Concept ·Reinforcement ratio A A In practical design,Ac is usually taken as the normal concrete area,without deduction (for the area of longitudinal reinforcement(纵向钢筋).• Reinforcement ratio c s A A   In practical design, Ac is usually taken as the normal concrete area, without deduction (扣除） for the area of longitudinal reinforcement（纵向钢筋）. Concept