Geometrical Non-linear Analysis Of Reinforced Concrete Frame Structures Based On Effective Stiffness

The analysis of second-order effect is a very important part for reinforced concrete member in structure design. Lots of researchers have made thorough progress, and even many achievements have been adapted in the standards. But because of the diversity of actual structures and the complexity of the issue itself, there still needs further research in this field.In this paper, for the purpose of considering the geometrical nonlinearity of plane reinforced concrete frame and space reinforced concrete frame, a new method is proposed. The main contents are summarized as follow:(1) The principle of geometrical non-linear analysis for plane reinforced concrete frame based on finite element method is introduced. The material nonlinearity of the structure was considered by the effective stiffness in current design standards. The geometric nonlinearity of the structure element was achieved by using the stiffness coefficient which is a function of the ratio of axial force and flexural rigidity of the column. The proposed method can be implemented by modifying the stiffness matrix of element of existing finite element program.(2) Based on geometrical non-linear analysis of plane reinforced concrete frame, the method for space reinforced concrete frame is proposed through modifying the stiffness matrix of element of existing finite element program.(3) A simplified approach for qualification of the axial forces of2D elements or3D elements for the first iteration is suggested. It does not have to do the iterative analysis, and the proposed method can be simplified.