Investigation of Minimum Longitudinal Reinforcement Requirements for Concrete Columns Using Present-Day Construction Materials. (Discussion by Douglas D. Lee)

The authors presented very useful experimental data on sustained loading of columns. As the authors alluded, the designer encounters the minimum column longitudinal reinforcement issue when the column sections are not governed by the strength and stiffness demands, but rather oversized for nonstructural factors such as architectural preference or constructibity. The section 10.8.4 of the current ACI Code accommodates this situation and permits the lowest reinforcement ratio of 0.5%. The authors stated in Conclusion No. 3 that a reduction of the current ACI Code requirement for minimum longitudinal reinforcement is not justified based on their study, in which they adopted a single, extremely high applied load level of 0.40fc'. Contrary to this conclusion, the discusser finds test data very encouraging for relaxing the current minimum reinforcement requirement.