Transmission Tower Structure Research Articles

Double Non-Linear Mechanical Characteristics of Transmission Tower Structure Based on Model Amendment

Transmission tower, being of evident nonlinear characteristic, is a complex space structure. Linear theory is generally adopted in the process of designing, which results in a waste of resource and disaster. Starting from the problems exiting in the process of transmission tower designing, the space beam element is adopted in the thesis, which reduces material nonlinearity through the rod end of the plastic method, and the geometric large deformation problem is involved by considering the amendment of the element stiffness matrix. Arc-length method of iterative computation is adopted as the solution method. On the premise of clarifying the process of dual non-linear solution, this thesis combines specific project example through self-organizing the finite element programming to calculate displacement - load curve, and the results show that the transmission tower structural system possesses obvious nonlinear characteristics. The research lays a foundation for improving the accuracy of space truss structure and developing the large specific finite element software.

Design of the Automatic Position Block for the Punched Holes on Angle Steel of Transmission Tower

It is proposed that the design and operation process of the automatic position block for the holes punching used for the angle steel of transmission tower structure. It consists of position block, slide block, screw, nut, motor, and controller. If the anchor points have been set, the hole punching position can be anchored automatically, and setting the anchor points are easy operated. It can equipped in punching press, and improve greatly the current hole punching process.

Nonlinear Analysis of Transmission Tower Structure by Three FEM Models

In this paper, three kinds of FEM models, i.e., the truss element model, the beam element model and the mixed beam-solid element model are utilized to simulate the full-scale field test of transmission tower. Based on Abaqus software, the geometric and material nonlinearity of the structure is considered. Comparing the numerical results with test data, it is found that the truss element model is no longer suitable and the mixed beam-solid element model is more accurate than the beam element model. Thus, using solid element to discrete the key nodes of the tower can greatly enhance the accuracy and reliability of the numerical prediction.

Behavior of self supported transmission line towers under stationary downburst loading

During the past decade, many electrical transmission tower structures have failed during downburst events. This study is a part of a research program aimed to understand the behaviour of transmission lines under such localized wind events. The present study focuses on assessing the behaviour of self supported transmission line towers under downburst loading. A parametric study is performed to determine the critical downburst configurations causing maximum axial forces for various members of a tower. The sensitivity of the internal forces developing in the tower's members to changes in the downburst size and location was studied. The structural behaviour associated with the critical downburst configurations is described and compared to the behaviour under 'normal' wind loads.

Latest Developments of Materials Used in Transmission Tower Structure

This paper discusses the status quo and development trend of transmission tower materials, points out that there will be higher requirements on the varieties and specifications of transmission tower material alongside the continuous construction of power grids. Tower materials will develop in the environmental-friendly, high-strength and conservation-oriented trend. In the future, the demand for Q420, Q460 high-strength and large-width angle steel will grow enormously; the steel tubular tower will be used in transmission lines more widely due to its excellent carrying capability; new materials like weathering cold-formed steel and composite material will be gradually used in transmission towers.

Two-Level Optimization Method of Transmission Tower Structure Based on Ant Colony Algorithm

This paper highlights a two-level optimization process combined with ant colony optimization algorithm (ACO)，which is applied to design the shape of the transmission tower structure, and compiles optimization design procedure for the solution of the structure shape with the MATLAB language. By comparing the different methods of the transmission tower structure optimization design, the ACO algorithm is demonstrated to be more accuracy and practical in dealing the complex optimizations problem, i.e. the combination of continuous variables and discrete variables. These calculation examples illustrate that the two-level optimization method is reliable and versatile.

