Guyed Mast Research Articles

Study on the response of a super high-rise guyed mast under synoptic winds based on aeroelastic wind tunnel test

The present study examines the aeroelastic properties and wind-induced displacement response of a super high-rise guyed mast, through a series of aeroelastic model wind tunnel tests. The simulated guyed mast with a prototype height of 356 m is a representative guyed mast in Asia and has not been reported in previous literature. The impact of wind speed on both the alongwind and crosswind displacement response and the Gaussianity along the heights of the aeroelastic model is then investigated using wind tunnel measurements. Furthermore, the characteristics of mode participation and the effect of wind velocity on this phenomenon, as well as the contributions of background and resonant dynamic response, are examined in both the alongwind and crosswind directions. The results indicate that the guyed mast displacement distributions along the heights are different from those observed in the conventional self-standing lattice towers. The characteristics of multi-mode participation are notable. As wind speeds increase, the alongwind resonant response peaks shift to lower frequencies and become less distinct. In contrast, the crosswind response peaks show no significant variation. The contributions of background and resonant response along the heights, respectively, exhibit a decreasing and an increasing tendency, and wind speed exerts an influence on these phenomena.

Comparative analysis of a tubular masts with a 80 m high

The article presents the structures of guyed masts that are used as supporting structures. Masts of this type consist of a vertical shaft connected to the foundation by means of guy wires. The work focuses on two designs of measuring masts with an identical shaft, but with a different number of guy ropes at the level. The static analysis was carried out taking into account the geometric nonlinearity of the guy wires and environmental loads. The results of the analysis indicate how the static scheme of the structure affects its behavior. The conclusions from the work are applicable to specific designs of tubular masts, but may be an inspiration for further research on structures of this type

Comparative analysis of guyed lattice mast computations in terms of American and European standard

The paper presents an analysis of a 100-meter wind measurement guyed mast located in the north-western part of the United States, in the state of Oregon. Using the RFEM software [1], the influence of the wind on the mast was analyzed according to the guidelines of two standards: American TIA-222-H [2] and European EN 1993-3-1 [3]. The purpose of this work is to show the differences between the results of static computations of the mast in terms of the considered standards. Due to the limited content of the work, the icing load on the structure was ignored in the analysis and the focus was on determining the response of the mast only in terms of wind action. The author tried to describe the differences in this respect between the standard guidelines [2] and [3]. The comments and conclusions regarding the analysis of guyed masts presented in the article have some practical aspects and can be used in design practice.

Optimal Schemes of Tall Pinned Masts

A procedure for simultaneous topology, shape, and sizing optimization of tall pinned guyed masts is presented in the paper, seeking the minimal total mass of the mast structure including guys. The typical schemes of tall telecommunication masts of four different heights with different antenna areas distributed in the top 15% of the mast height that is triangular in plan and supported by two to four guys' clusters are examined. The mast structure is optimized for self-weight and wind loading evaluated according to Eurocodes. Since the non-gradient stochastic optimization algorithm requiring thousands of problem solutions is used, the non-linear behaviour of the guyed mast is mimicked by a suggested approximate linear analysis procedure. The optimization constraints involve all strength, local, and global stability requirements. Analysis of the optimization results leads to the following most important findings: at equal conditions of the mast scheme, a higher number of guys' clusters always reduces the mast mass; in case of four guys' clusters levels the anchoring points of the top and the next-to-last level guys should be superposed. Also, the optimal ranges of pre-stresses in guys of different levels, their inclination angles, and the ratios of spans between guys' levels are provided.

Reconstruction of boundary layer wind field at the SEG plaza based on dual-lidar measurement and numerical simulation

On the basis of the boundary layer wind field data measured by two Doppler lidars, the correlations between wind speed and wind direction at the Shenzhen Meteorological Tower (SMT) and the Shenzhen Electronics Group (SEG) Plaza are analyzed, and the urban boundary layer wind field characteristics at the SEG Plaza are explored. The wind field characteristics during the May 18 vibration event of the SEG Plaza are then reconstructed by using the computational fluid dynamics numerical simulation method. Results show that: 1) The 10-min mean wind speed and wind direction between the two sites at a height of about 350 m high altitude are highly correlated despite the SMT is geographically 22.4 km from the SEG Plaza; 2) The mean wind profile exponent of incoming flow direction (wind direction SW) in the vibration event of SEG Plaza is obtained as 0.40 by combining the measured wind field result and CFD numerical simulation. At the building top, the wind profile exponent of the high-altitude guyed masts is about 0.22 due to the flow field is affected by the building itself, and the wind speed borne by the top height (about 350 m) of the guyed masts is about 9.64–10.64 m/s.

