Study On Bearing Behavior Of Large Diameter Cast-in-place Piles For Bridges Considering Scour And Material Degradatio

In recent years,with the rapid growth of bridge engineering,the safety issues of bridges cannot be ignored.As the foundation of bridge,bridge pile foundation bears the upper load and water scouring,meanwhile,the reinforced concrete material of pile foundation is continuously deteriorated and damaged by the erosion of atmosphere and water vapor,resulting in the decrease of pile foundation bearing capacity.That will cause great influence when the accident happens.In view of this,the monopile foundation of bridge was used as the research object.By improving the Najar energy theory,the damage factor calculation formula is derived,which can be brought into the concrete damage plasticity model to simulate the process of concrete plastic damage.The model was established by midas FEA NX finite element software to investigate the change law of the bearing performance of monopile foundation under the coupling condition of considering scour and material deterioration damage.The follows are the main research contents and results of this paper:(1)By improving the Najar energy theory and the current concrete structure design code,the damage factor calculation formula was derived,and combined with the verification of finite element examples,the formula fitted well with the test results.(2)The changes of load-bearing performance were investigated by scour simulation of undeteriorated monopiles.The greater the scouring depth,the greater the pile top displacement under the same vertical load;the longer the service time,the more the pile foundation vertical ultimate bearing capacity is reduced,when the bridge service for 100 a,the pile foundation bearing capacity decreases by 13.6%.(3)The changes in load-bearing performance were investigated through scour simulations of steel deteriorated monopiles The pile settlement before and after steel deterioration increases with the increase of service time.The pile undertaking capacity reduces with the add of service time,but the decrease is small,when the pile service for 100 a,the pile bearing capacity only decreases by 0.7%.(4)The changes in load-bearing performance were investigated through scour simulations of concrete deteriorated monopiles.The pile bearing capacity before and after concrete deterioration decreases with the increase of service time,and the decrease is greater than the effect of steel deterioration on the pile bearing capacity.(5)The changes in load-bearing performance were investigated through scour simulations of steel and concrete deteriorated monopiles by simulation consequence.The pile undertaking capacity reduces with the add of service time before and after the deterioration of both reinforced concrete and concrete.The settlement of the pile foundation increases significantly when both reinforcement and concrete are deteriorated,and the differences in settlement between the two cases increases with the increase of service time.Contrasting with the results of the previous analog,it can be concluded that the concrete deterioration has more influence on the pile foundation bearing capacity.