Study On Overall Stability Bearing Capacity Of Welded High Strength Steel I-Section Tapered Beam Column

In recent years,High strength steel(f_y=460MPa)welded I-section members have been successfully applied in many steel structure engineering,and achieved good economic benefits.To high strength steel and tapered members,the section should be wide and thin for the proper design,which leads to the local buckling of the web,but local buckling of web does not means the loss of bearing capacity.In order to achieve post-buckling strength,the web depth-to-thickness should be relaxed appropriately.which can save steel and lower cost.A finite element model is established by ANSYS to analysis high strength steel Q460 tapered and welded I-section in-plane ultimate carrying capacity.The initial geometric imperfections(both the global and local deflections)and residual stresses,as well as the geometrical and material nonlinearities were be considered.The reliability of the finite element model was validated by experimental results.The effects of the web depth-to-thickness ratio,flange width-to-thickness ratio,slenderness ratio,tapering ratio and eccentricity ratio on the stability capacity were investigated carefully.Without considering the residual stress for some members of the Q460 steel columns were re-calculated the ultimate capacity and analysis the influence of residual stress for ultimate capacity.Combined with the design formulas of CECS102:2002comparing the results of the finite element to modify the design formula of DSM method and the design formula of specification.The study shows that the ultimate capacity of column is reduced when increasing the web depth-to-thickness ratio,because of section stiffness decrease;Increasing flange width-to-thickness ratio will decrease the restriction in the web,the ultimate capacity of the columns is reduced;Along with the slenderness ratio of column increasing,the overall stiffness decreases,so the ultimate capacity will be reduced;By increasing tapering ratio,the ultimate capacity of the columns have a small change.Comparison of ANSYS results with the current design method in CECS102:2002shows that the later too conservatively predicts stability capacities of such members,while the proposed modified formulas are in good agreement with the numerical results.