Tower Model Research Articles

Experimental and analytical study on the performance of wind turbine tower attached with particle tuned mass damper

According to the global wind energy council report, a dramatic increase in the annual wind installations is needed to satisfy the goal of net-zero, which means there will be a large market for wind turbine towers. Therefore, the safety and suitability of wind turbine towers must be ensured by certain methods under wind and seismic excitations for reliable wind energy production. This paper presents a comprehensive study involving experimental, analytical, and computational approaches to study the performance of the particle tuned mass damper (PTMD) that is attached to a 1/20 scaled wind turbine tower model through a shaking table test. During the test, the overall performance of PTMD is analyzed under earthquake and equivalent wind excitations. The results indicate that PTMD can significantly mitigate the dynamic responses of the tower top and tower body. Then, a parametric study of PTMD is carried out to detail its damping mechanisms. The results show that the robustness of PTMD is good, and PTMD possesses a wider vibration control frequency band. Finally, based on the experimental test, a finite element model is built, and then a comparison of experimental and numerical results is conducted to investigate the vibration reduction effect of PTMD under coupled wind and earthquake excitations. The numerical simulation and experimental results agree well, and PTMD has good vibration reduction effectiveness under coupled wind and earthquake excitations. Besides, the numerical simulation indicates that aerodynamic damping can restrain the vibration of the wind turbine tower to a certain extent. Both the experimental and numerical results indicate that the PTMD can reduce the vibration of wind turbine towers significantly under wind and earthquake excitations.

Thermal Modeling of Umbilical Tower During the Lift-off Of a Launch Vehicle

Umbilical Tower (UT) forms a critical structure along with mobile service tower, launch pedestal and jet deflectors of a rocket launch pad. UT will be exposed to severe thermal environments during lift off of the launch vehicle owing to its close proximity. UT experiences thermal loads until the launch vehicle lifts off and clears it. Hence thermal environments need to be quantified to assess the survivability of UT for subsequent missions. This paper brings out the methodology developed for estimating different thermal environments experienced by UT structure during a typical rocket launch. The engineering method result in a quick estimate of flow properties of the plume from the rocket exhaust compared to CFD, which will be computationally intensive and time consuming to arrive a converged accurate solution for heat flux estimation. ISRO’s launch vehicles have first stage with Solid Rocket Motor (SRM) as core and solid motors/liquid engines as multiple strap-ons. Thermal loads to launch pad structures include radiative and convective heating from exhaust plumes. The aluminum particle laden exhaust plumes of solid rockets are dominating radiative heat source. Convective heating occurs from hot jets and direct plume impingement. The relative movement of launch vehicle with respect to UT structure is an important parameter affecting thermal environments. It varies for each launch depending on the vehicle variant and its lift-off trajectory. This calls for a detailed assessment of thermal loads for thermal adequacy studies. A finite element based thermal model for umbilical tower is also generated for thermal response studies and Thermal Protection System (TPS) design. The computed temperature levels at various location of UT structure are compared with measured values during typical lift-off. Results indicate that temperature levels of UT structure are within allowable limits and the adopted methodology can predict temperature within a maximum difference of ±5%.

Analysis of the Temperature Field Effect on the Thermal Stress of the Main Tower of Long-Span Suspension Bridges

To investigate the temperature field variation of the main tower of large-span suspension bridges, the Nanjing Xinshengwei Yangtze River Bridge was selected as the objective of the present study. The finite element model of the main tower was developed, and the analysis of the effect of the temperature field on the structure of the main tower was carried out. The calculation parameters of the temperature field of the main tower were determined, and the influence of the solar radiation temperature of the main tower within 24 h was investigated. Differences in the temperatures inside and outside the wall of the tower column were analyzed, and the thermal stress of the tower wall under the most unfavorable temperature difference was calculated. Results show that under the positive temperature difference, the area of tensile stress is mainly concentrated on the inner wall, the maximum value is located at the corner of the intersection of the tower wall, and the range of tensile stress is mainly diffused along the vertical wall. Under the action of negative temperature difference, the area of tensile stress is mainly concentrated in the outer tower wall, the maximum value is located in the upper part of the western outer tower wall, and the range of tensile stress is mainly diffused along the center of the tower wall to both sides. The maximum tensile stresses in the inner and outer tower wall are 2.8 MPa and 1.3 MPa, respectively, which meets the standard value of 2.85 MPa for the tensile strength of C60 concrete specified in the Chinese national standard.

