Nonlinear Stability Analysis Of Q690 High Strength Steel Round Pipe In Bending

High-strength steel(the standard strength value is not less than 460MPa)is developed with the improvement of new technology,which has the characteristics of high strength,good toughness and good weld ability.Some special structures in engineering,such as longspan transmission towers,wind power towers and high silos,may be subjected to bending moments in different directions under wind load or process load,and these structures usually adopt circular tube members.Up to now,there is little research on the mechanical properties of Q690 high-strength steel circular tube flexural members,especially the different failure characteristics and boundaries of flexural members when the length parameters change.Therefore,it is necessary to systematically analyze the mechanical properties of such members,so as to provide theoretical support and design basis for the wide use of Q690high-strength steel circular tube members in wind power towers,long-span transmission towers and transformation frames in the future.The paper mainly completes the following work:(1)Based on the existing axial compression bearing capacity test,the related finite element numerical model is established,and the accuracy and reliability of the finite element numerical analysis are verified by comparing the results of the finite element numerical analysis with the test data.(2)According to the distribution form of residual stress of Q690 high-strength steel tube obtained from existing tests,the residual stress is correctly applied to Q690 high-strength steel circular tube pure bending members by ABAQUS finite element software.(3)Combining the characteristics of the two research directions of high-strength steel members and steel shell structure,the influence laws of residual stress,geometric defects of pre-buckling deformation and plasticity on the failure modes and ultimate bearing capacity of Q690 high-strength steel circular tube members are obtained,and the different failure characteristics of the members are defined when the length parameters change.(4)Based on the results of finite element numerical analysis,the bending bearing capacity curve of Q690 high-strength steel tube is obtained based on the method in European steel structure design code EN1993-1-6(2007),and the influence parameters of bearing capacity curve in different stages are determined,and the calculation formulas of ultimate bearing capacity of members in different stages are put forward,which provides theoretical and design basis for engineering application.