• Wind and Structures
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• 제13권1호
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• pp.1-20
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• 2010

The recommended factored design wind load effects for overhead lattice transmission line towers by codes and standards are evaluated based on the applicable wind load factor, gust response factor and design wind speed. The current factors and design wind speed were developed considering linear elastic responses and selected notional target safety levels. However, information on the nonlinear inelastic responses of such towers under extreme dynamic wind loading, and on the structural capacity curves of the towers in relation to the design capacities, is lacking. The knowledge and assessment of the capacity curve, and its relation to the design strength, is important to evaluate the integrity and reliability of these towers. Such an assessment was performed in the present study, using a nonlinear static pushover (NSP) analysis and incremental dynamic analysis (IDA), both of which are commonly used in earthquake engineering. For the IDA, temporal and spatially varying wind speeds are simulated based on power spectral density and coherence functions. Numerical results show that the structural capacity curves of the tower determined from the NSP analysis depend on the load pattern, and that the curves determined from the nonlinear static pushover analysis are similar to those obtained from IDA.

• Architectural research
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• 제14권4호
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• pp.117-124
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• 2012

High rise office buildings represent one of the most energy-intensive architectural typologies. The growth of urban population necessitates sustainable high rise towers that lessen environmental impacts and energy consumption. Among various sustainable strategies, the integrated design is long known to be an important process that has great impact on building's sustainability. The framework for this paper is based on the case study of integrated towers that are located in different climate zones. The paper specifically addresses to what extent climate conditions influence the design of a high rise building and what kinds of the climate integrated design has been implemented. Qualitative case studies were carried out using published data and architectural drawing set. The technical work presented in the paper is based on computer simulation that examines the insolation analysis using hourly recorded weather data. The analysis results revealed that the site and building envelope integration and the site and building service systems have shown the most frequently employed in the integrated towers through the implementation of renewable resource integration, high performance envelopes and sustainable building service systems. Internal comfort and further energy saving in the integrated towers are offered through an automatic building management system. Due to the dynamic climate conditions, integration of building systems requires a sophisticated approach to building sustainability.

• Korean Journal of Hydrosciences
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• 제10권
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• pp.73-83
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• 1999

The intake towers of Buyeo W.T.P. in Keum river have being suffered from the sedimentation problems since the beginning of the operation. Impellers of the intake pumps have to the frequently changed due to the serious surface erosion. Thousands tons of sands are entrapped in the intake towers and equalization chambers of W.T.P. every year. Site surveying and numerical analysis were carried out to suggest an appropriate solution by understanding the general sedimentation regime of Keum river and causes of the sedimentation in the intake towers. Origin of the sediment could be found by the desk and site inspections. The validity of the used numerical models was examined by comparisons between the calculated bydraulic values and the measured ones during the specific periods. The design flow rate for the prediction of the future sedimentation regime of the rever was studied. The efficiency of the sediment control measures was also examined with the verified numerical models. Finally, it was found that the best solution could be a combination of three sediment control measures; increase the clearance between river bed and inlet, construct jetties at 2 kilometers upstream from the intake towers, and put vanes at the right side of the intake towers.

• International Journal of Fluid Machinery and Systems
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• 제4권1호
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• pp.150-160
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• 2011

This study focuses on the Achard turbine, a vertical axis, cross-flow, marine current turbine module. Similar modules can be superposed to form towers. A marine or river hydropower farm consists of a cluster of barges, each gathering several parallel rows of towers, running in stabilized current. Two-dimensional numerical modelling is performed in a horizontal cross-section of all towers, using FLUENT and COMSOL Multiphysics. Numerical models validation with experimental results is performed through the velocity distribution, depicted by Acoustic Doppler Velocimetry, in the wake of the middle turbine within a farm model. As long as the numerical flow in the wake fits the experiments, the numerical results for the power coefficient (turbine efficiency) are trustworthy. The overall farm efficiency, with respect to the spatial arrangement of the towers, was depicted by 2D modelling of the unsteady flow inside the farm, using COMSOL Multiphysics. Rows of overlapping parallel towers ensure the increase of global efficiency of the farm.

