Structural Dynamics and Assessment Laboratory, School of Civil Engineering, University College Dublin, D04 V1W8 Dublin, Ireland.
School of Civil Engineering, University College Dublin, D04 V1W8 Dublin, Ireland.
Sensors (Basel). 2022 Oct 1;22(19):7468. doi: 10.3390/s22197468.
In this paper, a field study is carried out to monitor the natural frequencies of Malahide viaduct bridge which is located in the north of Dublin. The bridge includes a series of simply supported spans, two of which collapsed in 2009 and were replaced. The replaced spans are stiffer than most of the others and these differences resulted in higher natural frequencies. An indirect bridge monitoring approach is employed in which acceleration responses from an instrumented train are used to estimate the natural frequencies of each span of the viaduct showing the locations of the two replaced spans with higher stiffness. For the indirect approach, an Ensemble Empirical Mode Decomposition (EEMD)-based Hilbert Huang Transform (HHT) technique is employed to identify the natural frequency of each span. This is carried out by analysing the Instantaneous Frequencies (IFs) from the calculated intrinsic mode functions. The average of the IFs calculated using 41 runs of the instrumented train (with varying carriage mass and speed for each run) are used to estimate the natural frequencies. To assess the feasibility of the indirect approach, a bespoke set of direct measurements was taken using accelerometers attached successively on each span of the viaduct. The free and forced vibrations from each span are used to estimate the first natural frequencies. The frequencies obtained from drive-by measurements are compared to those from direct measurements which confirms the effectiveness of indirect approaches. In addition, the instantaneous amplitudes of the drive-by signals are used to indicate the location of the stiffer spans. Finally, the accuracy and robustness of the indirect approaches for monitoring of multi span bridges are discussed.
本文对位于都柏林北部的马莱海德高架桥的固有频率进行了现场监测。该桥由一系列简支跨组成，其中两座在 2009 年发生倒塌并已更换。更换后的桥跨比大多数其他桥跨更刚硬，这些差异导致了更高的固有频率。文中采用了一种间接的桥梁监测方法，利用装有仪器的列车的加速度响应来估计高架桥各跨的固有频率，从而显示出刚度较高的两个更换桥跨的位置。对于间接方法，采用基于集合经验模态分解（EEMD）的希尔伯特黄变换（HHT）技术来识别各桥跨的固有频率。通过分析计算出的固有模态函数的瞬时频率（IF）来实现这一点。使用 41 次装有仪器的列车运行（每次运行的车厢质量和速度不同）计算出的 IF 的平均值来估计固有频率。为了评估间接方法的可行性，还使用附着在桥跨上的加速度计进行了一系列定制的直接测量。利用各桥跨的自由和强迫振动来估计第一固有频率。通过驾车测量得到的频率与直接测量得到的频率进行了对比，验证了间接方法的有效性。此外，驾车信号的瞬时幅值可用于指示更刚硬桥跨的位置。最后，讨论了间接方法在监测多跨桥梁时的准确性和鲁棒性。
