Material Nonlinearity Finite Element Analysis Of Beam-Columns

During combined action of axial force and bending moment, the strain and the curvature of the section centroid of beam-columns meeting bring coupling acting forth, the elasto-plastic problem of beam-columns was mianly concerned in this paper.to begin with, during material nonlinearity problem, both element stiffness matrix and structure stiffness matrix is varied with the nodal displacement, this problem can' t be solved by linear elasticity approach, it' s verity solution will gotten after repeated iterations. different alternative manners are used to compile routines to solve the nonlinear elasticity and elasto-plastic problem in this paper. the routines are used to the simulation of some reckon case.the outcome and the rapidity of convergence of different alternative manners are compared. the ultimate bearing pressure of the singleness material during simple bending stat was calculated by the the method of stratification.Secondly, during elasto-plastic analysis of beam-columns, both sectional stiffness matrix and element stiffness matrix were derived in elastic-plastic behavior, a new amend means of element stiffness matrix in the process of iteration was proposed. the difference of section curvature and internal force in the left and right section of the element was taked into account. nonlinear program of beam-columns was compiled according to aforesaid clue, and the result was compared with the finite element program ANSYS, the validity of element stiffness matrix and program was argumented.Finally, the program of bending moment-curvature relation of reinforced concrete section was compiled according to the bleeding deformation method, and the bending moment-curvature relational graph was simulated. to improve the bleeding deformation method, a increment- iteration alligation method was used to compile nonlinear program of reinforced concrete section in varied axial force, the section stiffness matrix was established according to the finite element virtual displacement theory, the state of axial force varied according to bending moment on reinforced concrete section was effective simulated by this program in this paper.