FNcD=-2FD 3d G a FNGE=O A B FAX=0 FNHF=+Fp III FAy=Fp SIL L FBy=FI 3d (2)计算各杆轴力 取截面I一Ⅰ以左 ∑F、=0 NGE ∑M4=0FNCD×3d+FP×d=0 NCD =-F/3 ∑MD=0FNm×3d+Fp×2d-FP×3d=0FNm=FP3 以下计算略。(2) 计算各杆轴力 取截面Ⅰ－Ⅰ以左： ∑Fy=0 FNGE=0 ∑MA=0 FNCD×3d+FP×d=0 FNCD= –FP /3 ∑MD=0 FNHF×3d+FP×2d–FP×3d=0 FNHF=FP /3 以下计算略