Capacity Of Tower Research Articles

Wind fragility assessment and sensitivity analysis for a transmission tower-line system

Wind fragility is essential to performance-based wind engineering, risk, and resilience assessment for transmission towers. However, it has not been sufficiently studied due to the key issues in performance evaluation and uncertainty treatment for transmission towers. The performance of high-rise structures can be severely weakened by geometric imperfections, but these impacts have not been well addressed for transmission towers. Besides, the current uncertainty treatment only considers the tower itself although the transmission tower is part of an interconnected tower-line system that has complex interactions with wind environment. Therefore, this paper provides a systemic solution for geometric imperfections of transmission towers, where the users can clearly observe the effect of geometric imperfections on the capacity and failure positions of transmission towers. On this basis, a wind fragility framework that incorporates the uncertainties of each line component, wind environment, and aerodynamic parameters is proposed for transmission towers. Finally, sensitivity analysis was conducted to identify the significant uncertainty parameters for tower capacity and demand by sensitivity diagram. It is found that in addition to the uncertainties of the tower itself, the uncertainties of wind profile exponent, outer diameter and aerodynamic parameter of conductors have significant effects on the fragility of transmission towers.

Comparison of the Influence of Double-Limb Double-Plate Joint on the Stability Bearing Capacity of Triangular and Quadrilateral Transmission Tower Structures

The axial stiffness of the connection joints in a transmission tower will affect the stability bearing capacity of the tower. The axial stiffness of different forms of connection joints has different effects on the stability bearing capacities of triangular and quadrilateral lattice towers. This paper takes triangular and quadrilateral lattice towers as the comparative research objects and considers the influence of the stiffness of the single-limb, single-plate joint (SLSPJ) and double-limb, double-plate joint (DLDPJ) of the tower. Under vertical load, the vertical stability bearing capacities of triangular and quadrilateral transmission towers are studied from hte three aspects of theoretical analysis, numerical simulation and test result analysis. The influence rules of the SLSPJ and DLDPJ on the vertical stability bearing capacities of triangular and quadrilateral transmission towers are clarified. Through the energy method, considering the influence of the axial stiffness of connection joints, the calculation expressions of the vertical stability bearing capacities of triangular and quadrilateral lattice towers are derived. Through quantitative analysis, it is found that the axial stiffness of the connection joints has a more significant influence on the vertical stability bearing capacities of triangular lattice towers. The finite element models of the triangular and quadrilateral lattice towers including the SLSPJ and DLDPJ are further established. Through nonlinear finite element analysis, it is found that the DLDPJ can improve the vertical stability bearing capacity of the triangular lattice tower by 22.7% and the quadrilateral lattice tower by 14.9%. Through theoretical calculation, the expressions of the vertical stability bearing capacities of the triangular and quadrilateral lattice towers including the SLSPJ and DLDPJ are obtained. Combined with the test results of the SLSPJ and DLDPJ, it is found that the DLDPJ can improve the vertical stability bearing capacity of the triangular lattice tower by 23.4% and the quadrilateral lattice tower by 15.6%. The research results show that the DLDPJ can improve the vertical stability bearing capacities of triangular and quadrilateral lattice towers. The improvement effect of the vertical stability bearing capacity of the triangular lattice tower is 1.50∼1.52 times that of the quadrilateral lattice tower. The research results can provide a reference for the engineering popularization, application, and design of the DLDPJ in transmission towers.

Numerical and full-scale test case studies on post-elastic performance of transmission towers

Post-elastic capacity of transmission tower is critical for the realistic assessment of tower vulnerability under the extreme loading conditions. This paper first presented a series of numerical simulations of a lattice transmission tower section under torsional (longitudinal) or bending (transverse) loading in both static and dynamic scenarios. From the results of the numerical simulations, four prototypes of lattice transmission towers were constructed and tested for the investigation of the post-elastic performances of the towers under different loading conditions. The tests results showed that there existed significant post-elastic strength reserve of the tower under investigation. For the towers tested in this research, the post-elastic strength reserve was 1.22 for flexure-torsion (i.e. tower under longitudinal loading) governed by diagonals, and 1.37 for bending (i.e. tower in transverse loading) governed by inelastic buckling of the main legs. Diagonal members affected the failure modes of transmission towers and their connection design may be a weak link in the development of their post-elastic capacity.

