Overall Buckling Study On Different Formed Steel Tubular Members Under Axial Compression

With the development of modern architecture and steel pipe manufacturing technology,circular steel tubes are widely applicated in power industry,long-span public buildings,bridge,and structures in ocean or mast,etc.Circular steel tubes are significant different each other in mechanical properties of materials,processing technologies,initial imperfections,and overall buckling behavior because of different formed processing technology.The design methods of current codes lack the background of the study on overall buckling behavior of different formed circular steel tubes under axial compression,especially,the distribution of residual stress,overall buckling performance,etc.Hence,it is difficult to guarantee the rationality and reliable of relevant engineering design.This paper introduce the engineering application and axial compressed stability performance of circular steel tubes,as well as,the summary of axial compression members' stability design method in global codes.In order to researching the overall buckling performance about different formed circular steel tubes,four major research contents and results are presented as follow:(1)The residual stress distribution in cross section is the most important precondition of overall buckling stability research;blind-hole method was used in this paper to measure the longitudinal residual stress of welded and hot-rolled circular steel tubes with the strength of Q690,Q420,and Q345,in order to research the residual stress values,distribution models,and calculation method influenced by different shapes,steel strength and location in the beginning solder point and the falling solder point at both the weld circular steel tubes ends.(2)The static axial compression experiment was accomplished,and the specimens about the experiment are 9 circular steel tubes shaped by high-frequency weld,submerged arc welded and hot-rolled with a strength of Q345.The experiment results that the overall buckling stability coefficient of this kind of member is beyond obviously the column curves in Chinese codes,Eurocodes and American codes,therefore,it is necessary to amend or present new column curves for different formed circular steel tubes axial compressed members.(3)This paper proceeded the finite element analysis for three types of different formed circular steel tubes with a strength of Q345,meanwhile,contrasting with the experiment results,and verified the accuracy and reliability of the finite element models.(4)Based on the measured residual stress distribution models,several main parameters that influenced the overall buckling stability coefficients of different formed axial compressed members were analyzed via the verified finite element models.In additions,on the bases of current design method in Chinese codes and Eurocodes,the paper has refitted the column curves,amended the calculation factors and presented a method,which is more applicable with overall buckling study on different shaped steel tubular.