The Research And Application Of Plane Equivalent Truss Model’s Nonlinear Finite Element Method

In order to simplify the finite element model, this article presents a new elementprocessing mode based on the theory of traditional finite element method and thetheory of plane equivalent truss model. The two-dimensional rectangular element isequivalent to the truss element, which is composed of six one-dimensional barelement. The constituent elements of the truss structure are two-force bars that onlybear axial force, so even if the structure is exposed to complex loads, equivalent trussmodel can use uniaxial constitutive relationship, rather than a complexmulti-parameter constitutive relationship. The equivalent model refers to anddevelops from the supporting spring stiffness equivalent method proposed by QinDong in his doctoral dissertation, and the superposition principle from the mechanicsof materials. This study includes following aspects.First of all, the researcher obtained the sectional area of each bar in the planeequivalent truss model by the stiffness equivalence. By selecting the simple supportedbeam, cantilever beam and cantilever column under different loads, and comparingthe equivalent truss model solution and structural mechanics solution with differentelement size, this study verified the validity of the equivalent method.Secondly, this study introduced the significance of nonlinear finite elementanalysis of reinforced concrete structure, and highlighted the relevant knowledge ofreinforced concrete’s model, constitutive relationships, the solution of the nonlinearequations and convergence criteria. When the nonlinear analysis of reinforcedconcrete was performed, this study focused on a different approach with thetraditional linear finite element when the structure is in some special status.Finally, this study selected the MATLAB language to write the core calculationprogram of the member’s the nonlinear analysis. The program can handle memberssuch as beams, columns. The constraints forms include simple supported constraintand fixed supported constraint, etc. The loads include concentrated load, uniformlydistributed load and triangle load, etc. This article made a comparison betweenexperimental results by other researchers and this plane equivalent truss modelsolution, with regard to the load and displacement plot, the carrying position and development trends of crack, etc. In this way, this study verified the feasibility of theMATLAB program, as well as validity of the new equivalent method.