Steel Buildings in Europe

Title Appendix A Worked Example: Wind action on a multi-storey building 8 of 18 3 - 29 8 Background factor   0,415 75,9 1 0,9 120 35 1 1 0,9 1 0,63 0,63 s 2                    L z b h B EN 1991-1-4 § B.2(2) 9 Mean wind velocity at the reference height z s v m ( z s ) = c r ( z s ) c 0 ( z s ) v b = 0,915 × 1,0 × 26 = 23,8 m/s EN 1991-1-4 § 4.3.1 10 Fundamental frequency n 1,x It is estimated by the simplified formula: n 1,x = h d 0,1 n 1,x = 0,1 35 10  = 0,9 Hz 11 Non dimensional power spectral density function   5 / 3 L s 1,x L s 1,x L s 1,x ( , ) 1 10,2 6,8 ( , ) ( , ) f z n f z n S z n   ( ) ( ) ( , ) m s s 1,x L s 1,x v z n L z f z n  2,87 23,8 ( , ) 0,9 75,9 L s 1,x    f z n Then:   0,0664 2,87 1 10,2 6,8 2,87 ( , ) 5 / 3 L      S z n EN 1991-1-4 § B.1(2) 12 Logarithmic decrement of structural damping  s = 0,05 EN 1991-1-4 § F.5(2) Table F.2 13 Logarithmic decrement of aerodynamic damping  a  a = 1,x e m s f 2 ( ) n m c b v z   = 1,25 kg/m 3 c f = c f,0 = 2,0 for d/b = 10/120 = 0,083 m e is the equivalent mass per unit length: m e = 150 t/m Therefore:  a = 0,026 2 0,9 150 10 2 1,25 120 23,8 3        EN 1991-1-4 § F.5(4) 14 Logarithmic decrement of damping due to special devices  d = 0 (no special device) 15 Logarithmic decrement  =  s +  a +  d = 0,05 + 0,026 + 0 = 0,076 EN 1991-1-4 § F.5(1)