Method to Determine Tensile Stress Alterations in Prestressing Steel Strands by Means of an Eddy-Current Technique

The increased demand for reinforced concrete elements, for example, in bridge construction, requires long-term monitoring using multisensor techniques. Dynamic load inspection and maximum load detection is now an important requirement to avoid overstressing in light of past building failures in Germany, Austria, Poland, and Russia. Magnetoelastic force measurement of prestressed reinforcing concrete cables is also an investigative method for detecting steel failures (McMaster, 1986; Cullity, 1972; Fabo, 2002). An examination of coil impedance measurements made using eddy-current sensors placed on mechanically stressed steel specimens demonstrates a high dependency on the magnetoelastic effect. This stress measurement on prestressings or other reinforced concrete cables can be achieved by calibration of the material properties and stabilization of the magnetization state at the working point.