Steel Buildings in Europe

Part 3: Actions 3 - 16 where: f L ( z s , n 1,x ) =     m s s 1,x z n L z  12. The logarithmic decrement of structural damping  s  s = 0,05 for a steel building (EN 1991-1-4 Table F.2). 13. The logarithmic decrement of aerodynamic damping δ a The logarithmic decrement of aerodynamic damping for the fundamental mode is calculated according to EN 1991-1-4 § F.5(4):   a = 1,x e m s f 2 ( ) n m c b v z  where: c f is the force coefficient in the wind direction c f = c f,0  r   (EN-1991-1-4 § 7.6(1) For common buildings, the reduction factors  r and   can be taken equal to 1,0. c f,0 is obtained from EN 1991-1-4 Figure 7.23.  is the air density as defined in EN 1991-1-4 § 4.5(1). The recommended value is:  = 1,25 kg/m 3 m e is the equivalent mass per unit length according to EN 1991-1-4 § F.4. For a multi-storey building, when the mass is approximately the same for all the storeys, it can be taken equal to the mass per unit length m . m e is therefore the total mass of the building divided by its height. 14. The logarithmic decrement of damping due to special devices  d  d = 0 when no special device is used. 15. The logarithmic decrement   =  s +  a +  d 16. The aerodynamic admittance functions R h and R b They are calculated using the equation given in EN 1991-1-4 § B.2(6) in function of parameters defined above: b , h , L ( z s ), f L ( z s , n 1,x ). 17. The resonance response factor R 2   b h L s 1, 2 2 , 2 S z n R R R x      18. The peak factor k p The peak factor can be calculated as (EN 1991-1-4 § B.2(3)):