Overall Stability Research Of Biaxial Symmetric I-shaped Cantilever Beam Under Combined Bending And Torsion

In the actual engineering, the cantilever steel beam is often suffering combinedbending and torsion because of the influence of eccentric load,and it’s bearingcapacity is always decided by stability.But the existing theories on the overallstability of the cantilever beam under combined bending and torsion are little.China’s"code for design of steel structures"(GB50017-2003) have not given the relatedcalculation formula on the problem." Technical code of cold-formed thin-wall steelstructures"(GB50018-2002) while gives the overall stability calculation formula ofthin-walled cold-formed steel beams under bending and torsion,But did not give therelated coefficient calculation method of a cantilever beam,and the formula is alsolimited to the thin-walled cold-formed steel beams.Therefore, to study the cantileverbeam’s overall stability under the action of combined bending and torsion issignificantly important.In the beginning,My thesis introduces the traditional theories on the overallstability of the cantilever beam, and analyze their limitation,and then put forward anew calculation on the overall stability of the cantilever beam under combinedbending and torsion by combining the form of formula in " code for design of steelstructures"(GB50017-2003).The new formula uses a new equivalent bending momentcoefficientβ(e/l,ξ)which contains the parameters ofe/landξto replace theoriginal coefficientβin the standard formula.So the new formula has the same formwith the standard formula,and it embodies the influence of torsion caused by aeccentric distance on the cantilever beam.Then I use the finite element analysissoftware ANSYS to establish the calculation model of cantilever beam by choosingreasonable parameters, and calculate the overall stability critical load and the newequivalent bending moment coefficientβ(e/l,ξ)of the cantilever beams withvarious height of cross section which suffer two forms of loads acting on differentflanges in different eccentric distances,And then analyze the relationship between therelative eccentricitye/l,the geometric parametesξand the new coefficientβ(e/l,ξ).Finally,I use the American data processing software Origin to fit the data ofparameterse/l,ξand coefficientsβ(e/l,ξ)by their relationship in the coordinatesystem,in order to get calculation formula of the new equivalent bending momentcoefficientβ(e/l,ξ)in the formula of overall stability of cantilever steel beam under the combined action of bending and torsion.