Transmission Tower Research Articles

Vibration Control of a Wind-Excited Transmission Tower-Line System by Shape Memory Alloy Dampers.

To be typical electrical power infrastructures, high-rise tower-line systems are widely constructed for power transmission. These flexible tower structures commonly possess small damping and may suffer strong vibrations during external excitations. The control approaches based on various devices have been developed to protect transmission towers against strong vibrations, damages, and even failure. However, studies on the vibrant control of wind-excited tower-line systems equipped with SMA dampers have not yet been reported. To this end, the control approach for wind-excited tower-line systems using SMA dampers is conducted. The mechanical model of the tower-line system is established using Lagrange’s equations by considering the dynamic interaction between transmission lines and towers. The vibration control method using SMA dampers for the tower-line coupled system is proposed. The control efficacy is verified in both the time domain and the frequency domain. Detailed parametric studies are conducted to examine the effects of physical parameters of SMA dampers on structural responses and hysteresis loops. In addition, the structural energy responses are computed to examine the control performance.

Wind Field Characteristics of Butte and the Influence on the Wind-Induced Responses of Transmission Towers

The computational fluid dynamics (CFD) simulation on the butte was carried out to obtain the wind field characteristics for a specific mountain in the hilly area of eastern China. Then, the speed-up ratios of butte at each location distributed by height were calculated. The simulation results were compared with the specified value of mountain wind field acceleration ratio in various codes. The finite element model of the transmission tower line system is established by ANSYS, and the wind-induced vibration response of the structural system under the single mountain wind field is calculated, which is compared with the results of flat ground. The results show that the mountain will hinder the fluid passing through it. There is a deceleration zone in front of the mountain and a flow separation phenomenon behind the mountain. The speed-up ratios at the butte top where accelerating effect are the biggest among all positions of the butte. As the height increases, they approach 1. The speed-up ratios calculated by the Chinese code and the Australian code are linearly changing along the ridge of the butte and are symmetric at the windward side and leeward side. The biggest speed-up ratios are calculated by the Chinese code, and the smallest ratios are calculated by CFD. The wind-induced vibration response of the transmission tower line system is influenced by the wind speed-up ratios and reaches the maximum at the top of the butte. The simulation results at the windward side are close to the values calculated by the Australia code and the Euro code, but at the top and leeward side, they are far smaller than others.

Influence of Refined Wind Load Parameters and Wind-Loading Mode on Wind-Induced Responses of a Long Cross-Arm Angle-Steel Transmission Tower

This study aims to investigate refined wind load parameters on main rods and the influence of wind-loading mode on wind-induced responses of the angle-steel transmission tower. The wind load parameters discussed in this study include drag coefficients, wind load distribution factors and skewed wind load factors. To achieve the aim, wind tunnel tests were conducted to explore aerodynamic loads for integrated frame, single frame, and main rod models of cross-arm and tower body. The wind load parameters of the different models were investigated. In addition, a series of wind-induced vibration simulation was applied to examine the wind-induced responses of an ultra-high voltage (UHV) transmission tower with a long cross-arm under concentrated and distributed wind loads. The simulated results under the two types of wind loads were compared. The results show that the longitudinal drag coefficients of the main rods are smaller than the values of the integrated frame, and equivalent on average to the values of the single frame. The experimental shielding factor of the cross-arm is larger than those in different standards due to the joint drag effects of leeward, upper, and lower faces of the cross-arm in the wind tunnel test. The experimented shielding factor of the tower body is in line with those referring to the Chinese and AS/NZS standards, and slightly larger than those based on the British and JEC standards. The skewed wind load factors of the main rod models are quite different from other models for cross-arm and tower body. The wind-induced vibration simulation suggests that, the wind-loading mode has limited impact on the displacements, accelerations, and gust factors of the transmission tower, but significantly influences the maximum normal stresses (MNSs) of the rods’ cross-sections. The MNSs caused by the distributed wind loads are obviously greater than those caused by concentrated wind loads, especially for the rods at the two ends of the cross-arm.