Influence of Initial Guy Tension and Antenna Masses in the Sensor Layout for Dynamic Characterization of Guyed Masts

Sensitivity analysis plays an important part in the validation of a sensor layout for the identification of the dynamic response of a system. Although sensitivity analysis has been implemented for this purpose in several civil engineering structures, there are still uncertainties in the case of more complex, nonlinear systems, such as guyed masts, where small changes in mass or stiffness can result in large variations of the general dynamic behavior. This paper describes the influence of antenna masses and initial guy tension variation in the total number and position of sensors required to assess the dynamic response of tall guyed mast telecommunication towers. For the study, the computational models of four different guyed masts were generated and a sensor layout was obtained for each model using a sensitivity analysis. Then, the proposed sensor layouts were verified for different initial guy tensions and total antenna mass of the system, by means of the Modal Assurance Criterion. The principal finding is that initial guy tension presents the highest influence on the variation of correspondence values between mode shapes, with modifications of these values in up to [Formula: see text]. This finding suggests that a preliminary sensor layout based on information provided by a computational model or structural drawings of a guyed mast may be rendered inefficient if there is variation in guy tension due to construction errors or relaxation of cables.

Vibration investigation for telecom structures with smartphone camera: case studies

Telecom structures such as high guyed masts are tall and flexible, so that not only the main structure but also the components (i.e., guy cable and antenna) suffer from vibrations induced by wind or earthquakes. The installation of contact inertial accelerometers for high guyed mast cables or antenna can be logistically challenging and the original vibration state may be influenced by these sensors. With convenient implementation and acceptable accuracy, computer vision technologies have been applied for vibration tests both in labs and field. In this paper, videos taken with smartphone cameras are processed to extract guy cable and antenna vibration information for telecom structures and, as a result, providing an efficient cost-effective method for vibration investigation of this type of structure. The video processing method can also be used in similar cases for other structures.

Modeling and Analysis of a Large-Scale Double-Level Guyed Mast for Membrane Antennas

This paper proposes a double-level guyed membrane antenna for stiffness improvement of a large-scale tri-prism deployable mast using the collapsible tubular mast (CTM). Initially, the construction of the antenna and the modeling of the CTM boom are illustrated. Afterwards, the central mast with isosceles triangular cross section is mathematically equivalent to a continuum beam, in which the equations of motion and the constitutive relations are derived. Based on the equivalent central beam, the double-level guyed mast for the membrane antenna is modeled as a 2(3-SPS-S) mechanism, and then velocity Jacobian matrices and stiffness matrices of SPS branches are constructed. Additionally, the total stiffness matrix of the equivalent mechanism is derived with the principle of virtual work and then evaluated as an accurate approach. Finally, with the aim to improve the static stiffness of the double-level guyed mast, the numerical analysis using the Genetic Algorithm (GA) is carried out for optimizing the distribution of guys in terms of anchor positions and attachment heights.

Effect of Welding Residual Stress on Along-Wind Fatigue Life of Welded Joints in Guyed Mast

On the premise of only considering along-wind effect on guyed mast, the influence of welding residual stress on the fatigue life of welded joints is evaluated in this paper. Since the sum of residual stress and along-wind-induced dynamic stress exceeds the yield strength of structural steel, the effect of residual stress relaxation is included in the numerical analysis. The multiscale finite element analysis of guyed mast is developed in order to capture accurately stress field distribution of welded joint for the “welding-wind-induced” case in which both residual stress and along-wind-induced stress are taken into consideration, and the stress response characteristics at fatigue critical point of welded joints are pointed out. It is found that the “welding-wind-induced” stress field of welded joint can be approximately considered as multiaxial proportional loading state and hence the stress-based von Mises criterion can be adopted to evaluate the fatigue life of welded joints. Based on the S-N curve of stress fatigue life for welded specimens with structural steel commonly used in guyed masts, the fatigue damage of key welded joints is predicted, and as a consequence, the influence of welding residual stress on the fatigue life of welded joints is discussed.

