| Due to the improvement of material processing and manufacturing processes in recent years,high-strength steel has been gradually applied to infrastructures such as buildings,bridges and wind power at home and abroad,and has achieved good economic benefits.Moreover,because of symmetrical section properties,large torsional stiffness,small wind receiving area and beautiful appearance,the circular hollow sections have been favored by engineering and architects,and has been widely used in engineering fields.However,compared with conventional steel,the mechanical properties of high-strength steel structural members are still not clear,and according to the codes and specifications,the current design methods of them are simply following the rules regarding the conventional steel.Therefore,based on the design provisions of the current codes and existing literatures,this study has carried out sufficient research to explore the local stability of four types high strength axially compressed steel stub columns,including Q460,Q690,Q960 and Q1350。The main research works covered in this dissertation include:(1)The experimental data of the existing literature were collated and summarized to establish an experimental database for the stability study of the high-strength steel circular stub columns,and the design methods of the current codes and specifications have been compared against the experimental results.Using the parametric modeling analysis platform to build the finite element model of the circular tube axial compression short column in batches;Combining theoretical deviations and the finite element results of the high strength steel axially compressed short columns of Q460,Q690,Q960 and Q1350,a more accurate and reliable equation for the slenderness limits of high strength steel axially compressed short columns was proposed.(2)The specifications of literatures regarding amplitude of the initial local geometrical imperfections of circular components are compared,and all types of initial geometrical imperdections are respectively assigned to axially compressed circular steel tubular members to conduct parametric finite element analysis,aiming at exploring its effects on the ultimate capacity of the columns.By comparing the numerical results of these components,the relationship between the influence of the initial geometrical imperfections on the ultimate bearing capacity of the high-strength circular steel tubular short-column and the member’s diameter-to-thickness ratio are finaaly obtained.(3)Based on the definition of ductility of circular stub columns under axial compression in the existing literature,this study deeply analyzed the ductility of high-strength steel axially compressed circular stub columns with the yield strength of 460 MPa,690MPa,960 MPa and 1350 Mpa,and then the relationship between the ratio of diameter-to-thickness and the ductility index of the members is obtained.In addition,the influence of the modification of the slenderness limits of high-strength steel circular stub columnss on their ductility performance are also researched.(4)At present,the design methods of buckling strength of conventional strength steel circular stub columns are given by several codes and specifications,but the research on bearing capacity of thin-walled members exceeding the slenderness limits are still insufficient.In this paper,the benchmarked finite element models are used to investigate the post-buckling strength of thin-walled members with large diameter-to-thickness ratio,and the design methods of the relevant specifications in the United States,Europe,Canada,Australia and China are compared against the numerical results.Applicability of the codified design methods with respect to the bearing capacity of axially compressed stub columns of four types of high-strength steel(Q460,Q690,Q960 and Q1350)tubes are detailed discussed and summarised. |
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