Steel Transmission Towers Research Articles

A study on the dynamic characteristics and ultimate capacity of steel transmission towers

The safety of steel towers strongly influences the reliability of power supply in transmission lines. The dynamic characteristics, non-linear behavior, and ultimate capacity of 345 kV steel transmission towers are mainly studied in this article. The approach in this article is based on the ensemble empirical mode decomposition method, the down-sampling process, and the Hilbert–Huang transform. This study intends to identify vibration characteristics and detect damage from the measured ambient vibration data. Two different types of tower used by Taiwan Power Company (TPC), suspension towers (Type B) and strain towers (Type E), are discussed in this study. According to the specifications of the TPC Standard Code, the applied loads on a tower in the transverse, longitudinal, and vertical directions are determined, and the applied forces are increased gradually until the tower fails. Finally, the ultimate capacity for the tower are found by using the stiffness matrix operation approach dealing with non-linear behavior. The results of this study will be a valuable reference for advanced studies and for improving the design of steel transmission towers in Taiwan.

Experimental Study on the Mechanical Behavior and Failure Mechanism of a Latticed Steel Transmission Tower

AbstractTransmission tower collapses caused by strong winds or severe freezing rains frequently occur in many parts around the world. To study the mechanical behavior and failure mechanism of tower structures under such environmental loads, three pairs of tower subassemblages, including one single-panel pair and two double-panel pairs, were designed and statically tested at Tongji University. The difference between the two specimens in each pair was that one had an additional diaphragm as a method of retrofitting while the other did not. One pair of double-panel specimens was tested to simulate and capture the failure pattern of transmission towers subjected to wind load. Correspondingly, two pairs were used to investigate the relevant response of structures under the combination of vertical ice and wind loads. A comparative study on strains at critical sections and local and global deformations as well as failure modes of the tower subassemblages was carried out. The favorable effects of adding the diaph...

Experimental study on multi-panel retrofitted steel transmission towers

Due to the increasing demands on power supply and telecommunication services, existing transmission towers are frequently being required to carry extra loads above their initial design limits. A range of methods have therefore been used to increase the capacity of existing towers by retrofitting them in some way. This paper addresses steel lattice transmission towers with main leg members retrofitted by steel angles through bolted double steel angle connectors, a method that is widely used in practice but to date with little experimental research to support it. Three unreinforced tower models and four groups of retrofitted tower models with and without preloading have been tested in the structural laboratories at the University of South Australia. The experimental results verify the effectiveness of the retrofitting method. Load sharing analysis shows that axial loads can be effectively transferred between original tower members and reinforcing members through the bolted-splice system. Preloading reduces the load sharing in reinforcing members in the early loading stage but does not have significant influence on the ultimate strength of the whole structure.

Electric Field Analysis of 220 kV Composite Material Tower Lines

Using the finite element analysis, this work analyzed the electric field distribution of 220kV transmission steel tower with double-circuit and composite material transmission tower with the same size, and compared the electric field effect of two materials transmission tower for surroundings. And this work compared the vertical and axial electric field distribution along transmission line of the two materials transmission tower. The results indicate the composite material tower can improve the environment of electric field near the transmission lines.

The Feasibility Study for New-Type Forging Flange of in Steel Tower

This paper presents a new-type forging flange used in steel transmission towers, that is to forge a same flange and same bolts in large a forging flange, in order to increase the strength and rigidity. This paper seted up finite element models of inner forging flange and outer forging flange. At the same time the article established finite element models of the new-type forging flange and new-type rigid flange used in engineering.The comparative analysis of the results shows that, the new-type forging flanges greatly improved the strength and rigidity of the joints because of the reasonable stress distribution and constraints of deformation.

The Feasibility Study for New-Type Forging Flange of in Steel Tower

This paper presents a new-type forging flange used in steel transmission towers, that is to forge a same flange and same bolts in large a forging flange, in order to increase the strength and rigidity. This paper seted up finite element models of inner forging flange and outer forging flange. At the same time the article established finite element models of the new-type forging flange and new-type rigid flange used in engineering.The comparative analysis of the results shows that, the new-type forging flanges greatly improved the strength and rigidity of the joints because of the reasonable stress distribution and constraints of deformation.

