This paper investigates the possibility of applying novel microwave sensors for crack\ndetection in reinforced concrete structures. Initially, a microstrip patch antenna with a split\nring resonator (SRR) structure was designed, simulated and fabricated. To evaluate the sensorâ??s\nperformance, a series of structural tests were carried out and the sensor responses were monitored.\nFour reinforced concrete (RC) beam specimens, designed according to the European Standards, were\ntested under three-point bending. The load was applied incrementally to the beams and the static\nresponses were monitored via the use of a load cell, displacement transducers and crack width gauges\n(Demec studs). In parallel, signal readings from the microwave sensors, which were employed prior\nto the casting of the concrete and located along the neutral axis at the mid-span of the beam, were\nrecorded at various load increments. The microwave measurements were analysed and compared\nwith those from crack width gauges. A strong linear relationship between the crack propagation\nand the electromagnetic signal across the full captured spectrum was found, demonstrating the\ntechniqueâ??s capability and its potential for further research, offering a reliable, low-cost option for\nstructural health monitoring (SHM).
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