基于车辆制动激励和小波包能量分析的连续梁桥基础冲刷识别方法

近年来，因基础冲刷引发的桥毁事故频发，冲刷会造成桥梁下部结构周围土体被破坏进而导致基础承载力下降，并且由于冲刷位置隐蔽增加了识别检测的难度。为了精准识别桥梁下部结构的基础冲刷损伤，利用车辆制动作用可引起更为显著的桥梁下部结构纵桥向动力响应这一特点，提出了一种基于车辆制动作用下桥梁动力响应小波包能量分析的连续梁桥基础冲刷识别方法。该方法选择典型三轴车制动作用作为动力激励，利用小波包对冲刷前后的车辆制动作用下桥墩顶纵桥向加速度响应进行分解，提出以小波包能量方差变化率作为冲刷识别指标，实现基础冲刷位置识别；进而通过数值模拟方法建立包含多种冲刷程度与对应测点冲刷指标值的样本库，拟合分析确定冲刷识别指标值与冲刷程度间的函数关系，通过识别出的各测点冲刷指标值基于模式反演方法实现冲刷程度的量化识别。一座混凝土连续梁桥工程实例的分析结果表明，该方法能够实现梁桥基础冲刷的定位和定量识别，抗噪能力强，且识别结果受桥面不平度、制动位置、车质量和初始车速等因素影响较小。该方法在试验过程仅需在桥墩顶安装加速度传感器，可借助常规的桥梁荷载试验项目实现，具有测试简便易行、识别精度好等特点，适于公路梁桥基础冲刷的快速检测。

Foundation Scour Identification Method Based on Vehicle Braking Excitation and Wavelet Packet Energy Analysis for Continuous Beam Bridges

In recent years, bridges have frequently failed as a result of scour. Scour will cause the soil around the bridge substructure to be washed away, decreasing the bearing capacity of the bridge foundation. However, the scouring position is concealed, which increases the difficulty of diagnosis. In order to accurately identify the foundation scour of a bridge substructure, the fact that vehicle braking can induce a significant longitudinal dynamic response in a bridge substructure was used to develop a foundation scour identification method for continuous beam bridges based on a wavelet packet energy analysis of the dynamic response under vehicle braking. In this study, the braking force of a typical three-axle vehicle was used as the excitation, the wavelet packet method was used to decompose the response of the acceleration before and after scour in the longitudinal direction of each bridge pier top caused by vehicle braking, and the wavelet packet energy variance variation rate was used as the scour identification index to locate the scour position. Then, a sample database containing various scour degrees and corresponding scour index values was established using numerical simulations. The functional relationship between the scour identification index and scour degree was determined using a fitting analysis, and then the scour degree was quantified and identified by the pattern inversion method. The analysis results of a concrete continuous beam bridge project showed that the method could be used to determine the location and quantitative identification of the foundation scour of a beam bridge with strong anti-noise ability, and the identification results were less affected by factors such as the vehicle weight at a braking position with bridge deck unevenness and the initial speed. The method only requires the installation of an acceleration sensor on the top of the bridge pier during the test process, which can be realized with the help of a conventional bridge load test project. It has the characteristics of a simple and easy test, good accuracy, and so on, and is suitable for the rapid detection of the scour of a highway beam bridge foundation.