Research On Eccentric Compression Bearing Capacity And Reliability Of H-Shaped High Strength Steel Member With Pitting Corrosion Damage

High strength steel has significant advantages.Compared with oridinary strength steel,it has higher strength.Besides,using it as the structural material would result in an increase in the clearance height of buildings,a reduction of the dead-weight of structures.Therefore,it has been increasingly applied in many landmark buildings such as the Water Cube,the CCTV Head-quarters and the Bird’s Nest.However,due to the physical and chemical properties of the steel,resulting in electrochemical reaction occurs with the corrosive medium and reduction of the member section.Corrosion can be divided into uniform corrosion and pitting corrosion.Recent studies only consider the impact of uniform corrosion but pitting corrosion can lead to concentrated reduction of the section,which affecting the safety of steel structures more severely than uniform corrosion.Therefore it is urgent to study the eccentric compression behavior of H-shaped Q690 high strength member with pitting corrosion.The statistical parameters of resistance uncertainties for corroded Q690 steel under eccentric loading have been obtained.Besides,evaluating methods of different loads has been deduced based on the characteristic of different types of load.The evaluating methods of resistance and load given above has been used to evaluating structural menbers.The study of reliability evaluation of corroded steel members has important theoretical significance and engineering practical value,which can provide theoretical basis for the strengthening of the in-service steel sturctures.In this paper,the eccentric compression behavior of H-shaped Q690 member with pitting corrosion damage is studied by finite element analysis.The detailed steps for reliability evaluation of existing corroded components have been put forward with specific example.The main contents are as follows:(1)An appropriate simplified pitting corrosion model was found to save the simulation cost.In that case,geometric models of H-shaped Q690 member with pitting corrosion were established.Uniaxial tensile tests were made to achieve the real material strength,elastic modulus,and poisson’s ratio.Based on the experimental data,the finite element models of H-shaped Q690 member with pitting corrosion were established in the general finite element software Ansys.(2)Parameter analysis of the eccentric compression component was carried out.The considered parameters include: different corrosion location,different corrosion depth with the same corrosion loss,different corrosion loss with the same corrosion depth and analyze the degradation of eccentric bearing capacity under varied factors.Based on the research,the predicted results of eccentric bearing capacity about parameters are achieved.(3)The statistical parameters of material property and geometry uncertainties of Q690 steels were obtained and then the statistical parameters of the model uncertainties of Q690 members with pitting corrosion for eccentric compression were calculated.Concise load correction tables which were deduced based on different characteristic of load are given for use.A mathematical model which considered resistence degradation and load evaluation for reliability evaluation of existing Q690 member is put forward.(4)Combined with time-dependent reliability evaluation theory a reliability evaluation of existing corroded Q690 member method was put forward.The detailed steps for reliability evaluation of existing corroded components have been put forward with specific example,in order to provide scientific basis for re-service,repairing or backout.