Study Of Local-overall Interactive Stability Of Corroded H-section Steel Beam-columns

Steel structure is widely used in practical engineering by virtue of its many advantages,but the problems of stability and corrosion restrict the use and development of steel structure.Compared with concrete members,steel structural members generally have a smaller cross-section,which is likely to cause overall buckling;On the other hand,in order to give full play to the properties of steel,the plate is designed to be thin and developed,which makes the steel structure face local stability problems.For the steel structures in service in corrosive environment,the section reduction or plate thickness loss caused by corrosion will further weaken the overall or local stability of the members,resulting in local-overall interactive buckling.Therefore,it is necessary to study the localoverall interactive stability of corroded members.In this paper,a combination of experimental research and numerical simulation was used to study the local-overall interactive stability bearing capacity of corroded H-section steel beam-columns.The main contents are as follows:(1)Surface data of corroded steel columns that obtained from artificial accelerated corrosion test was obtained from 3D scanning.The residual cross-sectional area of the plate was extracted layer by layer by using the improved layered algorithm,and the parameters for evaluating the degree of corrosion were proposed.(2)Load-carrying capacity tests of one H-shaped steel column without corrosion and two H-shaped steel columns with different degree of corrosion were carried out.The failure modes of the test specimens were identified,and the influence of corrosion on the stability of H-beam columns was analyzed.The results show that: the failure modes of test specimens vary from global buckling to local-global interactive buckling and then to local buckling with the increasing degree of corrosion;the weakening of plate thickness caused by corrosion leads to local buckling problem and finally leads to the decrease of ductility of specimens;degradation of ultimate bearing capacity increases with the increase of corrosion degree.(3)In order to accurately simulate the bearing performance of corroded members,finite element models considering true corrosion pattern were established in Chapter 4.The finite element analysis results show that finite element models considering true corrosion pattern are in good agreement with tests in terms of failure mode and ultimate bearing capacity;The stress cloud diagram shows the model has obvious stress concentration;when the corrosion is unevenly distributed along the length of members,the damage place is closer to the section where the degree of corrosion is relatively large,otherwise it tends to be mid-span.(4)The corrosion morphologies were simplified,and the parametric analysis of different degrees of corrosion under various slenderness ratios and various relative eccentricities was carried out.The results show that: with the same degree of corrosion,the degradation range of ultimate bearing capacity caused by corrosion is roughly the same;the corrosion degree of compression flange has the greatest effect on bearing capacity,and the corrosion of the web cannot be ignored;the comprehensive corrosion rate has considered the relationship above,and it can be used to evaluate the degree of corrosion and residual bearing capacity;The residual bearing capacity evaluation formula considering the local-overall interaction can estimate the degradation extent of bearing capacity.