## 1 Introduction  
Bridge inspection is essential for ensuring the safety of the public and the stability of the United States economy. It involves evaluating the structural conditions and integrity of bridges through quick, effective, and cost-efficient visual inspections suitable for a variety of structural applications. Additionally, bridge inspection includes the use of simple on-site testing methods to assess the structural integrity of bridges. However, a limitation of bridge inspections is the inability to thoroughly assess internal defects and deteriorations, particularly in reinforced concrete components, which are vital for accurately determining the true conditions of bridge structures. Furthermore, visual bridge inspections are subjective, leading to assessment discrepancies due to significant variations in judgments among different bridge inspectors [1]. Complementing the frequently used visual inspections, nondestructive testing and evaluation (NDT & E) techniques have gained popularity for their efficiency in assessing structures as they provide rapid and reliable assessments of bridge conditions without causing significant damage or interrupting traffic flow. This efficiency underscores their reliability and makes them a valuable tool in bridge inspection and maintenance [2, 3]. Among all NDT & E techniques, popular methodologies used to assess reinforced concrete (RC) structures involve acoustic-based and electromagnetic-based methods. Moreover, various assessment techniques are used to evaluate reinforced concrete structures. The acoustic-based assessment methods encompass techniques such as impact echo and ultrasonic pulse. The electromagnetic-based assessment methods for real-time monitoring [4; 5; 6] include ground-penetrating radars, infrared thermography, and radiography. In addition, several NDT methods were widely used to detect the defects in RC structures such as fiber optic sensors [7; 8], scanning laser Doppler vibrometer [9], and interfacial waves and transducer [10]. The techniques have demonstrated varying levels of effectiveness in assessing reinforced concrete members, highlighting the need for further research into their application in real-world inspection scenarios. It is, therefore, essential to acknowledge that each of the mentioned assessment techniques has its advantages and limitations depending on the type of reinforced concrete structure being inspected and what the objective of the structural evaluation is [11]. In its early development, the ground-penetrating radar (GPR) system was initially introduced to geophysics for soil exploration. As technology advanced and more sophisticated systems were developed in the early 1990s, the device began to be used in other areas, such as inspecting reinforced concrete structures. The system includes a high-frequency antenna that emits and receives electromagnetic pulses. These pulses travel into the ground or structure and are reflected when they encounter changes in electromagnetic properties due to embedded objects. A computer system then interprets the reflected pulses. The GPR method has been examined to assess bridge decks [12], determine rebar layout and size in concrete structures [13; 14; 15], and evaluate the concrete cover and overall thickness of concrete slabs [16; 17]. The capabilities of GPR have been extensively studied for various reinforced concrete structure assessments, including evaluating moisture levels [18], mapping deterioration in aging bridge decks [19], monitoring cracks [20], detecting rebar corrosion in concrete slabs [21; 22], visualizing embedded defects [23], identifying voids in grouted post-tensioned concrete ducts [24], assessing the impact of concrete mix variations and environmental conditions on defect detection [25], identifying anomalies in corrosion-induced bridge decks [26], visualizing defects in fiber-reinforced polymer-wrapped reinforced concrete slabs [27], and mapping rebar layers within reinforced concrete [28], and advanced techniques have been developed for GPR signal processing [29].