Comparison of Dynamic Analysis Methods in a Cable-Stayed Tower Under Extreme Wind Loads in Cuba

Several methods and investigations have been conducted in order to dynamically analyze the behavior of guyed mast telecommunication towers subject to wind loading, due to the importance of such structures in current society. Due to their slenderness, flexibility and lightweight, these structures are particularly susceptible to wind loads, being strong hurricane winds the cause of several tower failures in Cuba. This works conducts the study of a 120 meters tall guyed mast, model MAR 2008, facing extreme wind loads in two different locations. The structure is modeled using the computational assisted software SAP2000 and a dynamic analysis is undertaken using two methods: the equivalent static method "Patch Load" and the full dynamic method "Time History" using Direct Integration. The basic wind speeds are determined according to the Method of Independent Storms (MIS) and standard turbulence intensities for cyclonés regions. Synthetic functions are generated for different heights of the tower in order to apply the "Time History" dynamic method. Finally, a comparison is established between the results in terms of axial loads, joint reactions and displacements. The main conclusion of the study is that as the basic speed decreases, there is a higher resemblance in inner forces and displacements between the results obtained for the two studied methods.

Guyed Wind Turbine Towers: Developments and outlook

ABSTRACTIn the quest of reducing carbon emissions, sources of renewable energy, such as wind, are in high demand. Developers of onshore wind farms are increasingly faced with site conditions which are not ideal in terms of harvesting wind energy, such as forest, mountain areas or wind availability.This has several root causes such as: site scarcity, political instruments to ensure energy mix and lack of transmission. Some of the potential challenges for such sites are 1) larger hub height is required to maintain energy yield and reduce the turbulence intensity, 2) installation is costly, 3) road transport is costly from increased diameters of conventional towers, and 4) increased foundation cost for tall towers.Guyed masts have been applied within the field of telecommunications for many years. Previous comparisons of the advantages of guyed masts over self‐supporting towers highlights that positive properties of the guyed mast include: lower cost with height, less erection time and cost‐effective foundations.In order to reduce the cost of tall wind turbine towers a guyed wind turbine (GWT) tower concept, where the conventional steel tubular tower is supported by guy ropes (cable stays) just below the tip of the blade, has been proposed by Ramboll dating back to 2003. It is only in recent years that the hub heights relevant for application of this concept is coming into market. In 2013 Ramboll participated in a research project disclosing the use of guyed towers for constructing tall wind turbine towers, which demonstrated a significant positive cost impact and documented the technical feasibility of the concept.For the concept cost reductions are obtained through the entire supply‐chain of the wind turbine tower: steel consumption, foundations, transport and installation.The paper will give a general introduction to the guyed wind turbine tower concept and update with developments.

Replacement of two 320m masts in Sweden

ABSTRACTThrough the recent three years Teracom in Sweden have replaced two 320m guyed masts to new masts that are designed by Ramboll. Whilst the old mast in both projects was built in the 1960s and primary served as support for FM/TV broadcasting antennas, the background for the replacement is significant different. One mast was exposed from a fatal sabotage, where it was succeeded to have the new mast in service less than one year from this date. The other mast is placed in an area that experience heavy ice formation on a yearly basis and has been replaced due to a lack of fatigue capacity.The new masts have been designed by a full dynamic model, accounting for the local climatic conditions in respect to wind, ice, guy rupture and including maintenance‐free tuned liquid sloshing dampers at the top. For the guy ropes separate foundations have been designed; either gravity based or anchored into the bed rock where applicable. The design has been optimized with respect to the use of materials and particularly in respect to logistics and site work.As the major roll‐out of this type of masts generally went on some years ago, this paper will present some of the issues when designing and building 300m masts to current standards, including some of the specific challenges on the two projects. Topics from installation will also be described. In both project the existing mast (or what was left of it) was kept in service while building the new at less than 20m distance

