Study On Mechanics Analysis And Collapse Simulationof Narrow Base Steel Tower

In order to economize the earth occupy of transmission line towers in cities and suburban areas,a new type of tower—the narrow base steel tower was designed,which has the advantages of small root opening,small space,beautiful appearance,easy transportation and economy.At present,for the design of narrow base steel towers,there are not mature technical regulations at home and abroad for reference.Few studies are found on the narrow base steel towers.Therefore,it is urgent to carry out relevant researches on the structures of the narrow base steel towers.In this thesis,a new type of 110 kV hybrid narrow base steel towers is studied.Firstly,the test of full scale model of the narrow base steel tower is introduced.And test results of the displacement and strain response of the tower were obtained under various load conditions.The failure mode and the test data under the wind overload are taken.According to the test results of the true tower mode,the tower collapsing starts from the damage of the joint on the southeast corner of the tower leg.Secondly,the beam-rod element model and beam element model of the tower are established.On the other hand,the joint local structure on the southeast corner is considered as FEM meshes of three dimensional body elements.And the bolt connection and the other components of the tower except the joint is act as FEM meshes of the beam elements.The two scale elements are connected by MPC technique of FEM.Hence,a multi-scale FE analysis model is established to the narrow base steel tower.Finally finite element method is used to analyze stress and deformation states of the narrow base steel tower under the three mechanical models.The static analyses of the three models are carried out by using finite element method,and the computed results are compared with ones of experiment of the true model of the tower.Then the stress and deformation results from finite element analysis under three models are discussed in detail.In addition,the nonlinear analysis of the tower-leg joint of the multi-scale model of the narrow base steel tower under high wind and overload conditions is carried out to study the mechanical behavior of the tower leg joint of the narrow base steel tower structure.The FEM analysis result of the multi-scale model of narrow base steel tower verified that the damage of the tower is derived from the joint on the southeast corner of the tower leg.Furthermore,the beam element model and multi-scale model are used to simulate the collapse process of the narrow base steel tower under big wind overload condition.Thus the collapse mode of the tower was obtained,in which the effectiveness the FEM results is verified by comparison with the true test results.The research results in the present thesis can provide reference for the design and mechanical analysis of the similar narrow base steel tower structures.