This paper is reproduced from the proceedings of a
seminar on "Seismic Problems in Structural Engineering" arranged by the Departments of Civil Engineering and Extension Studies of the University of Canterbury, and held in Christchurch from May 13 to 16, 1968. Reinforced concrete, as customarily designed and detailed, and in contrast to structural steel, is essentially a brittle construction material. Brittleness can be a danger 
in regions prone to earthquakes. However, with due care in design and detailing, reinforced concrete structures can be made adequately ductile for good performance in earthquakes. This paper presents a rational design procedure to achieve ductility of reinforced concrete structures.