Evaluation Of The Corrosion Effects On Performance Of Composite Bridge In Service Based On Cellular Automata And Finite Element Method

The safety and performance of any national highway system depend on the condition of various compositions.The bridges are the fundamental component of the highway system,representing the important investment and strategic link of the transportation.With the increase of the service life of the bridge structures,the durability problem of bridges materials becomes more and more dangerous;the durability problem often causes the bridge to fail in advance.Many factors affect the durability of the bridge,such as the working environment,traffic volume,and material defects.Among these factors,According to the working environment,the durability of the existing bridges varies very significantly from one place to another.The research on durability and service life of bridges has become a major scientific and technological issue concerned by academic researchers in the world;It has become a hot and challenging research topic nowadays.So,it is essential to evaluate the durability of the bridges reasonably.In this research,the evaluation of the corrosion effects on the performance of composite bridge section caused by chloride ions during the service life is investigated.The chloride ions diffusion process in the concrete slab,reinforcement bars corrosion and the concrete cover cracking were simulated based on 2D-Cellular Automata method in MATLAB.The corrosion on the steel section of the bridge and the factors which lead to corrosion were analyzed.Then,the corrosion caused by chloride ions of weathering steel in the bridge section was simulated using 3D-cellular automata method.The degraded steel-concrete composite bridge section according to MATLAB calculation was analyzed based on finite element analysis software.The stresses and deformation of the degraded section were simulated and analyzed.Through the performance prediction of the composite bridge section,the numerical simulation and the performance of the service process of the composite bridge section under chloride ion corrosion were achieved.The results of 2D-Cellular Automata simulation showed that the corrosion of reinforcement bars in the concrete slab of the bridge starting after 70 years and the cracking time of concrete slab occurred after 9.8 years from the beginning of corrosion under the effect of chloride ions.Moreover,the corrosion ratio in reinforcement bars in the 100 th year was 11.81%.Also,the degradation of concrete resistance for tensile and compression reduces by(2.5-3%)every ten years and the degradation of steel bars resistance in the 100 th year was 6% under the effect of chloride ions.The 3D-Cellular Automata simulation showed that the corrosion ratio in the 100 th year was 10.64% and the thickness of steel sections was decreased by 1.8mm after a hundred year of service life.Also,degradation of steel resistance in the 100 th year was 5.5% under the effects of chloride ions.Finally,finite element analysis illustrates that the stress values of the concrete slab and steel beam increased significantly within the service life of the bridge structure,but it does not reach the allowable design values.The analysis results of the composite bridge section proved that the bridge is safe during the service period and it can still be used normally after 100 years.