A Wireless Passive Sensing System for Displacement/Strain Measurement in Reinforced Concrete Members

Abstract

In this study, we show a wireless passive sensing system embedded in a reinforced concrete member successfully being employed for the measurement of relative displacement and strain in a simply supported beam experiment. The system utilizes electromagnetic coupling between the transceiver antenna located outside the beam, and the sensing probes placed on the reinforcing bar (rebar) surface inside the beam. The probes were designed in the form of a nested split-ring resonator, a metamaterial-based structure chosen for its compact size and high sensitivity/resolution, which is at µm/microstrains level. Experiments were performed in both the elastic and plastic deformation cases of steel rebars, and the sensing system was demonstrated to acquire telemetric data in both cases. The wireless measurement results from multiple probes are compared with the data obtained from the strain gages, and an excellent agreement is observed. A discrete time measurement where the system records data at different force levels is also shown. Practical issues regarding the placement of the sensors and accurate recording of data are discussed. The proposed sensing technology is demonstrated to be a good candidate for wireless structural health monitoring (SHM) of reinforced concrete members by its high sensitivity and wide dynamic range.

A Wireless Metamaterial-Inspired Passive Rotation Sensor With Submilliradian Resolution

“…2). As proposed in [21] and shown in [22] for wireless displacement and strain monitoring of a structural beam, the response from each sensor can be acquired without parasitic coupling in case their central frequencies and bandwidths are set so as not to have a spectral overlap. Hence, by positioning multiple sensors along the beam, response from each sensor can either be acquired at once or at different time instants.…”

Wireless Monitoring of a Structural Beam to be Used for Post-Earthquake Damage Assessment

“…Finally, the interrogating antenna is brought close to the beam at a fixed position for a good electromagnetic coupling with the probes (see Figure 2-d). It is important that a fixed position is determined for the antenna, so that the disruptive effects of the concrete and the rebar grid do not dominate the coupling signal [7].…”

An electromagnetic sensing system incorporating multiple probes and single antenna for wireless structural health monitoring

“…The performance of the sensing system is tested in a reallife scenario by a simply supported beam experiment, where the NSRR probes are located on the rebars inside a reinforced concrete beam [8]. Vertical force is applied from the top, which results in a tensile strain at the rebars on the bottom, which is monitored by the sensing system.…”