课堂测试(7) M,ME dx+[IF M.·M El Gl Gl M,Mdx≠0[元,rd=0△1≠0JM,M=07x=0=61=0 ∫M2Mdx=0∫万 Tdx=0△2=0 T1·Tdx=0 Mdx=0「,7dx=0,=6=0 M,AMdx=0「,Tdx=0△=0 M,Mdx≠0∫T,dx=0a:=61≠0 「M4M≠07rd=0△≠0j2,Md=0j7d=061=8=0 JM. MAdr=0 JT, Tdx=0 =043=0 1X1+12x2+a3X3+4X4 1X1+14X4+△1F=0 1x1+52x2+62x3+a1x1+A2=0{x2=0 1X1+32X2+33+34X4+△3F=0 X2=0 641X1+6X4+△A=0 1X1+2X2+3X3+o4X4+△4F=0 x1≠0,X2=0,X3=0,X4≠0 对称结构的对称截面上的对称内力为0,反对称内力不为0 对称结构上作用了反对称载荷→二次超静定问题    31 1 32 2 33 3 34 4 3 X X X X + + + +  = F 0     21 1 22 2 23 3 24 4 2 X X X X + + + +  = F 0 11 1 12 2 13 3 14 4 1 + 0     X X X X + + +  = F 33 3  X = 0 22 2  X = 0 11 1 14 4 1 0   X X + +  = F 1 2 3 4 X X X X  = =  0, 0, 0, 0 对称结构的对称截面上的对称内力为0，反对称内力不为0 对称结构上作用了反对称载荷 二次超静定问题 课堂测试（7） d d i F i F iF l l p M M T T x x EI GI    = +   d d i j i j ij l l p M M T T x x EI GI    = +   1 2 M M x  = d 0  1 d 0 M M x F    1 d 0 T T x F  =  1 0   F 2 d 0 M M x F  =  2 d 0 T T x F  =  2 0  = F 3 d 0 M M x F  =  3 d 0 T T x F  =   = 3F 0 1 2 T T x  = d 0    12 21 = =0 1 3 M M x  = d 0  1 3 T T x  d =0    13 31 = =0 2 3 M M x  = d 0  2 3 T T x  = d 0    23 32 = =0 4 d 0 T T x F  =  1 4 M M x   d 0  1 4 T T x  d =0    14 41 = 0  2 4 M M x  = d 0  2 4 TTx  = d 0    24 42 = =0 3 4 M M x  = d 0  3 4 T T x  = d 0    34 43 = =0 41 1 42 2 43 3 44 4 4 0     X X X X + + + +  = F 41 1 44 4 4 + + 0   X X  = F 4 d 0 M M x F    4 0   F