Investigation of strain-sensing materials based on EM surface wave propagation for steel bridge health monitoring

This paper describes the exploration of a sensor concept for use in structural health monitoring. The sensor is based on the principle of electromagnetic (EM) surface wave propagation, and consists of a thin-layer of wave-guiding media attached to a metal base (e.g., steel bridge elements) and an EM wave emitter and receiver. Targeting at a low-cost and practical solution, various dielectric materials that facilitate EM wave propagation were examined. Low-density polyethylene was determined to have the most suitable dielectric properties and was selected for laboratory tests using tension coupon specimens. The tests of steel coupons with a low-density polyethylene strip indicated that the parameters of an EM wave (e.g., amplitude and phase) changed as the coupon specimens deformed. Therefore, the proposed sensor concept based on EM surface wave propagation can be a viable option for monitoring steel bridges.

Research highlights
► The use of electromagnetic (EM) surface waves within the millimeter wave range in sensing strains in steel members was proved viable.
► The proposed sensor uses the amplitude instead of phase of EM waves such that well-developed wireless communication devices can be used in the sensor.
► Composite materials with epoxy and various amounts of SiO2 and glass particles were tested for their ability to facilitate EM wave propagation.
► Low-density polyethylene may be used as the matrix for the future dielectric composite materials.