Dynamic reduction-based structural damage detection of transmission towers: Practical issues and experimental verification

Structural damage detection in large-scale three-dimensional spatial structures is a challenging problem. It is impractical to develop a general damage-detection method that is applicable to all types of structural systems and all kinds of damage. A practical and efficient structural damage detection method must consider the characteristics of the target structure and damage in the development stage. In 2009, Yin et al. [33] proposed a damage detection method for the health monitoring of transmission towers. The method was developed based on the dynamical finite element (FE) model reduction technique, which utilizes identified modal parameters, such as natural frequencies and mode shapes, with only a limited number of sensors. In Ref. [33], the proposed method was numerically verified by simulated noisy data from a three-dimensional transmission tower model for single and multiple damage cases. This paper discusses some practical issues related to the proposed method, such as sensor placement and computational efficiency. Rather than proposing a general sensor placement method, a set of preliminary sensor locations is determined based on engineering judgement. This set of sensor locations is then checked against the results of a sensitivity analysis to ensure that the measured data contain information for identifying all of the target damage scenarios. To reduce the required computational power, two simplified versions of the proposed method are presented. The proposed method is then verified with a scaled-down model of a transmission tower (2.4 m high) that was built at the Structural Vibration Laboratory (SVL) of the City University of Hong Kong. This paper reports the detailed experimental setup and the method of extracting the modal parameters from a series of free vibration tests with only a limited number of sensors. The verification results show that the proposed damage detection method identifies the damaged sub-structures in all of the experimental cases considered. It must be pointed out that the transmission tower structure, in its operating conditions, suffers from the effect of the forces transmitted from the cables it carries. The influence of this force on the damage identification result is great and can not be neglected in practice. In the present experimental case study, only a transmission tower-like structure without carrying the cables is investigated in laboratory conditions.

Dynamic characteristics of transmission line conductors and behaviour under turbulent downburst loading

During the past decade, many electrical transmission tower structures have failed during downburst events. This study is a part of a research program aimed to understand the behaviour of transmission lines under such localized wind events. The present study focuses on the assessment of the dynamic behaviour of the line conductors under downburst loading. A non-linear numerical model, accounting for large deformations and the effect of pretension loading, is developed and used to predict the natural frequencies and mode shapes of conductors at various loading stages. A turbulence signal is extracted from a set of full-scale data. It is added to the mean component of the downburst wind field previously evaluated from a CFD analysis. Dynamic analysis is performed using various downburst configurations. The study reveals that the response is affected by the background component, while the resonant component turns to be negligible due large aerodynamic damping of the conductors.

가공송전철탑 경량화 설계에 관한 연구

This paper presents the design factor of an overhead transmission tower structure in order to reduce the tower weight. The behaviour of transmission tower structures are affected by the horizontal angle of the tower structure, the equivalent wind pressure group, the slope of the main post of the tower, the separation of the internode and the use of high-strength materials in their construction. Tower weight can be reduced by approximately 30% reduce weight by means of optimal design based on a consideration of all the above factors. In addition, the design of the foundation of the tower with the shear key installation to increase horizontal support together with a modified angle of inclination to the ground can reduce by about 37% the amount of concrete used during construction. The area of ground disturbed by the construction of the tower foundation can thus be reduced by approximately 33%. Therefore it is possible to build an environmently-friendly T/L tower with the mechanical properties of existing towers.

A new framework for evaluating along-wind responses of a transmission tower

In this paper, an analytical framework to evaluate the along-wind-induced dynamic responses of a transmission tower is presented. Two analytical models and a new method are developed: (1) a higher mode generalized force spectrum (GFS) model of the transmission tower is deduced; (2) an analytical model that includes the contributions of the higher modes is further derived as a rational algebraic formula to estimate the structural displacement response; and (3) a new approach, applying load with displacement (ALD) instead of force, to solve the internal force of transmission tower is given. Unlike conventional methods, the ALD method can avoid calculating equivalent static wind loads (ESWLs). Finally, a transmission tower structure is used as a numerical example to verify the feasibility and accuracy of the ALD method.

A coupled finite element-optimization technique to determine critical microburst parameters for transmission towers

Most transmission line failures worldwide are attributed to high intensity wind events such as microburst. The velocity profile and loads associated with a microburst wind field vary significantly with the microburst configurations. An optimization technique is coupled with a finite element model in this study to identify the critical microburst parameters that lead to maximum forces in various members of a transmission tower structure. Moreover, the coupled genetic algorithms–finite element code is employed to determine the critical members that are likely to fail during a microburst event and the associated critical microburst configurations.

