Overall Stability Analysis Of Triple Tapered Double Symmetry Clamped Ⅰ-Beams

The benefits of using the tapered members are that the distribution of the cross section along the length happens to coincide with the internal force distribution. Under the precondition of meeting the strength requirements, tapered member can not only reduce the consumption of steel and the structural weight but also make the structure lighter and more attractive.As a result, the steel tapered member stability is one of the important issues that must be considered in the design process.Foreign scholars start their researches on tapered members at a earlier time and their results are mature.This thesis briefly describes the calculation rules for domestic and international norms on the tapered flexural members.There are a variety of stability theory about Flexural members,which are mostly based on prismatic members. Professor Tong derive the potential energy equation of the tapered beam considering the taper factor.According to the above three theoretical potential energy equation,this thesis derive the critcal load of the triple tapered double symmetry clamped I-beams.The formula of the first theory is very different from that of the other theory.comparing the results of theory with the finite element calculation, the potential energy equation of the tapered beam considering the taper factor get results with smaller error.When making a finite element analysis on the triple tapered double symmetry clamped I-beams,this thesis considers two facade form of the steel beam:the top flange tilt steel beam and the top flange level steel beam.This thesis also regard four factors on the influence of the steel beam overall stability including span,flange width,rate of taper,the portion of the first segment.Uniform load on the top flange, uniform load on the bottom flange,concentrated load on the top flange,concentrated load on the bottom flange have been also considered in the analysis of the overall stability.Through the analysis of the influence of the span,flange width,rate of taper,the portion of the first segment to the finite element solution,one can get:(1) Span and flange width have a very small influence on the error between theoretical result and the finite element result,while the impact of taper ratio is much larger.(2) With respect to the relative difference of the finite element result between the two facade form steel beam.Span and flange have a relatively small influence compared to taper ratio.Regarding to the load conditions,load on the top flange has a smaller relative difference compared with load on the bottom flange.(3) For the different portion of the first segment a.The critical lateral-tortional buckling load of the steel beam is greater as the a becomes bigger,and the extent of the growth is not great.The relative difference of the critical load of the two facade form steel beam also has a trend of increasing as the a becomes bigger.