Steel Lattice Towers Research Articles

Strain distribution and failure modes of steel lattice tower gusset plates as a function of their geometry

Steel gusset plates (SGP) are structural elements that connect and transfer loads among various members, such as beams, columns, and trusses, in steel structures like buildings, bridges, and lattice towers. Their geometry significantly affects structural performance, requiring a thorough analysis of strain distribution and failure modes to ensure the integrity and safety of structural systems. However, the design and evaluation of lattice tower gusset plates (LTGP) in particular, present challenges due to complex geometries and the lack of universally accepted design methods. This paper presents a comprehensive comparative study of the strain distribution and failure modes of LTGP across different geometries. Experimental tests were conducted using Digital Image Correlation (DIC) on specimens with different configurations, each featuring a single row of bolts. The force–displacement curves and strain distributions were analyzed to determine the influence of gusset plate width, end-distance, and the number of bolts on their behavior. The study compares the experimental data with the prescriptions of design standards. Additionally, it presents numerical modeling of LTGP connections using finite element analysis in ANSYS®, with validation against experimental results confirming model accuracy. The research program is further complemented by a parametric study examining the effects of end-distance, plate width, and bolt spacing on the ultimate strength of LTGP.

История башенных сооружений: прошлое и настоящее

Purpose: to make an analytical review of the existing literature and systematization by purpose in various eras of existence for tower structures, as well as to highlight the achievements of mankind in the development of steel lattice towers used as supports for radio-electronic equipment over the past 130 years. Methods: the method of analytical review of the evolution of tower structures from the initial stages of the development of society was used with a description of the vectors of development and expediency of the construction of these structures, followed by the conclusion of modern trends, especially aimed at the development of steel tower structures used for the support of radio equipment. Results: various review and analytical studies have been analyzed, which allow us to draw conclusions about the use of structures in the past and identify the global vector of development of tower structures in various cultures; a comprehensive assessment, analysis and formalization of information presented in the form of a concise overview was carried out, in addition, a comprehensive analysis of the development of steel lattice towers in domestic science of the USSR period was carried out, and modern trends in the development of steel lattice towers were reflected. The result of this work is a generalization of world and national research aimed at accumulating knowledge about the origin and vectors of future trends in the development of tower structures. Practical significance: the accumulation and analysis of existing knowledge about the history of the development of tower structures and their purpose in human economic and household activities in various epochs has been carried out. A systematic series of modern trends in the development of steel tower structures used as supports for radio-technical equipment is presented in order to determine the direction of future research.

Design of Modular High Temperature Sodium Solar Collection Subsystems

Optimised designs of 11.7MWth solar collection subsystem modules based on high temperature (740°C) sodium central receivers are investigated. Billboard and cavity receivers mounted on steel lattice towers are considered, and radially staggered and Cartesian heliostat field layouts are compared. A billboard receiver paired with a Cartesian heliostat field layout was found to give the overall lowest levelised cost of heat (LCOH), albeit with a significantly taller tower compared to using a radially staggered heliostat field layout.

Component-based modelling of single-leg bolted steel angle connections at elevated temperatures

As a vital part of contemporary society, steel lattice transmission towers and communication towers play an important role in the power transmission grid and telecommunication, respectively. Being often located in rural areas, they are prone to bushfire attacks due to heatwaves and droughts, which are becoming increasingly commonplace. However, unlike the steel members found in a lattice tower, the behaviour and material properties of which at elevated temperatures have been comprehensively studied and codified in design standards, the semi-rigid behaviour of the bolted connection between such members at elevated temperatures has not been investigated thoroughly. Therefore, this paper aims to investigate both the axial and rotational behaviour of single-leg bolted steel angle connections at both ambient and elevated temperatures. A theoretical model using the component method is firstly proposed to model the axial load-slip behaviour incorporating the temperature increase, with the effects of the bolt shear, plate bearing, friction between clamped members, bolt slip, and member elongation being considered. Once the axial load-slip model is proposed, the component-based model for describing the moment-rotation behaviour of the bolted connection is derived based on the load-deformation relations of individual bolts in the bolt group. The reliability of the theoretical model is then validated by modelling the connection behaviour obtained from previous connection test results. A three-dimensional finite element model is also constructed using ABAQUS software to further validate the accuracy of the proposed theoretical model for predicting the axial and rotational behaviour of single-leg bolted angle connections at elevated temperatures. It is demonstrated that the proposed component-based theoretical model for the bolted angle connection accounting for axial and rotational semi-rigidity as well as temperature elevation is capable of effectively capturing the load-deformation relationship for the single-leg bolted angle steel connections, and would be applicable to the study of steel lattice towers under bushfire attack.

