Steel Buildings in Europe

Part 3: Actions 3 - 15 6. The turbulence intensity I v ( z s ) If z min ≤ z s ≤ z max I v ( z s ) = k l / [ c 0 ( z s ) ln( z s / z 0 ) ] Else, if z s < z min I v ( z s ) = I v ( z min ) where: z max = 200 m 7. The turbulent length scale L ( z s ) If z min ≥ z s L ( z s ) = L t ( z s / z t )  Else, if z s < z min L ( z s ) = L ( z min ) where:  = 0,67 + 0,05 ln( z 0 ) [ z 0 in meters] L t = 300 m z t = 200 m Note: Some of the following parameters are determined using EN 1991-1-4 Annex B as recommended method. They can also be defined by the National Annex. 8. The background factor B 2 0,63 s 2 ( ) 1 0,9 1          z b h B L 9. The mean wind velocity v m ( z s ) The mean wind velocity at the reference height z s is calculated from: v m ( z s ) = c 0 ( z s ) c r ( z s ) v b Where v b is the basic wind velocity as defined in EN 1991-1-4 § 4.2(2). 10. The fundamental frequency n 1,x The procedure requires the determination of the fundamental frequency of the building in the wind direction. The following formula can be used for common buildings in order to get a rough estimation of the fundamental frequency in Hertz: n 1,x = h d 0,1 With d and h in meters. Complementary information can be found in the ECCS recommendations for calculating the effect of wind on constructions [11] . 11. The non-dimensional power spectral density function S L ( z s , n 1,x ) S L ( z s , n 1,x ) =       3 5 L s 1,x L s 1,x , 1 10,2 , 6,8 f z n f z n 