抄録
When a RC column is subjected to repeated lateral forces, such as earthquake loads, its plastic behavior is influenced considerably by the transverse reinforcing bars as they improve the strength and ductility of the concrete by confining the bulk expansion caused by the plastic deformation of the concrete. In order to estimate this confining effect quantitatively, the three-dimensional analysis becomes invaluable in comparison to the conventional two-dimensional way. The RC column is considered to be a hexahedral concrete element, with longitudinal and transverse reinforcing bars, and a bond between the concrete and the rebars. Concrete is represented by a three-dimensional isoparametric element, and the elastic-plastic conditions are judged at eight Gaussian points therein. In compressive regions, we assume the Drucker-Prager's yield criterion, the Naghdi's flow rule and the Prager's kinematic hardening rule modified by Ziegler. In tensile regions, when the maximum principal stress reaches the tensile strength, the cracking is asumed to occur. A reinforcing bar is assumed to be a one-dimensional bi-linear element considered to possess yield and strain hardening of steel. Bond is represented by a non-linear spring that connects the rebars to concrete. This development is applied to the analysis of a RC column specimen which is subjected to constant axial force and repeated lateral one. As a result the ultimate load, ductility, mode of failure, member stiffness, and its reduction in plastic range show a fairly good agreement in comparison to the experimentally observed test.
