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研究了长标距光纤布拉格光栅(FBG)传感技术,利用链式阵列方法采集梁的动态响应,实现了车速、频率和振型等动态参数的识别。对单个FBG施加预应力并将其封装成传感器,以扩展其标距测量范围。将跨度为4m的T型钢筋混凝土梁等分为8个单元,在每个单元安装标距为500mm且与中性轴平行的传感器,实现了对梁的整体监测。采用配重小车进行移动加载实验,基于时差定位法的原理分析中心波长时程曲线,以确定小车位置及所处时刻,从而实现了对车速的识别。采用激振器激励,以使梁产生自由振动。利用长标距FBG传感器以及梁顶部布置的压电式加速度计采集梁的动态响应信号,通过频域分析得到频率和振型。结果表明:采用链式阵列方法可以实现频率和振型识别,振型识别阶数与单个传感器的标距长度有关。
The FBG sensing technology with long gauge fiber is studied. The dynamic response of the beam is acquired by the chain array method, and the dynamic parameters such as vehicle speed, frequency and mode shape are identified. A single FBG is pre-stressed and packaged as a sensor to expand its gauge range. T-shaped reinforced concrete beams with a span of 4 m are equally divided into eight units, and sensors with a gauge of 500 mm and parallel to the neutral axis are installed in each unit to achieve overall monitoring of the beam. The counterweight trolley was used to carry out the mobile loading experiment. Based on the principle of time-difference positioning method, the central wavelength-duration curve was analyzed to determine the position of the trolley and the moment of the trolley so as to realize the recognition of the vehicle speed. Vibrator excitation, to make the beam free vibration. The dynamic response signal of the beam is acquired by using a long gauge FBG sensor and a piezoelectric accelerometer arranged at the top of the beam, and the frequency and the mode shape are obtained through the frequency domain analysis. The results show that frequency and mode identification can be achieved by using chain array method. The order of mode identification is related to the gauge length of a single sensor.