At the completion of the structural design of structural members of civil engineering structures, regardless of the area of reinforcement gotten, a certain minimum and maximum areas of reinforcement apply to ensure an economical, safe and robust structure. In addition to the minimum/maximum areas of reinforcement, there are also certain limitations applicable to the spacing of reinforcement where expedient. These can be found in the pages below congruent with the current Eurocode 2 (EC 2).
Further Reading
Bond, A.J., Brooker, O., Harris, A.J., Harrison, T., Moss, R.M., Narayanan, R.S., Webster, R. (2006). How to design concrete structures using Eurocode 2 (1st edition). The Concrete Centre, Surrey, UK