Study On The Influence Of Steel Casing On Dynamic Response And Toughness Of Pile Under Impact

Channel bridges are often threatened by ship collision,and the piles would be subjected to impact load inevitably.While the impact resistance and damage degree of the pile could be reflected by toughness.However,most of the piles actually exist in the form of steel-cased reinforced concrete piles(hereinafter referred to as steel casing composite piles)in engineering.It is urgent to study the dynamic response and toughness of pile under impact loading with the effect of steel casing taking into account.Therefore,with the support of the National Natural Science Foundation of China," Research on Quantitative Identification of Damage of Mixed Pile under Pier-Ship Collision Based on Toughness Dissipation Model",the dynamic response and toughness of steel casing composite pile under impact loading were studied in depth.The main research contents are as follows:1.Based on the validated numerical model of steel casing composite pile,the effect of steel casing on the dynamic response of pile under impact loading was studied.The results showed that the bearing capacity and stiffness of piles could be improved by the steel casing,the damage distribution and failure mode would also be changed.The interaction mechanism between steel casing and reinforced concrete piles was also studied.Finally,the influence of soil modulus,impact mass and velocity on the dynamic response of piles were compared.2.The parametric analysis was carried out on the size of steel casing.It was pointed out that the embedded depth of steel casing has a great influence on the dynamic response of piles,while the thickness of steel casing and the tangential interface condition of steelconcrete have limited influence.At the same time,it was pointed out that the interaction between steel casing and core concrete under impact loading is mainly governed by the normal pressure.Based on the comparison,the recommended values of steel casing size parameters in engineering were put forward.In addition,the sensitivity of the recommended values to soil modulus and the impact energy was analyzed.The results showed that the recommended values are universal for different soil modulus and impact energy.3.Based on the energy response analysis of steel casing composite piles,the effect of steel casing on the toughness dissipation process of pile was obtained.And the toughness dissipation law of steel casing composite piles under impact was summarized.On this basis,the impact resistance index and damage degree index of piles based on toughness and it's degradation were proposed.