Study On Long-term Working Characteristics Of Large Diameter Piles Of Inland River High-piled Wharf

To overcome the influence of large variation range of water level on Inland river high-piled wharf construction,steel tube reinforced concrete piles have been widely applied in the inland river high-piled wharf engineering practice.In accordance with the safety evaluation technology of in-service high-pile wharf structure,which is the project of the Ministry of transport construction.This paper base on terminal Phase II project of Orchard Port,the research of bearing capacity and long-term performance of steel tube reinforced concrete pile is commenced through the laboratory model test and theoretical analysis.The main research contents and conclusions are as follows:(1)The model is designed in accordance with the Phase II project of Orchard Port.Experimental study on bearing capacity of concrete structure under 6 kinds of working conditions was carried out.It is found that when the thickness of steel tube is small(D/??20),the deformation of steel tube can keep in pace with that of internalreinforced concrete under the condition of stress level bellows 0.45,and the restraint effect of steel tube on the core concrete is not obvious on this occasion.At the same time,the steel tube has a hoop effect on the core concrete under the condition of high stress level which is higher than 0.45,the hoop effect can restrain the development of microcracks,so as to enhance the ductility and ultimate bearing capacity of the piles.The hoop action of the steel tube to the core concrete increases with the increase of the thickness of the steel tube.(2)The model test study on the performance of steel tube-reinforced concrete pile conducted under bending load.The result shows that for the pile whose slenderness ratio is lower than 8,the existence of the steel tube can enhance the ductility of the component in the three-point loading mode in comparison with the brittle failure of plain concrete structure and reinforced concrete structure.Its failure mode is ductile failure.At the same time,the existence of steel tube can greatly improve the ultimate bending moment of such piles.(3)In this paper,the creep regularity of core concrete under long-term load is studied.The main variable parameter is the thickness of steel tube.It is found that under the low stress level which is lower than 0.45,the creep law of the core concrete of steel tube reinforced concrete member is similar to that of the concrete structure which shows that the development of the early stage is faster and it reversed in the end.Creep value and creep coefficients are less than the theoretical value of the concrete of the same age.The greater the thickness of the steel tube,the smaller thecreep value of the concrete under the same age.(4)Compared with the typical creep model of concrete,it is found that the creep prediction of concrete with such structure under the axial load of stress level below0.45,the deviation is small compared with calculation results of MC90 model and ACI209 model.At the same time,the finite element software LINK3 D is used to simulate the long-term performance of the piles,and the results were consistent with the experimental results.