A research study was conducted to determine the history of the strand development length equation. The strand development length equation was first introduced in the 1963 ACI Building Code and was adopted by AASHTO in 1973. The original research that formed the basis for the derivation of the strand development length equation was conducted at the Portland Cement Association (PCA) in the late 1950s and early 1960s. ACI Committee 423 derived and proposed the development length equation based on a reappraisal of the PCA results. The intent of the committee in deriving the development length equation was to provide a "reasonable mean" for the data points rather than a conservative estimate
