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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.Keywords: optical fiber sensing technology, high-speed demodulation, heavy vehicle identification, bridge health and safety monitoring system, orthotropic steel box girder

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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.

Monitoring the train vibration is an important issue in subway safety management and maintenance. Aiming at the problems of traditional technology for detection and acquisition of subway vibration, such as unable to achieve dynamic detection or evaluation, and unable to give early warning to the changes of subway tunnel structure, this paper proposes a method to obtain and predict the vibration reduction effect based on grating array. The method uses short-time power spectral density (PSD) to extract train vibration signal, and uses Z-vibration level (VLz) to obtain the vibration reduction effect of subway track. A model based on deep forest (DF) is improved to predict the variation trend of vibration reduction effect. The experimental results on the actual train data illustrate that the proposed method can accurately extract the train vibration signal, and the model can effectively forecast the vibration reduction effect, which has a lower error precision and shows improved performance over other prediction models.