Wind-Induced Response Control of a Television Transmission Tower by Piezoelectric Semi-Active Friction Dampers

To be a typical flexible structure with small damping, a high-rise television (TV) transmission tower is sensitive to wind excitations. The response control of TV transmission towers by semi-active friction dampers under strong external excitations is still very limited and the parametric study on control performance has not been systematically investigated. To this end, the semi-active control of a wind-excited TV transmission tower by piezoelectric friction dampers is conducted in this study. A fine finite element (FE) model of a real TV transmission tower is constructed and then a two-dimensional (2D) dynamic model is also established. The analytical model of a semi-active friction damper based on piezoelectric actuators is then established with damper stiffness considered. The equations of motion of the tower with friction dampers are then established. The local feedback control algorithm based on nonlinear Reid damping mechanisms is used to command piezoelectric friction dampers for wind-excited towers. A high-rise TV transmission tower in China is used to investigate the validity of the proposed semi-active control approach and compared with that of passive control. Furthermore, a detailed parametric investigation is conducted to examine the influence of gain coefficient, damper stiffness, hysteresis loops, damper force, and wind loading intensity on control efficacy. The analytical results indicate that piezoelectric friction dampers with optimal parameters are beneficial to the vibration mitigation of TV transmission towers under different wind loading intensities.

Quantification of the Seismic Behavior of a Steel Transmission Tower Subjected to Single and Repeated Seismic Excitations Using Vulnerability Function and Collapse Margin Ratio

Transmission towers are a vital lifeline for modern living and are crucial structures that must remain operational even after a seismic event. However, the towers are largely designed to withstand the effects of wind alone and not earthquakes, and the seismic influences on tower design and construction have hitherto been ignored. The purpose of this study was to evaluate the seismic performance of a latticed steel transmission tower-line system that is subjected to a variety of seismic situations (Far-Field, Near-Field and Repeated Earthquakes) using probabilistic vulnerability functions and Collapse Margin Ratios in accordance with FEMA-P695. Nonlinear Time History Analyses were performed by incorporating an array of 36 strong ground motions to develop the Incremental Dynamic Analysis and to generate the fragility functions for three performance limit states as referenced in FEMA 356. The results showed that the single event seismic performance of the tower is better than its performance after multiple ground motions owing to aftershock impact, while near-field excitations led to greater susceptibility and fragility than far-field scenarios. Thus, near-field ground motion is more harmful to the tower and could result in its failure or collapse with only a small reduction in damage relative to the impact of the aftershock.

Filament-wound glass-fibre reinforced polymer composites: Potential applications for cross arm structure in transmission towers

Filament-wound glass-fibre reinforced polymer composites: Potential applications for cross arm structure in transmission towers

Stochastic Analysis of Fatigue Damage of Transmission Tower-Line System Using Kriging and Bayesian Updated Probability Density Evolution Methods

The wind-induced fatigue damage is an important reason for the structural deterioration of transmission tower-line systems. The study of the fatigue damage of transmission towers is a basic requirement to ensure their normal service. To simulate the fatigue damage evolution occurring in the joints of the tower, a verified hybrid multiscale finite element (FE) model is first developed by concurrent modeling and substructuring techniques. Second, a fatigue damage model based on continuum damage mechanics is calibrated by conducting a fatigue crack initiation experiment and integrated into the FE material model by subroutines technique. Third, an improved Bayesian updated probability density evolution method (BUPDEM) with higher efficiency is proposed based on the Kriging method. Finally, based on the multiscale FE model and the damaged material model, the strategies for stochastic analysis of fatigue damage of transmission tower-line systems are proposed together with a numerical example for illustration. The results of the example show a good accuracy of the proposed BUPDEM.

Study on Wind Loads of Different Height Transmission Towers under Downbursts with Different Parameters

Disaster investigation results have shown that most wind-induced damage to transmission towers is related to downbursts. To clarify the effects of downbursts’ parameters on transmission towers with different heights, studies were conducted on five transmission towers with different diameters under static and moving downburst wind conditions. As a comparison, the responses of the towers under normal wind conditions were studied. The results showed that the effect of downbursts on the response of the transmission tower increased with the distance between the downburst center and the tower (r) when r < 1.0 Djet (Djet is the jet diameter of downburst) and then decreased when r > 1.0 Djet. The effects of jet diameter on the response of transmission towers with different tower heights were similar. As the jet diameter increased, the response of the tower continued growing until it reached a peak value and then steadily decreased soon thereafter. When the tower height was below 81.5 m, the wind load of the downburst on the transmission tower was significantly greater than that of the normal wind. As the tower height increased, the ratio of the transmission tower’s response under the two types of wind fields rapidly declined to about 0.91–1.01.