Optimal allocation model of forest fire detection towers in protected areas based on fire occurrence risk: Where and how to act?

Forest fire detection towers are crucial in supporting rapid firefighting actions in conservation units and thus reducing environmental, social, and economic damages. Thus, the aim was to evaluate scenarios for optimal allocation of forest fire detection towers, according to the risk of occurrence, in the Caparaó National Park, Brazil. Thus, by geotechnological analysis, the areas most susceptible to forest fires and the optimal locations for installation of detection and monitoring for these events were delimited. To run the proposed models, biological, physical, socioeconomic, and meteorological variables were used. From the application of the methodologies, it was observed that 76.70% of the study area was covered by low, moderate, and shallow fire risk classes, while high and very high-risk classes were concentrated in the buffer zone. The scenario with 45 towers was considered the most advantageous, given that they presented viewing levels above 70% and a lower cost per hectare viewed than the scenario with 48 towers. Results showed no critical risks of fire occurrence within the conservation unit, but preventive measures are still needed to avoid fire spread, particularly near the buffer zone. The study's methodologies can be applied in other areas to improve forest fire prevention and control efforts.

Wind-Induced Responses of Corroded Angle-Steel Transmission Tower

Corroded transmission towers, whose load-bearing capacities are lowered, are suffering from wind-induced damage. By simulating the member corrosion through section thinning, the structural dynamic finite element model of an angle-steel transmission tower with a corrosion depth of 0 mm to 1.4 mm was established using ANSYS/LS-DYNA software. The incremental dynamic analysis method was used to study the collapse mode of the tower under different degrees of corrosion, as well as the effects of corrosion on structural self-vibration characteristics, wind-induced member stress, and tower-top displacement. The results show that with the corrosion deepening, the first three vibration frequencies decrease, and the torsional mode becomes the first mode. When the corrosion depth is smaller, the overall structure failure occurs under strong wind. The failure starts at the most unfavorable oblique rod between the upper and middle cross arm, then expands to the rods under the lower cross arm. When the corrosion depth is larger, the overall structure failure occurs restrictedly between the upper and middle cross arm. Internal axial force and bending moment redistribution happen when corrosion deepens. Under the critical failure state, the oblique rods are always at a high stress level, while the stresses of the main rods decrease. Corrosion has a stronger impact on component strength and stability than on structural stiffness.

Research on the Overstrength Performance of Lateral Force-Resisting System of Guangzhou West Tower Based on Story Overturning Moment

ABSTRACT The factors of the building’s structure’s overstrength performance need to be researched to decrease the large amount of the structural materials and the investments caused unreasonably by the overstrength performance. Taking the Guangzhou West Tower as an example, the main reasons why the Guangzhou West Tower model structure was not damaged after encountering an earthquake (PGA = 620 gal) in the shaking table test was revealed. The overstrength performance of lateral force-resisting system of the Guangzhou West Tower building’s structure was researched, which is caused by the artificially adjusted earthquake influence coefficient of the long-period segment of response spectrum. The response spectrum analysis and the elastic/plastic incremental dynamic time history analysis were conducted to obtain the overstrength coefficient of the lateral force-resisting system that was calculated with the overturning moment at structural base. The analysis results showed that the yield overturning moment at structural base exceeds the seismic demand at the point where PGA = 400 gal, which could verify the reliability of the results of shaking table test. The artificial magnification of the long-period segment of response spectrum and the irrational correlation between the seismic grade and the building’s height are important reasons that increase the overstrength capacity of long-period building’s structure.

Research on Dynamic Characteristics Detection Method of Tall Power Transmission Tower

In addition to the gravity of the structure itself and the supported object, the open-air high-rise supported steel structure tower mainly bears dynamic loads. Take the transmission line tower as an example, such as wind load, conductor galloping, tower vibration and sudden unbalanced tension caused by line breaking. It is necessary to study the dynamic characteristic parameters to know the structural resistance to dynamic load. Therefore, from the perspective of dynamic safety evaluation, this paper designed the acquisition method of dynamic characteristic parameters and established a reliable finite element modal analysis model of transmission tower. Finally, the dynamic characteristic parameters such as natural frequency, vibration mode and amplitude of transmission line steel tower were obtained. It was found that the inclined material of the transmission tower might be unstable when the high-order natural frequency resonance occurred, which had important practical significance for structure design optimization and safety evaluation.

