DEFORMATIONOF BEAMS DUE TO BENDING 86-2 APPROXIMATE DIFFERENTIAL EQUATION OF THE DEFLECTION CURVE OF THE BEAM AND ITS INTEGTION I\ Approximate differential equation of the deflection curve x M>0 1M(x) El f"(x)<0 Small f()defo =士 ≈m0±f"(x) p(f2 + 2 x∴f"(x)=± M() E M<0 f(x)=-M(x) El (2) f"(x)>0 Formula (2) is the approximate differential equation of the deflection curve§6-2 APPROXIMATE DIFFERENTIAL EQUATION OF THE DEFLECTION CURVE OF THE BEAM AND ITS INTEGTION z z EI 1 M (x) =  1、Approximate differential equation of the deflection curve z z EI M x f x ( )  ( ) =  Formula (2) is the approximate differential equation of the deflection curve. EI M x f x ( )   ( ) = − …… （2） ( ) (1 ) 1 ( ) 2 3 2 f x f f x    +   =   Small deformation f x M>0 f (x)  0 f x M<0 f (x)  0 (1)