Structural Nonlinear Damage Identification Using the Residual Deviation Distance Conversion Index of the Time-Domain Model

Steel structures such as transmission towers may have cracks and other damages during the service period. When the structure vibrates, the cracks will open and close, which makes the structure have nonlinear characteristics of variant stiffness. In order to identify this type of nonlinear damage, a time-domain damage identification method based on the residual deviation distance (RDD) of the autoregressive conditional heteroskedasticity (ARCH) model is proposed. First, the basic theory of the ARCH model is introduced, and the methods of model order determination and parameter estimation are given. Then, the time-domain nonlinear damage characteristics are analyzed, and the second-order variance (SOV) index based on the ARCH model is introduced. Considering that both the ARCH model coefficient and the RDD contain nonlinear information, a conversion index is constructed using the Euclidean distance (ED) of the ARCH model coefficients before and after the damage. On this basis, an RDD conversion index is further proposed to improve the identification accuracy. Finally, a three-storey frame experiment and a complex transmission tower model experiment are used to verify the effectiveness of the proposed method. The experimental results show that the proposed RDD conversion index can better identify the location of structural damage, and the identification results of the RDD conversion index are obviously better than those of the SOV conversion index and the ED conversion index.

Review: Fire in Paradise: An American Tragedy, by Alastair Gee and Dani Anguiano

Review: Fire in Paradise: An American Tragedy, by Alastair Gee and Dani Anguiano

Investigation on aerodynamic characteristics for steel tubular cross-arms of transmission tower under skew wind

A study of the aerodynamic characteristics of steel tubular butterfly-shaped cross-arms in a transmission tower head under skew wind is presented. A wind tunnel test was conducted under skew wind by using a scaling model, and a numerical simulation was performed with a high-precision three-dimensional tower head model. The drag coefficient, skew wind load factor, and wind load distribution factor of the cross-arms obtained from the experiment and numerical simulation were identified and compared with those acquired from different codes. It is concluded that the indirect force measurement method was found to underestimate aerodynamic forces acting on windward cross-arms. For single cross-arm, the horizontal cross-arm showed stronger shielding effect than the inclined cross-arm. A fitting formula for the skew wind load factor of the cross-arm is proposed, and values obtained from it matched experimental and simulation data well. A comparison between calculated and measured wind load distribution factors showed that although longitudinal load distribution factors calculated with the Chinese standard (2018) were consistent with measured data, calculated transverse load distribution factors did not match measurements well. It is suggested that the effect of the transverse lift wind force should be considered in the calculation of wind load distribution factors.

Research about the on-line system for monitoring the geological subsidence of transmission tower based on high-precision positioning of Beidou

This article proposes an innovative method to achieve Beidou high-precision positioning. Then, the online monitoring physical information system of transmission pole tower is constructed with Beidou high precision positioning and inclination measurement information as the data source. The perception layer is Beidou high-precision positioning sensor and inclination measurement sensor, the data transmission layer is the way of combining wireless private network with wired private network, and the application control layer is the data processing center, which presents the results of analyzing sensor data to the user in a visual interface. The system can send an early warning message to the user at the very early stage of the deformation of the transmission pole tower, So that the user can take measures in time.

A Review on Analysis and Design of Transmission Tower

Abstract: The structural planning and design process involves not just imagination and intellectual thinking, but also a thorough understanding of structural engineering science, as well as practical knowledge of modern design codes and bye laws, as well as a wealth of experience, intuition, and judgement. The goal of standards is to ensure and improve the safety of people and the environment. Tower is a steel structure developed by maintaining a delicate balance between economics and security. The transmission tower, in particular in order to establish a comfortable environment, the first thing that must be considered is safety. For the benefit of the beings in the immediate vicinity As a result, the transmission tower must be built and maintained properly. Therefore, the transmission tower has to be constructed with a proper care and maintenance. By normal designing and analysis of the tower it requires a more time so we adopt different softwares to obtain the results. So, analysis and designing of a transmission tower is done by “STAAD.Pro V8i”. Keywords: Transmission Line Tower, Analysis, Design, Staad-pro.

