係を定式化することによって、鉄筋の断面減少率を把握することができることを見出し、本発明に至った。 The present inventors fixed the optical fiber sensor on the steel material, paying attention to the relationship between the corrosion expansion of the steel material due to corrosion and the cross-sectional reduction rate, and corroded the steel material determined from the strain of the optical fiber sensor in a corrosive environment in concrete. By formulating the relationship between the expansion strain and the cross-sectional reduction rate of the steel material, it has been found that the cross-sectional reduction rate of the reinforcing bar can be grasped, resulting in the present invention.
すなわち、本発明の鉄筋の断面減少率推定方法は、鋼材の表面に光ファイバセンサを固定させる工程と、前記光ファイバセンサ中を伝搬する光波の特性変化を検証することによって、腐食生成物の発生による前記鋼材の腐食膨張ひずみを検出する工程と、鋼材の断面減少率と鋼材の腐食膨張によるひずみとの関係を示す予め定められた関数を用いて、前記検出したひずみに対応する鋼材の断面減少率を推定する工程と、を含むことを特徴とする。 That is, in the method of estimating the cross-section reduction rate of a reinforcing bar according to the present invention, generation of a corrosion product is performed by fixing an optical fiber sensor on the surface of a steel material and verifying characteristic changes of light waves propagating in the optical fiber sensor. The cross section reduction of the steel material corresponding to the detected strain using a predetermined function showing the relationship between the step of detecting the corrosion expansion strain of the steel material by the above and the cross section reduction rate of the steel material and the strain due to the corrosion expansion of the steel material Estimating the rate.
これにより、本発明者らは、鋼材の断面減少率を定量的に把握することを可能とした。以下、本発明の実施形態について、図面を参照しながら具体的に説明する。 As a result, the present inventors have been able to quantitatively grasp the cross-sectional reduction rate of the steel material. Hereinafter, embodiments of the present invention will be specifically described with reference to the drawings.
図１は、本実施形態に係る光ファイバセンサのコンクリート中の鉄筋などの鋼材に設置する方法を示す図である。構造物の鉄筋５９にひずみを検出する検知部を有する光ファイバセンサ６１が備えられている。これにより、長距離伝送が可能な光信号を用いることができ、非破壊で多点計測を行なうことが可能となる。また、鉄筋５９と光ファイバセンサ６１を被覆する被覆部を備えていても良い。被覆部を備えることによって、鉄筋コンクリート構造物内に設置する前に鉄筋が錆びてしまうことを回避することが可能となる。 FIG. 1 is a view showing a method of installing on a steel material such as a reinforcing bar in concrete of the optical fiber sensor according to the present embodiment. An optical fiber sensor 61 having a detection unit for detecting a strain on the reinforcing bar 59 of the structure is provided. Thus, an optical signal capable of long distance transmission can be used, and multipoint measurement can be performed nondestructively. Moreover, you may provide the coating | coated part which coat | covers the reinforcement 59 and the optical fiber sensor 61. FIG. By providing the covering portion, it is possible to prevent the rebar from rusting before installing in the reinforced concrete structure.
図２は、本実施形態に係るひずみセンサの概要を示す図である。図２に示すように、鉄筋などの鋼材に直接光ファイバセンサを設置せずに、別途鋼材に光ファイバセンサ１４を巻き付けた腐食センサ１１として設置しても良い。この腐食センサ１１は、鉄製の鋼材としてのみがき棒鋼１２と、みがき棒鋼１２の表面に巻回され、ひずみを検出する検知部１３を有する光ファイバセンサ１４と、を備えている。腐食センサ１１の埋設深さは、構造物の鉄筋と腐食成分の環境が同等になるよう鉄筋と同じ深さにすることが好ましい。みがき棒鋼１２に代えて、埋設する構造物と同じ鉄筋を用いても良い。また、腐食センサ１１は、みがき棒鋼１２と光ファイバセンサ１４を被覆する被覆部１５を備えていても良い。被覆部１５を備えるので、鉄筋コンクリート構造物内に設置する前にみがき棒鋼１２が錆びてしまうことを回避することが可能となる。 FIG. 2 is a view showing an outline of a strain sensor according to the present embodiment. As shown in FIG. 2, instead of directly installing the optical fiber sensor on a steel material such as a reinforcing bar, it may be installed as a corrosion sensor 11 in which the optical fiber sensor 14 is separately wound on a steel material. The corrosion sensor 11 is provided with a steel bar 12 only as a steel material made of iron, and an optical fiber sensor 14 wound around the surface of the polishing bar 12 and having a detection unit 13 for detecting strain. The embedded depth of the corrosion sensor 11 is preferably the same depth as that of the reinforcing bar so that the environment of the reinforcing bar of the structure and the corrosion component is equal. Instead of the polished steel bar 12, the same rebar as that of the structure to be embedded may be used. Further, the corrosion sensor 11 may be provided with a covering portion 15 for covering the polishing steel bar 12 and the optical fiber sensor 14. Since the covering portion 15 is provided, it is possible to prevent the steel bar 12 from being rusted before installing in the reinforced concrete structure.