• 대한전기학회논문지:전력기술부문A
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• 제55권5호
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• pp.195-201
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• 2006

Tower footing resistance and fault current division factor are important design factors for evaluation of the lightning performance of the transmission line and/or design of the grounding electrode system. The periodic measurement of those factors are also important to verify that the grounding performance of the towers has been maintained good. However, the direct measurement of those factors in operating or energized condition is very difficult because of many practical reasons, such as the difficulty of disconnecting overhead groundwires from the tower under test. With supports by GECOL (General Electricitiy Company of Libya), we had a special chance to conduct Fall-Of-Potential (FOP) test on the energized 220 kV transmission towers before and after disconnecting the overhead groundwires from the towers under test. In this paper, the FOP test results on the towers and the fault current division factors estimated from the comparision of the FOP tests with and without overhead groundwires were presented. The computer models for the FOP test simulations were also constructed to find that the simulated results agreed very well with the measured ones.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 추계학술대회 논문집 전력기술부문
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• pp.20-22
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• 2003

This paper focuses on the effects of wind pressure on transmission towers. It recommends the need for an application method to strengthen some existing towers, especially those in areas regularly affected by typhoons, and to be applied to new constructions. Some considerations taken into account were modifying existing towers exposed, which can cause significant damage to the power system and the effects of damage on third parties.

• 국제초고층학회논문집
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• 제5권4호
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• pp.305-318
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• 2016

In the design of super-tall towers, engineers often find the conventional frame systems used in countless buildings in the past decades incapable of providing the required form, performance and constructability demanded by super-tall heights. The strength of the diagrid as a structural system in high-rise towers is the total flexibility it affords the designer as an adaptable, efficient and buildable scheme. Using fundamental engineering principles combined with modern computational tools, designers can take minimum load path forms to create rationalized diagrid geometries to create optimized, highly efficient towers. The use of diagrid frames at SOM has evolved as a structural typology beginning with the large braced frames on the John Hancock Center and continued in modern applications proving to be a powerful system in meeting the demands of supertall buildings.

• Steel and Composite Structures
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• 제26권1호
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• pp.45-53
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• 2018

Experimental investigations have revealed significant mismatches between analytical estimates and experimentally measured deflections of transmission towers. These are attributed to bolt slip and joint flexibility. This study focuses on effects of joint flexibility on tower deflections and proposes criterions for permissible deflection limits based on the stresses in joints. The objective has been framed given that guidelines are not available in the codes of practices for transmission towers with regard to the permissible limits of deflection. The analysis procedure is geometric and material nonlinear with consideration of joint flexibility in the form of extension or contraction of the cover plates. The deflections due to bolt slip are included in the study by scaling up the deflections obtained from analysis by a factor. Using the results of the analysis, deflection limits for the towers are proposed by limiting the stresses in the joints. The obtained limits are then applied to a new full scale tower to demonstrate the application of the current study.

• Computational Structural Engineering : An International Journal
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• 제2권1호
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• pp.25-32
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• 2002

Natural draught cooling towers often develop visible crack structures as consequences of progressive damage processes over their life-time. The aim of this paper is a numerical demonstration of the progressive damage process of cooling towers, representatively for the reinforced concrete structures, in order to improve the durability and extend the life-time of structures subjected to such damage processes. For the analyses, the applied material model for reinforced concrete will be briefly introduced. An existing natural draught cooling tower with a pronounced crack structure, in which this crack structure indicates the typical damage pattern of large cooling towers will be numerically simulated. The change of dynamical behavior of the structure with regard to natural frequencies, reflecting the global damage process due to the degrading stiffness of the structure in dependence of the load type and intensity, will be presented and discussed.

• Wind and Structures
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• 제4권6호
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• pp.495-504
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• 2001

With a newly developed multi-force-balance system(MFB), a twin-tower structure was studied for its wind-induced responses. The MFB system allowed the twin towers, which were linked structurally, to be treated as a single structural system with its corresponding modes of vibration involving coupled motions of the two towers. The towers were also studied using a more conventional force balance approach in which each tower was treated as an isolated structure, i.e., as though no structural link existed. Comparison of the results reveals how the wind loads between the towers are redistributed through the structural links and the modal couplings. The results suggest that although the structural links usually have beneficial impacts on wind-induced response, they may also play a negative role if the frequency ratios of pair modes are near 1.0.