e-mosty September 2017: Mersey Gateway Bridge. Arenales Bridge. Mersey Gateway Bridge. Arenales Bridge. BLWT. - Page 42

Mean wind velocity and intensity of turbulence profiles were investigated for different roughness and we obtained information on type and quality of the boundary layer. The special devices like grids or foil and 2D barriers (Fig. 11) were inserted along wind tunnels according 1. The results of the experimental measurements in BLWT STU for different barriers (height B=150-200 mm) and comparison with EN 1991-1-4 2 are shown in Fig. 12. The boundary layer simulation was developed and is uniform in the area of test section used for experiments on models. The mean velocity profiles in the ABL simulations proved to be in good agreement with logarithmic law. The best results gave us barrier with height 150 -170 mm. The detailed measurements of the wind action, especially near the ground, help us to prepare boundary layer in BLWT STU according to EN 1991-1-4. We can classify ABL simulation and terrain roughness in STU wind tunnel between the III and IV terrain category, which corresponds to the roughness of terrain in Bratislava and cities in Slovakia. Experimental measurements in BLWT STU so far have ensured height of boundary layer about 1.05 m and scale factor - SF 366 - 390. Figure 11: Arrangement of Boundary layer - plastic FASTRADE 20, barrier 100-250 The roughness length for area with regular cover of buildings or vegetation - terrain category III z 0 = 0.3 m, our ABL simulation with value z 0 = 0.7 – 0.77 m is closer to the terrain category IV, where z 0 = 1 m (area with at least 15 % of the surface is covered with buildings their height exceeds 15 m). Figure 12: The profile of mean wind velocity compared with EN 1991-1-4 3/2017