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Considering Wave Passage Effects in Blind Identification of Long-Span Bridges

机译：考虑波通桥梁横跨桥梁识别的影响

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Long-span bridges usually experience different input excitations at their ground supports that emanate from differences in wave arrival times, and soil conditions, as well as loss of coherency in arriving waves. These spatial variations can drastically influence the dynamic response; hence, this phenomenon must be considered in any vibration-based identification method. There are numerous Multi-Input Multi-Output (MIMO) identification techniques that may be applied to data recorded at long-span bridges that experience spatial variations in their input motions. However, inertial soil-structure interaction effects severely reduce the accuracy of these techniques because the actual Foundation Input Motion (FIM) cannot be recorded during earthquakes. In this study, we present an extension to a novel blind identification method that we had developed earlier, which enables the method to handle multiple input motions. For the sake of simplicity, we only consider wave passage effects - that is, all unknown input motions are assumed to be identical except for a known/unknown phase-delay. This method comprises two steps. In the first step, the spatial time-frequency distributions of recorded responses are used for extracting the mode shapes and the modal coordinates. This is achieved through a Blind Source Separation (BSS) technique. In the second step, cross relations among the extracted modal coordinates are used for identifying the natural frequencies, damping ratios, modal contribution factors, along with the unknown input motions through a least-squares technique. Both simulated and experimental examples are provided, which suggest that the method is capable of accurately identifying the dynamic characteristics of long-span bridges from recorded response signals without the knowledge of input motions, even in the presence of wave passage effects due to phase-delays.
机译：长跨度桥梁通常在其地面支持中遇到不同的输入激励，从波浪到达时间和土壤条件的差异以及到达波浪中的一致性损失。这些空间变化可以大大影响动态响应;因此，必须在任何基于振动的识别方法中考虑这种现象。存在许多多输入多输出（MIMO）识别技术，其可以应用于在长跨度桥梁上记录的数据，该数据在其输入运动中经历空间变化。然而，惯性土结构相互作用效应严重降低了这些技术的准确性，因为在地震期间无法记录实际的基础输入运动（FIM）。在这项研究中，我们向我们早先开发的新颖盲识别方法展示了一个新的盲识别方法，这使得该方法能够处理多个输入动作。为了简单起见，我们只考虑波通效应 - 即，除了已知的/未知的相位延迟之外，所有未知的输入动作都被认为是相同的。该方法包括两个步骤。在第一步中，记录响应的空间时频分布用于提取模式形状和模态坐标。这是通过盲源分离（BSS）技术实现的。在第二步中，提取的模态坐标之间的交叉关系用于识别天然频率，阻尼比，模态贡献因子以及通过最小二乘技术的未知输入运动。提供了模拟和实验示例，这表明该方法能够精确地识别来自记录的响应信号的长跨度桥的动态特性，而不是输入运动的知识，即使在由于相位延迟而产生的波通道效应。

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