Numerical Analysis Of Seismic Performance Of Reinforced Concrete Bridge Piers With Non-uniform Corrosion In Coastal Areas

China has made leapfrog development and outstanding achievements in the construction of sea-crossing bridges,but the complex marine environment is an important factor affecting the durability design of bridges in coastal areas.Due to the active seismic fault zones in China,it is particularly important to study the seismic performance of reinforced concrete bridges in complex marine environments.Piers in the marine environment usually undergo non-uniform corrosion along the elevation,and the corrosion situation becomes extremely complex with the location of the plastic hinge region of the pier in the marine environment zone.In addition,the sea salt particles in the ocean atmosphere will adhere to the reinforced concrete piers with a certain distance from the coastline with the sea wind,which will cause different degrees of corrosion on the windward side and leeward side of the components.Considering the above two nonuniform corrosion cases,the separation models were established based on the Open Sees finite element program to carry out fine simulation of the pier,and the seismic performance of the pier under the two non-uniform corrosion cases was analyzed and discussed,providing a reference for the design and construction,safety maintenance,repair and strengthen of bridges and other infrastructure.The main research contents of this paper are as follows:(1)The separation model was used for fine simulation of reinforced concrete components.The concrete and reinforcement used solid elements and line elements respectively,and the bond slip between reinforcement and concrete was simulated by zero-length elements.Compared the representative bond slip constitutive models with the test results,then selected FIB Model Code 2010 as the bond slip constitutive model.Based on the Open Sees finite element program and STKO visualization software,the uncorroded center pull separation models were established to verify the feasibility of the modeling method.(2)Based on the uncorroded separation model,considering the influence of corrosion on the mechanical properties and bonding properties of reinforced concrete materials,the corroded reinforced concrete beam model under monotonic load and the locally corroded reinforced concrete pier model under cyclic load were established respectively to verify the feasibility of the modeling method under corrosion.The results indicated that the cracking damage of uncorroded bending beams considering bond slip was more consistent with the test phenomenon.The separation pier model considering corrosion could simulate the transfer of plastic hinge areas caused by local corrosion.(3)In the marine environment,there is sufficient oxygen in the spray splash area,which is often scoured by the sea water,and the corrosion is the most serious.Therefore,the piers in the marine environment suffer non-uniform corrosion along the elevation.Considering the influence of uniform corrosion and pitting corrosion,the separation models of corroded piers in the spray area with service life of 0～100 years were established,and the seismic performance of piers with service life and damage development process were analyzed by fine simulation.The results showed that when the splash area was located 200～700 mm above the foundation,after 60 years of service,the plastic hinge region completed the transfer,and the bond slip damage area of the foundation gradually disappeared.The degradation rate of peak horizontal load capacity increased with the increased of corrosion degree.After severe corrosion of bars,they yielded prematurely,and the displacement ductility coefficient of bridge piers with higher corrosion degree was actually higher.Therefore,the displacement ductility coefficient could not be accurately used to evaluate the ductility of corroded bridge piers.Redefining the ultimate displacement of corroded piers to describe their displacement ductility after corrosion,the results indicated that the corrosion displacement ductility coefficient could accurately characterize the decrease in ductility of corroded piers.(4)Sea salt particles in the ocean atmosphere attach to the surface of reinforced concrete piers at a certain distance from the coastline with the sea wind,which will cause different corrosion degrees on the windward side and leeward side of the piers,and will also have adverse effects on the seismic performance of components.The separation models of piers with different corrosion ratios on both sides of the positive(high corrosion rate)and negative(low corrosion rate)loading were established,and its seismic performance and damage development process were studied by refined simulation.The results indicated that the height of the final damage area in the compression zone of the concrete on the side with high corrosion rate was relatively high.The bond slip on the side with higher corrosion rate above the foundation was significantly greater than that on the side with lower corrosion rate.Unilateral corrosion reduced the overall seismic performance of the component,but overall,the peak horizontal load capacity of the severely corroded side was slightly lower than that of the less corroded side.As the corrosion ratio increases,the cumulative energy consumption in the negative direction of loading was significantly higher than that in the positive direction of loading.The equivalent stiffness in the negative direction of loading was higher than that in the positive direction of loading.Calculated the displacement ductility coefficient under corrosion conditions,and the results once again indicated that the corrosion displacement ductility coefficient could accurately characterize the decrease in ductility of piers as the degree of corrosion increases.