Bridge Scour Monitoring using Smart Rocks Based on Magnetic Field Interference


In this study, two types of smart rock were proposed to monitor bridge scour effect, including a direction-unknown (DU) smart rock and a direction-known (DK) smart rock. The DU smart rock is a concrete ball containing a cylindrical magnet, and the DK smart rock is also a concrete ball but contains a magnet whose direction is always pointing to the projected direction of the ambient magnetic field (AMF) in the horizontal plane. Based on the theory of magnetic field, the distribution of the magnetic field induced by DU and DK smart rock was derived. Algorithms were developed to localize the position of the two smart rocks under the AMF. Field tests were conducted at a bridge pier, and the intensity and direction of the AMF at the test site were measured by using a magnetometer and a home-made device, respectively. Results showed that presence of steel reinforcement and steel girders in the bridge changed the distribution of the geomagnetic field. The algorithms were able to localize the position of both the DU and the DK smart rocks with satisfied accuracy. Compared with the DU smart rock, the amount of calculation to localize DK smart rock was reduced. However, the measurement error was increased due to the instability of its direction from varying AMF caused by environmental factors such as passing vehicles on the bridge.


Civil, Architectural and Environmental Engineering

Research Center/Lab(s)

INSPIRE - University Transportation Center


Financial support for this study was provided by the US Department of Transportation Office of the Assistant Secretary for Research and Technology under Cooperative Agreement No. OASRTRS-14-H-MST, by Missouri Department of Transportation, and by the Fundamental Research Funds for the Central Universities of China under No. DUT17RC(3)076.

Keywords and Phrases

Concretes; Electromagnetic field effects; Geomagnetism; Magnetic fields; Magnets; Structural health monitoring; Bridge scour; Cylindrical magnets; Environmental factors; Geomagnetic fields; Magnetic field interference; Noncontact measurements; Steel girder; Steel reinforcements; Rocks; Magnetic field; Non-contact measurement; Smart rock; Structural health monitoring

International Standard Serial Number (ISSN)


Document Type

Article - Journal

Document Version


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© 2018 Institute of Physics - IOP Publishing, All rights reserved.

Publication Date

01 Aug 2018