As part of a more general effort to refine current assessment guidelines and various approaches to estimate ultimate/plastic rotation angle and/or drift-based limit states for members and overall structural systems in Reinforced Concrete (RC) existing buildings, a dedicated research effort is given to the improvement of the understanding of seismic response and failure mechanisms and on the refinement of assessment procedures for columns, super columns and shear walls. This paper presents preliminary results of analyses focusing on 2D response of square columns. For this purpose, force-displacement curves and yield and ultimate rotation angle/drift ratios of square RC columns experimentally tested by various researchers are investigated. Results are then compared to those reported experimentally and predictions by national and international standards (namely ASCE41-13, EN 1998-3: 2005 and NZSEE2006). Cumbia is used as the analytical tool to predict the response of the member. In the analytical model developed in Cumbia, both section and member analysis approaches are based on plane sections-remain-plain assumption and estimation of the plastic hinge length. Moreover RC square columns designed with NZS3101: 1970 – 2006 are investigated with the proposed method and results (in terms of ultimate drift ratio) are compared to ones predicted by other available procedures. This method will later be used to propose a simple procedure in order to predict the drift capacity of RC columns without determining the response of the member.