由平衡条件: 刚结点B处,杆端弯矩应满足平衡条件 ∑MB=0 MtM DC=0 3E/ 6BA-FPI/8+4EI 8BA=0 c 7EI6B1-Fp/8=0 8 BFpA2/56EI 将代入(a)(b)式,则: MB=3EM·Fp/56EI +3Fp56 °MBC=Fp8+4EM·Fp2/56E=-3Fp56 MCB=+FPl/8+2EI/L. Fpl2/56El=+9Fp/56• 由平衡条件： • 刚结点B处，杆端弯矩应满足平衡条件 • ∑MB=0 MBA+M BC =0 • 3EIθB /l – FP l /8+4EIθB /l =0 (c) • 7EIθB /l – FP l /8 =0 • θB=FP l2 /56EI • 将θB代入(a) (b)式,则: • MBA= 3EI/l · FP l2 /56EI = +3FP l/56 • M BC=-FP l/8+4EI/l · FP l2 /56EI = - 3FP l/56 • MCB=+FP l/8+2EI/L · FP l2 /56EI = +9FP l/56