Research On The Buckling Behavior Of 800MPa High-strength Steel Welded I-section Members Under Axial Compression

Utilizing the high strength steel will lead to the reduction of cross-section size,and the instability problems of axial compression member will become more prominent.It is possible to increase the utilization of steel by considering the post buckling bearing capacity of axial compression members with larger width-thickness ratio.For the stability-related design of the axial compression member,the Chinese code GB50017-2003,Code for Design of Steel Structure,only considers the over-limit of the height-thickness ratio of the web by setting the stiffeners or calculating the effective width,which is not beneficial to improve the utilization of steel.In this paper,in order to promote the application of 800 MPa high strength steel,the experimental and finite element researches were carried out to analyze the impacts of slenderness ratio,width-thickness ratio,residual stress and strength of steel plate on buckling behavior of the welded I-section members under axial compression,and the design methods of overall and related buckling were obtained.The main contents included:?1?As to the common I-section form in the practical engineering,three series overall15 members were designed,and then the experiment of axial compressive stability was carried out.The tests included the measurement of steel properties and the initial geometric defects,and the ultimate bearing capacity,the load-displacement and load-strain curves were obtained.The results showed that the stress-strain curves of800 MPa high strength steel had no obvious yield platform and the experimental ultimate bearing capacity was higher than that of values calculated by the codes of GB50017-2003,Eurocode 03 and ANSI/AISC 360-10.And all the specimens without exceeding the limit value occurred overall buckling,while the specimens with plate out of limits occurred related buckling.?2?The finite element model considering geometric initial defects and welding residual stress was established by ANSYS software.The simulation conclusion containing failure modes,the load-displacement and ultimate bearing capacity were consistent with the experimental results,which were proved that the finite element model can simulate the overall stability and local buckling of plate accurately.?3?The results of parametric analysis showed that the ultimate bearing capacity of members decreased as the residual compression stress increased,and the residual stress had a great influence on the ultimate load and can't be ignored.The ultimate bearing capacity increased as the steel strength and width-thickness ratio of plate increased,and the increasing range dropped as the slenderness ratio increased.?4?By comparing with the main current codes,the column curves around the weak axis were suggested to use the curve“a”of GB50017-2003 and curve“a₀”of Eurocode 03,and two columns were fitted based on the Chinese code and American code respectively.Two design methods,according to the American code named ANSI/AISC 360-10 and the direct strength method,which can estimate the ultimate bearing capacity of axial compression columns with an over-limited width-thickness ratio or height-thickness ratio.And the calculated value of two design methods were compared with the test and finite element results,which verified the reliability of the formula.