Analysis Of Polyline Simply-support Structure Of Variable Cross-section

In the actual building structures, every building structure belongs to the spacestructure and bears forces from all directions in space, each member in the structurecontacts with the other member and forms the three-dimensional stress system.However, if commencing directly on the spatial structure of the stability analysis is avery difficult thing when to analysis the static and the stability theory of the spatialstructure, however, simplifying the calculation model of the spatial structure to theplanar structure calculation model by a specific method to expand the analysis isfeasible. Simplifying the spatial structure simplified as the planar structure for the staticand the stability of the spatial structure to analyze the deformation and the stability ofthe simplified plane structure.The research object is the pole structures systems basing on the stability theory ofthe variable axially load compression member.For the static analysis, taking a variablecross-section structure consisting of two-lever folding bar as the research object,considering the bar’s end rotation and the nonlinear of structure, using the staticequilibrium method to derive the structure’s deformation equation when bearingcomplicated loads; Basing on the derived theory to derive structure’s global deformationwhen using the different loading mode, according to conversion relationship of the localcoordinate system and the overall coordinate system.For the stability analysis, using theRitz-Timoshenko method to derive the critical load of structure and analyze thestructural stability.Taking a main truss from an engineering project of the double-layercylindrical lattice shell as the research object, using the equivalent stiffness method tosimply the main truss structure as a plane structure,choosing ANSYS to analyze thesimplified structure’s displacement and stability,comparing the result of the softwarecalculated value and the theoretical value to indicate the correctness and the practical ofthe theory. The main results are:①Since each computing unit in the structure of multi-lever system use the localcoordinate system and the overall structure use the global coordinate system, therefore,under the premise of considering structural deformation to create the transformationrelationship of the calculated unit between the local coordinate system and the globalcoordinate system.②In the unit local coordinate system, using static equilibrium method when the structural deformation in a particular state of the force balance to establish theequilibrium differential equation, solving the equation to calculate the unit’sdeformation equation when bearing complex loads. Using Ritz-Timoshenko method toderive the critical load of structure and analyze the structural stability.③Using ANSYS software to analyze the displacement values when the structureis in the same calculation model, calculating the critical load of the structure by themethod of eigenvalue buckling analysis. The result that comparing the ANSYScalculation value and theoretical calculation value is the theoretical value is greater thanthe value calculated by the ANSYS software, therefore, this result indicates that theaffects of structural nonlinear can not be ignored.④After the ANSYS eigenvalue buckling analysis, adopting an initial geometricdefects to analyze the nonlinear buckling. The results show that the value of thenonlinear buckling analysis is lower than the value of the linear elastic eigenvaluebuckling analysis.⑤Using the equivalent stiffness method to simply the main truss structure as aplane variable cross-section multi-segment bar structure of two simple supported endsmode, choosing ANSYS software to analyze the simplified structure’s displacement andstability, comparing the result of the software calculated value and the theoretical valueto indicate the correctness and the practical of the theory.