송전철탑의 풍응답 감소를 위한 마찰형 보강기구의 에너지 소산특성 분석 실험

Friction-type reinforcing members(FRM) to enhance the resistance to wind loads of a transmission tower through both stiffness strengthening and damping increase are energy dissipation devices that utilize bending deflection of a tower leg. In this paper, the hysteretic behavior of the transmission tower structure with FRMs was experimentally investigated through cyclic loading tests on a half scale substructure model. Firstly, the variation of friction forces and durability of the FRM depending on the type of friction-inducing materials used in the FRM were examined by performing the cyclic loading tests on the FRM. Secondly, cyclic loading tests of a half-scale two-dimensional substructure model of a transmission tower with FRMs were conducted. Test results show that the FRM, of which desired maximum friction force is easily regulated by adjusting the amplitude of the torque applied to the bolts, have stable hysteretic behaviors and it is found that there exists the optimum torque depending on a design load by investigating the amount of energy dissipation of the FRMs according to the increase of torque.

Behaviour of guyed transmission line structures under downburst wind loading

Past experience indicates that the majority of failures of electrical transmission tower structures occurred during high intensity wind events, such as downbursts. The wind load distribution associated with these localized events is different than the boundary layer wind profile that is typically used in the design of structures. To the best of the authors` knowledge, this study represents the first comprehensive investigation that assesses the effect of varying the downburst parameters on the structural performance of a transmission line structure. The study focuses on a guyed tower structure and is conducted numerically using, as a case study, one of the towers that failed in Manitoba, Canada, during a downburst event in 1996. The study provides an insight about the spatial and time variation of the downburst wind field. It also assesses the variation of the tower members` internal forces with the downburst parameters. Finally, the structural behaviour of the tower under critical downburst configurations is described and is compared to that resulting from the boundary layer normal wind load conditions.

Nonlinear finite element analysis of latticed transmission towers

Current design practices for transmission tower structures are based on 3D linear elastic truss analyses and on full-scale testing experience. This paper reviews current practices and presents a nonlinear analytical technique for accurate simulation and prediction of the ultimate strength and behaviour of transmission towers under static load conditions. Both geometric and material nonlinearities are accounted for in the analysis. A formex formulation is used for the automatic generation of data that is necessary for the analysis. The behaviour of four different full-scale towers is described and the predicted results are compared with tests.

Formex Formulation of Transmission Tower Structures

The formex formulation of the topological configuration, geometry, load and support conditions of self-supporting or free-standing transmission towers is presented. In the formulation, a natural normat coordinate system is used. The tower topology is formulated according to member types and orientations within the tower. The formex formulation is implemented as a preprocessor for a general elasto-plastic nonlinear large displacement analysis program for transmission tower structures. The data generated from the formex formulation is transformed into an AutoLISP file that can be loaded and used by AutoCAD. Throughout the paper, it is assumed that the readers are familiar with the basic concept and terminology used in formex algebra.

Secondary Stresses on Transmission Tower Structures

The power industry is moving toward the use of high‐voltage transmission lines on tall, flexible towers. These towers are designed for heavier loadings than were previous towers, but the secondary effects of tower displacement tend to be ignored in the present day tower analysis. This paper examines the secondary effects from the large displacement of flexible towers, reviews the secondary stresses arising from joint rigidity and member continuity, and examines the reliability of tower strength predicted by the ASCE design guidelines. More realistic tower test acceptance criteria and a more reliable tower design methodology are suggested.

Rapid methods for transmission tower structural analysis and design

The electric transmission system power flow equations bear a striking similarity to force-displacement characteristics of pin-joint structures such as electrical transmission towers. In this paper, the structural analog to the electric power system equations is made in vector-matrix terms and contemporary techniques are applied for rapid analysis and design of transmission towers. In particular, the linearized power flow technique and the Kron reduction technique for impedance matrix modification are applied in order to radically increase the speed of analysis of transmission tower structures. The increase in speed and the nature of the problem formulation allows structural design techniques in reasonable digital processing times.