The use of S460 steel grade in the construction of OHL transmission towers

AbstractThe article describes structural solutions and specialised testing of innovative steel lattice towers intended for 400 kV overhead line (OHL). A unique aspect of the preformed research is the use of S460 steel grade in the structure of such transmission towers. This new series of towers was developed in reference to current EN 50341‐2‐22:2016 standard that introduces higher safety standards for OHL towers. A full‐scale prototype was developed and analysed, where the verification of the standard load‐bearing capacity was done and proceeded by the destructive test in order to determine the ultimate capacity of the new tower typology. The article presents the obtained results, the justification for the use of S460 steel grade and a comparative analysis with the classical engineering procedures. A good agreement between a theoretical model and the test results is demonstrated.

Re-design and Analysis of 220 KV Multi – Circuit Transmission Tower

A transmission tower or power tower is a tall structure, typically a steel lattice tower, which is employed to support an overhead power line. Economic losses will be the consequence of any transmission line system failure that disrupts the energy supply. This article describes the MD (300-600 Dev./D.E.-00) NT +9M body extension redesign and structural analysis for a 220 kV multi-circuit transmission tower. This paper pertains to the failure transmission tower structure and implementation of the failure structure through the use of CAD, ANSYS, and analytical and experimental testing. Experimental testing in 2018 resulted in the failure of this MD type transmission tower. The research conducted in this paper is the first to analyse and track the progression of failure of a segment of a transmission structure, in contrast to previous studies that have examined the behaviour and failure of a single tower. To accomplish this, a distinctive CAD/numerical model is developed in this paper. This article will provide a comprehensive discussion of the formulation and validation of the various components of this CAD/numerical model, which are reported in various sections of paper. This study helps build transmission towers to handle rising voltage and power demands in electrical networks.

Construction and implementation of a mathematical model for damping vibrations of high-rise buildings and structures using reactive dampers

The problem of developing a computational model of an active vibration damping system of a high-rise building during an earthquake using a simple and suitable calculation scheme for high-rise buildings is considered. An approximate finite element model is presented that adequately describes the dynamic characteristics of a high-rise building. A mathematical model of a steel lattice tower is considered as an example. The ratio equations and displacement difference equations describing the behavior of reactive dampers installed in the tower are presented. An approach to optimizing the parameters of relative motion is presented. The calculation of vibration damping of a tower with reactive dampers installed on one and two levels is shown. The classification of forces with different physical properties and affecting the movement of mechanical systems is presented.

Development of seismic fragilities for a base station steel lattice cellular tower

A large portion of the country of Turkey is located in a very high seismic region known as a first-degree earthquake zone where earthquakes occur frequently. Earthquakes result in damage to infrastructure including base station towers and subsequently failure of mobile communication networks. The loss of functionality of mobile communication networks following an earthquake has a direct impact on emergency response and both short and long-term recovery phases. Understanding both these phases requires systematic modeling of infrastructure components, which rely on fragility curves representing the probabilistic relationship between seismic intensity and damage. This study focuses on the development of damage fragility curves (fragilities) for an archetypical mobile cellular tower, namely a 55 m tall steel lattice tower (SLT) used in base station towers in Turkey. Nonlinear time history analysis was performed using a robust suite of far field ground motion records to model the performance of the archetype tower and develop damage fragilities for five specific damage states which were defined in terms of likely performance: damage state 0 (no damage), damage state 1 (uninterrupted communication), damage state 2 (communication interruption), damage state 3 (communication failure), damage state 4 (structural failure). While fragility curve has been developed for lattice towers of different types and sizes in the literature, there is no specific study for 55 m SLT and the novelty of this study is that the resulting SLT archetype fragilities can serve as a benchmark dataset for use in community-level risk and resilience analyses to improve response and recovery planning following earthquakes.

Finite Element Modelling of a Transmission Steel Lattice Tower Based on LiDAR Point Cloud Data

AbstractThis article presents an innovative modelling method, which can serve as a set of guidelines for future applications related to point cloud data processing of steel lattice structures used for FEA modelling purposes. This method is fully automated, resulting in repeatable results and saving time required for manual data processing. The study investigated two types of input point cloud data, aerial and terrestrial, and compared the resulting model to an idealized model based on design documentation. Results showed that the LiDAR point cloud data is a good source of information for reconstructing a geometric CAD model and can be implemented in FEA. The impact of point cloud data usage for FEA modelling is demonstrated by investigating differences between FEA results of the point cloud‐based and idealized models, allowing for an understanding of the influence of real‐life imperfections on force redistribution across the analyzed structure and ultimate forces reached by members loaded in compression. This modelling method and analysis can serve as guidelines for future applications related to point cloud data pro‐cessing of steel lattice structures used for FEA modelling purposes.

