Analyses Of Behavior Of Pile Foundation Subjected To Lateral Loading Considering Reinforcement Yielding And Concrete Damage

With the development of the national economy,the number of buildings such as high-rise buildings,docks,cross-sea bridges offshore drilling platforms and offshore wind turbines has been increasing rapidly,and the pile foundation has been widely used.Pile foundation not only needs to bear the vertical structure caused by the superstructure and the pile itself,but also need to bear the horizontal load caused by earthquake action,wind and waves,vehicle braking action and arched of the the upper structure.Domestic and foreign scholars have done a lot of work on the study of the horizontal bearing characteristics of pile foundation,but seldom considering the yield of steel reinforcement and concrete damage.Horizontal loads are even a controlling factor in engineering such as bridge engineering,marine engineering,and so on.Therefore,it is of great theoretical and practical significance to consider the effect of steel yield and concrete damage on horizontal bearing capacity.In this paper,based on the horizontal loading insitu test of the pile foundation,a numerical model is established by using the finite element analysis software ABAQUS.In the analyses,the Mohr-Coulomb model is used for the soil,the smeared cracking model is used for the concrete,the ideal elastic-plastic constitutive model based on the Mises yield criterion is used for the steel.By comparing the displacement curve of the pile head,the displacement curve of the pile and the stress-strain curve of the concrete and the steel,we can see that the model can accurately reflect the behavior of the pile foundation under the horizontal load.The results show that under the action of high level lateral load,analysis without considering the damage of concrete and the yield of the steel bars does not accord with the actual test results.This shows the necessity of considering the yield of steel and the damage of concrete.Then the influence of soil parameters,pile parameters and external conditions on the horizontal bearing capacity of pile foundation is analyzed,including soil elasticity modulus,soil friction angle,soil cohesion,pile diameter,reinforcement rate,pile length,vertical load level,etc.The results show:(1)Increasing the friction angle in the soil can significantly improve the bearing behavior of the pile foundation and increase the ultimate capacity;Increasing the elastic modulus of the soil can enhance the bearing capacity of the pile to a certain extent;In the case of large soil stiffness,the lateral displacement of the pile head depends only on the deformation characteristics of the pile itself;Increasing the cohesion of the soil can also improve the horizontal bearing capacity of the pile foundation.(2)The allowable values of the horizontal bearing capacity are mainly controlled by the cracking of the pile body with low reinforcement ratio,however for the pile with high reinforcement ratio,the allowable value of the horizontal bearing capacity is controlled by the horizontal displacement of the pile head;Increasing pile diameter can significantly improve the bearing capacity of pile foundation.(3)The vertical load transmitted by the superstructure is beneficial to the decrease of the lateral displacement of the pile,but at the same time increases the maximum bending moment of the pile,and considers V = 0.4 ~ 0.6Vult as the optimal vertical load level.Based on the pile foundation of actual engineering,the numerical model of pile group is established,and the influence of different pile number on the horizontal bearing capacity of pile group foundation is analyzed and arrive at the displacement curves of the pile head in different cases.It is concluded that increasing the number of pile groups can improve the horizontal bearing capacity of pile foundation.