Study On Calculation Method And Numerical Simulation Of Bearing Capacity For Concrete-filled Steel Tubular Piles

As we all know,the foundation of the transmission tower is different from the general form of foundation.In addition to the gravity load of the superstructure,it also bears the lateral loads such as wind load,breakage tension and seismic load during the actual application process,resulting in being subjected to combined load of tension and bending moment.Therefore,the foundation of the transmission tower needs to be considered more complex than the basic form,and a reasonable foundation design plays an important role in the security of the entire power system.As one of the main forms of transmission tower foundations,pile foundation can be used on special ground such as river courses,soft soil,and self-gravity collapsible loess,and has been widely used in practical projects.However,owing to the complex and changeable contraction site and condition,the existing foundation forms have gradually failed to meet the needs of the engineering project.With the continuous development of the pile foundation technology,people have put forward higher requirements for the pile foundation.It is an important direction for the future development of pile foundation technology to seek a form of pile with more conveniences for construction and better bearing performance.The paper closely follows the research trend in this field of engineering at home and abroad,and proposes the possibility of the application of concrete-filled steel tube piles(CFST piles)in transmission towers.At present,although the CFST piles have been used in some projects,as a new type of pile,the related theoretical research still lags behind the practice,and mainly focuses on the study of compressive performance,limiting the generalization and application of CFST pile to a certain degree.Therefore,it is necessary to study the bearing capacity performance of the CFST piles.Based on the above discussion,this paper study the bearing capacity performance ofconcrete-filled steel tube piles from the following three aspects:1.Study on Calculation Method of Flexural Capacity of CFST Piles under Combine Load of Tension and Bending MomentBased on the idea of finite element,the finite strip method for calculating the flexural bearing capacity of CFST piles was proposed,and the corresponding MATLAB calculation program was compiled to calculate the cross-sectional bearing capacity of CFST piles under tension and bending loads.Based on the calculation results of the finite strip method,the change rule of T-M normalized curves of CFST piles under different pile thicknesses,reinforcement ratios,and pile diameters was analyzed.In addition,a formula method for calculating the flexural bearing capacity of CFST pile are proposed,and the relevant parameters are given.2.Study on Horizontal Bearing Characteristics of CFST Pile Based on ABAQUSThree-dimensional finite element numerical simulation of CFST piles is performed using the universal finite element analysis software ABAQUS.By consulting relevant literature,various calculation parameters for steel tubes,concrete,steel bars,and soil layers required in numerical simulation were determined,including physical and mechanical performance indexes,constitutive relations,contact surface parameters,etc.According to the above analysis,the effects of different pile parameters and soil conditions on the horizontal bearing capacity of CFST piles were studied to provide reference for related research and application.3.Research on Simplified Method for Calculating Horizontal Bearing Capacity of CFST Pile Based on p-y Curve MethodBased on the p-y curve method,fully considering the influence of different factors on horizontal bearing capacity of CFST piles,a total of 192 test pieces were designed.According to the calculation results of all test specimens,combined with nonlinear fitting and regression analysis,a simplified calculation formula for the horizontal bearing capacity of CFST piles in soft clay was established to provide reference for the theoretical research,normative formulation and practical application of concrete-filled steel tube piles.