Investigation of analytical relations on the effect of confinement in the design of reinforced concrete columns

Concrete core capability of a reinforced concrete columns to withstand compressive strain caused by the confinement pressure increases. In order to ensure proper lateral deformation capacity of reinforced concrete columns enclosing the bars should be increased according to the axial load. On the other hand, the strength and flexibility of each reinforced concrete is enhanced by improving the enclosure of plastic hinge areas. This ensures improved seismic stability during an earthquake. One of the most important characteristics of concrete structures against the forces of earthquake is their ductile behavior. Finding the values for standard plasticity due to the complexity of the structural behavior and the lack of explicit all its influencing factors, is associated with many problems. Also various regulations are expressing the different criteria for ductility. The purpose of the present study is to provide a confinement criterion based on the need for ductility. In this article, we review the various regulations, is extracted relations for design of enclosed transverse reinforcement of two type of columns, with circular and rectangular sections, In the case of medium and high ductility. In order to verify the relations, reinforcement values for designing reinforced concrete columns evaluated with the values obtained from Iranian national regulations relations. The results of the proposed relations show that the values of the design reinforcement of sections for both levels of ductility is reduced .