Research On Nonlinear Aanalysis Of Steel Beam And Steel Frame

The structures discussed in the paper are steel structures, for steel has high strength, light weight, good rigidity, good deformation ability etc, so it is suitable for big span, the super high rise building and Super-heavy buildings。The steel has good material qualitative and isotropic, most conforms to the general engineering mechanics basic assumption, and It’s has good plasticity and toughness, can have large deformation. Generally can use ideal elastic-plastic constitutive relationship to simulate it, so for the steel whether the theoretical calculation or software analysis has better stability.Simply supported, continuous beam, steel framework in the structure analysis belongs to the structure types of the simple ones. The article did not analysis the plastic and nonlinear analysis of the complex structures at the very start. But combination of the ideal elastic-plastic constitutive relationship, In view of the above several simple structures, based on elastic analysis, To analysis the plastic bearing capacity and the plastic deformation capacity from several aspects respectively. On the basis of the theoretical calculation, use ANSYS software to analysis material nonlinearity and geometric nonlinear of each structure.Based on the above goal, the paper studies the main work including:First, the paper begin with narrate the concept of nonlinear and plastic, discuss the classification of structure nonlinear analysis, there are three kind of nonlinear analysis, the article mainly discuss Material nonlinearity and geometric nonlinear, Introduce ANSYS nonlinear analysis function.Secondly, Analysis the plastic bearing capacity influences by different forms of section, Therefore Summarized that when section area more away from neutral axis, the smaller increase of the plastic limit bearing capacity of the relative to elastic limit bearing capacity. As for simply supported beam use plastic hinge method and plastic zone method to calculate it respectively, then Comparing the two kinds of difference method, reach a conclusion that the simplified plastic hinge method is not only convenient and shall be applicable to the actual project;Thirdly, for the statically indeterminate beam go about with the analysis of span ratio and different ways of loading, To its plastic deformation and the requirements of the bearing capacity, When the structure under different ways of loading, which means when statically indeterminate beam is the single span loading and two span loading does not affect the ultimate bearing capacity of the structure, both limit load are equal, But the plastic hinge occurrence order are different, And plastic deformation capacity is different either.For the continuous beam the bigger difference of span ratio, The ultimate bearing capacity is lower.According to the different of span ratio Draw the Load-deflection figure of a super than static and second super static beam, it’s Can be observed that the span ratio has Significant Effect on structure bearing capacity and deflection.Fourthly, on the analysis of the steel frame, first use matrix displacement method to calculate the steel frame ultimate bearing capacity when beam-column corolla and Beam-column differ long, and plot stiffness variation curve, Analysis the influence of the bearing capacity by length of beam. For two cross unilateral and bilateral loading compared their Load-deflection curve, we will found that two curves variation similarity. But plastic hinge appear in different order. it is obvious that lateral force has significant influence on the ultimate bearing capacity of steel frame.At the last, the paper analysis the steel frame second order effect, and calculated structure critical load by ANSYS, plot the elastic buckling and plastic buckling curve of steel frame, makes a comparative study, Elastic buckling for it without considerate the yield strength of the material so we can get high bearing capacity, which is far more than plastic buckling which consider the yield strength, So elastic buckling can’t be adopted in engineering design.