Research On Random Restoration Force Model Of Pitting Corrosion Steel Column In General Atmospheric Environment

Columns are the main vertical load-bearing member of the steel frame structure,and their hysteretic response under earthquake will directly affect the seismic performance of the whole structure.However,many existing steel structures that have been exposed to the general atmospheric environment for a long time are difficult to avoid corrosion through protection,structural measures and maintenance systems.Corrosion damage generally includes uniform corrosion and pitting corrosion: the mechanism of mechanical properties degradation of steel caused by uniform corrosion is relatively simple,and the equivalent thickness reduction is usually considered in structural analysis.However,due to the complexity of geometric levels,pitting damage not only weakens the crosssectional area of frame columns,causing problems such as reduction of bearing capacity,degradation of stiffness and reduced stability.Randomly distributed rust pits on the surface will also cause local stress concentration,resulting in uneven degradation of the seismic performance of the frame column.The restoring force model is the basis of the seismic analysis of the structure.In order to discuss the effect of pitting damage on the restoring force model of steel frame columns,this paper systematically carries out pitting morphology analysis,pitting steel and hysteretic behavior research of pitting steel columns,reveals the random distribution model of the existing steel recovery force model parameters with the degree of pitting corrosion,and thus establishes a stochastic restoring force model of pitting steel columns in general atmospheric environment.The main research contents of this article include:(1)Using three-dimensional non-contact surface topography instrument to scan the surface of artificial accelerated corrosion and natural corrosion specimens for mesocharacteristics.The macro-and micro-evaluation methods and index systems of pitting corrosion degree of steel were proposed.The variation rules of various evaluation indexes under different pitting corrosion degrees were explored,and then the distribution model of characteristic parameters of pitting corrosion in general atmospheric environment was established.(2)The numerical analysis method is used to reconstruct the pitting corrosion morphology of the steel plate.A simplified calculation method for the material parameters of the traditional mixed strengthening model is proposed.By conducting a large number of pitting steel plate numerical simulation work,the similarities and differences of the deterministic and random degradation rules of the steel under pitting damage are discussed,The stochastic distribution model of pitting steel mixed strengthening parameters and the degradation law of distribution characteristic parameters were studied,and the random restoring force model of pitting steel was established.(3)Based on the stochastic constitutive relationship of steel,a finite element model of pitting H-shaped steel columns was established,and the key parameters of the skeleton curve,unloading stiffness and reloading curve under cyclic reciprocating load were studied.Degradation law.A pitting steel column skeleton curve constitutive model,an unloading stiffness degradation model,and a non-linear reloading curve model are proposed respectively.A random recovery force model for pitting steel columns describing the relationship between load and displacement is established.