Numerical Analysis on Residual-Stress in Direct Welded Joint of Long Span Transmission Steel Tower

The direct welding K-joint of steel tubular members is a kind of usual joint of Steel Tube Tower for Large Crossing of Transmission Lines. However, the dynamic stress-strain and the subsequent formation of residual stress produce in welding process,which are the main factors affecting the load carrying capacity, so it is necessary to research and analyze.Based on thermoelastic-plastic theory, the use of ANSYS Software thermal - structural coupling function and the indirect method, combined with element birth and death technology. The temperature field and stress field calculations have been residual stress and deformation distribution. Providing a reference for direct welding joint of steel tubular members of temperature field, stress and deformation are analizes.

Rain-Wind-Induced Analysis of Transmission Steel Tower

Rain-Wind-Induced Analysis of Transmission Steel Tower

Rain-Wind-Induced Analysis of Transmission Steel Tower

The paper established a finite element model of DZV674 linear tower (500 kV Shiyang - Wuyi transmission project) by ANSYS and studies its dynamic properties. Its first 10 order modes and natural vibration period are obtained. Based on the principle of Kaimal power spectrum and linear filtering method (AR) for simulation time-history of fluctuating wind speed, power spectrum simulation program of wind-speed is got by using Matlab. The rain load simulation is finished on the former simulation.The dynamic analysis of the transmission tower is calculated subject to wind load and rain-wind load.The results demonstrate that wind is the main design load in rain-wind-induced, but the effect of rain shouldn’t be neglected.

The Simplified Analytical Method for Computing Dynamic Characteristics of Transmission Steel Towers

Based on vibration theory, simplified analytical methods for computing the first natural vibration frequency and mode of transmission steel tower are investigated, which has improved the currently applied method. The method for frequency includes parameters of lumped mass such as tower head or cross arm, and can show the influence of section of tower main leg. The method for mode considers tower height, root space and head width. Examples of some typical transmission steel towers show that the dynamic characteristics computed with the simplified analytical methods are close to those of the Finite Element Method. Then the methods given in this paper are superior to the present methods used in engineering and have a better generality, which are suitable to different tower type structures.

Structural topology optimization of high-voltage transmission tower with discrete variables

In order to solve the structural optimization problem of long-span transmission tower, topology combination optimization (TCO) method and layer combination optimization (LCO) method based on discrete variables are presented, respectively. An adaptive genetic algorithm (AGA) is proposed as optimization algorithm. Four methods: cross-section size optimization (CSSO) method, shape combination optimization (SCO) method, the TCO method and the LCO method, are utilized to optimize the transmission steel tower, respectively. The topology optimization rules are presented for the TCO method, and the layering optimization rules are presented for the LCO method. A high-voltage steel tower is analyzed as a numerical example to illustrate the performance of the proposed methods. The simulation results demonstrate that the calculated results of both the proposed TCO method and the LCO method are obviously better than those of the CSSO method and the SCO method.

Some Advances in the Application of Weathering and Cold-Formed Steel in Transmission Tower

Application of weathering and cold-formed steel in transmission lines can reduce steel consumption and environmental pollution. Some advances in the studies on the weathering and cold-formed steel in transmission tower are introduced. Firstly, corrosion-resistant tests of weathering steel samples under different simulating technical atmospheres were carried out separately for 240 hours. It shows that the corrosion degree of joint samples is higher than that of single chip samples, and the corrosion-resistant performance of weathering steel is superior to common carbon steel. The corrosion-resistance of weathering steel meets with the requirement of transmission tower. Secondly, experiments and finite element analysis for cold-formed angles and a 220kV prototype tower were completed, and the stability coeffi-cient fitting curves as well as the modification formulas of slenderness ratio for cold-formed members were determined. According to the structural characteristics of transmission towers, four sections of cold-formed angles with different sections and slenderness ratios were selected in this study. The finite element model well predicted the buckling behav-iour of the cold-formed members. Ultimate loads calculating by the fitting curve were well agreed to the experimental values, especially for the members with small slenderness ratios. Weight of the cold-formed steel tower can be reduced by more than 5 percent after considering the strength enhancement. Cost of the weathering and cold-formed steel transmission tower is nearly equivalent to that of hot-rolled steel tower with hot galvanizing.

