A Combined method of AC Impedance Measurement and BE Inverse Analysis for Detecting Corroded Rebar in Concrete Structure

提出了一种有效的边界元反分析方法，用于检测混凝土结构中钢筋的锈蚀位置和锈蚀速度。该方法由两个步骤组成。这些步骤的概要如下：第一步是结合电位测量和边界元逆分析对腐蚀位置进行有效的非破坏性检测。该步骤的边界元反分析方法是在已有的边界元直接腐蚀分析方法的基础上发展起来的。在该方法中，将钢筋网中的锈蚀部分近似为一个圆，即将圆中的钢筋部分视为锈蚀。以半径r和坐标(x，y)为设计变量，以电势实测值与计算值之差为最小代价函数。腐蚀和未腐蚀部分的极化特性假定为gi…。甚至更多。最小化是通过使用单纯形法来实现的。通过算例验证了该方法的有效性。第二步是对第一步检测到的腐蚀部位的腐蚀率进行识别。通过对交流阻抗法的改进，实现了腐蚀速率的识别。利用边界元逆分析对交流阻抗法进行了改进。首先从实验上验证了混凝土区域的电势可以用拉普拉斯方程来描述。利用边界元方法求解拉普拉斯方程，求出混凝土区域内任一点的电势，然后利用少量混凝土结构表面测得的电势数据估算钢筋表面锈蚀部位的位置和复阻抗(由复阻抗得到锈蚀率)。反问题中要最小化的代价函数是电势的实测值和计算值之间的差的函数。通过一个埋设钢筋的混凝土棱柱试件的算例验证了该方法的有效性。较少

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 non-destractive 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 non-corroded parts are assumed to be gi … More 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