Combination of modes Combination of modes ·SRSs ·cac F.=aX.G. sa-oas,s. 8561+2以 P0-T+4k6+广方 ar ofthndtmode With Torsion vibration Only under X dir.Eq. 入 工x,0, 旧 ++8 Bunch of plates Fo=.X,G Fn=《,y,YG =a,yrpG .Undor two directions excited How many modes should be composed?Tota? Combination of two dirction t Sa=5:+0.53,厅 how角any Sm=5+(0.85S,)月 地04 Combination of modes § SRSS å å å = = = = = 2 1 2 1 Ek j n i ji i n i ji i j ji j j ji i S S X G X G F X G g a g Combination of modes § CQC å å= = = m j m k S Ek jk S j S k 1 1 r T j k T T j k T T jk l z z l l z z l l r 2 2 2 1.5 (1 ) 4 (1 ) 8 (1 ) - + + + = － coupling factor of i-th and j-th mode . rjk With Torsion vibration q Plan irregularity q Torsion should be concerned carefully q Bunch of plates What’s different between regular and irregular structure? O n ly und e r X d ir. E q . ( ) O n ly und e r Y d ir. E q . ( ) W ith a n a n g le o f θ to X D ir. E q . c o s sin n ji i i 1 tj n 2 2 2 2 ji ji ji i i i 1 n ji i i 1 tj n 2 2 2 2 ji ji ji i i i 1 tj x j yj X G X Y r G Y G X Y r G g f g f g g q g q = = = = = + + = + + = + å å å å tji j tj i ji i Yji j tj ji i Xji j tj ji i F r G F Y G F X G a g j a g a g 2 = = = tj g 2 2 2 2 ( 0 .85 ) ( 0 .85 ) Ek y x Ek x y S S S S S S = + = + n Under two directions excited Combination of two direction excited 1 0.85 How many modes should be composed? The numbers should satisfy that the 90% mass are participant in the vibration. According to some rules, based on the codes or on the required of engineering needed. Total? How many?