The seven-wire strands are the crucial components of prestressed structures, though their performance inevitably degrades with the passage of time. The ultrasonic guided wave methods have been intensely studied, owing to its tremendous potential for full-scale applications, among the existing nondestructive testing methods, for evaluating the stress status of strands. We have employed the theoretical and finite element methods to solve the dispersion curve of single wire and steel strands under various boundary conditions. Thereafter, the singular value decomposition was adopted to work with the simulated and experimental signals for extracting a feature vector that carries valuable stress status information. The effectiveness of the vector was verified by analyzing the relationship between the vector and the stress level. The vector was also used as an input to establish a support vector regression model. The accuracy of the model has been discussed for different sample sizes. The results show that the fundamental mode dispersion curve offset on the high-frequency part and cut-off frequency increases as the boundary constraints enhance. Simulated and experimental results have demonstrated the effectiveness and potential of the proposed support vector regression method for evaluating the stress level in the strands. This method performs well even at low stress levels and the reliability can be enhanced by adding more samples.

七线绞合线是预应力结构的关键组成部分，尽管其性能不可避免地会随着时间的流逝而降低。在现有的无损测试方法中，超声波导波法在全面应用中具有巨大潜力，可用于评估钢绞线的应力状态，因此受到了广泛的研究。我们采用理论和有限元方法来求解单线和钢绞线在各种边界条件下的色散曲线。此后，采用奇异值分解来处理模拟和实验信号，以提取承载有价值的应力状态信息的特征向量。通过分析矢量和应力水平之间的关系，验证了矢量的有效性。该向量还用作建立支持向量回归模型的输入。已针对不同样本量讨论了模型的准确性。结果表明，随着边界约束的增加，基模频散曲线在高频部分偏移，并且截止频率增加。仿真和实验结果证明了所提出的支持向量回归方法用于评估钢绞线应力水平的有效性和潜力。该方法即使在低应力水平下也能表现良好，并且可以通过添加更多样本来提高可靠性。结果表明，随着边界约束的增加，基模频散曲线在高频部分偏移，并且截止频率增加。仿真和实验结果证明了所提出的支持向量回归方法用于评估钢绞线应力水平的有效性和潜力。该方法即使在低应力水平下也能表现良好，并且可以通过添加更多样本来提高可靠性。结果表明，随着边界约束的增加，基模频散曲线在高频部分偏移，并且截止频率增加。仿真和实验结果证明了所提出的支持向量回归方法用于评估钢绞线应力水平的有效性和潜力。该方法即使在低应力水平下也能表现良好，并且可以通过添加更多样本来提高可靠性。