Development length of reinforcing bars — Need to revise Indian code provisions

The bond between concrete and reinforcement bars is very important to develop the composite behaviour of reinforced concrete. Bond strength is influenced by several factors such as bar diameter, cover of concrete over the bar, spacing of bars, transverse reinforcement, grade and confinement of concrete around the bars, aggregates used in concrete, type of bars and coating applied on bars, if any, for corrosion prevention. In the Indian code on concrete structures which was revised in the year 2000, the provisions regarding development length remained unchanged. Many of the above parameters are not considered in the revised code. Hence in this paper, the Indian code provisions are compared with those of American code provisions (which consider all these parameters). The effect of high strength concrete, self consolidating concrete and fibre reinforced concrete on the development length is also discussed. A formula for inclusion in the Indian code is also suggested based on recent research.