工程力学问题求端点挠度和转角

1个回答

  • 设截面A形心为座标原点,X轴正向向右、Y轴正向向下

    弯矩方程 M(x) = -F(L/2 -x) -FL = F.x -(3/2)FL

    AC段挠曲线近似二阶微分方程 EI.y"ac = -M(X) = (3/2)FL -F.x

    一次积分得:EI.y'ac = (3/4)FL.x -(F/2).(x^2) +D1 , ①

    再次积分得: EI.yac = (3/8)FL.X^2 -(F/6).(X^3) +D1.x +D2 , ②

    A处边界条件:x=0, y'=0, y =0, 代入①②式得:D1=0, D2=0

    即: θac =y'ac = [(3/4)FL.x -(F/2).(x^2)]/EI ,③

    yac =[(3/8)FL.X^2 -(F/6).(X^3)]/EI ,④

    将x = L/2 代入③、④式,得截面C的转角及挠度:

    θc =[(1/4)F.L^2]/EI

    yc =[(1/96)F.L^3]/EI

    梁自由端转角θmax =θc =[(1/4)F.L^2]/EI

    按叠加原理计算梁自由端的最大挠度:

    ymax = yc +(L/2).θc

    =[(1/96)F.L^3]/EI +(L/2)[(1/4)F.L^2]/EI

    =[(13/96)F.L^3]/EI