Characterization of Long-chain fatty ester (Loxiol GXX): A study on heat transfer of spray tower

Loxiol GXX is a type of commercial long-chain fatty ester that is produced by a reaction between long-chain fatty acid and long-chain fatty alcohol. The characterization of Loxiol GXX were carried out in terms of its structure, chemical and thermal properties. The result of pore size distribution (PSD) showed that 18% of the product is less than 250 µm. Then, the results from X-Ray Diffraction (XRD) and Fourier Transform Infra-Red (FTIR) confirmed the crystalline structure and functional groups of the sample. Further analysis by Differential Scanning Calorimetry (DSC) gives the results of thermal properties, which were used in evaluating the extension capacity of spray tower cooling load at different feed rate. It is expected that the findings from this study will be useful in contributing to the knowledge of long-chain fatty ester’s characters and up-scaling of chemical plant. For the current spray tower plant, it was concluded that the existing cooling capacity of 160 kW is possibly enough to provide heat exchange up to 2000 kg/hr feed rate.

Influence of Double-Limb Double-Plate Connection on Stable Bearing Capacity of Quadrilateral Transmission Tower

Transmission tower connection joint is an important connection component of the tower leg member and diagonal member. Its axial stiffness directly affects the stable bearing capacity of a transmission tower. The axial stiffness of the joint is mainly related to the connection form of joint. This paper takes the double-limb double-plate connection joint as the research object. Through the comparative study with the single-limb single-plate connection joint, the influence law of single-limb single-plate and double-limb double-plate joint on stable bearing capacity of quadrilateral transmission tower is studied from three aspects of model test, theoretical analysis and numerical simulation. Through the scale model test, it is found that the elastic stiffness of the double-limb double-plate joint is 3.12 times that of the single-limb single-plate joint, which can increase the bearing capacity of the joint by 26.1%. Through the energy method, the theoretical calculation expression of the stable bearing capacity of the quadrilateral tower considering the influence of the axial stiffness of the joint is derived. Compared with the effect of the single-limb single-plate connection joint, the double-limb double-plate joint can improve the stable bearing capacity of the quadrilateral tower by 15.6%. Considering the influence of geometric nonlinearity of tower and connecting joint, it is found that the double-limb double-plate connecting joint can improve the nonlinear stability bearing capacity of a transmission tower by 14.9%. The results show that the double-limb double-plate connection joint can not only improve the bearing capacity of the joint, but also greatly improve the stable bearing capacity of the tower. The research results can provide reference for the engineering application and design of double-limb double-plate connection joints.

Performance based assessment of transmission lines to seismic events

Typical transmission line steel lattice towers are not designed for seismic excitations, based on the assumption that their ultimate limit state is governed by climatic actions (wind and ice). However, it is not unusual for line inspection reports to indicate the observation of moderate to severe structural damages after intense ground motions, which can ultimately reduce the capacity of tower elements. Performance-Based Earthquake Engineering (PBEE) assessment is a modern technique to earthquake resistant design frequently adopted for building frame structures, but not yet employed in the design of transmission line supports, to the best of the authors’ knowledge. The present article evaluates the seismic performance of two typical 230kV transmission towers in a PBEE framework, considering artificial and actual ground motions based on Chilean seismicity. Time-domain nonlinear dynamic analysis is employed to numerically obtain tower responses considering distinct earthquake loading scenarios according to two model configurations: stand-alone and tower-line section. Significant structural damage was detected even for moderate ground motions, which might reduce the tower capacity to future climatic events. The estimated failure probability for the ultimate limit state was found greater than the recommended values in the standard IEC 60826 (2017).

Comparative Study on the Cooling Characteristics of Different Fill Layout Patterns on a Single Air Inlet Induced Draft Cooling Tower

To enhance the cooling capacity of a single air inlet induced draft cooling tower (SIDCT), the stepped fill layout pattern is proposed in this paper. A three-dimensional numerical model is established and validated by field measurement data. The cooling capacity of towers equipped with uniform fill and stepped fill is compared under various crosswind velocities (0 m/s–12 m/s) and crosswind angles (0°–180°). The results showed that the ventilation rate of the total tower with stepped fill is increased. Under the studied crosswind velocity and angle, the cooling capacity of the stepped fill tower is superior to the uniform fill tower. After using stepped fill, the mean drop of outlet water temperature rises by 0.29 °C, 0.27 °C, 0.17 °C, 0.10 °C, and 0.19 °C, corresponding to crosswind angles from 0° to 180°. The increment of cooling capacity is the maximum under the crosswind angles of 0° and 45° and is the minimum under the crosswind angles of 90° and 135°. The maximum increased value of N is 0.65 under the crosswind velocity of 4 m/s, 0.85 under 8 m/s, and 0.95 under 12 m/s.