鋼材が腐食すると腐食生成物が生じ、体積膨張が生じる。鋼材に腐食が生じた場合には、光ファイバセンサも引き延ばされるので、光ファイバセンサのひずみを計測すれば鋼材の腐食膨張が検知可能となる。その挙動は、環境条件やコンクリートによって異なるため、光ファイバセンサを鋼材に巻き付ける際には、密着するように、好ましくは引張力が加わるように巻き付ける。これにより、膨張側・収縮側両方のひずみが計測できるようになる。 Corrosion of steel materials results in corrosion products and volumetric expansion. When corrosion occurs in the steel material, the optical fiber sensor is also stretched, so if the strain of the optical fiber sensor is measured, the corrosion and expansion of the steel material can be detected. Since the behavior differs depending on the environmental conditions and concrete, when the optical fiber sensor is wound around a steel material, it is wound so as to be in intimate contact, preferably in a tensile force. This makes it possible to measure the strain on both the expansion side and the contraction side.
また、鋼材に光ファイバセンサを巻き付ける際には、光ファイバセンサを、直線状に貼付したり、波状に曲折して貼付したりしても良いが、好ましくは周回するようにらせん状、またはループ状に巻き付ける。異形鉄筋に巻き付ける場合は、リブあるいは節に沿って巻き付けると容易である。周回数は多いほど腐食部分と光ファイバが重なるので早期に検知するが、周回数が多すぎると鋼材への腐食因子の到達を妨げることになる。らせん状に巻く場合の周回数は、目安としてファイバ長（ｍｍ）／鋼材表面積（ｍｍ2）が０．０１〜２である。いずれにしても、鋼材に生ずる腐食の変化を光ファイバセンサが検出できれば良い。また、検知部はＦＢＧ（Fiber Bragg Gratings）センサ等を用いることができ、検知部が長いほど、あるいは多いほど好ましい。 In addition, when the optical fiber sensor is wound around a steel material, the optical fiber sensor may be attached in a straight line or may be bent and attached in a wave shape, but preferably it is a spiral or loop so as to circulate. Wrap around the shape. When winding around deformed bars, winding along ribs or joints is easy. As the number of cycles increases, the corrosion portion and the optical fiber overlap, so detection is performed early. However, if the number of cycles is too large, the arrival of the corrosion factor to the steel material is impeded. The number of turns in spiral winding is, as a standard, the fiber length (mm) / the surface area of the steel material (mm 2 ) 0.01 to 2 . In any case, it is only necessary for the optical fiber sensor to detect a change in corrosion occurring in the steel material. Further, an FBG (Fiber Bragg Gratings) sensor or the like can be used as the detection unit, and it is preferable that the detection unit is longer or more.
被覆部は、構造物の鉄筋と腐食成分の環境が同等になるよう同じ配合または同じセメント水比であることが好ましい。少なくとも予防的には腐食因子の侵入を妨げないように、また、早期に腐食因子が鋼材に到達するように、水セメント比を構造体コンクリートと同等か高めにする。被覆部は、ひび割れることなく鋼材を保護できるよう、３〜１５ｍｍの厚さのモルタルが好ましい。また、分離やブリーディングが生じないように混和材を使用することが好ましい。 It is preferable that the covering portion has the same composition or the same cement water ratio so that the environments of the reinforcing bar and the corrosive component of the structure are equal. The water-cement ratio is made equal to or higher than that of the structural concrete so that the corrosion factor reaches the steel material at an early stage so as not to prevent the penetration of the corrosion factor at least preventively. The covering portion is preferably a mortar having a thickness of 3 to 15 mm so as to protect the steel without cracking. In addition, it is preferable to use an admixture so as not to cause separation or bleeding.
