材料力学的真正问题

BC段拉力=根号3 * f = 1.732 * 20 = 34.64 kn = 34640n。

BD段最大弯矩在B点M = 0.5 * 20 * 1000 = 10000nm。

查表可知，工字钢截面面积为21.516 cm 2，弯曲截面系数w = 102 cm 3。

圆管截面积= π (625-400) = 706.85 mm 2

δ= 40000/706.85 * 10 6 = 56.58 * 10 6pa = 56.58 MPa 160/56.58 = 2.8 > 2安全

BC段δ= 34640/21.516 * 10 4 = 16.09 * 10 6pa = 16.09 MPa

BD段δ= m/w = 10000/102 * 10 6 = 98 * 10 6pa = 98 MPa