## 1 Introduction  
As bridge spans increase, main beams become more slender, and wind loads and wind-induced vibration problems become more prominent [1, 2, 3, 4]. Vortex-induced vibration (VIV) is a type of wind-induced vibration that occurs easily at low wind speeds. When airflow passes over the main beam surface, vortices are shed periodically and alternately, generating periodic vortex-induced forces (VIFs). The main beam undergoes VIV under the action of these VIFs. When the shedding frequency of the vortices approaches or matches the natural frequency of the main beam, vortex resonance occurs [5, 6, 7]. Many bridge main beams worldwide have experienced VIV, including the Tokyo Bay Bridge in Japan [8], the West Approach Bridge of the Great Belt East Bridge in Denmark [9], the Volga River Bridge in Russia [10], the Humen Pearl River Bridge in China [11], and the Xigangmen Bridge [2], among others. Although VIV does not lead to catastrophic failure, it can affect driving comfort, and prolonged vibration may lead to structural fatigue damage [1, 5, 6]. Therefore, studying VIV characteristics is crucial for ensuring both driving and bridge safety. Wind tunnel testing is one of the most commonly used methods to study VIV. To ensure flow similarity between models and prototypes, the similarity criteria related to the flow must be matched. However, owing to limitations in wind tunnel size, wind speed, and other factors, the Reynolds number, one of the similarity criteria, often differs by several orders of magnitude between experimental and actual bridge values [12]. This discrepancy may cause deviations between the experimental and actual results, which could hinder the design of wind-resistant bridges [13, 14]. Main beams of large-span bridges often adopt streamlined box girders with favorable aerodynamic shapes [15, 16]. Earlier studies suggested that for main beam cross-sections with distinct edges, the aerodynamic coefficient variations with the Reynolds number could be ignored, as they have fixed flow separation points [17]. However, subsequent studies revealed that even main beams with distinct edges can exhibit Reynolds number effects [9, 13, 18, 19]. Many scholars have conducted in-depth studies on the effects of the Reynolds number on the aerodynamic forces and VIVs of main beams and other structures. In terms of aerodynamic forces, [PERSON] et al. [12] conducted static tests to study the effects of the Reynolds number on the pressure distribution and aerodynamic forces of twin-box girders in the range of 1.05 \(\times\) 104 \(<\)\(Re\) < 8.93 \(\times\) 104. They reported that as the Reynolds number increased, the size of the separation bubble and the drag coefficient decreased. In a large Reynolds number range (104 \(<\)\(Re\) < 107), [PERSON] and [PERSON] [9, 18] reported that with the increase in the Reynolds number, the drag coefficient of the bridge section decreased first and then remained constant, and the lift coefficient decreased first and then increased. The pitching moment coefficient was basically unchanged. [PERSON] et al. [19] reported that as the Reynolds number increased from 0.25 \(\times\) 106 to 1.0 \(\times\) 106, the drag coefficient of the rectangular section increased, whereas the lift and pitching moment coefficients remained constant. [PERSON] et al. [20] examined the effects of the Reynolds number on the aerodynamic characteristics of airfoils and reported that as the Reynolds number increased, the drag coefficient decreased, and the lift coefficient increased. [PERSON] et al. [21] studied the effects of the Reynolds number on the aerodynamic forces of streamlined twin-box girders and reported that the drag and lift coefficients obtained from low-Reynolds-number wind tunnel tests were lower. [PERSON] et al. [22] conducted force measurements to study the effects of the Reynolds number on the aerodynamic characteristics of double-deck bridges as the Reynolds number increased from 1.3 \(\times\) 106 to 6.1 \(\times\) 106.