腐食を検出する場合、ダミーセンサを併せて用いることが望ましい。ダミーセンサは、腐食センサ１１の全表面に防錆処理を施したダミーセンサを用いても良いし、または、みがき棒鋼１２と線膨張係数が実質的に同等でかつ鉄筋より腐食しにくい第２の棒材と、第２の棒材の表面に設けられ、ひずみを検出する光ファイバセンサとを備えるダミーセンサを用いても良い。 When detecting corrosion, it is desirable to use a dummy sensor in combination. The dummy sensor may use a dummy sensor in which the entire surface of the corrosion sensor 11 has been subjected to anticorrosion treatment, or the second one having substantially the same linear expansion coefficient as that of the polished steel bar 12 and less corrosion than rebar. A dummy sensor may be used that includes a bar and an optical fiber sensor provided on the surface of the second bar and detecting strain.
そして、ダミーセンサを同環境に設置し、ダミーセンサによって腐食以外の要因で生じたひずみを検出し、ダミーセンサで検出したひずみを用いて、検出したひずみを補正しても良い。これにより、例えば、温度ひずみなどの腐食以外の要因で生じたひずみの影響を除去することが可能となる。 Then, a dummy sensor may be installed in the same environment, a strain generated by a factor other than corrosion may be detected by the dummy sensor, and the detected strain may be corrected using the strain detected by the dummy sensor. This makes it possible, for example, to remove the influence of strain caused by factors other than corrosion such as temperature strain.
すなわち、コンクリートには、温度・湿度やコンクリートの収縮、外力によって様々なひずみが生じる。従って、少なくとも鋼材や腐食センサ１１よりも腐食しにくいダミーセンサを使用し、そのひずみ挙動と比較して腐食を判定する。ダミーセンサは、被覆モルタルにエポキシ樹脂などで被覆し、中性化や劣化因子の侵入を防いで内部の炭素鋼の腐食を防ぐ方法がある。または、炭素鋼と線膨張係数が同等のステンレス（例えば、SUS410など）を使用する。 That is, in the concrete, various strains occur due to temperature and humidity, shrinkage of the concrete, and external force. Therefore, at least a steel material or a dummy sensor that is less likely to corrode than the corrosion sensor 11 is used, and corrosion is determined in comparison with its strain behavior. The dummy sensor is coated with an epoxy resin or the like on a coating mortar, and there is a method of preventing the carbon steel inside from being corroded by preventing carbonation and penetration of deterioration factors. Alternatively, stainless steel (such as SUS410) having a linear expansion coefficient equal to that of carbon steel is used.
ここで、光ファイバセンサによって得られた鋼材の腐食膨張ひずみと、予めひずみに対応する鋼材の断面減少率を求めておけば、鋼材の断面減少率を定量的に把握することが可能となる。なお、本明細書では、光ファイバセンサの検出値を腐食膨張ひずみに変換するが、設置方法や対象物が同じであれば光ファイバセンサの検出値そのものと鋼材の断面減少率の関係を求めても良い。 Here, if the corrosion expansion strain of the steel material obtained by the optical fiber sensor and the cross-sectional reduction rate of the steel material corresponding to the strain are obtained in advance, it becomes possible to grasp the cross-sectional reduction rate of the steel material quantitatively. In this specification, although the detected value of the optical fiber sensor is converted to corrosion expansion strain, if the installation method and the object are the same, the relationship between the detected value of the optical fiber sensor itself and the reduction rate of the cross section of the steel is determined. Also good.
断面減少率は、腐食した鉄筋の腐食部を剥がしたり、クエン酸水素二アンモニウム水溶液により腐食部を溶解させたりして太さを測定すれば良い。また、顕微鏡で切断面を観察して断面減少率を求めても良い。腐食膨張ひずみの量が異なる鋼材を採取し、その断面減少率を測定し、予め、相関性を求めておく。 The reduction in area may be measured by removing the corroded portion of the corroded rebar or dissolving the corroded portion with an aqueous solution of hydrogen diammonium hydrogen citrate to measure the thickness. Alternatively, the cross-sectional reduction rate may be determined by observing the cut surface with a microscope. Steel materials having different amounts of corrosion expansion strain are collected, their cross-sectional reduction rates are measured, and correlations are obtained in advance.
ここで鉄筋種類や径に応じて、光ファイバセンサのひずみと鋼材の断面減少率の関係は若干異なってくるので、条件ごとに両者の関係を求めてもおくことが好ましい。腐食センサ１１を用いる場合は、その仕様ごとに両者の関係を求めておけば良い。両者の関係は、実験室で求めても良いし、実構造物においてデータを蓄積しても求めても良い。 Here, since the relationship between the strain of the optical fiber sensor and the cross-sectional reduction rate of the steel material is slightly different according to the type and diameter of the reinforcing bar, it is preferable to find the relationship between the two for each condition. When the corrosion sensor 11 is used, the relationship between the two may be obtained for each specification. The relationship between the two may be determined in the laboratory, or data may be stored or determined in the actual structure.
