Research On Seismic Damage Of Steel Frame Beam And Structures Under Offshore Atmospheric Environment

Earthquake disasters have caused a large number of economic losses and casualties.Therefore,the seismic performance of the structure has become the focus of structural safety performance.The steel structure is widely used in various important buildings due to excellent seismic properties such as ductility,stiffness and strength.However,due to the poor anti-corrosion property of metal materials,especially under the offshore atmosphere with high humidity and chloride ion concentration,steel is more prone to mechanical performance degradation,resulting in deterioration of seismic performance of steel structures.Aiming at the above problems,this paper studies the seismic damage evolution law of corroded steel structures through three methods of material,component and structure through the combination of experiment and finite element simulation.The main work and conclusions are as follows:(1)Simulate the offshore atmospheric environment through test methods,accelerate the corrosion of 24 steel specimens,and conduct material tests on specimens with different degrees of corrosion.Corrosion steel shows the severity of corrosion by the weight loss rate.The mechanical performance of the steel increase with the increase of weight loss rate.The main indicators are the yield stress,ultimate stress,elastic modulus and elongation of the test piece.Finally,the regression expression of the experimental data between each index and the weight loss rate is established.(2)In the aerosol simulation laboratory,the offshore atmospheric environment corrosion of the 4 steel frame beam specimens was carried out,and the pseudo-static test was carried out on the 9 steel frame beam members with different degrees of corrosion and the width-thickness ratio of the plates,combined with the test results and The damage theory studies the influence of the degree of corrosion on the damage index of the strength,resistance to deformation and energy dissipation of the specimen.The results show that the initial stiffness and strength of the rusted specimens are reduced due to the influence of corrosion,so the seismic capacity is relatively poor,and the strength and stiffness reduction increase with the increase of the weight loss rate,and the damage accumulation is also faster.The specimen with a larger aspect ratio has a larger bearing capacity due to the size effect,and the probability of yielding is greater,and the range of buckling is more widespread,so the damage accumulation of the specimen is faster.The development of damage has the characteristics of accelerating and increasing,and the images and features of the damage curves of each test piece are similar to the power function.(3)Based on the experimental results,the influences of the displacement amplitude and the loading path on the damage accumulation are obtained.Combined with the existing earthquake damage model,a new two-parameter model of damage is proposed.The model especially considers the damage in the elastic stage,which is more in line with the damage.Classical damage index definition.According to the characteristics of the test piece and the test results,the parameters of the damage model are determined,and the model calculation results are compared with the test results to test the rationality of the model.Finally,the corresponding damage index of the seismic damage grade of the steel frame beam is determined,and the basis for the evaluation of the damage grade of the steel frame beam of this type is provided.According to the test skeleton curve and hysteresis curve of the test piece,the skeleton and hysteresis simplified model of the restoring force model are determined.Combined with the damage model proposed in this paper,the cyclic degradation coefficient of hysteresis is determined,and the damage-recovery model of steel frame beam based on damage is finally established.(4)According to the steel frame beam damage model and the steel frame column damage model established by the previous research of the research group,the theoretical damage weight model is used to establish the structural damage model.Through the ABAQUS,the finite element model of the steel frame structure test piece that has been tested by the research group is established.The deformation and energy consumption of the test steel frame are obtained by simulation,and the damage curve is drawn based on the structural damage model.According to the failure state of the test specimen and the damage index calculation result,the relationship between the structural failure state and the damage index is established to evaluate the post-earthquake damage of the steel frame structure.