Structural analysis of guyed steel telecommunication towers for radio antennas

The usual structural analysis models for telecommunication and transmission steel tower design tend to assume a simple truss behaviour where all the steel connections are considered hinged. Despite this fact, the most commonly used tower geometries possess structural mechanisms that could compromise the assumed structural behaviour. A possible explanation for the structure stability is related to the connections semi-rigid response instead of the initially assumed pinned behaviour. This paper proposes an alternative structural analysis modelling strategy for guyed steel towers design, considering all the actual structural forces and moments, by using three-dimensional beam and truss finite elements. Comparisons of the above mentioned design models with a third alternative, that models the main structure and the bracing system with 3D beam finite elements, are made for three existing guyed steel telecommunication towers (50m, 70m and 90m high). The comparisons are initially based on the towers static and dynamic structural behaviour later to be followed by a linear buckling analysis to determine the influence of the various modelling strategies on the tower stability behaviour.

Probability density evolution analysis on dynamic response and reliability estimation of wind-excited transmission towers

Transmission tower is a vital component in electrical system. In order to accurately compute the dynamic response and reliability of transmission tower under the excitation of wind loading, a new method termed as probability density evolution method (PDEM) is introduced in the paper. The PDEM had been proved to be of high accuracy and efficiency in most kinds of stochastic structural analysis. Consequently, it is very hopeful for the above needs to apply the PDEM in dynamic response of wind-excited transmission towers. Meanwhile, this paper explores the wind stochastic field from stochastic Fourier spectrum. Based on this new viewpoint, the basic random parameters of the wind stochastic field, the roughness length z0 and the mean wind velocity at 10 m heigh U10, as well as their probability density functions, are investigated. A latticed steel transmission tower subject to wind loading is studied in detail. It is shown that not only the statistic quantities of the dynamic response, but also the instantaneous PDF of the response and the time varying reliability can be worked out by the proposed method. The results demonstrate that the PDEM is feasible and efficient in the dynamic response and reliability analysis of wind-excited transmission towers.

Steel transmission towers: some current topics

AbstractIn developed countries the environmental impact of the traditional transmission towers is no longer accepted. Currently available design solutions with acceptable appearance are not employed in the developing countries, mainly for cost reasons. In the developing countries the use of the traditional lattice transmission towers will continue employing steel angles. A comparison of the available design specifications for steel angles in transmission towers is presented.

Mechanical characteristics of line post type polymer insulation arm for 154 kV

This paper describes the mechanical characteristics of a 154 kV line post type polymer insulation arm that functions both as the steel arm and as the porcelain insulator of the currently used steel transmission towers. The 154 kV line post-type polymer insulation arm consists of polymer composite insulators, called units, that include two horizontal units with an open angle, to respond to a longitudinal load of 40 kN, and a suspension unit to respond to a vertical load. Its installation length is about 2.3 m. Samples of the insulation arm were installed at different places on an electric wire to form a truss structure and a frame structure, in order to examine their mechanical characteristics. For the truss structure, neither remarkable bending stress nor torsional stress was observed in the FRP core. The mechanical force design of the insulation arm can be evaluated in reference to the axial force of the FRP core only. The buckling coefficient, for evaluating the axial force of the insulation arm with the truss structure, was experimentally identified. Moreover, we were able to show that a static load test, for evaluating the mechanical force performance of the insulation arm against a longitudinal load, is more severe than an impact load test at the same longitudinal load. ©1998 Scripta Technica, Electr Eng Jpn, 126(2): 23–30, 1999

