Experimental Study On Shaking Table Test Of Steel Frame Structure Under Offshore Atmospheric Environment

Steel structure has been widely used in our country because of its good seismic performance.At present,more and more scholars begin to pay attention to the seismic behavior of steel structure in their service period.The steel structure in the offshore atmospheric environment is prone to corrosion due to the long term effect of moist air and chloride ion erosion.The main effect of corrosion on the steel structure is the deterioration of the mechanical properties and the reduction of the geometric dimensions of the steel members,it leads to the decrease of the bearing capacity and deformation performance of the components and structures,which threatens the safety and normal use of the structure.At present,the research on steel structure corrosion is mainly focused on the material and component level,but the research on the seismic behavior of the corroded steel frame structure is less.In this paper,two steel frame models with different corrosion degrees are designed,The shaking table test of the two model structure is carried out to study the dynamic characteristics,displacement response,acceleration response and the change rule of the failure mode.Specific research on the following aspects:(1)In this paper,two five-layer steel frame structures with different corrosion ratios were designed.and one of them is accelerated corrosion by simulating the atmospheric environment(corrosion for 120 days),the other is not treated as a contrast,and then shaking table tests were carried out,the damage model of structure under different earthquake intensity was observed,The dynamic characteristics of the model and acceleration response,displacement response,shear and strain were studied.The analysis results show that the main influence of corrosion on the overall structure is: the natural frequency of the structure decrease,damping ratio,strain,displacement response increase and the reducing of acceleration and shear.;The failure mode of two model structure is similar,the structure has local bucking failure modes at end of beams,the degree of plastic deformation of corrosion model is larger than that of non-corrosion model.When the input acceleration peak value is less than 0.396 g,the seismic response of two models is similar,with the increase of the seismic intensity,the difference of seismic response between two structures is more obvious;the research results can provide experimental support for the safety assessment of corroded steel frame.(2)Based on the experimental results,The numerical modeling of corroded steel frame structure is established by ABAQUS.The time history analysis of the model is carried out,The natural vibration period,acceleration response and displacement response of the model are compared with the experimental results,the results show that the calculation results agree well with experimental results,It confirmed that the finite element analysis of the corroded steel frames that considering the weakening of section and material mechanical properties can accurately reflect the actual degradation process.proved the accuracy and reliability of the method,it can provide the basis for further study in the evaluation of the seismic performance of existing steel structure.