## 1 Introduction  
Bridges play a critical role in the sustainability of economic, social, and cultural life as fundamental components of transportation networks. These essential structures are known to experience performance losses over time due to various natural disasters (e.g., earthquakes and floods) or human-induced factors (e.g., overloading and construction defects). Identifying and evaluating such damages is crucial for ensuring the long-term safe usage of bridges. This assessment is typically performed using various methods, including static and dynamic loading tests, numerical analyses via the finite-element method, visual inspections, and various damage detection techniques. However, many of these methods provide limited information or pose a risk of causing damage to the structure. At this point, Non-Destructive Testing (NDT) methods emerge as a more effective and practical solution for assessing bridge performance. These methods enable the reliable evaluation of structural performance by determining dynamic characteristics without causing any harm to the structure. Highways and bridges are regarded as significant indicators of a country's level of development. Developed countries utilize computer-aided Bridge Management Systems (BMSs) to identify and resolve issues related to their existing bridges. By employing these BMSs, countries conduct a general condition assessment of their bridges based on scoring systems tailored to their national criteria [1]. While visual inspection forms the basis of these scoring systems, each country also incorporates its own advanced scoring criteria. For instance, in the United States, photographs of bridge components are taken and digitized in a computer environment to calculate crack dimensions [2]. In Japan, the scoring process has been automated, moving away from human dependency through the use of a fuzzy logic-based artificial neural network program [3]. Developed countries use this general condition information for various purposes, such as prioritizing maintenance and repair work, planning future costs, predicting the future condition of a bridge, and estimating its remaining service life. This approach enables highways to be used continuously and safely without interruption. For example, a 1991 study in Japan revealed that 18,000 of 60,000 bridges required strengthening [4]. Similarly, in the United States, the total cost of maintaining and repairing 540,000 bridges was estimated to be approximately USD 200 billion [5]. Bridges are fundamental components of national and international transportation networks, not only in developed countries but also in developing nations and many regions worldwide. These structures play a critical role in ensuring the sustainability of economic, social, and cultural life. However, in many areas, the structural condition of bridges is typically addressed only when issues arise during their service life. Inspections conducted in response to unplanned problems often lead to disruptions in transportation, unforeseen costs, and significant time losses. Preventing such situations is essential to ensure the safe, efficient, and long-lasting use of bridges. In particular, reliable, effective, and cost-efficient methods for condition assessment have become a priority research area in engineering to avoid transportation disruptions and enable rapid interventions. Traditional assessment methods, such as visual inspection, often fail to provide sufficient information and are subject to personal interpretation. Procedures like core sampling, on the other hand, pose a risk of causing physical damage to the structure. In contrast, non-destructive testing (NDT) methods offer a modern alternative for evaluating the performance of bridges. These methods enable the direct acquisition of crucial information, such as dynamic characteristics (e.g., natural frequencies, mode shapes, and damping ratios), without causing harm to the structure.