Structural health monitoring of maglev guideway PC girders with distributed long-gauge FBG sensors

Abstract

Summary Health monitoring for maglev guideway PC girders is critical to ensure the safe operation of a high-speed maglev train. A long-gauge fiber Bragg grating (FBG) sensor has been recently developed to achieve the high-precision distributed macro-strain measurements and the capability of dynamic testing. This paper presents an integrated strategy for health monitoring of maglev PC girders equipped with the developed FBG sensors. Using the quasi-static measurements under the maglev train load that is uniformly distributed over the span, the deflection and the flexural stiffness of the PC girder can be evaluated. Using the dynamic measurements of the free vibration after the quick passing of the maglev train, the modal parameters of the girder is determined, based on which the flexural stiffness can be calculated in a different way. Using the long-term quasi-static measurements with no maglev train passing by, the deflection can be estimated due to the other effects such as temperature variation, concrete creep, or prestress loss. If assuming that the prestress loss is the only cause of the long-term deflection, the prestress loss can be determined according to its quantitative relation with the strain variation. Through analytical investigations and field testing on a typical maglev PC girder, the ability of the FBG sensors to evaluate the deflection, stiffness, modal parameters and prestress loss is validated.