Frequency Domain Analysis of Alongwind Response and Study of Wind Loads for Transmission Tower Subjected to Downbursts

Downburst is one of the high-intensity winds that cause transmission tower failures. The regulations of transmission tower-line systems under downburst wind loads cannot meet the design requirements at present. In this paper, the calculation formulas of the background and resonant components of transmission tower under downburst wind loads are obtained, based on the modal analysis theory of non-stationary wind for the single-degree-of-freedom system in the frequency domain. The effects of structural dynamic characteristics, damping ratio, and mean wind speed vertical profile on dynamic effect on structural response are discussed. Then the equivalent static wind load (ESWL) is obtained according to the maximum response and compared with the finite element method (FEM) in the time domain. Applications of these formulas are addressed to the cases from the empirical model of Holmes and field record of a rear flank downdraft (RFD). The results show that the maximum responses obtained by the current formulas match well with those from the modal decomposition method and dynamic analysis with FEM. The internal forces of tower members calculated by ESWL based on maximum response are closer to the results from FEM than those calculated by downburst loads recommended in ASCE guidelines. The presented framework can be used to assist the wind-resistant design of transmission towers considering downburst wind load.

Hierarchical Transmission Tower Detection from High-Resolution SAR Image

The small scale of transmission towers and the environmental diversity around their situations make their detection in Synthetic Aperture Radar (SAR) images a challenging task. This paper presents a new hierarchical detection algorithm for transmission towers. First, Signal-to-Clutter Ratios (SCRs) of pixels are calculated. Afterwards, a SCR threshold is set. Since transmission towers possess strong scattering characteristics, pixels with SCRs above the threshold are considered as potential transmission tower pixels. Second, spatial densities of potential transmission tower pixels are calculated. According to the aggregation characteristics of transmission tower pixels, some potential transmission tower pixels with small spatial densities are removed. The remained potential transmission tower pixels are considered as candidate transmission tower pixels. The candidate transmission tower pixels are grouped by the nearest neighbour scheme such that in each group the distance between pixels is under a given threshold. Thus, each of the groups is viewed as a quasi-transmission tower. Convex-hulls of quasi-transmission towers are built, and then Minimum Bounding Rectangle (MBR) for each convex-hull is generated. According to the rectangle aspect ratios of MBRs, the real transmission towers are extracted. C-band HH-polarization GaoFen-3 (GF-3) amplitude images are used for experiments and four of the most popular transmission tower detection algorithms are selected as comparing algorithms to validate the proposed algorithms. The detection performance of transmission towers is evaluated with detection rate and quality factor. Experimental results verify that the proposed algorithm can efficiently and accurately detect transmission towers while maintaining the transmission tower geometry to a certain extent, which indicates that the proposed algorithm is efficient and promising.

Stability design of axially loaded stringer-stiffened moderately-thick cylindrical shells in steel tubular transmission towers

Steel tubes internally stiffened with stringers are promising structural members of long-span transmission towers, but the study on its stability design remains insufficient. To gain insight into the inelastic buckling behavior of the tubes, compressive tests of 33 specimens are conducted. Using the test results, finite element (FE) models are first established and validated. Then, the adequacy of an equation in the literature for predicting elastic buckling stress is investigated via FE analysis (FEA), and a correction coefficient is proposed to diminish the discrepancy between the predicted and the FEA results. Afterward, the FE-based inelastic analysis is performed, wherein the initial imperfections including the local dimples, out-of-roundness, and residual stress were considered in the FE models. The effects of the imperfections on the ultimate strength are investigated. Further, the effects of the length to diameter ratio, diameter to wall thickness ratio, and stringer’s number and size on the reduction factor are investigated. Comparatively, the effect of the diameter to wall thickness ratio on the reduction factor is the most significant. The test and FEA results show that the axial ultimate strength is insusceptible to the initial imperfections. In addition, to achieve an efficient design, the restriction of the height to thickness ratio of stringers is suggested to avoid the stringer instability. Finally, the corresponding formulas for design are presented.

A Transmission Tower Tilt State Assessment Approach Based on Dense Point Cloud from UAV-Based LiDAR

Transmission towers are easily affected by various meteorological and geological disasters. In this paper, a transmission tower tilt state assessment approach—based on high precision and dense point cloud from UAV LiDAR—was proposed. First, the transmission tower point cloud was rapidly located and extracted from the 3D point cloud obtained by UAV-LiDAR line patrol. A robust histogram local extremum extraction method with additional constraints was proposed to achieve adaptive segmentation of the tower head and tower body point cloud. Second, an accurate and efficient extraction and simplification strategy of the contour of the feature plane point cloud was proposed. The central axis of the tower was constrained by the contour of the feature plane through the four-prism structure to calculate the tilt angle of the tower and evaluate the state of the tower. Finally, the point cloud of tower head from UAV-based LiDAR was accurately matched with the designed tower head model from database, and a tower head state evaluation model based on matching offset parameters was proposed to evaluate tower head tilt state. The experimental results of simulation and measured data showed that the calculation accuracy of the tilt parameters of transmission tower body was better than 0.5 degrees, that the proposed method can effectively evaluate the risk of tower head with complex structure, and improve the rapid and mass intelligent perception level of the risk state of the transmission line tower, which has a wide prospects for application.

