Bending-Axis Effects on Load-Moment (P-M) Interaction Diagrams for Circular Concrete Columns Using a Limited Number of Longitudinal Reinforcing Bars

A rectangular reinforced concrete column usually has a strong axis and a weak axis. Bending about the strong axis results in a larger bending strength; on the other hand, bending about the weak axis results in a smaller bending strength. Since longitudinal reinforcing bars are usually uniformly distributed around the perimeters of circular columns, there is no strong or weak axis being defined for circular reinforced concrete columns. As a result, bending-axis effects on circular concrete columns using a large number of longitudinal reinforcing bars have traditionally been neglected. However, considerable bending-axis effects on circular concrete columns using a limited number of longitudinal reinforcing bars may exist and should not be neglected. An example of a circular reinforced concrete column using six longitudinal reinforcing bars is presented in this paper to demonstrate the bending-axis effects on the nominal axial compression-bending moment strength (Pn-Mn) interaction diagram of the column. A final Pn-Mn diagram that considers the bendingaxis effects is also presented in this paper.