Research On Multi-scale Numerical Simulation Of Bearing Capacity Of Concrete Bridge Structure Considering Rebar Corrosion

In order to meet the needs of China’s economic development,a large number of highway bridges have been built in our country,of which reinforced concrete bridges account for more than 90%,and a considerable number of coastal bridges are in the marine erosion environment,which is very easy to cause corrosion of steel bars due to chloride corrosion in the sea water,resulting in concrete cracking,resulting in serious durability problems of the structure in a short time.However,how to evaluate the bearing capacity and health status of reinforced concrete bridges in the near design life is an urgent problem to be solved.Therefore,it is of great significance to study the corrosion process and long-term performance evolution of reinforced concrete bridges for the maintenance,reconstruction and future design of existing bridges.Aiming at the durability of reinforced concrete bridges,this paper proposes a multiscale coupling analysis method for durability of reinforced concrete beams.Based on the lattice model and the finite element model of reinforced concrete,a multi-scale reinforced concrete durability analysis model is established.On the basis of improving the model,the mesoscale chloride ion penetration model,the steel corrosion model and the macro level reinforced concrete model are coupled and analyzed to study the structural performance evolution of reinforced concrete bridges.The main research results obtained in this paper are as follows:(1)Based on the existing research,the cell shape and meshing method of the chloride ion permeation model are improved.A quadrilateral infiltration unit based on the lattice model grid is established in the chloride ion penetration model,so that the lattice model and the chloride ion penetration model can be coupled for analysis.This modeling method makes the data exchange between models more concise,and it is more in line with theory when considering the chloride ion diffusion stress effect.In this paper,the coupled model can simulate the chloride ion penetration process in concrete and the cracking process of concrete caused by steel bar corrosion expansion,and obtain the uneven steel bar corrosion patterns with different corrosion time.(2)In this paper,a multi-reinforced aggregate delivery model and a multi-reinforced concrete corrosion expansion model are established to simulate the chloride ion penetration process,the steel corrosion process and the concrete cracking process in the concrete when the multiple reinforcements are arranged.The simulation results show that the corrosion of the steel bar and the resulting cracking process of the concrete are affected by many factors: such as the positional relationship between the steel bars,the diameter of the steel bars,and the thickness of the concrete protective layer.(3)A multi-scale coupling analysis method for durability of reinforced concrete beams is proposed.Combining the meso-reinforced steel corrosion model with the macroreinforced concrete model,and taking into account various factors such as aggregate,concrete cracking,and steel corrosion,the time-varying curve of the bending capacity of the reinforced concrete beam is obtained through numerical simulation and calculation.The standard solid slab bridge of diameter is used to study the bending capacity.In the environment of high chloride ion erosion,the flexural load-bearing state of the solid slab bridge is analyzed by the corrosion process of the steel bar.Through simulation,the safe service life of the solid slab bridge is about 33 years.