Operation Status Monitoring of Transmission Tower in Power System based on Data Fusion

This paper studies the application of data fusion technology in power system to solve some difficult problems in this complex energy system. A transmission tower identification and bird nest detection method based on corner, line, color and shape features is proposed. Through LSD (Line Segment Detection) and Harris corner detection method, the straight line segment and corner point in the image are extracted respectively. Combined with triangle method, the actual tilt angle of tower is measured; According to the nesting rule of birds in transmission towers, the basic unit segmentation algorithm of transmission towers is proposed, and the basic unit segmentation of transmission towers is realized by using the local maximum of the target pixel row statistical histogram. The algorithm proposed in this paper can effectively solve the problems of on-line measurement of tilt angle of transmission tower and on-line detection of bird's nest, which will lay a theoretical foundation for on-line monitoring of transmission tower status.

Fiber element modeling of circular double-skin concrete-filled stainless-carbon steel tubular columns under axial load and bending

Circular concrete-filled double-skin steel tubular (CFDST) columns with external stainless-steel are high-performance composite columns that have potential applications in civil construction including the construction of offshore structures, bridge piers, and transmission towers. Reflecting the limited research performed on investigating their mechanical performance, this study develops a computationally efficient fiber model to simulate the responses of short and slender beam-columns accounting for the influences of material and geometric nonlinearities. Accurate material laws of stainless steel, carbon steel, and confined concrete are implemented in the mathematical modeling scheme developed. A new solution algorithm based on the Regula-Falsi method is developed to maintain the equilibrium condition. The independent test results of short and slender CFDST beam-column are utilized to validate the accuracy of the theoretical solutions. The influences of various column parameters are studied on the load-axial strain [Formula: see text] curves, load-lateral deflection [Formula: see text] curves, column strength curves, and interaction curves of CFDST columns. Design formulas are suggested for designing short and beam-columns and validated against the numerical results. The computational model is found to be capable of simulating the responses of CFDST short and slender columns reasonably well. Parametric studies show that the consideration of the concrete confinement is important for the accuracy of the prediction of their mechanical responses. Furthermore, high-strength concrete can be utilized to enhance their load-carrying capacity particularly for short and intermediate slender beam-columns. The strengths of CFDST columns computed by the suggested design model are in good agreement with the test and numerical results.

Analysis of transmission line tower subjected to wind loading

Heavy electrical transmission lines are carried by transmission line towers at a suitable and safe height above the ground. These towers must bear its own weight and distress created by transmission line wires. Despite that it should also survive against all-natural factors such as fierce winds, earthquakes, and snow loads. For a safe and cost-effective design, transmission line towers must fulfil both all structural and electrical standards. This manuscript discusses the numerous types of transmission towers and their configurations as per the Indian Standard IS 802:2015. Further this paper contains the details of the design and simulation of 500 kV double circuit conductors, which is one of the commonly adopted transmission towers. For the said purpose STAAD Pro. V8i Select Series, computation tool has been adopted which is based on the finite element computations. During computational analysis wind load, structural dead load, and seismic load according to IS:1893:2002 (part 1) has been considered. The clearance from the ground (h1), the lowermost conductor wire's maximum sag (h2), conductor wires' vertical spacing (h3), and the distance between the earth wire and the highest conductor wire in terms of vertical distance (h3), all are added up to get the final height of transmission tower which is 43.5 m. The earth wire is also known as the ground wire, is always sited at the very topmost of the steel tower. It features an 8.32 m square base with a width of 8.32 m. The three major phases of the fragility analysis procedure for transmission towers under wind loading are as follows: Nonlinear dynamic analysis, regression analysis, and creation of Wind loadings and uncertainty models. After that, the random variables and probability distributions corresponding to them are examined. Finally, based on the commonly adopted transmission towers a hypothetical case study has been conducted for a real-world functioning tower which is subjected to wind loading along with other critical loadings. The obtained result shows that if we are considering a larger number of uncertain characteristics, then it causes the fragility curve to become more disperse, and further it is observed that the angle of attack for the wind load has a substantial effect on the fragility curve.