## 3 SHM of Bridge, AI and Recent Technologies
### SHM of Bridge and AI and Drone Technology  
One of the most important technologies used in civil projects today is drone technology. Micro air vehicles (MAVs) and unmanned aerial vehicles (UAVs) fall under the category of drones [128; 129; 130]. Several categories have been introduced for drones. These categories can be based on the physical characteristics (weight, dimensions, and structure) or performance (duration, height, flight range, or controllability) of drones. Nowadays, with significant advances in the UAV industry, this technology can be present in a wide range of construction industry. One of the most important engineering sections that saw fundamental changes with the introduction of this technology was SHM [131; 132; 133]. Due to the structure of bridges, it may not be easy to access them from all angles for visual inspection. Drones are one of the best ways to get real-time information on the SHM system. Drones may be remotely piloted by a human operator or fly with varying degrees of autonomy. This level  
Figure 4: An overview of the most popular learning algorithms in data-driven SHM systems.  
of independence can range from co-piloting (using the autopilot) to flying without a pilot. Drones are able to fly in any direction by harnessing the power of aerodynamics. Therefore, these airborne gadgets may be piloted remotely or with the help of pre-flight programming and dynamic automated systems. The employment of UAVs in SHM systems has several benefits, including their portability, rapid speed, high degree of maneuverability, and low power requirements [134; 135]. UAVs have a wider range of applications than their image and video capabilities would suggest. They are also capable of being fitted with additional sensors for vibration-based analysis methods [105]. In a study, [PERSON] et al. investigated the relationship between SHM systems and the applications of UAVs. They stated that UAVs have the potential to consolidate many stationary monitoring system components into one easily transportable mini-SHM. Also, they listed a set of different applications for damage detection and localization by UAVs in SHM systems. Figure 5 shows some of these applications [105].  
The role of artificial intelligence in connection with drones can be discussed from several angles. The first place where artificial intelligence can be useful is that it can be used to develop software that controls the direction and route of drones in semi-autonomous and fully-autonomous systems. This software can help improve the performance of drones [105]. Even though drones are used on a frequent basis, it will be hard to quantify and analyze the data collected because there is so much of it. In addition, transferring the data obtained from the health monitoring of the structure by drones, such as photos and videos, to the sensors is another challenge in this field. In these cases, too, they can play an effective role in converting the obtained data and images and transferring them to the sensors by leveraging the capabilities of artificial intelligence systems [136; 137]. Also, the systems that are based on the ground and perform control and evaluation of safety, security, and airspace awareness for UAV systems also need to use artificial intelligence solutions due to their complexity. It should also be noted that the simultaneous use of drones in SHM systems and emergence of new technologies such as image processing, combined with a new generation of machine learning algorithms (deep learning networks), and a new generation of sensors, the IoT, 5G and 6G networks, has caused more and more researchers to use drones to monitor the health of bridges.  
Figure 5: The varied applications of UAVs in the field of damage assessment in SHM systems.