Fiber Bragg grating strain sensors for reinforced concrete girders

In a extensometer, a fiber Bragg grating is attached at two ends of the inner tube, therein the separation of these two bonding ends defines the gauge length of the sensor. To measure compressive and tensile strain, the grating is required to exist in a state of permanent tensile strain equal to the largest compressive strain it is ever likely to experience. The fiber Bragg grating strain sensors are bonded on the concrete surfaces of H154 and the reinforcing steel bar surfaces of H158 girders to measure the compression and tension strain separately. When the reinforced concrete girders are loaded by the jack, theirs strain are measured by the shift quantity of reflected Bragg wavelength in these sensors. The experiment indicates that as an absolute measurement component, the fiber Bragg grating offers the effective monitoring for RC girder, whereinto, the tension strain is ~1000 me, and the compression strain is ~1500 me.