Study On Mechanical Property Of Steel Box Girders With Pitting Corrosion

Corrosion is one of the most important factors which influence the durability of steel structure.In this article,the widely used steel box girders were studied with experimental and FEA methods.The mechanical properties of corroded steel girder were researched,and the influences of pitting corrosion to web of steel box girder were mainly studied too.The main contents can be concluded to 4 parts in this article.(1)Mechanical property of girders under uniform corrosion and pitting corrosion were compared,uniform corrosion were accelerated with 3 girders by cycle immersion;pitting corrosion were simulated by mechanical processing on 6 girders,tests study and finite elements analysis were also conducted to figure out the influence of the geometry dimensions and distribution of pitting on the bearing capacity and failure modes of steel girders.It was indicated that weight loss ratio was a key factor which affects the material properties and bearing capacities of girders under the influence of uniform corrosion,while weight loss ratio cannot measure the degree of pitting corrosion in a comprehensive way;depth of pitting was an important factor that influence the ultimate bearing capacities of girders for the reason that ultimate bearing capacity declined with the increase of pitting depth at the same DOP;bearing capacity of girders under pitting corrosion decreased with the increase of DOPV,stiffness of web with pits declined obviously compared with the webs without pitting corrosion;buckling may occurred in advance when DOPV reach to a certain degree,which means pitting corrosion may affects the failure modes of girders.(2)Shearing buckling load and shearing stiffness of webs were calculated based on the boundary condition of simply supported on four edges together with shearing ultimate bearing capacities,formula was also raised to calculate shearing critical load for shearing panels under the influence of pitting corrosion.It was indicated that DOPA and DOPV can respectively describe the change of initial shearing stiffness and elastic-plastic critical load in a preferable way;formula to calculate the elastic-plastic critical load was also put forward.(3)Shearing buckling load of the web of steel box girder under the influence of pitting corrosion was calculated with the constraint of flange taken into consideration;formula to calculate the shearing buckling was also modified to calculate the shearing buckling strength of steel box girders;maximum error of this formula was less than 5%.The corrosion volume of pitting(DOPV)was a key factor which affected the shearing buckling strength;formula with a comprehensive coefficient was also raised to calculate the buckling strength of steel box girders,this formula can be widely used for its applicability.(4)Formula for shearing ultimate bearing capacity was raised based on tests and finite element analysis,the constraint of flange was also taken into consideration,the formula value was conservative compared with the FEA value,which means this formula has a ample safety reserve;comparing with DOPV,coefficient ? could describe degree of pitting of steel box girders with different aspect ratio and ratio of height to thickness;a formula to calculate shearing ultimate bearing capacity was also put forward,this formula value was respective conservative.