Integrated Optimization Framework for the Design and Scheduling of Batch Cooling Water Networks

Cooling water system (CWS) research traditionally focuses on the interactions between the cooling water network (CWN) and cooling tower performance, with a continuous background process. Very limited research has considered the integration of batch production and utility systems. This work presents a mathematical framework for the synthesis and optimization of a CWS consisting of multiple cooling towers operating with a batch background process. The CWN exhibits a series configuration, which is characterized by cooling water reuse. A batch CWS superstructure is developed which represents all different pairings between the cooling towers and the batch background network. It is worth mentioning that in previous research, the utilization of cooling water reuse opportunities was constrained by temperature only; however, due to the nature of batch processing, the utilization of cooling water reuse opportunities is subject to both temperature and time constraints. The benefits of this research for retrofit design is the increase in cooling tower availability. In the case of grassroots design, the capital expenditure for cooling tower capacity is reduced. The mathematical model is developed as a mixed-integer nonlinear programming (MINLP) problem within the GAMS platform. The MINLP is solved by making use of the BARON solver ensuring global optimality. Two illustrative examples are presented. Results indicate a 0.45% increase in the annual profit, a reduction of 42.1% in the total recirculating cooling water requirement, and a 25.3% increase in the average overall cooling tower effectiveness. Capital costs and plant area savings were introduced through a reduction in the number of cooling towers required from 3 to 2. The makeup water consumed was also reduced by 6.3%; this reduced the operational costs and plant water footprint. One of the drawbacks of the model presented is the computational time requirement. Future work will address this concern by implementing decomposition and investigating the use of alternative batch background scheduling formulations.

Wind-Resistant Capacity Modeling for Electric Transmission Line Towers Using Kriging Surrogates and Its Application to Structural Fragility

Wind loading on a transmission tower structure is jointly influenced by the wind field, structural parameters, and the geo-spatial configuration of the transmission line. Considering the multi-parametric effect, this paper aims at developing a limit capacity model for transmission towers under strong winds. To this end, the limit capacity of the tower is expressed via two equivalent means: one is the limit wind speed as a function of the wind angle of attack and the span of transmission line; the other is a limit capacity surface with three fundamental wind load components as the principal axes. An adaptive kriging surrogate modeling is constructed to approximate the function/surface with structural uncertainties considered. The performance of the surrogate model is improved by adding support points and then evaluated by the overall accuracy validation and local error check. A numerical example demonstrating the feasibility of the surrogate modeling for the limit capacity of the transmission tower under winds is presented. Finally, a fragility assessment concerning a practical transmission line and towers subjected to typhoons is accomplished using the established limit capacity model of the tower.

Study on the effects of apex angle of the delta-type radiator on thermo-flow performance of natural draft dry cooling tower

A numerical model was established to reveal the effects of apex angle of the vertical arranged delta-type radiators on thermo-flow performance of natural draft dry cooling tower. When radiator number is fixed, a large apex angle along with the corresponding long tower base diameter contribute to tower performance improvement. The wide apex angle slightly mitigates air inflow deviation at radiator’s inlet and draws in more fresh air. The long base diameter alleviates the adverse impacts of internal vortex formed after air inflow convergence on heat transfer of the downstream radiators. The maximum increment of cooling capacity of the tower 15.6% is achieved under the medium wind speed of 8 m/s as apex angel increases from 48° to 60°. As wind speed further increases, sideward and leeward radiators suffer a sharp performance decline, and their performances achieve much smaller enhancement brought by apex angle increase, compared with windward radiators. So downwind deflection of internal rising airflows is more severe under a larger apex angle. When tower base diameter is fixed, larger apex angle results in fewer radiators. Although cooling capacity of the entire tower drops under this strategy, the greater heat dissipation capacity of windward radiators under a larger apex angle would gradually make up the defect of fewer radiators as wind speed increases. However, using larger apex angle but fewer radiators causes an aggravated air inflow rate imbalance among the radiators, which accelerates performance degradations of leeward radiators.

