30 F34y=-225 37.5 F34x=-45 3 75 5F3x=30 结点3:∑M4=0 F35y=-15 Fx×2+30×2-375X4+75X2=0 35x 30KN X F35=(F35x/35)×k35=-33.5kN 3y=(F353x)×k3s=-15kN ∑M5=0F34x×2-30×2+37.5×4=0 34x 45KN FN34=(F34x/34)×13=-503kN F34=(F3434x)×l34=-22.5kN结点3: ∑M4= 0 F35x×2+30×2–37.5×4+75×2=0 F35x= –30kN FN35=(F35x/l35x)×l 35= –33.5 kN F35y=(F35x/l35x)×l 35y= –15 kN ∑M5 = 0 F34x×2–30×2+37.5×4 =0 F34x= –45kN FN34=(F34x/l34x)×l 34= –50.3 kN F34y=(F34x/l34x)×l 34y= –22.5 kN