弯曲应力 第7次作业 4-1(b) 2 F4=5×==2kN,F=3kN F= F,=2kN, M,=F, x3=6kN.m Fs2=-FB=-3,M2=F4×3=6kNm 4-1(g) FA=FB=×(20×2+10×4)=40kN Fs1=40-10×1=30kN,M1=-80+40×1-×10×1×1=-45kNm Fs2=40-20-10×2=0,M2=-80+40×2-20×1-×10×2×2=-40kNm 2(b) BC:Fs(x)=30+15x,M(x)=-30x--x CA:F(x)=45,M(x)=-30(1+x)-15(0.5+x) 45kN 剪力图 1275kN 弯矩图 2(c) FA=FB=×(3×8+75)=495kN AC F5(x)=49.5-3x M(x)=495x~3x2弯曲应力 第 7 次作业 4-1 (b) F F M F kN m F F kN M F kN m F kN F kN S B A S A A A B 3, 3 6 . 2 , 3 6 . 2 , 3 5 2 5 2 2 1 1 = − = − =  = = = =  = =  = = 4-1(g) F M k N m F k N M k N m F F k N S S A B 10 2 2 40 . 2 1 40 20 10 2 0, 80 40 2 20 1 10 1 1 45 . 2 1 40 10 1 30 , 80 40 1 (20 2 10 4) 40 2 1 2 2 1 1 = − −  = = − +  −  −    = − = −  = = − +  −    = − = =   +  = 4-2(b) : ( ) 45, ( ) 30(1 ) 15(0.5 ) 2 15 : ( ) 30 15 , ( ) 30 2 CA F x M x x x BC F x x M x x x S S = = − + − + = + = − − 4-2(c) 2 3 ( ) 49.5 ( ) 49.5 3 : (3 8 75) 49.5 2 1 2 x M x x F x x AC F F k N S A B = − = − = =   + = 45kN 剪力图 127.5kN.m 弯矩图