A new method is proposed to monitor dynamic displacement for flexural structures especially. In this method, the distributed macro-strain is first obtained using long-gage fiber Bragg grating sensors. Then, the conjugated beam theory is applied to calculate the displacement. To verify the method, a cantilever beam, installed with the proposed sensors, is subjected to free vibrations. The results from the proposed method agree well with those measured by the traditional displacement transducer as the error for the first three peak values is less than 5%. A finite element model of a simply supported multi-girder bridge is also simulated with a truck load. The results show that the proposed method can evaluate dynamic displacement accurately as the error for the maximum displacement is less than 3% in all the cases. Finally, the method is verified using simply supported beam models subjected to random dynamic loads. However, the sensor gage length shows some influence on the results. To ensure exact measurements, the sensor gage length should be limited to be smaller than 1/20 of the beam length. Considering other advantages of fiber optic sensing, the proposed method shows promise in the field of long-term structural health monitoring.

This study is concerned with the fatigue performance of adhesively bonded anchorage for carbon fiber reinforced polymer (CFRP) tendons subjected to cyclic loading. Series of monotonous and cyclic experiments under different stress amplitudes and loading frequencies were carried out in order to investigate the mechanical performance of bonded anchorage systems for CFRP tendons and to study the influence of cyclic loading on the anchoring performance. The fatigue damage and the relationships between damage, loading frequency and interfacial temperature rise of anchorage systems were analyzed. The results show that cyclic tension-tension loading is instrumental in enhancing the synergistic interaction between the anchorage components and it also stabilizes the entire anchorage system performance provided that the stress amplitude is kept lower than 10% of the ultimate tensile capacity of the anchorage systems and the maximum stress is less than 50% of the ultimate capacity of the anchorage system. The loading frequency influences significantly the temperature variation in the anchorage system. A high loading frequency may result in a sharp temperature rise at the early-stage and mid-stage of cyclic tension-tension loading, followed by a rather stable late stage. This phenomenon of temperature rise during fatigue tests may indicate the extent of fatigue damage in the anchorage system.

Current displacement measurement methods cannot cope with the demands of the long-term measurement of small-or medium-span concrete bridges because of some technology or economic challenges. In this article, a displacement measurement method is proposed for concrete bridges based on fibre-reinforced polymer-packaged optical fibre sensors. The sensing principle and manufacture process of the proposed sensor are introduced as well as the strain sensing property. Then, a relationship is established between the strain and the displacement based on the distributed strain monitoring. Finally, some field tests are implemented using a simply supported concrete bridge. The tests include static loading test, dynamic loading test with specific speeds and dynamic random traffic loading test. The field test results show that the proposed method can measure the displacement of concrete bridges under traffic loads with reasonable accuracy. Moreover, different types of sensor distributions are proposed to investigate the displacement measurement effects to optimise the sensor installation. Although the sensors cover only some key parts of the girder, the results also verify the accuracy of the proposed method. Therefore, the proposed method can be implemented in concrete bridges in future.

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