Seismic behavior of RC columns with circular, square and diamond sections

A numerical solution procedure based on the finite grid element method and an iterative procedure is developed with considerations of two different nonlinear stress-strain relations for confined core concrete by stirrups and for unconfined cover concrete. The lateral load-displacement curves can be obtained numerically, where the effects of geometrical nonlinearity, plastic hinge zone, bond slip of reinforcement and shear deformation are taken into account. Then 14 large-scale column specimens, including six circular columns, four square columns and four diamond columns, are designed and investigated experimentally under low frequency cyclic lateral load with very high constant axial load level. The comparison of the numerical results with the experimental results is undertaken and shows a good agreement. Finally, some recommendations on the limit values for the axial compressive stress ratio of RC columns with circular, square and diamond sections are made. (C) 2007 Elsevier Ltd. All rights reserved.