Two-stage identification of interlayer contact loss for CRTS III prefabricated slab track based on multi-index fusion

Abstract

To accurately identify the potential contact loss of the China railway track system (CRTS) III prefabricated slab track, a finite element model with contact loss of self-compacting concrete (SCC) under transient impact was established. Then the vertical accelerations near impact points on the track slab surface were extracted to obtain damage-sensitive indices in the time and frequency domains. The indices were initially normalized to obtain independent items of evidence before the Dempster-Shafer (D-S) evidence theory was used to fuse these into one. Finally, a two-stage identification was performed to identify the damaged SCC area, comprising a rough identification (Stage I) and a precise identification (Stage II). The research results show that the damage indices extracted based on the transient impact response change abruptly at the damage location, and that can be used for damage identification. However, the use of a single index to determine the damage of the impact point may be misjudged. In Stage I, five damage indices of acceleration were fused to magnify the difference between the damaged point and undamaged point, thereby improving the accuracy of finding damage. In Stage II, in the area where more impact points were added, a fusion of three indices of acceleration response, that is, the absolute mean of the time domain, the maximum amplitude of the frequency domain, and the power density ratio, further narrowed down the area where damage exists. As a result, when the contact loss of SCC is greater than 50% along the thickness direction, the identification accuracy can be as high as 70% to 80%. The two-stage identification method proposed in this study can greatly improve the efficiency of interlayer damage detection of slab tracks and is expected to provide effective technical support for damage identification of track structures in the future.

摘要

目的

无砟轨道层间损伤削弱了轨道结构的整体刚度,有可能影响列车运行的平稳性和安全性。本文旨在分析层间损伤对轨道板振动响应的影响规律,构建一种快速精准的损伤识别方法,以期为无砟轨道层间损伤识别提供参考。

创新点

1. 基于振动响应的特征指标,提出无砟轨道层间脱空损伤的两阶段识别方法;2. 建立精细化有限元仿真模型,实现对CRTS III型板式无砟轨道自密实混凝土损伤的准确识别。

方法

1. 利用室内足尺模型试验验证含层间脱空损伤的板式无砟轨道有限元模型的合理性(图8);2. 通过仿真模拟,获取时域和频域内对层间脱空敏感的损伤特征指标(图10、12和13);3. 运用D-S证据融合理论对多个损伤特征指标进行融合,并采用包括损伤区域大致识别(阶段I)和精确识别(阶段II)的两阶段识别方法实现对自密实混凝土损伤区域的识别(图24和25)。

结论

1. 从时域和频域提取的5个损伤指标可全面反映隐藏在振动信号中的损伤信息,但仅使用单一损伤指标很难保证识别的准确性。2. 证据理论的应用可充分利用多个损伤指标之间的互补信息,降低识别的不确定性;在识别阶段I,通过融合损伤指标均可准确确定不同脱空区域的位置。3. 损伤识别的准确性与损伤程度呈正相关;在识别阶段II,当自密实混凝土的脱空损伤程度大于50%时,识别精度可达到70%~80%。