Analysis of the effect of seasonal climate changes on cooling tower efficiency, and strategies for reducing cooling tower power consumption

Cooling towers are widely used in chemical industries to cool water with ambient air that is susceptible to weather changes not only during the day, but also during the year, resulting in challenges to cooling towers design and operation. In the design phase, the difficulties to determine the cooling tower capacity arise not only from the uncertainty of cooling water consumption but also from ambient temperature variations, which have a direct impact on the volume of cooling tower fill and fan power. Wide temperature variations can result in cooling towers that excessively cool water during significant portion of the year. Moreover, an oversized cooling tower brings challenges to the plant operation, since the cooling tower turndown must be high to account for the colder days. The mathematical model of cooling tower operation that is composed by mass and energy balances, and by cooling tower characteristic equations can be simulated to design cooling towers, and forecast their performances in four Brazilian cities (Manaus, Salvador, São Paulo and Porto Alegre). Analyzing the results enables the calculation of the cooling tower slack, and the required turndown during the year in these four cities. This work proposes strategies for cooling tower fan operation to reduce the slack, and estimates the electrical energy cost reduction if such strategies are implemented.

Peningkatan Performansi Cooling Tower Tipe Induced Draft Counter Flow Menggunakan Variasi Bentuk Filler

This study aims to build and test a cooling tower. Cooling tower is a heat exchanger that functions to cool the hot water from the condenser and throw heat into the atmosphere at a power plant. This is done so that the temperature of the hot water from the condenser can cool as the original condition. One component of the cooling tower compiler is filler. Filler is a component that is very influential on cooling tower performance, where the contact surface between water and air is expanded and the contact time is extended. The study was conducted experimentally using the NTU (Number of Transfer Unit) method. The variations made in this study are straight filler, zig zag, and wavy shape. The parameters observed are the rate of heat transfer, cooling tower capacity and the effectiveness of the cooling tower.

Fragility modelling framework for transmission line towers under winds

Extreme winds may expose overhead transmission lines to loads that may result in the collapse of transmission towers leading to severe economic losses. This paper develops a modelling framework to assess the fragility of transmission towers under extreme winds such as tropical storms. To this end, the wind loading on a transmission tower is represented by a combination of three wind load components (i.e., the transverse and longitudinal tower loads as well as the wire load) expressed in terms of three key wind load-related input parameters (wind speed, wind angle of attack and horizontal span of the transmission line). The wind load-carrying capacity of towers is accordingly defined by a three-dimensional convex-curve surface with the three wind load components as the principle axes. A kriging surrogate model is established for the tower capacity surface as a function of uncertain structural parameters, based on the results from the nonlinear static analysis of the tower and Latin-hypercube sampling. Accordingly, the limit state function would suggest tower failure if the wind load effect exceeds the tower capacity defined by the surface. In this framework, the tower fragility is established by the Monte Carlo simulation. If the wind intensity, wind direction and line configuration are known, the wind load components can be evaluated. Utilizing the surrogate model, the capacity surfaces of sample towers are also obtained in terms of the simulated uncertain structural parameters simulated. Comparison between the estimated wind load components and the simulated sample surfaces yields the fragility curve. The proposed framework is demonstrated by a numerical example, as well as an application to a typhoon scenario analysis in which the failure probability of a real-world long-distance transmission line is assessed.

Structural capacity of a wind turbine tower considering fatigue damage over time

The extremely changing nature of the wind action generates fatigue effects on wind sensitive structures, such as Wind Turbines (WT). Here, the wind-induced response over time of a WT tower located in Oaxaca, Mexico, is calculated considering fatigue damage. The analyses consider three main stages: time cero (at the moment of the tower installation, considering no damage), service time, considering different levels of damage at the tower’s base (corresponding to 20, 24, 30, 40 and 43 years), and time near the collapse limit state of the tower (about 47 years). In order to characterize these effects, a methodology that uses an ARMA model to simulate time-series of turbulent wind speed, and a non-lineal fatigue damage model is proposed. The structural capacity of the tower is obtained over time and details about the impact of wind-induced fatigue on the capacity of the WT are highlighted.

