Analysis Of The Effect Of Podium On The Piles Of The Main Building's Rigid Pile Composite Foundation Under Seismic Loading

As a kind of ground treatment method with good economical and applicability,rigid pile composite foundation has been widely used in our country.In recent years,the construction industry has flourished and there are many highrise buildings.Due to the different requirements for use,the architectural forms are diversified,and high-rise buildings with podiums are more common in life.It is necessary to study the characteristics of the interaction between superstructures,rafts,cushions,and piles under the action of earthquakes.Through the proposed construction of a 15-storey high-rise office building with a podium,ABAQUS finite element software is used to analyze the interaction between the superstructure and the foundation.To study the effect of the podium on the internal forces of piles in a rigid pile composite foundation under earthquake.The main contrast factors are: The effect of the number of spans and layers of the podium on the internal forces of the pile in the rigid pile composite foundation;Analysis of changes in internal forces of piles in high-rise buildings with or without podiums;Analysis of the performance of its piles under earthquakes in high-rise buildings with podium and basement;Analysis of internal forces of piles under different site characteristics cycles and seismic waves;The influence of the podium in different foundation sets on the piles of the main buildingThe main conclusions obtained are as follows:(1)Under the action of earthquakes,the internal force of each row of piles under the main building is consistent along the length of the pile.With the increase of the number of podium spans,the maximum axial force value,the maximum bending moment value and the maximum shear force value of the podiums in different layers all showed a downward trend.The fewer the number of podium layers,the greater the contribution of the number of podium spans to the reduction of the maximum axial force of the main building pile.Selecting the number of layer and the number of span that can make the axial force of the pile smaller will be beneficial to save the project cost,and the form of the podium where the number of podium is less than the number of three-span podium is to be avoided.(2)As the number of podium layers increases,the number of spans corresponding to the minimum value of the pile's maximum bending moment in the main building also gradually increases.With the increase of the number of podiums spans,the pile's maximum bending moment value of the main building of different layers of the podium has a decreasing trend.(3)The more spans of podium,the greater the effect of the number of podium layers on the shear of the main building piles.When the number of layers is the same,the more the number of podium spans,the smaller the maximum shear value of the main building piles.At the junction of soil layers,the shear force value gradually increases,even larger than the shear value of the pile end,where the pile body is prone to damage,so the top of the pile body and the center of the pile body must be reinforced.(4)The existence of a podium has an advantageous effect on the internal forces of the main building piles.When the podium has three layers and three spans,the axial force,bending moment and shear force of the main building piles are about 60% of the axial force,bending moment and shear force of the main building piles without a podium.Therefore,the main high-rise buildings in the project should be equipped with multi-slayer and multi-span auxiliary podiums to reduce the internal forces of the main building piles.(5)When the building has a basement,the maximum bending moment and the maximum shear force of the pile are larger than the conditions without the basement under the action of the earthquake.The maximum axial force of the main building pile when there is no basement is greater than the maximum axial force of the pile when there is a basement.(6)Under the effect of the same level of different seismic waves,the internal forces of the piles have the same tendency.The input of different seismic waves has the greatest influence on the bending moment of the main building piles,and has the smallest influence on the axial force of the main building piles.The axial force and moment and shear force of the pile body increase with the increase of the site characteristic period,but the increase is slightly smaller.(7)The composite foundation treatment method for the podium foundation has a great influence on the internal force value of the main building pile.The influence of the change of podium foundation on the moment and shear force of the main building pile is greater than the axial force of the piles.As the superstructure has a podium,the load of the main building will spread along the podium to both sides.Therefore,proper handling of the podium foundation can effectively reduce the internal force of the main building foundation.It is also necessary to consider the difference in settlement between the main podium.After the foundation of the podium has been treated,it can effectively bear the load of the main building.Therefore,the most reasonable way should be selected when designing the podium foundation.