We present and demonstrate a novel fiber Michelson interferometer based on cascaded twin core fiber (TCF) and side-hole fiber (SHF) for curvature measurement. The interferometer is fabricated by fusing the TCF and SHF. The interferometer can measure curvature and temperature by monitoring the wavelength change of interferometer spectrum. The experiment investigated sensor’s spectral responses to the curvature at different bending directions. Experimental results show that the bending sensitivities of the sensor are -6.968 nm/m-1 and 6.978 nm/m-1 at the bending direction of 0° and 180°, respectively. The temperature sensitivity of the interferometer is 10.37pm/°C.
In order to meet the research of bridge health and safety monitoring system, and provide heavy vehicle load
spectrum for the research, the heavy vehicle classification identification system was designed based on high-speed FBG
demodulation system and FBG sensing test technology according to the structure characteristics of the large span
orthotropic steel box girder cable-stayed bridge. The heavy truck load cases were designed for the loading test, and
heavy vehicle classification standard was provided of the identification system according to the loading test.
The various fiber Bragg grating(FBG)sensors such as FBG force rings, differential FBG displacement cells, FBG
strain sensors and FBG temperature sensors had been used to monitor the strengthening and maintenance process of the
continuous concrete beam bridges and the continuous concrete rigid frame bridges which are the part of Wuhan Second
Yangtze River Bridge. In the strengthening and maintenance process, the tension force of the external prestressed
tendons, the cracks change and intensity of cross sections had been monitored to insure the instruction safety, study the
effect of strengthening and maintenance, and verify the design theories of strengthening and maintenance. Also the
reference state criterion for long-term bridge health monitoring had been provided according to the monitoring results.
During the construction and service period of concrete bridges, the cracks often influence the quality of the project
even the safety of the structure. An effective and long-term crack monitoring of concrete bridges with the appropriate
choice of displacement sensors is imperative under the situation. The differential fiber bragg grating displacement cell is
based on the composite structure which consisted of pulling spring and cantilever. It has realized differential measure of
normal FBG displacement sensor and has solved the serious problem of temperature disturbance. The differential fiber
bragg grating displacement cell has the advantages of high accuracy, anti-interference, long distance transmitting and
good durability etc. In this paper, the differential fiber bragg grating displacement cells were applied to monitor the
cracks of web slabs during the tension process of external prestressed tendons when the continuous prestressed concrete
box girder bridges and continuous concrete rigid frame bridges were maintained and reinforced. A group of typical
cracks of web slabs was selected respectively in the continuous prestressed concrete box girder bridge and the
continuous concrete rigid frame bridge. And a group of three sensors were installed across the three cracks. The external
prestressed tendons had been tensioned by four grades. Then the widths of these cracks were recorded in accordance
with the four tension grades of the external prestressed tendons: before tension, 10% tension, 80% tension, 100%
tension. The results of the differential FBG displacement cells used during the process of tension of external prestressed
tendons show that the cracks monitoring data are accurate and in accordance with the cracks changing rule.