求められた断面減少率によって、鉄筋を取り出さず、既に知られた鉄筋の断面減少率と耐荷力の関係に基づいて実構造物の耐荷性能を評価することが可能となる。 With the calculated cross-sectional reduction rate, it is possible to evaluate the load-bearing performance of the actual structure based on the already-known relationship between the cross-sectional reduction rate of the rebar and the load resistance without removing the rebar.
[検証例]
次に、検証例について説明する。図３は、電気腐食試験の概要を示す図である。直径３０ｍｍで長さが３５０ｍｍのみがき棒鋼６０（JIS G3108）を用いる。このみがき棒鋼６０の体積はＶとする。表１の光ファイバセンサ６１（φ150μm）を巻き付け、ケーブル６２を接続して、コンクリート６４に埋め込む。その際、水平方向のかぶりを左右均等に１３５ｍｍとし、深さ方向のかぶりを上端から５０ｍｍ、および下端から２２０ｍｍとする。これを供試体６６とし、この供試体６６を、内法が３１０ｍｍの容器６９内で水没させて、水中で供試体から１０ｍｍ離れた位置に、陰極材としての銅板電極６８を設ける。銅板電極６８は、幅が１００ｍｍであり、長さが３００ｍｍであり、ケーブル７０が接続されている。また、供試体６６上で、銅板電極６８と対向する位置に防水型ゲージ７２を設置する。
[Example of verification]
Next, a verification example will be described. FIG. 3 is a diagram showing an outline of the electrocorrosion test. A steel bar 60 (JIS G3108) is used only with a diameter of 30 mm and a length of 350 mm. The volume of this polished steel bar 60 is V. The optical fiber sensor 61 (φ 150 μm) of Table 1 is wound, and the cable 62 is connected and embedded in concrete 64. At that time, the fog in the horizontal direction is uniformly 135 mm in the left and right, and the fog in the depth direction is 50 mm from the upper end and 220 mm from the lower end. This is used as a specimen 66. This specimen 66 is submerged in a container 69 of 310 mm in inner diameter, and a copper plate electrode 68 as a cathode material is provided at a position 10 mm away from the specimen in water. The copper plate electrode 68 has a width of 100 mm and a length of 300 mm, and the cable 70 is connected. In addition, a waterproof gauge 72 is installed on the specimen 66 at a position facing the copper plate electrode 68.
光ファイバセンサ６１の巻き付け方は、以下の通りである。すなわち、コンクリート中において端部から２０ｍｍの部分から巻き始められ、１周するごとにみがき棒鋼６０の長手方向に２５ｍｍ進むように巻き付ける。各区間は、１０ｍｍの間隔を有する。みがき棒鋼に対する光ファイバケーブルの巻き方は、一定の張力下、例えば、巻き付け時に多少の引張ひずみが出ていることを確認した上で、巻き付け作業を行ない、測定部の両端は接着剤で固定する。その結果、コンクリート中のみがき棒鋼６０では、両端から２０ｍｍの部分が２つ、光ファイバセンサが１周巻き付けられる２５ｍｍの部分が８つ、各区間の間隔として１０ｍｍの部分が７つで、合計３１０ｍｍとなっている。このみがき棒鋼をコンクリート（水セメント比60％，28日圧縮強度41N/mm2）に埋め込んだ。脱型後、コンクリートから露出した棒鋼は腐食しないように被覆処理し、材齢２２日まで湿潤養生を行なった。 The winding method of the optical fiber sensor 61 is as follows. That is, in concrete, winding is started from a portion of 20 mm from the end, and it is wound so as to advance 25 mm in the longitudinal direction of the polishing bar steel 60 each time it goes around. Each section has a spacing of 10 mm. As for how to wind the optical fiber cable to the polished steel bar, for example, after confirming that a slight tensile strain is generated under constant tension, perform the winding operation and fix the both ends of the measurement section with the adhesive. . As a result, in the case of only steel in concrete 60, two 20 mm portions from both ends, eight 25 mm portions around which an optical fiber sensor is wound one round, seven 10 mm portions for each section, a total of 310 mm It has become. This polished steel bar was embedded in concrete (water cement ratio 60%, 28-day compressive strength 41 N / mm 2 ). After demolding, the steel bar exposed from the concrete was coated so as not to corrode, and wet curing was performed until the age of 22 days.
