结点法列力矩方程 AD PI2NoAyt P/2 N AD 3xa /2P A N D P/2 AD AC B Y X E K A 6×a X=O Y=3P YB=3P N 取结点A AD AD ∑M x AD Nc×a+(4-P/2)a=0,Nc=5P/2 SM=0 Y AD AD AD YA×a+(Y4-P/2)·a=0,YAD=-5P2 2a N AD YAnA=-5√2P/2结点法列力矩方程 P/ 2 P P P P P P/ 2 A F C E D B G I J H 6a L K 3a YA XA YB XA = 0 YA = 3P YB = 3P 取结点A YA A NAC NAD P/ 2 2 0 5 2 0 ( / ) , / , N a Y P a N P M AC A AC D  + −  = =  = 5 2 2 2 Y P / a a NAD = AD = − YA A NAC NAD P/ 2 XAD YAD x l y l l XADYAD NAD y AD x AD AD l Y l X l N = = 2 0 5 2 0 ( / ) , / , Y a Y P a Y P M AD A AD C  + −  = = −  =