Determine the equation of the deflection curve of the beam shown in Fig. P.16.12. The flexural rigidity of the beam is EI.
Answer:
Taking moments about D,
R_{\mathrm{A}}\times4+100-100\times2\times1+200\times3=0from which
R_{\mathrm{{A}}}=-125\,\mathrm{N}Resolving vertically,
R_{\mathrm{{D}}}-125-100\times2-200=0Therefore,
R_{\mathrm{B}}=525\,\mathrm{N}The bending moment at a section a distance z from A in the bay DF is given by
M=+125z-100[z-1]^{0}+\frac{100[z-2]^{2}}{2}-525[z-4]-\frac{100[z-4]^{4}}{2}in which the uniformly distributed load has been extended from D to F and an upward uniformly distributed load of the same intensity applied from D to F.
Substituting in Eqs (16.31),
u^{\prime\prime}=-{\frac{M_{y}}{E I_{y y}}},\quad ν^{\prime\prime}=-{\frac{M_{x}}{E I_{x x}}} (16.31)
E I\left({\frac{\mathrm{d}^{2}v}{\mathrm{d}z^{2}}}\right)=-125z+100[z-1]^{0}-50[z-2]^{2}+525[z-4]+50[z-4]^{2}
E I\left({\frac{\mathrm{d}\upsilon}{\mathrm{d}z}}\right)={\frac{-125z^{2}}{2}}+100[z-1]^{1}-{\frac{50[z-2]^{3}}{3}}+{\frac{525[z-4]^{2}}{2}}+{\frac{50[z-4]^{3}}{3}}+C_{1}
E I v={\frac{-125z^{3}}{6}}+50[z-1]^{2}-{\frac{50[z-2]^{4}}{12}}+{\frac{525[z-4]^{3}}{6}} +\frac{50[z-4]^{4}}{12}+C_{1}z+C_{2}
When z = 0, υ = 0 so that C_{2}=0, and when z = 4 m, υ = 0, which gives C_{1}=237.5. The deflection curve of the beam is the