Tower Structure Research Articles

Harnessing the joint effect of approach bridges in arch bridge construction: an analytical study on thrust stiffness and elevation error mitigation

Achieving full equilibrium for the horizontal component force of the backstay in cable-stayed arch bridges is challenging, and the stiffness of the buckle tower has a notable influence on the overall shape of the main arch structure. Increased stiffness in the buckle tower leads to reduced construction complexity. Therefore, this study proposed a method of enhancing the longitudinal thrust stiffness of the buckle tower using the joint effect of approach bridges. A sensitivity analysis was conducted on the approach bridge–composite buckle tower structure to determine the optimal combination method, resulting in the formulation of an analytical expression for the thrust stiffness of this structure. In this study, numerical analysis was performed to explore the composition mechanism of the thrust stiffness influenced by the pier–girder connection, and we discussed the applicability of the joint effect of approach bridges during the cantilever assembly process of arch ribs. The following conclusions were obtained: 1) prior to installing the main girder of the approach bridge, when the steel buckle tower and the junction pier have already been secured, the most effective approach is to form a “T” rigid structure by firmly connecting the main girder of the approach bridge with the composite buckle tower. This configuration provides self-weight deflection and pier–girder rotation restriction effects. 2) The study presents analytical formulas for the completely rigid pier–girder connection of the approach bridge–composite buckle tower structure, partially rigid pier–girder connection, and pre-deviation. Combined with the calculation program, this can guide structural design. 3) When a large downward elevation error of the arch ribs occurs in the middle and later stages, the cable force needed to install new arch segments becomes overly large. Therefore, the joint effect of approach bridges can be utilized to substitute for a portion of the cable force, effectively reducing potential elevation errors that might arise in subsequent arch ribs in the absence of this joint effect.

Engineering geological map of the riverfront in the old city of Mosul

The local and central governments focused on the right side of Mosul for urban development, especially after the destruction that occurred during its liberation. The view of the study area on the river and the green spaces on the other side of the river drew the attention of the Municipality of Mosul to develop it into a tourist attraction that reflects the cultural aspect of this ancient city. 26 exploratory boreholes were drilled in the study area, with depths ranging from 10 to 20 meters, and their geotechnical specifications were determined. In this study, the Pearson correlation coefficient was used to identify the parameters that have the greatest influence on the geotechnical specifications of the layers and to classify the engineering classes. Interpolation was used in Arc GIS to compare the distribution of geotechnical properties in the three layers at depths of (3, 6, and 9 m) and to calculate the average values of geotechnical properties from a depth of (1.5 - 9 m). The specifications were classified into five classes using a classification of the different characteristics. Geotechnical maps of the study area were created to show the distribution of engineering properties and their classification into isotropic zones, allowing each application zone to be provided with the appropriate building type. The results revealed that the northwestern part of the area is best suited for towering structures, while the rest of the neighborhoods were considered less suitable.

Global Displacement Reconstruction of Lattice Tower Using Limited Acceleration and Strain Sensors

Displacement is an important parameter for evaluating structural performance. However, the accurate measurement of global dynamic displacement remains a challenging task. To solve this problem, this paper proposes a global dynamic displacement reconstruction method for lattice tower structures, fusing limited acceleration and strain data. First, the strain-displacement mapping method for cantilever beams with variable cross-sections is presented and then extended to lattice towers. Thereafter, a modified multi-rate data fusion algorithm incorporating Kalman filtering and the proposed strain-displacement mapping methods is developed to fuse the acceleration and strain data to reconstruct the global dynamic displacement of the tower. The numerical simulation, model test and full-scale test demonstrate that the reconstructed dynamic displacements using the proposed method agree well with the reference values in both the time and frequency domains, and the parametric analysis has also been carried out, exhibiting great robustness and high reconstruction accuracy.

