Project/Area Number 
10450045

Research Category 
GrantinAid for Scientific Research (B)

Allocation Type  Singleyear Grants 
Section  一般 
Research Field 
Materials/Mechanics of materials

Research Institution  Tokyo Institute of Technology 
Principal Investigator 
AOKI Shigeru Graduate School of Infromation Sci. and Tech., TOKYO INSTITUTE OF TECHNOLOGY, Associate Professor, 大学院・情報理工学研究科, 教授 (90016436)

CoInvestigator(Kenkyūbuntansha) 
AMAYA Kenji Graduate School of Infromation Sci. and Tech., TOKYO INSTITUTE OF TECHNOLOGY, Associate Professor, 大学院・情報理工学研究科, 助教授 (70251642)

Project Period (FY) 
1998 – 1999

Project Status 
Completed (Fiscal Year 1999)

Budget Amount *help 
¥11,100,000 (Direct Cost: ¥11,100,000)
Fiscal Year 1999: ¥1,200,000 (Direct Cost: ¥1,200,000)
Fiscal Year 1998: ¥9,900,000 (Direct Cost: ¥9,900,000)

Keywords  AC impedance method / Potential mapping method / Boundary element method / Inverse analysis / Concrete structure / Corroded rebar / Polarization curve / Nondestructive test / 鉄筋コンクリート / 鉄筋腐食位置の同定 / ラプラス方程式 / 精度向上 
Research Abstract 
An effective boundary element inverse analysis method was developed to detect the corrosion location and corrosion rate of rebars in a concrete structure. This method consists of two steps. The outlines of these steps are shown below. The first step is the effective nondestractive detection of corrosion locations by combining potential measurement and boundary element inverse analysis. The boundary element inverse analysis method for this step was developed based on the boundary element direct corrosion analysis method, which had been developed before. In this inverse method, the corroded part in the rebar net was approximated as a circle, i.e., the part of the rebars in the circle is taken to be corroded. The radius r and the coordinates (x, y) are taken as design variables, and the difference between the measured and calculated values of potential is taken as the cost function robe minimized. The polarization characteristics of the corroded and noncorroded parts are assumed to be gi
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ven. The minimization is performed through use of the Simplex method. The usefulness of the method was demonstrated by solving an example problem. The second step is the identification of the corrosion rate of the corroded part which was detected in the first step. The identification of the corrosion rate is performed by improving the AC impedance method. A boundary element inverse analysis was utilized to improve the AC impedance method. At first, it was verified experimentally that the potential in the concrete domain is described with the Laplace's equation. The potential at any point in the concrete domain can be calculated by solving the Laplace's equation with the boundary element method.Then, an inverse problem was formulated in which the location and the complex impedance (corrosion rate can be obtained from the complex impedance) of corroded part on the surface of a rebar are estimated from a small number of potential data measured on the surface of a concrete structure. The cost function to be minimized in the inverse problem is a function of difference between the measured and calculated values of potential. The validity and efficiency of the proposed method were demonstrated with an example in which a prismatic concrete block specimen with an embedded piece of rebar was used. Less