Performance‐based wind engineering assessment of a telecommunication mast

AbstractThe study adopts the Performance‐Based Design concept to analyse the structural behaviour of a telecommunication steel lattice tower equipped with wind speed and strain sensors located in Central Hungary. Bayesian updating is utilised to combine the information from the relatively short measurement collected at the site with a longer dataset from a neighbouring measurement location. A finite element model is developed to analyse the performance of the tower in probabilistic terms using Monte Carlo simulation with Latin hypercube method. The probability of failure is assessed for both serviceability and ultimate limit state verifications. This study aims to demonstrate the potential of combining the performance‐based wind design framework and monitoring system.

INFLUENCE OF BOLTED SPLICE CONNECTIONS ON THE GLOBAL BEHAVIOUR OF STEEL LATTICE TELECOMMUNICATION TOWERS

The bolted joints in the leg and the bracing members of the lattice transmission towers are always subjected to predominant axial forces, which will cause joint slip that greatly affects the global be-haviour of the whole structure. The paper shows the results of the numerical modelling of the re-sponse of the steel lattice communication tower, with height h = 40.5 m located in Rzeszów. A comparison was made of five tower models, differing in the characteristics of the joint force-elongation relationship, including stiffness of the components and also joint slippage, coming from Category A joints. The paper presents the difference in displacements and rotations of chosen tower panels, internal forces in leg members, as well as in the fundamental flexural frequency obtained without considering the force-displacement characteristic and with four different ways of modelling of joints behaviour

Analysis of the stability behavior of cross bracings in transmission towers based on experiments and numerical simulations

Angle steel towers are widely used in various transmission lines owing to their convenient connections, easy availability, simple production processes, and high efficiencies. Cross bracings play an important role in resisting wire tension, wind, and snow loads as the main support components ensuring the stability of an angled steel tower. Thus, an analysis of the buckling resistance of cross bracings is significant in improving the bearing capacity of transmission towers. In this study, full-scale tests of equal-leg and unequal-leg angles in planar tower sections were conducted. The influence of the axial force ratio on the stability of a cross bracing was studied based on numerical simulations and compared with the current codes. The results revealed that the failure mode of an equal-leg angle cross bracing was always out-of-plane buckling, whereas the final failure mode of an unequal-leg angle steel cross bracing could be out-of-plane buckling or both out-of-plane and in-plane co-buckling. With an increase in the axial force ratio, the buckling resistance of the cross bracing decreased rapidly, with over 40% decline in the amplitude. The buckling resistance of the unequal-leg angle was approximately 20% higher than that of the equal-leg angle at all axial force ratios. Compared with the current codes for tower structures, we discovered that the code values and finite-element results were considerably different. Notably, the calculation methods of ASCE 10-15 and EN1993-3-1 neglect the variation in the effective length with the axial force ratio. Although DL/T 5154-2012 considers the effect of the axial force ratio, the values are all greater than the finite-element results. The findings of this study can help elucidate the cross bracing stability in angle steel lattice towers.

Estimation of dynamic wind forces on a steel lattice tower based on generalized wind force spectra

This article presents a method for estimating dynamic wind forces on a steel lattice tower. The spectra of local wind forces are derived based on generalized wind force spectra, which have considered the coherence between different axial wind forces under the skewed wind. With the established cross-power spectral density (PSD) matrix of wind forces, the fluctuating wind forces can be simulated in the time domain using the harmony superposition method. The wind tunnel experiments on a typical transmission steel lattice tower are introduced. Using the test data, the coherence of wind forces on different body axes is analyzed, and the corresponding empirical function is fitted. With the empirical PSDs of the generalized forces obtained in the previous wind tunnel experiments, the dynamic wind forces on the transmission tower are simulated in target wind environments. The dynamic responses of the tower are calculated under the estimated wind forces and compared with the measurements in the aeroelastic wind tunnel experiments. Results reveal that the proposed approach to estimating distributed dynamic wind forces on a steel lattice tower performs effectively.