Dynamic characteristics of segmental assembled HH120 wind turbine tower

The analysis of dynamic characteristics is crucial in the design of wind tower structures. The dynamic behavior of wind towers is primarily influenced by structural stiffness and mass distribution. In particular, the segment thickness of prefabricated concrete towers should be selected and optimized based on computed results of stress distribution in order to achieve the desired dynamic performance. The main objective of this research is to investigate the effects of design factors, such as segmental thickness and top mass of wind blades, hub, and nacelle, on the natural frequencies and vibration modes of the precast concrete towers. For the finite element analysis, a high-rise wind turbine tower with a hub height of 120 m (HH120 tower) is utilized. Finally, the theoretical model for the reduced degrees of freedom system is validated using the results from the finite element analysis.

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.

Thermodynamic properties and switching dynamics of perpendicular shape anisotropy MRAM

The power consumption of modern random access memory (RAM) has been a motivation for the development of low-power non-volatile magnetic RAM (MRAM). Based on a CoFeB/MgO magnetic tunnel junction, MRAM must satisfy high thermal stability and a low writing current while being scaled down to a sub-20 nm size to compete with the densities of current RAM technology. A recent development has been to exploit perpendicular shape anisotropy along the easy axis by creating tower structures, with the free layers’ thickness (along the easy axis) being larger than its width. Here we use an atomistic model to explore the temperature dependent properties of thin cylindrical MRAM towers of 5 nm diameter while scaling down the free layer from 48 to 8 nm thick. We find thermal fluctuations are a significant driving force for the switching mechanism at operational temperatures by analysing the switching field distribution from hysteresis data. We find that a reduction of the free layer thickness below 18 nm rapidly loses shape anisotropy, and consequently stability, even at 0 K. Additionally, there is a change in the switching mechanism as the free layer is reduced to 8 nm. Coherent rotation is observed for the 8 nm free layer, while all taller towers demonstrate incoherent rotation via a propagated domain wall.

Comparison of stiffness degradation in fatigue-loaded concrete cylinders and large-scale beams

Wind and wave loads subject the tower structures of wind turbines to bending stress. The resulting initial linear strain gradients in the tower cross-section cause fatigue-induced degradation of the concrete at the outer edge of the structures. As the number of load cycles increases, stresses are gradually redistributed to the inner cross-section of the structure consequently. Most of the test results documented in the literature were obtained from small-scale concrete specimens or small-scale components. In those cases, the stiffness and stress redistributions occurring in the real component can only be insufficiently derived, and possible scale effects cannot be taken into account. Besides, available test results for individual component tests are mostly only for load cycles up to 2⋅106. However, significantly lower load levels and thus higher number of load cycles are expected to occur in wind turbines compared to usual fatigue tests. To deal with this issue, extensive fatigue tests on small cylindrical specimens as well as large-scale beams in the very-high-cycle fatigue range are carried out in this work. The test results of both cylindrical and beam specimens show the typical three-phase stiffness curves known from the literature. These curves exhibit a disproportionate decrease at the beginning of the loading, followed by a constant decrease in stiffness, and finally, a greater decrease in stiffness shortly before failure. Moreover, the stiffness curves from the tests on both specimen types show good agreement. It can be concluded that the results from small cylindrical specimen tests can be transferred to large-scale structural components.

The stable embedding tower and operadic structures on configuration spaces

The stable embedding tower and operadic structures on configuration spaces

Weight Optimization of Tower Structures with Continuous Variables using Jaya Algorithm

Weight Optimization of Tower Structures with Continuous Variables using Jaya Algorithm

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.

Mn0.6Ni1.4Co2Oy micro-nano tower structure with tunable spectral selectivity interface for infrared stealth and solar selective coating application

In order to make full use of solar energy and solve the problem of functional incompatibility between solar and infrared spectra, the present work has cleverly aimed at the problem by designing Mn0.6Ni1.4Co2Oy multi-functional interface. The Mn0.6Ni1.4Co2Oy coating was obtained by a simple vacuum spraying method. It was found that the coatings prepared with the appropriate amount of MNC/resin ratio (5:5) possessed the high solar absorptivity (0.915) and low infrared emittance (0.245) at ambient temperatures, as well as excellent heat-collecting properties, which suggests that the structure of the Mn0.6Ni1.4Co2Oy is maximally preserved. Notably, the DSC results confirm that the introduction of Mn0.6Ni1.4Co2Oy into the resin can strengthen the thermal stability of the coating, which is mainly attributed to the fact that Mn0.6Ni1.4Co2Oy can effectively prevent the chain segment movement of the resin. Furthermore, the addition of low-emissivity aluminum powder further reduced the emissivity of the coating to 0.142 and the absorbance/emissivity ratio to 6.22 at room temperature. The coating demonstrated remarkable thermal stability and infrared stealth performance even at 300 °C, meeting the basic requirements of solar selective absorption. This work provides a low-cost and simple spray method for fabricating Mn0.6Ni1.4Co2Oy solar selective absorption coating with great potential in high-temperature infrared stealth applications.

