Research On Static Performance Of Concrete Filled Steel Tublar Piles With Circular Section

At present,concrete-filled steel tube pile foundation is widely used at home and abroad.This paper proposes a new type of pile foundation,which is put into the soil by concrete-filled steel tube pile with combined forces of compression and torsion.Due to the better mechanical properties of concrete-filled steel tube pile foundation in the elastic stage,this paper takes the bearing capacity formula of round steel tube concrete pile in the elastic stage of compression and torsion combination as the research purpose,takes the test as the basis,and USES ABAQUS finite element simulation software to conduct in-depth research and analysis on the whole process and the mechanical properties in the elastic stage.The bearing capacity formula of the regression elastic stage lays a foundation for the application of precession concrete-filled steel tube pile foundation.In this paper,the preliminary preparation,loading process and post-processing of the test are summarized in detail.The design and fabrication process of the specimen and the measurement of material properties are introduced.The test loading device,loading system and data collection are introduced in detail.The phenomenon and data after the experiment are analyzed.The results show that:(1)for the same set of specimens,the bearing capacity of the elastic stage is the largest when the axial compression ratio is 0.25,and a larger axial compression ratio will lead to the early failure of the specimens;(2)increasing the steel content of specimens significantly improves the bearing capacity of specimens.The finite element simulation software ABAQUS was used to establish the torsional model of concrete-filled steel tube pile under compression.On this basis,a typical calculation example is established and the stress cloud diagram of steel tube and concrete at each feature point is extracted.The stress cloud map of steel tube and concrete at the elastic stage and the maximum bearing capacity stage of each specimen was extracted and analyzed.The results show that:(1)the stress state of steel tube and concrete in each stage can well explain the phenomenon during the loading process;(2)when the axial pressure ratio was 0.25,the specimens showed good mechanical properties in the elastic stage.In the parameter analysis,the transformation parameters are axial compression ratio,concrete strength,steel strength and steel percentage.The results show that the bearing capacity of pile specimens increases obviously when the axial compression ratio is 0.25,and the bearing capacity decreases if the axial compression ratio is too large.With the increase of concrete strength,steel strength and steel content,the bearing capacity of members increases gradually.The maximum torsional bearing capacity formula and the torsional bearing capacity formula at the elastic stage of pile members are given for the convenience of practical application.