Nonlinear response and modelling of RC columns subjected to varying axial load

This paper presents findings on the effects of nonproportionally varying axial load on the response of RC cross-sections. It is shown that the history of the axial load has a significant effect on the moment-curvature and axial load-bending moment interaction diagrams of RC columns. The results indicate that under uncoupled variations in axial and lateral loads the section capacity can be significantly lower than is deduced from current design interaction diagrams. Thus, the weak-beam strong-column behaviour, which is the objective of current seismic design codes, may be jeopardized. The paper also presents a comprehensive review of different analytical models for RC columns. Advantages and short-comings of these models, especially in the light of representing varying axial loads, are discussed. The effect of varying axial load on the response of RC members and structures is presented. It is shown that the global effect of varying, especially nonproportionally varying, axial load is significant. Possible remedies and recommendations for future experimental and analytical research are presented.