Modeling guyed towers of transmission lines in the assessment of backflashover occurrence

This paper evaluates the modeling of guyed towers of transmission lines in EMT-type programs to assess the backflashover occurrence of transmission lines and proposes a new modeling approach to be applied for this kind of towers. Two approaches to model the guyed towers by the revised Jordan model were evaluated: (i) the approach of CIGRE Brochure 63 that suggests representing the tower surge impedance as the parallel of the surge impedances of the mast and the guyed wires, ignoring the mutual coupling among them, and (ii) a new approach assuming the surge impedance of all the conductors in the tower section, guyed and mast conductors, including their mutual coupling effect. The evaluations considered the results provided by the Hybrid Electromagnetic Model (HEM) as reference for assessing the quality of the approaches. The approach (i) provided results of lightning overvoltage significantly lower than the reference, HEM model, leading to an underestimation of the probability of backflashover of the line. On the other hand, the approach (ii) was responsible for the results closest to those provided by HEM, indicating its quality, and the recommendation of applying this proposed approach for modeling guyed towers in the evaluations of backflashover occurrence.

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

Deformations of a three-dimensional model of a trihedral double lattice rod tower

Introduction. The calculation of deformations of spatial structures, as a rule, is carried out numerically on the basis of the finite element method. With the development of computer mathematical systems for regular systems an opportunity to obtain analytical solutions appeared. Such solutions can be used as test ones to evaluate numerical solutions and for preliminary calculation of a structure at design stage. The task has been set to derive deformation dependences of a spatial truss under various loads from its size and number of panels.
 
 Materials and methods. The truss of the tower structure is statically determined. The calculation of force values in the bars is performed by cutting out nodes in a Maple symbolic mathematics system. The Maxwell – Mohr formula is used to determine the displacement of a node at the top of the frame, considering only the longitudinal deformations of the rods. From the generalization of a series of analytical solutions for trusses with consecutively increasing number of panels onto an arbitrary number of panels the sought formula is derived by the induction method.
 
 Results. An algorithm of derivation of formulas for the deflections of a building along two mutually perpendicular horizontal axes under the action of lateral uniformly distributed nodal loads is presented. Effort distribution patterns are obtained for the truss rods and analytical stress dependences of some rods on the number of panels are found. Linear asymptotics of the solutions for the number of panels and the points of extremum are found and computed.
 
 Conclusions. The considered model of the spatial statically determined tower truss allows deriving exact formulas for deformations under the action of various loads within the limits of the adopted model. It is possible to use derived formulas for a preliminary estimation of designed structure and to apply as test ones for numerical calculations. The extremum points and analytical expressions for asymptotes allow the derived formulas to be used for solving stiffness optimization problems of a structure.

Design of rapid erection system for transmission lines for disaster rescue

The rapid erection system of transmission lines in disaster relief can restore the power supply in the disaster area in a very short time. It takes a long time to construct transmission lines in post-disaster relief and reconstruction. This paper designs the transmission line erection system with the idea of light quality and modularization and puts forward the dimensions and structures of auxiliary hoisting towers and overhead towers. Then, considering that the transmission line is a tall flexible structure, which is very sensitive to wind load, the finite element model of the transmission tower is established to analyze the simultaneous stress of the overhead tower and the lifting tower under extreme conditions. The study verifies the feasibility and stability of the designed transmission line rapid erection system.

Experimental Study on Effect of Water Depth on Earthquake Response of a Deep-water Cable-stayed Bridge Tower

With the aim of investigating the effect of water depth on the earthquake response of a deep-water cable-stayed bridge tower, this study designed and manufactured a large-scale bridge tower model, taking a cable-stayed bridge across a deep reservoir of a hydropower station as a reference. Under the boundary conditions similar to the reference, shaking table tests were conducted to reflect the structural response of the bridge tower under white noise and earthquake actions at different water depths. The time history curve of the bridge tower’s structural response was recorded and used to investigate the variations in the natural frequency, displacement, stress and strain of a deep-water cable-stayed bridge tower at different water depths under earthquake actions. The results showed that the natural frequency of the bridge tower decreased almost linearly with the increase in the water depth. The displacement at the tower top increased gradually with the increase in the water depth under earthquake actions. In addition, the stress and strain at the tower bottom increased almost linearly in the transverse direction and nonlinearly in the longitudinal direction with the increase in the water depth.