Nonlinear dynamic analysis of a 3D guyed mast

Guyed masts are examples of structures extensively used in civil engineering. During the service life of the structure, the guys tension values can vary due to various circumstances. The consequences can range from operational difficulties to failure of the structure or some of its components. Thus, a study of the sensitivity of the dynamic response of a guyed mast to the initial pretension of the guys becomes relevant. A three-dimensional guyed mast is herein represented by a beam column and one level of three nonlinear inclined cables, with a prescribed dynamic lateral load acting on the mast. The second-order effect of the axial load due to the cables pretension on the mast is also considered. The load is designed to avoid resonance effects and meet the maximum displacement limits within the Euler–Bernoulli theory used in the beam-column model. The guys behavior is governed by cable nonlinear equations that account for the extensibility and the initial deformed configuration due to gravity. An ad hoc algorithm was developed by the authors as a tool to analyze 3D guyed masts with an arbitrary number of guys and levels of guys. The partial differential equation system is discretized using finite elements and solved in the time domain through Newmark and Newton–Raphson algorithms. A natural vibrations study shows that a single eigenvalue could be associated to local cable or mast modes or global cable–mast modes, depending on the initial pretension. The displacements of the mast at two strategic points exhibit a rich range of dynamic responses, showing different bifurcation patterns, which can turn from periodic to nonperiodic motions within small ranges of variation of the initial pretension.

Experimental study of mechanical properties of steel cables

Guyed masts are structures particularly sensitive to various types of nonlinarities. Static calculations of masts should be performed in accordance with EN 1993-3-1 using global elastic analysis. This is justified in the case of pre-stretched cables on mast guys, characterized by a constant value of the modulus of elasticity. In the case of non-stretched cables this approach is inappropriate, because permanent rope elongations caused by the applied load can significantly reduce the stiffness of the mast. The paper presents the preparation process of rope samples for experimental tests and preliminary results of tests aimed at determining the actual stress – strain relation of the rope and estimation a constant elastic modulus E of the cable after a few cycles of loading and unloading. The results of the obtained tests are introductory to further numerical analysis of guyed masts, including physical nonlinearity of guys.

Blast Demolition Study of Guyed Masts

Demolition of guyed masts is usually carried out by cutting down some of the supporting guy cables using an explosive in such a way that the mast can fall into the desired direction. Without the cable supports, guyed tubular masts are very slender structures which are susceptible to local buckling based on the internal force distribution. If this local buckling occurs at the early stage of the demolition processes, it can cause uncertainty in the failure mechanism. The risk of undesirable demolition outcome due to this uncertainty can be mitigated by using controlled detonation setups. In this paper, a sensitivity analysis is presented using a case study to determine the influence of the explosive detonation time on the collapse development and pattern of the guyed mast. Then, the results of the sensitivity analysis are systematically categorized using cluster analysis to show possible types of collapse regimes which can be used to setup a controlled demolition scheme.

Analysis of guyed masts by the stability functions based on the Timoshenko beam-column

A new formulation for the analysis of guyed towers in which the mast is modeled as a continuous equivalent beam-column on non-linear elastic supports, is proposed. Because second-order effects must not be neglected and given the importance of consider the shear deformation in the analysis of this type of structures, the method proposes the calculation of the second-order deformation using the stability functions based on the Timoshenko beam column. The equivalent beam-column properties of the mast are calculated depending on the pattern construction of the tower and the guys are replaced by non-linear elastic supports. Based on the catenary configuration of the cable, the spring constant is obtained from the secant modulus of the cable. In order to validate the proposed method, a comparative study is carried out analyzing a guyed mast using the proposed method and a numerical model through the use of finite elements. As a main conclusions we will mention that, the proposed method are sufficiently accurate compared to the finite element method, confirming the validity of the hypotheses adopted in the development of the method and; the reduction of the computational effort, since the structure does not need to be discretized into a large number of elements for the convergence.

18.02: Optimisation of masts and towers

ABSTRACTWithin the last decades the need for tall structures has accelerated with the requirements for effective communication especially the advent of radio, radar and television. Latest the exponential growth in the use of cellular phones has meant a new era for towers and masts.There are many challenges for the engineers associated with these tall and slender structures especially when it concerns guyed masts. Many experts have stated that “a guyed mast is one of the most complicated structures an engineer may be faced with”. This statement is unfortunately underlined by the fact that the number of collapses of masts is relatively far greater than for other types of structures.The overall layout of telecommunication masts and towers is governed by the requirements to the transmission and receiving conditions. Added hereto the access and working conditions for installation and service are important issues for the design.A total optimising of towers and masts to the functional, economical and environmental requirements is a job for specialists, and it should normally take into account the total lifetime of the structure. However the optimising is often only focused on minimising the direct costs for the establishment of the structure, neglecting the many other factors influencing the “correct” optimisation.The extensive increase in the number of new masts and towers in the last few years, especially due to the expansion in the cellular telephones, has resulted in increased concern of the aesthetic appearance of these structures and this is an additional challenge to the designers.This paper gives an introduction to the optimisation of these structures and examples of designs are presented.

