SBIR/STTR Phase I: New Magnetoelastic Force/Corrosion Sensor for Cable-Stays in Bridges Using Measurement of Anhysteresis Curve

Infratech Inc, Silver Spring MD

Investigators

Abstract

This Small Business Innovation Research (SBIR) Phase I project will investigate the feasibility of direct measurement of live forces in civil infrastructures such as the cables of cable-stayed bridges, using a new magnetoelastic sensor. Knowledge of stress conditions is essential for detection of stress changes due to fatigue, overload, or corrosion and thereby, to prolong a structure's service life and/or to improve its performance. Knowledge of the stress state is also valuable for evaluating the structural integrity of cables during and after natural disasters such as earthquakes or severe winds. These measurements should be made rapidly and cost-effectively. Conventional sensors, such as strain gages and accelerometers, do not respond to stress directly. The new magnetoelastic sensor depends on the magnetic properties of structural steels in a stressed state. The sensing circuit is external to the steel, simple to install, and sensitive to in-situ stress with an error less than 3%. A magnetic property called the anhysteresis curve is measured. The commercial application of the new magnetoelastic force/corrosion sensor is in maintenance and repair of cable-stays in bridge structures and numerous other steel and metal-based infrastructural elements. The end-users include infrastructure managers, bridge engineers, and officials of transportation authorities of Federal and local governments.