Reconstruction of dynamic wind forces on a transmission steel lattice tower using aeroelastic wind tunnel test data

This article reports a methodology for estimating dynamic wind forces on a steel lattice tower by using limited structural displacements. The methodology involves combining the modal state-space system model and a Kalman filter-based algorithm. For convenient application, the equivalent concentrated forces are taken as the inversing objects, representing the distributed wind forces on a lattice tower. The corresponding equivalent cantilever model of the lattice tower is utilized, in which the stiffness matrix is estimated by a modified flexibility approach. Based on the modal superposition principle, the dynamic wind forces in physical space are reconstructed using the identified input modal wind forces. The scheme of the dynamic wind force reconstruction is designed in detail. A typical transmission steel lattice tower is considered, and the aeroelastic wind tunnel experiments are performed. The performance and effectiveness of the proposed scheme are investigated based on numerical simulations and wind tunnel tests. It is indicated that the reconstructed dynamic wind forces can produce equivalent dynamic responses to the actual. Besides, it performs robustly on the effect of measurement noise. Although the modal force identification is sensitive to the modeling error of structural natural frequency, the effect can be judged according to the change in the power spectra of the identified modal force. The proposed inversing approach can serve as a useful tool to evaluate dynamic wind forces on steel lattice towers with limited response measurements.

Reliability Parameter Evaluation of Wind Turbine Based on Minimization of Dynamc Loads Acting on Power Plant Structural Components

An evaluation method of minimization of dynamic loads of big wind wheels with horizontal axis of rotation by replacing a steel lattice tower with a concrete tube was considered as the basic approach to obtain the calculated data of wind power plant reliability evaluation parameters based on dynamic loads minimization acting on power plant structural components. A certain degree of dynamic load minimization acting on vanes based on duly system preparation for external disturbances due to prediction of wind speed and power of electric energy input resulted in load minimization per a vane by 20 %. The problem of parameter reliability evaluation of wind power plant based on minimization of dynamic loads acting on power plant vanes under the condition of duly system preparation for external disturbances was solved enabling increasing of run-to-failure mean time by 8 %. Evaluation analysis of dynamic load minimization acting on power plant structural elements based on optimization model that accounts drive loading conditions at various operation conditions of wind electrical power plant was performed, as the result of rotor system load (“wind wheel - the driving gear”, “gear - generator”) decrease constitutes 20 %. The problem of reliability evaluation parameters of wind electric power plant based on dynamic load minimization acting on power plant structural elements was solved by implementing optimization model of drive loading conditions at various operational conditions of wind electric power plant increasing the rotor system (“wind wheel - driving gear”; “gear - generator”) run-to-failure mean time by 18 %. It was found that the proposed methods of efficiency improvement of wind power plant control enable to increase the operation lifecycle of wind power plant by 26 %.

Load-slip behaviour of single-leg bolted angle steel connections at elevated temperatures

Steel lattice transmission towers and communication towers are vital infrastructure components of power grid and telecommunication systems, respectively. They are usually located in rural or urban wildland areas and can be prone to bushfires or wildland fires in the current climate of heatwaves and droughts. However, an understanding of the resilience of steel lattice towers in fire has not received due attention. Such lattice structures are commonly made from steel angle members with bolted connections in which slippage might occur inevitably due to relatively larger size of bolt holes for erection purpose. Therefore, this paper investigates the axial load-slip behaviour of the single-leg bolted angle steel connections at elevated temperatures for the steel lattice structures. A three-dimensional finite element model is developed for the investigation by using ABAQUS software. Temperature-dependent material nonlinearities and the interaction of structural components at elevated temperatures are taken into account in the model. An effective approach of generating bolt pretension and the quasi-static analysis method using the dynamic explicit procedure are adopted for the analysis. The reliability of the developed finite element model is validated by comparing its predictions with available experimental results reported in the open literature. By using the validated finite element model, extensive parametric studies are conducted to elucidate the effects of the change in the angle section dimension, the direction of applied loading, the grade, size and number of the bolts on the load-slip responses of the connections at elevated temperatures. A simplified theoretical model in component formulation form is proposed and verified for predicting the axial load-slip curves of the single-leg bolted angle steel connections at elevated temperatures and would be applicable to advanced analysis of steel lattice structures considering joint slip.