Instabilities of Elastic and Spinning Systems: Concepts and Phenomena

Bifurcational instabilities of increasing complexity are described, with instructive and intriguing applications. Multiple folds in the gravitational collapse of a star triggers a discussion about possible sequencing of folds. Columns, rings and a quirky floating log illustrate safe and dangerous pitchforks, with self-weight models as lecture demonstrations. Localized buckling is employed by biologists using magnetic tweezers to twist a DNA molecule and evaluate a cutting and de-knotting enzyme. Unfolding of complex bifurcations into “structurally-stable” forms by a number (codimension) of perturbations illuminates the imperfection-sensitivity of shells, and the interactive buckling of a guyed mast at a hyperbolic-umbilic catastrophe. Spinning of primitive planets introduces secondary bifurcations, while Kirchhoff’s analogy is displayed for rods and spinning tops. Examples of gyroscopic stabilization and levitation mimic the “traps” that are used in modern experimental physics to hold in place individual electrons and neutrons.

Nonlinear dynamics of guyed masts under wind load: Sensitivity to structural parameters and load models

As the wireless communications spread, there is an increasing demand of antenna supporting structures. Guyed lattice towers (masts) are chosen for economical reasons when there is enough space for their location. Radio and television industries employ structures that can attain heights up to 600 m and communication towers for mobile phones are approximately 60 m though higher structures are also constructed. For the latter, guyed masts are indicated. Nowadays, the demand for more accurate and reliable communication systems poses more stringent structural requirements since to attain high quality in signal transmission, small magnitude motions of the supporting structures are usually needed. The design of these structures is, in general, carried out following the standard codes and simplified models. Despite the large potential of adverse impact, the dynamic actions as wind and earthquakes, are not usually addressed in detail with exception of special cases. In this work, a parametric study on the effect of three relevant parameters (i.e. guy pretension, structural damping, mast stiffness) on a guyed mast is carried out. A typical structure under wind load is analyzed using a finite element model. Two load representations are employed; the mean component is obtained following procedures from standards and is the same for both load models. The fluctuating part of the wind load is then added. In the first model, the turbulent component is represented by a time series obtained by means of the Spectral Representation Method including temporal and spatial correlations. The second model is a simpler approach, in which the temporal component of the wind load is represented through a harmonic function. The resulting transverse displacements and cable tensions histories are analyzed to assess the dynamic structural response. It is observed that the structure is more sensitive to the guy pretension when compared with the other two variable parameters. Also, it was verified that the stochastic load is a more adequate option to model the wind. These two findings are crucial in the design of this type of structures.

Fuzzy pattern recognition technique for crack propagation on earplate connection of guyed mast under wind load

A 2-stage damage identification technique is presented for identifying crack lengths on cable-tower connections of guyed masts. It is based on fuzzy pattern recognition theory and uses the cable force and the strain at the key locations of the earplate connection as input parameters. The methodology is developed with a numerical model under stochastic wind excitation and verified by numerical simulation and experiment. First, the relationships of cable force, strain on the connection, and crack length are explored. The wind-induced responses of guyed mast are analyzed under different wind speed and directions to form a database of cable forces. The responses of a typical connection with different crack lengths are simulated to investigate the strain sensitivity to crack propagation. Its results are used to form a second-stage strain database. The first stage of the fuzzy identification consists in identifying the interval of cable forces on the basis of cable force measurements. Then, a subjection degree function is formed between the measured strain and the developed strain database to judge the damage state of the connection by identifying the existence of a crack and estimating its length. The results of a numerical case study and further experiment are presented and show the potential and practicability of the technique to estimate the right range of crack length on earplates. Therefore, the proposed technique is practical and feasible to predict the damage state of earplate and can provide valuable prewarning information for structural safety.