FN=2×300=600kN,2A=FN2_600×103 15294mm,A1=1765cm 选择100×100×101926lcm2) 第3次作业 FN 3.1M23,N33 3EA 3EA3EA 3EA F=F==10kN.F,=0 M1=△1=FM1=10×103×100 EA=210×X10°×100=0467m a=0467m(→),δ,=0467m(↓) d(x)=d+42-d (x)=2(d1+22,x) 4 Fdx 4Fl d(△/)= M=[d(△) (d rEd, d2100 100 10(19.261 ) 1529.4 , 17.65 170 600 10 [ ] 2 300 600 ,2 2 2 1 2 3 2 1 2 cm mm A cm F F k N A N N   = =  =  = = = 选择  第 3 次作业： 2-7 EA Fl EA Fl EA Fl EA Fl EA l F EA l F EA l F l N N N 3 3 3 3 3 3 3 1 2 3 + = − = +  = + + ( ) 3 =  = → EA Fl u l D 2-12 mm EA F l l l k N F F F F N N N N 0.467 210 10 100 10 10 1000 10 , 0 2 3 3 1 1 2 1 2 3 =      =  = = = = = = = 0.467mm(→), = 0.467mm()  Cx  Cy 2-15 1 2 0 2 1 2 1 2 1 2 1 2 1 1 4 , ( ) ( ) 4 ( ) ( ) 4 ( ) , ( ) Ed d Fl l d l x l d d E d Fdx d l x l d d x A x d l d d d x d l     =  = − +  = − = + − = +  F F F