The paper illustrates the development and the application of an active monitoring system, and analyzes the investigated dynamic behaviour of the structure where the system is applied. The system is installed on a 250 m suspended arch steel bridge that has been instrumented with sensors of different type. This work focuses on the employed methodologies and obtained results related to the dynamic monitoring of the bridge. The use of the Operational Modal Analysis techniques with data-driven stochastic subspace identification algorithms allows the extraction of the structural dynamic characteristics: natural frequencies, damping ratios, and mode shapes. These data are in overall accordance with those calculated through the computational model utilized by the active monitoring system. Besides, the definition of a range of scattering of modal parameters, under specific conditions, has been obtained. The bridge has very low vibration frequencies, below 1 Hz for all significant modes. The outcomes indicate that the estimation of dynamic characteristics and the corresponding accuracy is influenced by several factors, including the length of the accelerometric acquisitions and the followed specific procedures. The impact of environmental factors, with particular reference to the temperature, is examined. Compared to the damping ratio, the natural frequency shows higher estimation accuracy and marked sensitivity to the environmental factor. Consequently, in the selection of benchmark for damage detection, it should be taken into account that the two modal parameters have specific criticalities. Once that the modal parameter has been chosen, values outside the estimated uncertainty range can be considered as alarm triggers.

中文翻译：

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定制的主动监控系统，用于结构控制和维护优化

本文说明了主动监控系统的开发和应用，并分析了研究该系统所在结构的动态行为。该系统安装在250 m的悬​​挂式拱形钢桥上，该桥已装有不同类型的传感器。这项工作集中在所采用的方法论上，并获得了与桥梁动态监测有关的结果。将操作模态分析技术与数据驱动的随机子空间识别算法结合使用，可以提取结构动力特性：固有频率，阻尼比和振型。这些数据总体上与通过主动监控系统使用的计算模型计算出的数据一致。除了，在特定条件下，已经获得了模态参数散射范围的定义。该电桥的振动频率非常低，在所有有效模式下均低于1 Hz。结果表明，动态特性和相应精度的估计受几个因素影响，包括加速度计采集的长度和遵循的特定程序。检查了环境因素的影响，尤其是温度。与阻尼比相比，固有频率显示出更高的估计精度和对环境因素的显着敏感性。因此，在选择损伤检测基准时，应考虑到两个模态参数具有特定的临界度。一旦选择了模态参数，