PRACTICAL IMPLEMENTATION OF PHOTOGRAMMETRY FOR THE MODELLING OF A CYLINDRICAL HISTORICAL BUILDING

Abstract. This work deals with the image capture for close-range photogrammetry in the context of the modelling of a round tower with repetitive texture (made of bricks), both inside and outside. For that purpose we test different acquisition strategies that differ in terms of camera path (straight or circular) and number of images acquired at each camera position, that is with or without oblique images. Besides, the formula to compute the curvilinear base according to a given overlap rate between successive frontal photos are written for each strategy. The comparisons rely on the observation of the aspect of the different dense point clouds (noise, holes), the deformation seen in the orthomosaics and values extracted from the photogrammetric projects such as metric accuracies with GCP. Our results confirm some art rules.

Integrating a passive downdraught evaporative cooling tower into a Saudi house - The impact of climatic conditions on PDEC performance

The Kingdom of Saudi Arabia (KSA) generates the most electricity of any country in the Gulf region, and virtually all that electricity is produced by the burning of fossil fuels - natural gas and crude oil. The residential sector accounts for about 50% of the total electricity demand in the Kingdom, and around two-thirds of that electricity consumption is used for air conditioning. As the Kingdom transitions away from its reliance on fossil fuels, reducing air conditioning energy demand in dwellings becomes a key objective. Passive cooling systems can significantly reduce cooling energy loads for buildings while maintaining thermal comfort. This study investigated the potential of integrating a passive downdraught evaporative cooling (PDEC) tower into a typical Saudi Arabian villa. A computational model of a spray PDEC tower was developed in IES-VE software and calibrated against field data. Then, an actual Saudi villa was monitored, modelled, and validated before a PDEC tower was digitally integrated into the villa. Finally, the villa and its PDEC digital twin were used to conduct a series of parametric analyses to determine the PDEC performance in different rooms and cooling energy consumption in the villa as functions of wind speed and direction. The research found that, counterintuitively, higher wind speeds reduced the effectiveness of the PDEC system to cool rooms in the villa and that wind direction also played a role in the degree of cooling experienced in different villa spaces. In the summer season, the results indicated that the total villa energy consumption was approximately 32,415 kWh in the base case, with cooling energy representing 88% of the total energy used (28,337 kWh). The integration of the PDEC tower resulted in a reduction of approximately 22% in cooling energy consumption, from 28,337 kWh to 22,032 kWh, while the PDEC was operational continuously throughout the day.

Modeling and modal analysis of the structure of long-span transmission tower

The structure of the long-span transmission tower is a typical nonlinear structure with the characteristics of great height, large line span, heavy overall weight and flexible tower body. The current design code only analyzes the traditional tower types, but the analysis of the truss structure of transmission tower is limited. Aiming at improving the design defects of the structure of long-span transmission towers, this paper uses the finite element software APDL to build the three-dimensional finite element model of a long-span transmission tower, to carry out the modal finite element analysis as well as to extract the specific parameters of each modal finite element mode: Modality, Natural frequency of vibration, Periodicity. The results show that the natural vibration period of the main machinery of this type of steel transmission tower is about 0.37–1.37 s; The structure of the long-span transmission tower has certain displacements in six degrees of freedom, in which the value of the X-dimensional displacement is the largest. There are some large displacements and local torsion in the high-order mode, combined with the results of modal analysis, so it is suggested to consider the structural improvement or external reinforcement of the weak parts of the long-span transmission tower.

Refrigeration equipment model construction based in data center cooling station

ABSTRACT The energy consumption of data centers (DCs) is rising year by year, and cooling station accounts for more than 40% of the total DCs’ energy consumption, which has a huge energy-saving potential. Building models for whole DCs’ cooling station can help predict total power to improve the energy efficiency of the system, before this, establishing a single model for each component is a basic work. This paper mainly studies the chiller and cooling tower models and compares the predictive performance of the empirical model, hybrid model, and neural network model of chillers and cooling towers. Giving the model selection scheme of the chiller and cooling tower for the establishment of the whole system of the refrigeration station. For the chiller model, the Yoshida function model in empirical models has the highest accuracy with a mean square error of 0.0592, followed by the neural network model with a mean square error of 0.2, and the hybrid model has a lower accuracy than the former two models. For the cooling tower model, the empirical models and the neural network model have similar accuracy, and both are higher than the hybrid model.