Layout and cross-sectional size optimization of truss structures with mixed design variables based on gradient method

The object of the study was truss-type rod structures, which were investigated for the purpose of finding the optimal design solution in a mixed (continuous and discrete) space of variables. The parameters of the geometric scheme of the truss, as well as the dimensions of the cross-sections of its elements, were considered as design variables. The stated optimization problem is represented as a nonlinear programming task, in which the objective function and nonlinear constraints of the mathematical model are continuously differentiable functions of the design variables. The system of constraints includes strength and stability inequalities, formulated for the design cross-sections of the rod elements of the structure, which is subject to the effect of the design load combinations of the ultimate limit states. As a part of the system of constraints, the displacement constraints formulated for the specified structural nodes, which is subject to the action of design load combinations of the serviceability limit states, are considered. To solve the stated optimization problem, a method of the objective function gradient on the surface of active constraints was used, with the simultaneous elimination of residuals in the violated restrictions. For design variables, the variation of which must be performed according to a given set of possible discrete values, a discretization procedure for the optimal solution obtained in the continuous space of design variables is proposed. A comparison of the proposed optimization methodology with alternative metaheuristic methods and algorithms reported in the literature was performed. On the considered problem of parametric optimization of a 47-span tower structure, a design solution with a weight of 835,403 kg was obtained, which is 1.53...4.6 % better than the optimal solutions obtained by other authors

Features of a finite-element modeling of a tubular tower for a wind-power unit

Introduction. Being indisputably relevant, an identification of the features of modeling tower structures can simplify the work of engineers and simultaneously move the design decision-making to a qualitatively new level.Aim. To assess the effect, caused by some particular features of a computational modelling, on the resulting parameter, representing the frequency behavior of a tubular tower for wind-power units.Materials and Methods. Numerical studies were conducted using a domestic SCAD Office programming and computing suite. In computational modeling, 41st, 42nd, 44th and 50th FE types were used. During the assessment of effects, caused by the finite element type, calculations of a cylindrical tower with fixed parameters were performed, taking into account variations in the type and size of the FE. Estimating factors in calculations included: variations in stresses, as well as in the frequency of first-mode natural oscillations. During the comparison of stress values, the plate of the third from the fixed base row was taken as the design one. Turbowind T600-48 and Eviag EV 100 were considered as wind turbines.Results. A sufficient discretization value of the computational model for determining the frequency of natural oscillations equals to nR = 12, since a further increase in the value of nR will lead to variations in the frequency of natural oscillations by less than 1%. The individual frequencies of 0.275 and 0.825 Hz were determined for an Eviag EV 100 wind turbine. For a Turbowind T600-48, the range of resonant frequencies is determined due to the presence of a variable rotor speed: starting and maximum frequency ranges of 0.255–0.765 and 0.383–1.149 Hz, respectively.Conclusions. During the modeling of a tower in the SCAD Office PCS, it is feasible to use the 44th type of finite elements, taking into account the obtained sufficient discretization value. The obtained spectrum of natural and resonant frequencies allows avoiding the appearance of a resonant effect when making design decisions.

