Non-linear Finite Element Analysis Of3D Reinforced Concrete Based On The Secant Stiffness

Complex nonlinear properties are showed in loading reinforced concretestructures.With the rapid improvement of computer technology, finite element methodas a effective method of numerical simulation is widely used in the nonlinear analysis ofreinforced concrete by scholars from various countries, hoping to get good results insimulating the nonlinear characteristics of reinforced concrete.The previous research in two dimensional nonlinear finite element analysis madeby Vecchio’s research group and our group is the basis of this paper. In this paper, athree dimensional nonlinear finite element analysis of reinforced concrete was finishedon the basis of the Modified Compression Field Theory (MCFT). The following workwas completed:①A new three-dimensional element suitable for the MCFT was established.Cracked concrete was an orthotropic solid continuum material which the cracks areuniformly distributed in. The relationship between the average stress and the averagestrain of the new materials could be got from the test. Using the MCFT in thethree-dimensional finite element analysis, an appropriate element was needed to adaptwith it.②The displacement loading mode suitable for the3D analysis was refined.Nonlinear finite element analysis of the reinforced concrete structure was the same withthe structure test.There were two loading control modes, the force loading mode and thedisplacement loading mode. Through the force loading mode, ascending curve of theforce deformation relationship of reinforced concrete structure could be got.But togetting the whole process curve, the displacement loading mode should be used.Therefore, the displacement loading mode could be used to rearch the performance ofreinforced concrete structures after the maximum load.③The calculation point translation algorithm to solve the secant stiffnessnumerical problem was mentioned. The secant stiffness iteration method was used in thenonlinear finite element analysis in this paper.Because of the complexity of theconstitutive model of reinforced concrete, secant stiffness numerical anomaliesencountered inevitably in3D finite element analysis.To get the rational analysis result,the numerical problem should be solve.④The inheritance problem of the3D hysteresis analysis of the reinforced concrete was solved. Along with the three directions, there are three sets of history variables. Theinheritance problem of these history variables should be resolved. The inheritanceproblem would directly affect the stability and accuracy of the analysis results.Through the work of this paper, some achievements were got:①The nonlinear finite element analysis program of reinforced concrete wascreated based on the finite element analysis algorithm and the element type mentionedin this paper.②The monotonic and hysteretic analysis of the beam under the bending andtorsion, the shear plate and the shear walls with flanges was finished,using the newprogram.Good simulation results were achieved, and the program was proved to beeffective.