Lightning Flashover Characteristics of a Full-Scale AC 500 kV Transmission Tower with Composite Cross Arms

Overhead transmission lines (OTLs) have always been the major means of power delivery. With the significant increase of transmission voltage and transmission capacity, the dimensions of transmission towers are increasing accordingly, resulting in extensive occupation of land resources. Towers with composite cross arms are a promising solution to this problem, considering the remarkable performance of composite line insulators. In this research, a full-scale alternating current (AC) 500 kV model of a transmission tower with composite cross arms is manufactured and applied under a lightning overvoltage of different polarities. The developing process of streamer-leader discharge is recorded with a high-speed camera, and the major path of the flashover is identified. The flashover voltages are measured and corrected to standard conditions while considering the air humidity and air density, and clearly confirm the polarity effect. The tower’s lightning-withstand level is calculated based on the tower structure and the flashover characteristics. Based on the results obtained from full-scale experiments, the feasibility of composite cross arms is confirmed, and a structural optimization is proposed.

Wind load identification of lattice towers using multi-source heterogeneous monitoring data

Wind load is one of the governing design loads for lattice tower structures. However, such information is difficult to be measured directly, and the traditional indirect identification methods highly depend on the accuracy of finite element model and are limited to fluctuating wind loads. To solve this problem, a novel wind load identification method from limited multi-source heterogeneous monitoring data is proposed. First, the complex model of a lattice tower is simplified into a reduced-order model based on the similarity principle of dynamic characteristics. And then, limited strain and acceleration data are fused to reconstruct wind-induced responses and modal parameters based on Kalman filter algorithm and mode-superposition method. Finally, the total wind loads, including both mean and fluctuating components, are obtained from identified modal parameters and modal responses. Numerical simulation of a lattice tower verified that the proposed method can reconstruct wind load and base reaction forces with high accuracy, and the anti-noise analysis shows that the proposed method has strong noise robustness. Moreover, the field test of a transmission tower during Typhoon Mangkhut was further carried out to validate the proposed method.

Study of the Prevention Method of ±800 kV Transmission Tower Foundation Deviation

The stability of transmission tower bases is key to ensuring the safe operation of power lines. This paper proposes a joint displacement-control technique for foundation-inclined piles and prestressed foundation tie beams to address the problem of tower base displacement and durability degradation caused by environmental factors. A finite element model of an exposed-pile transmission tower conforming to the structural characteristics of the actual line tower was established based on the current situation of Tower 292 of the ±800 kV Tianzhong line in Xinjiang, China. Three different displacement-control schemes were analyzed under the combined effects of tower line load, ice-cover load, and wind load, including changing exposed pile height, changing inclined pile tilt angle, and increasing the prestressed foundation tie beam. The analysis shows that the combined displacement-control technology of foundation-inclined piles and prestressed foundation tie beams can reduce the horizontal displacement of EHV tower foundations by more than 50%, which greatly reduces safety problems caused by tower displacement and effectively improves tower durability.

Evaluation of the Ultimate Collapse Load of a High-Voltage Transmission Tower under Excessive Wind Loads

Several high-voltage transmission towers failed under excessive wind loads in a mountainous and exposed area. This study discusses the efficient and reliable modeling of lattice towers dominantly loaded by wind, a scenario which led to a collapse cascade in a high-voltage transmission line. The ultimate load-bearing capacity had to be estimated and the failure positions identified. Finite Element Analysis was employed through static analyses, Linear Buckling Analyses (LBA) and RIKS analyses (Arc-Length method) in Abaqus 2021. With the purpose of improving the accuracy in the simulation of structural instabilities of complex lattice structures, the model sensitivity to superimposed geometrical imperfections and the joint stiffness of the truss connections were investigated in brace and lattice structure sub-assemblies. Afterwards, linear analyses and non-linear analyses with imperfections were performed on the single tower model. The analysis proved that solely excessive wind can cause such failure on the lattice structures, and the critical structural elements have been correctly identified. The investigation proved that the towers had not been under-designed with respect to the standards valid at the time of erection. However, they were not designed for this exceptional storm event, and evidence was provided that wind alone could bring about the collapse. It is nevertheless not recommended to increase the safety factors in general for the design of such structures, but to base the assumed loading on actual and local wind and service load measurements.