図３および図４に示したように、コンクリート試験体を２０℃一定の水中に浸漬し、陰極材となる銅板を配置して、みがき棒鋼６０を陽極材として２００ｍＡの一定電流による電食試験を行なった。試験中には８区間において、光ファイバセンサによりみがき棒鋼６０の腐食膨張ひずみを連続的に計測した。 As shown in FIGS. 3 and 4, the concrete test body is immersed in water at a constant temperature of 20 ° C., and a copper plate serving as a cathode material is disposed, and an electrolytic corrosion test with a constant current of 200 mA is performed using the polished steel bar 60 as an anode material I did. During the test, the corrosion expansion strain of the polished steel bar 60 was continuously measured by an optical fiber sensor in eight sections.
光ファイバセンサにおいて、以下の式により、波長からひずみに変換し、腐食によるひずみの変化を確認した。 In the optical fiber sensor, the wavelength was converted into strain by the following equation, and the change in strain due to corrosion was confirmed.
コンクリートにひび割れ発生後、試験体のコンクリート部分を除去してみがき棒鋼６０を取り出し、６０℃の１０％クエン酸水素二アンモニウム水溶液に浸漬させ、腐食生成物を除去した。試験前および腐食生成物を除去後に、ノギスを用いてみがき棒鋼６０の直径を各区間でそれぞれ１０点計測して、平均直径から断面積をそれぞれ算出し、腐食後における断面減少率を算出した。 After cracking occurred in the concrete, the concrete portion of the test body was removed, and the polished steel bar 60 was taken out and immersed in a 10% aqueous solution of diammonium hydrogen citrate at 60 ° C. to remove corrosion products. Before the test and after removing the corrosion products, the diameter of the rod steel 60 was measured at 10 points in each section using a vernier caliper, the cross-sectional area was calculated from the average diameter, and the reduction in area after corrosion was calculated.
その結果、表２に示すように試験終了時の８区間はそれぞれ腐食の状態は異なり、腐食膨張ひずみおよび断面減少率の結果は各区間で異なる値となった。光ファイバセンサはらせん状に設置しているため、円周方向に換算して鉄筋の腐食膨張ひずみとした。 As a result, as shown in Table 2, in the 8 sections at the end of the test, the state of corrosion was different, and the results of the corrosion expansion strain and the reduction in area became different values in each section. Since the optical fiber sensor is installed in a spiral shape, it is converted to the circumferential direction to determine the corrosion expansion strain of the reinforcing bar.
以上説明したように、本発明によれば、予め定められた関数に基づいて、光ファイバにより検出したひずみに対応する鉄筋の断面減少率を推定するので、ひずみを検出することによって断面減少率を求めることが可能となる。これにより、鋼材の断面減少率を定量的に把握することが可能となる。 As described above, according to the present invention, since the cross-sectional reduction rate of the rebar corresponding to the strain detected by the optical fiber is estimated based on a predetermined function, the cross-sectional reduction rate is detected by detecting the strain. It can be determined. Thereby, it becomes possible to grasp | ascertain quantitatively the cross-section reduction rate of steel materials.
１１ 腐食センサ
１２、６０ みがき棒鋼
１３ 検知部
１４、６１ 光ファイバセンサ
１５ 被覆部
５９ 鉄筋
６２ ケーブル
６４ コンクリート
６６ 供試体
６８ 銅板電極
６９ 容器
７０ ケーブル
７２ 防水型ゲージ
DESCRIPTION OF SYMBOLS 11 Corrosion sensor 12, 60 Polished steel bar 13 Detection part 14, 61 Optical fiber sensor 15 Covering part 59 Reinforcement 62 Cable 64 Concrete 66 Specimen 68 Copper plate electrode 69 Container 70 Cable 72 Waterproof gauge
Claims (4)
前記鋼材の表面に光ファイバセンサを固定させる工程と、
前記光ファイバセンサ中を伝搬する光波の特性変化を検出することによって、腐食生成物の発生による前記鋼材のひずみを検出する工程と、
鋼材の断面減少率と鋼材の腐食膨張によるひずみとの関係を示す予め定められた関数を用いて、前記検出したひずみに対応する鋼材の断面減少率を推定する工程と、を含むことを特徴とする断面減少率推定方法。 A cross sectional reduction rate estimation method for estimating a reduction rate of a cross section of a steel material which is reduced by corrosion of the steel material,
Fixing an optical fiber sensor to the surface of the steel material;
Detecting a distortion of the steel material due to the generation of a corrosion product by detecting a characteristic change of a light wave propagating in the optical fiber sensor;
Estimating the cross-sectional reduction rate of the steel material corresponding to the detected strain using a predetermined function indicating the relationship between the cross-sectional reduction rate of the steel material and the strain due to the corrosion expansion of the steel material. Cross section reduction rate estimation method.
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