Mechanical behavior of steel transmission tower legs reinforced with innovative clamp under eccentric compression

Most steel lattice towers have been in service for over 20 years in China. Many existing towers are now required to carry higher loads than those for which they were originally designed because of new heavier devices and revised wind design codes. An effective way of increasing the carrying capacity of a tower is to reinforce its core leg members by attaching additional elements with bolted connections. However, the reinforcing methods proposed in previous studies require drilling into the core leg members, which results in considerable construction inconvenience. Therefore, an innovative clamp-type (IC) method is proposed herein. To evaluate the effectiveness of the proposed IC method, this paper presents results from 90 new cases comprising 10 eccentric compression tests and 80 finite element (FE) analyses of the load capacity of starred compound members, by varying the interconnector arrangement, form, spacing and bolt row, and slenderness ratio of the compound members. The experimental results show that the compound members with the IC interconnector mainly exhibit buckling failure in the core member. However, in the case of instability about the imaginary axis, the bearing capacity of the compound members with the IC interconnector is approximately 41%–62% higher than that of the single angle member. A nonlinear FE model is developed, which considers the material, contact non-linearity, and geometric imperfections. The FE model is validated against the experimental test results, which show good agreement, both in terms of failure mode and load–displacement curve. The validated FE model is used to conduct a parametric analysis to investigate the effect of slenderness ratio on the bearing capacity of the compound member. Four width–thickness ratios of connected angles and five IC interconnector spacings are considered in the parametric study. The bearing capacity values obtained from the experimental tests and FE analyses are used to assess the performance of current design guidelines. The results show that the current DL/T 5154-2012 code is too conservative by an average value of 30%. Therefore, a kd coefficient method is proposed to improve the prediction accuracy of the bearing capacity, and the method is verified against the FE and test results of the compound member with the IC interconnector under eccentric compression tests.

Determining the Optimal Scalar Intensity Measure of Floor Communication Towers

Various structural types and ground motion characteristics lead to distinct intensity measures of structural seismic performance. For the lattice high-rise steel structure of communication towers, determining the intensity measures to adjust ground motion is critical. Additionally, a crucial problem is whether the ground motion intensity parameters of pulse-like ground motion and ordinary ground motion are consistent. In this study, a standard floor four-leg angle steeled communication tower was considered the study object, and 50 pulse-like ground motions and 50 ordinary ground motions were identified to form a pulse-like ground motion set and ordinary ground motion set, respectively. For comparative analyses, 15 ground motion parameters, including amplitude, spectrum, duration, and energy parameters, were selected. The results revealed that for the lattice towers, such as communication tower, under the action of pulse-like ground motion or ordinary ground motion, efficiency, practicability, and sufficiency should be considered. Furthermore, the most suitable intensity measure was the spectral acceleration corresponding to the natural period of the tower. This study provides a basis for selecting the ground motion for dynamic time history analysis of the lattice steel tower.

Wind-induced fatigue analysis of high-rise guyed lattice steel towers

Wind-induced fatigue is a major issue for the design of slender high-rise structures. However, there are still few studies focused on this topic, resulting in a lack of practical design procedures for this type of structures. This paper aims to fill this gap by presenting a complete and practical methodology for the wind-induced fatigue life assessment of high-rise towers and its application to a 120 m cable-stayed steel tower composed by a modular lattice. The wind actions were considered as the sum of the quasi-static component according to international codes and a numerically generated, trough an ergodic stochastic process, turbulent component which is based on the Kaimal wind spectrum. Real wind measurements were also taken for a period of 15 months on a nearby MET station which, when compared with the normative scenario, proved to be much less conservative and were not used for the safety analysis. The wind velocities were used as inputs for a nonlinear dynamic analysis from which stress time histories were derived for 10 potentially critical structural details. The damage in each detail was computed through the application of the Rainflow counting algorithm and Palmgren-Miner’s damage accumulation law, indicating the connection region between the modules as the critical detail with respect to fatigue damage.

Weight optimization of steel lattice transmission towers based on Differential Evolution and machine learning classification technique

Transmission towers are tall structures used to support overhead power lines. They play an important role in the electrical grids. There are several types of transmission towers in which lattice towers are the most common type. Designing steel lattice transmission towers is a challenging task for structural engineers due to a large number of members. Therefore, discovering effective ways to design lattice towers has attracted the interest of researchers. This paper presents a method that integrates Differential Evolution (DE), a powerful optimization algorithm, and a machine learning classification model to minimize the weight of steel lattice towers. A classification model based on the Adaptive Boosting algorithm is developed in order to eliminate unpromising candidates during the optimization process. A feature handling technique is also introduced to improve the model quality. An illustrated example of a 160-bar tower is conducted to demonstrate the efficiency of the proposed method. The results show that the application of the Adaptive Boosting model saves about 38% of the structural analyses. As a result, the proposed method is 1.5 times faster than the original DE algorithm. In comparison with other algorithms, the proposed method obtains the same optimal weight with the least number of structural analyses.