Estimates of the yield curvature for design of reinforced concrete columns

A recent advance in displacement-based seismic design procedures relies on an estimated yield displacement as the basis for determining seismic design forces in order to satisfy seismic performance objectives. Simple expressions for the yield curvature of circular and rectangular reinforced concrete column cross sections are presented here, based on moment–curvature analyses. The estimated yield curvatures correspond to the flexural strengths determined using Eurocode 2, and thus are useful for the practice of earthquake-resistant structural engineering. Unlike earlier proposals, the expressions presented here account explicitly for the axial load ratio. These expressions are presented in terms of the depth of tension steel, which is shown to be preferable to the overall section depth, used in a previous recommendation. An example illustrates the preliminary design of a bridge pier using Yield Point Spectra and the recommended expressions for estimating the yield curvature.