Overall Stability Research Of Steel I-Beams With Two Simple Supported Ends Under Combined Bending And Torsion

The researches of the steel beam integral stability problems have achievedfruitful achievements in a long history. However, due to the restriction of manyconditions, the inside rules about the overall stability of the steel I-beam sufferingcombined bending and torsion were still rare. Because these problems were widelyexisted in engineering, we must inevitably increase the study of the similar problems.In term of the basic theory, this thesis introduced the present several differentoverall stability theories, and pointed out the scope of their application. It wasconcluded that traditional theory result was also enjoying practical value. Based onthese different overall stability theories,we presented the related theories of thedeveloped countries, and obtained the further understanding about the developmenttrend of overall stability.Compared with the past elastic theory research, the steel I-beam sufferingcombined bending and torsion had brought some parts of steel structure elements intoplastic state when the steel I-beam was in overall stability state, and reduced ultimatebearing capacity of elements. However, the previous issue was difficult to solve theproblem, with the development of numerical analysis method and the finite elementsoftware, such problems could be calculated accurately and quickly.So based on the finite element software ANSYS, the author developed the initialnonlinear model and the nonlinear model with imperfection using APDL of ANSYSand C language, which could create initial stress to describe the residua stress. Theresidual stress might be concluded in models, and then the ultimate load can becalculated.Additionally, this thesis innovatively proposed the concept of reduction factorand global simplification about the subjects based on plenty of numerical analysis.This article built four models of two eccentric loading cases and two different actionspots and did a series of numerical calculation, obtaining the fitting formulae andparameter values range. This provided reference for design of steel structures in nextrevision on Code.