The synchronous monitoring of girder strain during the prestressing-construction of long span rigid frame-continuous-beam bridge based on FBG sensors

The paper aims to verify the accuracy and feasibility of the application of FBG sensors in the engineering monitoring of large bridge, especially in the construction monitoring, and to explore new-type sensing technique applied in the construction monitoring of bridge. Basing on the life-cycle monitoring system structure of Dongying Yellow River Bridge, a great deal of FBG sensors are laid in the key sections of this bridge to monitor the strain and temperature in the phase of construction and service. During the construction of longitudinal prestressing of main girder, the signals of central wavelength of the some FBG sensors located in the controlling positions, are synchronously collected with the optical fiber grating demodulator and its accessories, and then the strain-time history curves are gained. Through setting up the finite element model of construction process, monitored values and theoretical values are compared, and the relative errors between them are analyzed. It is found that monitored values are basically accordant with theoretical values and the relative error increases with the elongation of the prestress pipeline but the max value is 11.4%. The conclusion shows that the measuring precision of FBG sensor is high and it can be applied in the strain monitoring of large bridges during the course of construction.