154kV用耐張形高分子絶縁アームの機械的特性

This paper describes the mechanical characteristics of a 154 kV line post type polymer insulation arm which has both the functions of a steel arm and a porcelain insulator of a presently used transmission steel tower. The 154 kV line post type polymer insulation arm consists of polymer composite insulators called units which include two horizontal units with an open angle for responding to a longitudinal load of 40 kN and a suspension unit for responding to a vertical load. Its installation length is about 2.3m. Samples of the insulation arm were installed at different places of an electric wire, to form a truss structure and a lahmen structure, for examining their mechanical characteristics. For the truss structure, it was clarified that neither remarkable bending stress nor torsional stress is generated in the FRP core, and that the mechanical force design of the insulation arm can be evaluated in reference to the axial force of the FRP core only. Furthermore, the buckling coefficient for evaluating the axial force of the insulation arm with the truss structure was experimentally identified. Moreover, it was clarified that a static load test for evaluating the mechanical force performance of the insulation arm against a longitudinal load is more severe than an impact load test at the same longitudinal load.

Ultimate Load Capacity of Single Steel Angles

The performance of steel angles is of great interest to the field of electrical transmission tower design. In a lattice structure, the most common type of member used is the single angle. In such an application, the angles are subjected to both tension and compression. The ultimate compressive load capacity of single steel angles subjected to eccentrically applied axial load is investigated in this paper. Seventy‐five full‐scale tests were done with data collected in the elastic, inelastic, and postbuckling regions of the member's performance. Test specimens were made of A36 steel angle sections connected to the end plate by bolts. The end plates were supported using a ball joint in an attempt to model end conditions that were unrestrained against rotation. The results of the tests were compared with predicted load capacities obtained from ASCE Manual 52 for the Design of Steel Transmission Towers (1988), which is the design guide for lattice steel transmission towers.

Behavior of Single‐Angle‐Compression Members

Published research indicates a lack of test results for single‐angle‐compression members with low slenderness ratio. In order to bridge this gap, 50 stocky single‐angle struts were tested as part of a truss. The test procedure and the results from these tests are given and discussed. The behavior of these members varies depending on their end connection detail, their slenderness ratio, and the width/thickness ratio of the angle leg. Six possible modes of failure were identified. The design rules for single‐angle‐compression members given in the AISC Design Specification, and the ASCE Manual 52 for the Design of Steel Transmission Towers are evaluated.

Effect of clamping pressure and joint geometry on corrosion induced bowing and distortion of bolted joints in weathering steel

Field experience with bare weathering steel indicates that bolted joints of sufficient stiffness will resist the distortion caused by the pressure of corrosion products forming within the joint. As a result of these observations, guidelines were previously written for the design of joints in transmission towers and similar structures. To gain more information on the pressure caused by corrosion-product formation, specimens were exposed to the atmosphere for test periods of up to seven years. The test specimens include stacks of Cor-Ten A steel (A242 Type 1) and carbon steel compressed together with spring washers and exposed at Monroeville, Pennsylvania, and the 800-foot lot, Kure Beach, North Carolina. Also, stacks of Cor-Ten A steel and carbon steel compressed together at lower pressures were exposed in Monroeville. Various joints of Cor-Ten B steel (A588 Grade A), including geometries that did and did not meet the previously developed guidelines, were exposed at both sites, along with test joints similar to those used on a transmission tower and comparison joints modified to meet the guidelines. The results of the stack tests indicate that at sufficiently high initial force no expansion of the stacks occurs, but at very low pressures there will be continuous expansion of stacks. Cor-Ten A steel was found to produce more expansion than carbon steel at similar initial pressures. Bolting, as specified, with A325 bolts minimized distortion caused by corrosion product pressure for a given joint design. At both sites, stiffer joints produced less distortion at free edges; however, joints that met the guidelines of free edge distance did not eliminate the distortion. Joint designs that met the guidelines developed very little bowing between bolts during exposure at either site. Also, tests of comparison specimens showed that the bowing between bolts in a transmission-tower joint with A325 bolts can be reduced significantly by simply reversing one set of details so that the spacing meets the guidelines. All observations confirm that the use of the previously published guidelines for the design of bolted joints in bare Cor-Ten steel transmission towers and similar structures will prevent excessive bowing and joint distortion.