Research On Flexural Capacity Of Cold-formed Steel Double Limbs Built-up Box Beams

This paper mainly describes the detailed study resulted on flexural capacity ofcold-formed steel built-up box girder by numerical analysis, and the conclusions of the paperare listed as follows.The experiment has completed15double limbs built-up cold-formed steel box beams,and observed failure characteristics and ultimate flexural capacity and ductility of specimens.Then analysed the influence of the spacing of screws, height to width ratio and width tothickness ratio on the mechanical performance of the specimens. The results of the tests showthat: beside screw failure of few specimens, failure modes of other specimens were localbuckling and the influence of height to width ratio and width to thickness ratio of section isgreat and the influence of the spacing of screws and span to height ratio is small for theflexural capacity.Parametric study analysis was carried out to mainly determine the effect of the spacingof screw, height to width ratio and width to thickness ratio. Compared with analysis andexperimental results, both are well tallied with each other, the accuracy of the finite elementmodel is proved. The results of the study indicate that the spacing of screw varies changedfrom150mm to600mm, it found there is little impact on the flexural capacity of beam,"Minimum and Maximum screw space" are presented. The flexural capacity and ductilitycoefficient will be increased with the increase of height to width ratio and width to thicknessratio of section, it is shown that the spacing of screws has little impact on specimens.On the basis of introducing the effective width method of Chinese specificationGB50018-2002and American specification AISI2007, the flexural capacity of double limbs,built-up cold-formed steel box beams are respectively calculated by both specifications andthe results are also compared with the finite element analysis results. The calculation results inthe effective cross section method by AISI and GB50018-2002tend to be safe. The resultscalculated by GB500182002are more conservative than the results calculated by AISI2007and the ratio of both is increased with the increase of height to width ratio and width tothickness ratio of the section.Lastly, the calculation results of Bending Modulus Reduction Method were comparedwith the results of finite element parametric analysis. The calculation results are closed withthe analysis results. It is means further illustrate Bending Modulus Reduction Method isfeasible and high precision.