Parallel Bayesian probabilistic integration for structural reliability analysis with small failure probabilities

Bayesian active learning methods have emerged for structural reliability analysis and shown more attractive features than existing active learning methods. However, it remains a challenge to actively learn the failure probability by fully exploiting its posterior statistics. In this study, a novel Bayesian active learning method termed ‘Parallel Bayesian Probabilistic Integration’ (PBPI) is proposed for structural reliability analysis, especially when involving small failure probabilities. A pseudo posterior variance of the failure probability is first heuristically proposed for providing a pragmatic uncertainty measure over the failure probability. The variance amplified importance sampling is modified in a sequential manner to allow the estimations of posterior mean and pseudo posterior variance with a large sample population. A learning function derived from the pseudo posterior variance and a stopping criterion associated with the pseudo posterior coefficient of variance of the failure probability are then presented to enable active learning. In addition, a new adaptive multi-point selection method is developed to identify multiple sample points at each iteration without the need to predefine the number, thereby allowing parallel computing. The effectiveness of the proposed PBPI method is verified by investigating four numerical examples, including a turbine blade structural model and a transmission tower structure. Results indicate that the proposed method is capable of estimating small failure probabilities with superior accuracy and efficiency over several other existing active learning reliability methods.

High-Performance Solid Raft Foundations with Bottom Cutouts for Lightweight Tower Structures

High-Performance Solid Raft Foundations with Bottom Cutouts for Lightweight Tower Structures

Statistical analysis of wind load probabilistic models considering wind direction and calculation of reference wind pressure values in Liaoning Province, China

Wind pressure serves as the fundamental base for architectural design, particularly the reference wind pressure value, which affects the reliability and economy of high-rise, towering, and large-span structures. To facilitate the calculation of reference wind pressure values for design reference periods, load codes from various countries offer probabilistic distribution models for wind speed or reference wind pressure. However, the application of a uniform load probabilistic distribution model for calculating the reference wind pressure for the reference period often results in overestimation or underestimation of the reference wind pressure. To this end, this study collected annual maximum wind speed data from 34 meteorological stations in Liaoning Province, a region in Northeast China, and established extreme value type I, extreme value type III, lognormal, and generalized extreme value distribution models for the annual maximum wind speeds using the maximum likelihood method and method of moment, respectively. The goodness-of-fit test was conducted utilizing the Kolmogorov–Smirnov method. The results showed that the extreme value type III model and the method of moment achieved the best goodness-of-fit for the probabilistic distribution of annual maximum wind speeds. Based on the measured wind direction data corresponding to the annual maximum wind speed, joint probability density functions and cumulative probability density functions of wind speed and wind direction were established. Finally, the influence of different load statistical periods on the reference wind pressure was analyzed.

Towers and hierarchies in the Standard Model from Emergence in Quantum Gravity

Based on Quantum Gravity arguments, it has been suggested that all kinetic terms of light particles below the UV cut-off could arise in the IR via quantum (loop) corrections. These loop corrections involve infinite towers of states becoming light (e.g. Kaluza-Klein or string towers). We study implications of this Emergence Proposal for fundamental scales in the Standard Model (SM). In this scheme all Yukawa couplings are of order one in the UV and small Yukawas for lighter generations appear via large anomalous dimensions induced by the towers of states. Thus, the observed hierarchies of quark and lepton masses are a reflection of the structure of towers of states that lie below the Quantum Gravity scale, ΛQG. Small Dirac neutrino masses consistent with experimental observation appear due to the existence of a tower of SM singlet states of mass m0 ≃ Yν3\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ {Y}_{\ u_3} $$\\end{document}Mp ≃ 7 × 105 GeV, opening up a new extra dimension, while the UV cut-off occurs at ΛQG ≲ 1014 GeV. Additional constraints relating the Electro-Weak (EW) and cosmological constant (c.c.) scales (denoted MEW and V0) appear if the Swampland condition mν1\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ {m}_{\ u_1} $$\\end{document} ≲ V01/4\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ {V}_0^{1/4} $$\\end{document} is imposed (with ν1 denoting the lightest neutrino), which itself arises upon applying the AdS non-SUSY Conjecture or the AdS/dS Distance Conjecture to the 3d vacua from circle compactifications of the SM. In particular, the EW scale and that of the extra dimension fulfill m0MEW ≲ 102V01/4\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ {V}_0^{1/4} $$\\end{document}Mp, thus relating the EW hierarchy problem to that of the c.c. Hence, all fundamental scales may be written as powers of the c.c., i.e. m• ∼ V0δMp1−4δ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ {V}_0^{\\delta }{M}_p^{1-4\\delta } $$\\end{document}. The scale of SUSY breaking is m3/2 ≲ 7 × 105 GeV, which favours a Mini-Split scenario that could be possibly tested at LHC and/or FCC.

