我的计算结果,FB亦是向上。 计算过程如下: . (1)取梁CDE段为隔离体: ΣMC =0, FD.3m -(2KN/m).4m.2m =0 FD =5.3KN(向上) ΣMD =0, 10KN.3m -FC.3m +(2KN/m).4m.1m =0 FC =12.7KN(向上) . (2)取梁ABC段为隔离体: FC的反作用力FC' =(38/3)KN(向下) ΣMB =0, 6KN.m -FAy.4m -FC'.2m =0 6KN.m -FAy.4m -12.7KN.2m =0 FAy = -4.85KN(向下) ΣFx =0, FAx =0 ΣMA =0, 6KN.m +FB.4m -FC'.6m =0 6KN.m +FB.4m -12.7KN.6m =0 . FB = 17.55KN(向上)验算: ΣFy =0, FAy +FB -FC' =0 -4.85KN +FB -12.7KN =0 FB = 17.55KN(向上),与用ΣMA =0方程计算结果相同