Yield curvature for the design of normal- and high- strength circular reinforced concrete columns
Significant research efforts have been going on for the development of displacement-based seismic design methodologies, recognizing the shortcomings of traditional, code specified force-based seismic design procedures. Recent advances in displacement-based seismic design of columns rely on the estimates of yield curvature for the determination of seismic design forces to meet the specified seismic performance levels. This paper presents simple expressions to estimate effective yield curvature for normal- and high- strength circular reinforced concrete columns based on moment-curvature analyses of 200 column sections. Such expressions can be programmed into spreadsheet format and can be used for the displacement-based design of columns. Influence of different parameters on the effective yield curvature has also been quantified. Effective yield curvature is presented in terms of the gross diameter of the section and the yield strain of longitudinal reinforcement together with three modification factors that take into account the effect of the strength of concrete, axial load ratio and the amount of longitudinal reinforcement. An example illustrating preliminary design of bridge column based on the developed expression of yield curvature is presented.