PERILAKU STRUKTUR TOWER TRANSMISI TIPE SUSPENSION TERHADAP BEBAN ANGIN

The need for electricity supply in Indonesia is getting bigger along with the higher population growth. This gives encouragement to stakeholders to expand infrastructure development in the electricity sector. Nationally, the biggest demand for electricity is industrial sector, followed by household, business, and general sectors. In its application, the tower transmission structure has a major role to distribute the electricity needs in general. Transmission tower structure is classified as Truss structure. The truss frame is a structure consisting of a combination of rods forming triangular structures connected to each other, and encumbered in their joints. With the concept of balance of style and design of the existing code can be determined the capacity of tower and the response of the structure when carrying the primary loads, especially wind loads.

중고층 모듈러 건축공사 타워크레인 위치 및 제원 선정 모델 개발

중고층 모듈러 건축공사 타워크레인 위치 및 제원 선정 모델 개발

Capacity of a transmission tower under downburst wind loading

The wind velocity profile over the height of a structure in high intensity wind (HIW) events, such as downbursts, differs from that associated with atmospheric boundary layer (ABL) winds. Current design codes for lattice transmission structures contain only limited advice on the treatment of HIW effects, and structural design is carried out using wind load profiles and response factors derived for ABL winds. The present study assesses the load-deformation curve (capacity curve) of a transmission tower under modeled downburst wind loading, and compares it with that obtained for an ABL wind loading profile. The analysis considers nonlinear inelastic response under simulated downburst wind fields. The capacity curve is represented using the relationship between the base shear and the maximum tip displacement. The results indicate that the capacity curve remains relatively consistent between different downburst scenarios and an ABL loading profile. The use of the capacity curve avoids the difficulty associated with defining a reference wind speed and corresponding wind profile that are adequate and applicable for downburst and ABL winds, thereby allowing a direct comparison of response under synoptic and downburst events. Uncertainty propagation analysis is carried out to evaluate the tower capacity by considering the uncertainty in material properties and geometric variables. The results indicated the coefficient of variation of the tower capacity is small compared to those associated with extreme wind speeds.

Holistic Approach for Retrofit Design of Cooling Water Networks

Optimization of closed-loop cooling water systems (CCWS) is essential to reduce operating and capital costs. These systems are generally designed with heat exchangers in parallel arrangement. Although this arrangement is easy to operate, it results in inefficient use of cooling tower capacity and incurs more capital and operating costs. Existing CCWS can be retrofitted by changing heat exchangers from parallel to series or series/parallel arrangement. Previous research on cooling water retrofit design is mainly focused on methods to reduce cooling water flow rate without considering cooling tower operation, pressure drops, and capital costs. With pressure drop and capital cost considerations, minimizing cooling water flow rate does not necessarily give the optimum savings. In the present paper, a holistic approach for retrofit design of CCWS involving multiple cooling towers and heat exchangers is presented by considering exchanger network pressure drops, cooling tower operation, and piping costs besides ...

Experimental Study on Mechanical Behavior of Wind Turbine Frustum Tower

One scale model of 1.5MW wind turbine frustum tower in Baiyun Obo was carried on pseudo-static test. The failure mechanism and characteristics, stress changes and distribution laws, hysteresis performance and ultimate bearing capacity were studied. Test results show that the wind turbine tower belong to the sudden extreme point instability failure; the buckling bearing capacity is as the ultimate bearing capacity of tower. The maximum stresses of tower mainly distribute at the variable wall thickness section and bottom, while other parts basically dont yield. This indicate that the material utilization of this kind of tower structure remains relatively low, structural design has yet to be improved, at the same time recommends that reasonable strengthen measures should be taken at the weakest part of tower. The P-Δ hysteretic curve of tower shows anti-"S" shape, the overall strength and stiffness degenerate more rapidly, which indicates that the plastic deformation and energy dissipation capacity of frustum tower is poor. The test conclusions could reflect the stress condition of prototype tower and provide references for design.

Inspection and Evaluation of Load-Bearing Capacity of Single Tower Composite Girder Cable-Stayed Bridge

In order to evaluate single tower composite girder Cable Bridge actual bearing capacity and working property on design using load, a single-tower composite girder cable-stayed bridge is taken as an example, by means of static load test, dynamic load test, reasonably measures evaluates the single tower composite girder cable-stayed bridge's bearing capacity. The static load test measure static properties of bridge structure (static strain, static deflection, etc.), dynamic load test, measure the dynamic properties of bridge structure (vibration frequency, damping, forced vibration amplitude, impact coefficient, etc.). Results show that the rigidity strength integrity and dynamic characteristics of bridge structure are favorable; the structure’s bearing capacity is favorable.