Abstract
This study investigates the applicability of an embedded EM sensor using a series of experimental studies. To verify the embedded EM sensor, the magnetic hysteresis of various types of PS tendons is measured. After that, the embedded EM sensor is embedded into the concrete and the possibility of obtaining measurements is verified. Finally, the downscaled PSC girder specimen having a sheath with a different curvature is fabricated and the influence of the sheath curvature is investigated. The magnetic hysteresis was changed constantly even though the type of PS tendon was changed, and the embedded EM sensor can measure the magnetic hysteresis, even in the concrete and curved sheath. The area of magnetic hysteresis was decreased according to the increase in the tension force, but the actual values were different according to the number and cross-sectional area of tendons and the initial state of sensors. To compensate for the measured data, the tensile force was converted to the tensile stress and the area ratio was used to compensate for the initial value of the EM sensor. According to the test results, the embedded EM sensor could be applied to the actual PS girder and it can measure the actual tension, which includes the friction loss.
Highlights
Structural health monitoring (SHM) has become a very important process with the aging of constructed infrastructure worldwide
As prestressed concrete (PSC) bridges age, the tensile forces in the prestressing strands weaken owing to a variety of losses, including instantaneous losses such as elastic shortening, friction, and anchorage sets, which occur at the time of transfer of the prestressing force, as well as time-dependent losses owing to steel relaxation, and the concrete creep and shrinkage that occur after transferring the prestressing force and during the lifetime of the member
This study investigated the applicability of an embedded EM sensor, which can be embedded in a PSC girder, for use with actual PSC girders
Summary
Structural health monitoring (SHM) has become a very important process with the aging of constructed infrastructure worldwide. The elastomagnetic (EM) sensor was used to measure steel cables of cablestayed bridges [16], and experiments were performed to verify the permeability changes according to the stress and temperature [17]. To measure the magnetic responses of PS tendons that do not appear outside the PSC girder, an embedded EM sensor was proposed [18]. In this study, the variations in magnetic hysteresis according to the tensile force of three types of PS tendons (B, C, and D) were measured using the embedded EM sensor. The magnetic hysteresis of three types of PS tendons, which was affected by a stepwise tensile force variation introduced by a universal testing machine (UTM), was measured using the embedded EM sensor to. The area of the hysteresis curve is highly sensitive to changes in the physical properties and cross-sectional area of the tendon
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