Equilibrium condition N=a,A+a,A,=0,A1+7p)=a,A 4=A+月p)=A+贸 Concept n As is transform section or equivalent section for reinforcement(折算为混凝土截面积)• Equilibrium condition 0 (1 ) A n N c Ac s As c Ac   c            n A A n A  Ac   c  s (1 ) 0  n As is transform section or equivalent section for reinforcement（折算为混凝土截面积） Concept