Formula omitted] effect of slender RC columns under seismic load

Abstract

This study investigates the seismic P – Δ effect in slender reinforced concrete (RC) columns on the basis of the layered section method. For an effective analysis of the cyclic behavior of RC columns, which show changes in the load–displacement relationship according to the magnitude of the applied axial force, the layered section approach is adopted, and a procedure for the indirect implementation of the bond–slip effect into the stress–strain relationship of the reinforcing steel is used [Kwak HG, Kim JK. Implementation of bond–slip effect in analyses of RC frames under cyclic loads using layered section method. Engineering Structures 2006;28(12):1715–27]. To verify the validity of the method and to identify the significance of various effects in terms of the global response of the slender RC columns, nonlinear dynamic analyses are conducted for 60 sets of horizontal and vertical earthquakes with practical ranges of slenderness and stability coefficients. On the basis of the obtained numerical results, the influences of axial force, the P – Δ effect and the effect of a vertical earthquake on the structural response are reviewed. Their relative contribution is also assessed. In addition, the applicability of the capacity-demand diagram method in the seismic design of RC structures is reviewed by comparing the results obtained from the introduced method with those from rigorous nonlinear dynamic analyses.