Feasibility study of a steel-UHPFRC hybrid tower for offshore wind turbines

A steel-ultra high performance fibre reinforced composites (steel-UHPFRC) hybrid tubular tower structure (≥100m) is proposed and its feasibility to support an offshore wind turbine (OWT) with a 10 MW rotor is investigated in this paper. The hybrid tower combines a reinforced UHPFRC tube at the bottom and a steel tube at the top. Two numerical models are established to calculate the ultimate and fatigue loads for the hybrid tower and a standard steel tube tower as a reference. A simplified method is proposed to estimate the ultimate strength of the reinforced UHPFRC tube section, while a method based on the S–N curves is used to check its fatigue strength. It is found that the hybrid tower can satisfy design requirements and has a much longer fatigue life compared to the reference steel tower. Furthermore, the total material cost of the hybrid tower is found to be only 58% of that of the reference steel tower, while the masses of these two towers are kept close.

Research on online monitoring technology for transmission tower bolt looseness

Minor damages such as tower bolt looseness are difficult to detect through manual inspections. Operational modal analysis plays an important role in the online monitoring of transmission tower structure safety. However, the traditional analysis methods select feature parameters manually, and the deviation generated will directly affect the estimation accuracy of structural modal parameters. This article proposes a method for diagnosing tower bolt looseness without human intervention. This method can reduce the influence of background noise greatly through data cleaning and data fusion. Besides, the intelligent feature recognition of vibration acceleration time-domain signals based on an improved 1DCNN algorithm can improve the monitoring accuracy and speed significantly. The effectiveness of the method has been validated by conducting dynamic response tests on a 110KV transmission tower under different bolt loosening conditions. In the end, an online monitoring technology for transmission towers bolt looseness has been developed and successfully applied to the Guangdong power grid. The results show that this method has high identification accuracy and provides a new approach for online monitoring of tower bolt looseness.

Study on mechanical properties of wind turbine tower reinforced by ribbed interlayer

In order to avoid the economic loss caused by the demolition and reconstruction of old steel wind turbine towers and to meet the demand of new generating units for tower strength and stiffness, this paper proposes a laminated ribbed structure for strengthening old wind turbine towers based on the concept of hollow laminated steel pipe concrete. The four interlayer ribbed reinforced cylinder specimens were made of two steel cylinders, both round and concentric, with vertical stiffening ribs evenly arranged on the inner surface of the outer cylinder and the outer surface of the inner cylinder, and concrete was poured between the two cylinders. The number of cavities, concrete thickness and shear-to-span ratio were used as the test parameters to conduct compression-bending tests on five specimens. The test results show that: the damage phenomenon of the specimen is obvious, the material performance of each component is fully played, and the stiffening ribs can effectively alleviate the local bulging of the specimen; in terms of ultimate bearing capacity, the most influential is the shear-to-span ratio, the smaller the shear-to-span ratio, the larger the ultimate bearing capacity, increasing the concrete thickness and the number of cavities can effectively improve the ultimate bearing capacity; in terms of initial stiffness and ductility, the increase of the number of cavities will significantly improve the initial stiffness and ductility of the specimen. In terms of initial stiffness and ductility, increasing the number of cavities will significantly improve the initial stiffness and ductility of the specimen. The reinforcement effect of sandwich layer with ribbed structure on the tower structure is remarkable. The finite element analysis software ABAQUS was used to establish a model consistent with the test, and the calculation results were compared with the test results to verify the feasibility and accuracy of the established model and the material intrinsic structure relationship. On this basis, typical members are selected, and the stresses and plastic strains are combined with the longitudinal stresses and plastic strains to analyze the whole process of the stresses in the reinforced barrel of the sandwich ribbed structure in depth. The research results provide the theoretical basis and experimental basis for wind turbine tower reinforcement.