Chinese Country Report 2012 - Revision of wind loading code and ...

2.5 Along-wind dynamic response factorThe expression of along-wind dynamic response factor has been changed to as follows:2z( z) 12gI10Bz1 R(2.5)Bz ( z)kH( z)(2.6)a1 1 x zzx21(1 x24/31 1 )R (2.7)630 fx , x 5(2.8)11 1kw w 0Where Bz= background response factor; R = resonant response factor; f 1= structural naturalfrequency; 1=structural damping ratio; k w= modification factor of ground roughness (1.28,1.0, 0.54 and 0.26 for A, B, C and D); ( z)= modal shape; 1 x , z = correlation coefficient;k, a 1 = coefficient given in Table 2.3.Table 2.3 Values of coefficients k and a 1Ground roughness A B C Dbuildingk 0.944 0.670 0.295 0.112a 1 0.155 0.187 0.261 0.346towerk 1.276 0.910 0.404 0.155a 1 0.186 0.218 0.292 0.376The values of zwill be increased because of the increase of g and I 10 though the theory andmethodology used kept in the same (Figure 2.3). The base shear and moment of wind load is increasedfor high-rise buildings with total height below 350m (Figure 2.4).Figure 2.3 Difference of dynamic response factorsFigure 2.4 Difference of shear force