Research On The Improvement Of Bearing Capacity Of Transmission Line Tower And Its Foundation

Transmission line system is an important guarantee of power consumption in modern life,which is composed of transmission line,transmission tower,foundation and so on from top to bottom.The destruction of the transmission line,tower and foundation will lead to the paralysis of the whole transmission line system and cause huge losses,so the security of the transmission line system is particularly significant.In this paper,each component of the transmission line system is taken as the research object,the mechanical performance of the transmission line system is systematically studied from the aspects of theory,test and numerical simulation.First,taking the transmission line tower as the research object,according to space truss method,the calculation program of the basic lattice tower cell is compiled by using MAPLE mathematical software,in the multi-layer tower cell,under the action of vertical load,bending moment,shear force and torque,the theoretical calculation expressions of the internal forces of the main rod,inclined rod and transverse rod are derived,and the interaction among the main rod,inclined rod and transverse rod of the tower is further studied.In multi-layer tower cell,under various working conditions,the influence law of cross rod stiffness on the internal force distribution of the main rod and inclined rod is given,and the role of cross rod in transmission line tower structure is obtained.The calculation expression of the stable bearing capacity of the transmission line tower structure is derived by using energy method,and the calculation expressions of the stable bearing capacity of the tower are given respectively corresponding to 30°,45°and 60° angle between inclined rod and horizontal direction.The influence of transverse rod stiffness on the stable bearing capacity of transmission line tower structure is studied,and the influence of the angle between the inclined rod and horizontal direction on the stable bearing capacity of the transmission line tower is given.The influence law of the angle between the inclined rod and horizontal direction(5°?85°)with the stable bearing capacity of the tower is obtained.Based on stability theory of the main rod and inclined rod of the tower,stable bearing capacity of triangular and quadrilateral steel towers is studied theoretically,and the corresponding triangular and quadrilateral angle steel tower test models are built.Stable bearing capacity of triangular and quadrilateral angle steel towers is studied by theory,test and numerical simulation.Beam-bar element models of the tower cell with the circular tube main rod and angle steel inclined rod,and shell element models of single-plate and double-plate connections are established respectively,and the initial defects of the tower are considered.The influence of connection joints on the nonlinear stable bearing capacity of triangular and quadrilateral towers is studied.Catenary method and energy method are used to calculate the static and dynamic performance of the transmission line respectively,and the catenary equation of wire sag is established.Combined with the field measurement of the project,the accuracy of catenary method is verified.The calculation expression of the vibration period of the catenary which is affected by the bending deformation energy and not affected by the bending deformation energy is derived by using energy method,and the oscillation period of the catenary is measured by setting up an experimental device to verify the correctness of the theoretical calculation expression.Finally,a new type of tower foundation,single pile cross beam self-balanced foundation,which has the advantages of simple structure,good overall performance,fast construction and good economic benefit,is put forward on the basis of full-scale test and numerical simulation.The mechanical characteristics and failure mode of the new foundation are studied.The nonlinear finite element model of soil-concrete-rebar is established.Considering the nonlinear contact between soil and concrete,the load-unload analysis of the model is carried out,and the analysis results are compared with the tests.Through the analysis,the ultimate bearing capacity of the new foundation is obtained,and the failure form,weak position and reinforcement stress of the new foundation under load are obtained,which provides a basis for the design of the new foundation.