2、分配系数分配弯矩 截取结点1,由平衡条件得: M1+M13+M1+M1=02 式中:MiA=S1Aq MIB=SIB MIB MIC MIC=SIC MiA M M S1A+S1A+S1A∑S截取结点1，由平衡条件得： M1A + M1B + M1C + M1 =0 式中： M1 A = S 1 A  M1 B = S 1 B  M1 C = S 1C   =- = - 2、分配系数分配弯矩        M 1  S 1A+ S 1A+ S 1A M 1  ∑S M1B  1 M1  M1A  M1C 