第25次作业: 3-12(c M BC: M()=F,aE=X aM CD: M(x)=Fbl, aM DA: M(x)=FB/-Fx NpB(Fx×x+FBlx+(FB1-Fx)×l=0 4F/ FI 0 3eI BEI 3 FR 32 3-12(e) aM 1: M(x)=Fcx aM M(x)=Fca, OF 3: M(x)=Fca-Fr OM =a OF EILJCFCXXxdx+ Fax adx+l(Fca- Fx)xadx=0 7F 0 BEI 2ET 3F (个),F BF (),FAx=F(-)第 25 次作业： 3-12(c) ( ) 32 3 0 3 8 4 ( ( ) 0 1 : ( ) , : ( ) , : ( ) , 3 3 2 0 2 0 0 =  − = =        =  +  + −  =   = − =   = =   =    F F EI Fl EI F l F x xdx F l ldx F l Fx ldx EI l F M DA M x F l Fx l F M CD M x F l x F M BC M x F x B B l B l B l B B B B B B B B 3-12(e) ( ), ( ) 14 3 ( ), 14 3 0 3 2 7 ( ( ) 0 1 3: ( ) , 2 : ( ) , 1: ( ) , 3 3 0 0 0 =  =  =  − = =      =  +  + −  =   = − =   = =   =    F F F F F F EI Fa EI F a F x xdx F a adx F a Fx adx EI a F M M x F a Fx a F M M x F a x F M M x F x B A y A x C a C a C a C C C C C C C C