Economic and effective evaluation of the actual condition of a bridge is an important issue for bridge maintenance and preservation. The current condition of the bridge is usually far more different from the construction design and also with the bridge being in service for few years, a quantitative evaluation is essential. Assimilating reviews and comparisons of traditional inspection and evaluation methods, this paper promotes the concept of application of wireless sensors developed at the Bridge Research Center for rapid installation and low power requirements for in-service real-time bridge inspection. The concept focuses on obtaining useful data such as strain, displacement, frequency for estimating the actual characteristics of the bridge while in service, thus avoid closing the traffic as compared to traditional load test which needs traffic closure causing inconvenience to public and indirectly affecting economy. Plans and procedures of the field inspection are detailed as well as the data processing and the analysis results are presented. The effectiveness and feasibility of the proposed real-time inspection based on wireless sensors approach are illustrated via the practical inspection of a deck beam bridge.
In this paper Jiles-Atherton model, a phenomenological model, is proposed to model physical properties of structural steel and magnetite(corrosion product). The Jiles-Atherton model parameters based on mean field approximation were optimized to simulate the curves obtained from magnetic measurements using conventional quasi-static method. Results from hot rolled steel, a low carbon steel, were simulated using Jiles model to understand and correlate the measured and simulated curves. Hysteresis curves for magnetite, one of the most prevalent corrosion product and the only ferromagnetic component, are obtained to simulate the effect of corrosion products on the magnetic measurements of corroded structural steel. Since corrosion is initially a surface phenomenon, high frequency measurements were suggested from the simulations obtained to reduce the skin depth estimates and increase the accuracy of corrosion measurement.
Magnetic measurements were performed on steel cables subjected to a magnetic field and the response measured without contact using Faraday's law, to estimate the effect of temperature and corrosion on magnetic properties of structural steel. Magnetic measurements were compared with electrochemical measurements to correlate corrosion quantitatively in terms of mass loss. The results obtained from the present work are helpful in bounding the achievable sensitivity for conventional magnetoelastic corrosion sensing and for suggesting the need for alternate techniques.