The aging and deterioration of bridges is becoming an increasing burden for transportation management systems as it requires increasing investments for the proper maintenance of a large number of bridges. Significant savings can be achieved by timely maintenance work. To achieve this, it is necessary to improve existing methods of inspection and monitoring of the condition of bridges to make their implementation cheaper, faster, and more reliable. In the last ten years, a significant number of unmanned aerial vehicles have appeared on the market. This paper presents their applicability for assessing the condition of bridges. It includes the following: important characteristics and selection criteria of unmanned aerial vehicles and associated equipment for collecting data on the condition of bridges; a description of the application of unmanned aerial vehicles to conduct a visual inspection on bridges; possibilities of monitoring bridges using data recorded by the unmanned aerial vehicle; a review of the key shortcomings that limit their application in everyday practice.

Shock Transmission Units (STU), also known as Temporary Connection Devices (TCD) or Lock-up Devices (LUD), are mechanical devices that provide a simple and economical way to improve the resistance of existing bridges. They are mainly used for retrofitting existing bridges to accommodate higher-intensity earthquakes and breaking loads defined by new design codes for which the existing bridges do not have sufficient load-bearing capacity. The basic idea of a shock transmission unit is to distribute seismic or other sudden impact loads only to different substructure elements of the bridge so that the bridge behaves as a rigidly connected structure. In the case of slowly acting loads such as temperature, creep, and shrinkage, the shock transmission units are not activated, so that the different parts of the bridge-bearing structure can move independently of each other. They behave like "seatbelts for bridges" because they restrain bridge movement for sudden dynamic loads but allow free movement under slowly acting static loads. To determine the real contribution of STU to the bridge stiffness and consequently, to the global dynamic behavior of the bridge in regular operating conditions, modal parameters such as natural frequency, mode shapes, and damping were determined on the pedestrian bridge, which had been strengthened with shock transmission units. The modal parameters were determined using operational modal analysis and the numerical model. This paper shows the difference between the experimental and numerical modal parameters and draws conclusions about the impact of the shock transmission units on global bridge stiffness. A proposal is also given for the numerical modeling of shock transmission units and their influence on the overall seismic action.