• Wind and Structures
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• 제31권6호
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• pp.533-548
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• 2020

Despite the current technologic developments, failures in existent tensile fabric structures (TFS) subjected to wind do happen. However, design pressure coefficients are only obtained for large projects. Moreover, studies on TFSs with realistic supporting frames, comparing static and dynamic analyses and discussing the design implications, are lacking. In this study, fluid-Structure analyses of a TFS supported by masts and inclined cables, by subjecting it to different wind speeds, are carried out, to gain more understanding in the above-referred aspects. Wind-induced stresses in the fabric and axial forces in masts and cables are assessed for a hypar by using computational fluid dynamics. Comparisons are carried out versus an equivalent static analysis and also versus loadings deemed representative for design. The procedure includes the so-called form-finding, a finite element formulation for the TFS and the fluid formulation. The selected structure is deemed realistic, since the supporting frame is included and the shape and geometry of the TFS are not uncommon. It is found that by carrying out an equivalent static analysis with the determined pressure coefficients, differences of up to 24% for stresses in the fabric, 5.4% for the compressive force in the masts and 21% for the tensile force in the cables are found with respect to results of the dynamic analysis. If wind loads commonly considered for design are used, significant differences are also found, specially for the reactions at the supporting frame. The results in this study can be used as an aid by designers and researchers.

• 한국항공우주학회지
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• 제35권7호
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• pp.575-580
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• 2007

카나드 형상 고기동 항공기의 개념 설계 단계에서 높은 받음각 항공기 정적 안정성 분석을 위해 저속 소형 풍동시험을 수행하였다. 본 연구에서는 1/50축척의 일반적인 카나드-동체-날개 형상을 소형 풍동시험 모델로 사용하였다. 높은 받음각 비선형특성을 포함한 정적 안정성을 분석하기 위하여 카나드 굽힘에 따른 수직 꼬리 날개 효과를 분석하였다. 또한 높은 받음각에서 Nose Chine 효과를 분석하였다. 실험 연구에서 얻은 결과를 토대로 카나드 형상 항공기 높은 받음각 정적 안정성에 미치는 형상 변화 효과를 분석할 수 있었다.

• 한국태양에너지학회 논문집
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• 제35권3호
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• pp.49-56
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• 2015

This paper presents a comparative operating characteristics of static var compensator(SVC) and static synchronous compensator(STATCOM) for compensating the reactive power in the Jeju power system. There are two kinds of reactive power compensating systems, which are active and passive system in the applications of the line commutated converter type high voltage direct current (LCC-HVDC). In the Jeju power system, two STATCOMs as active compensating system have been operating. Even though STATCOM has good performance compared with SVC, economical efficiency of former system is not good to the latter system. So, it is necessary to examine the performance and economical efficiency depend on the intention before appling the system. To compare the operating characteristics of two systems in the Jeju power system, simulations have been carried out for case studies that both of the HVDC system have transient state by using PSCAD/EMTDC program.

• Wind and Structures
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• 제21권2호
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• pp.241-272
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• 2015

In the current study, dynamic and quasi-static analyses were performed to investigate the response of multiple-spanned and single-spanned transmission line conductors under both downburst and synoptic winds considering different wind velocities and different length spans. Two critical downburst configurations, recommended in the literature and expected to cause maximum conductor reactions, were considered in the analyses. The objective of the study was to assess the importance of including the dynamic effect when predicting the conductor's reactions on the towers. This was achieved by calculating the mean, the background and the resonant reaction components, and evaluating the contribution of the resonant component to the peak reaction. The results show that the maximum contribution of the resonant component is generally low (in the order of 6%) for the multiple-spanned system at different wind velocities for both downburst and synoptic winds. For the single-spanned system, the result show a relatively high maximum contribution (in the order of 16%) at low wind velocity and a low maximum contribution (in the order of 6%) at high wind velocity for both downburst and synoptic winds. Such contributions may justify the usage of the quasi-static approach for analyzing transmission line conductors subjected to the high wind velocities typically used for the line design.

• Wind and Structures
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• 제21권6호
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• pp.609-623
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• 2015

Seismic reliability analysis of a jacket-type support structure for an offshore wind turbine was performed. When defining the limit state function by using the dynamic response of the support structure, a number of dynamic calculations must be performed in a First-Order Reliability Method (FORM). That means analysis costs become too high. In this paper, a new reliability analysis approach using a static response is used. The dynamic effect of the response is considered by introducing a new parameter called the Peak Response Factor (PRF). The probability distribution of PRF can be estimated by using the peak value in the dynamic response. The probability distribution of the PRF was obtained by analyzing dynamic responses during a set of ground motions. A numerical example is presented to compare the proposed approach with the conventional static response-based approach.

• Steel and Composite Structures
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• 제21권3호
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• pp.517-536
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• 2016

Thick steel plate is commonly found with mega steel structures but its properties have not been fully explored. Grade Q345GJ-C steel plate with thickness ranging from 60 mm to 120 mm are studied in this paper. Both the static and cyclic performance of material in different directions (horizontal and through-thickness directions) and locations (outer surface, 1/4 thickness and mid-depth) are experimentally obtained. The accumulative damage during cyclic loading is also calculated by using bilinear mixed hardening (BMH) constitutive relationship together with the Lemaitre's damage model. Results show that the static properties are better at the outer surface of thick steel plates than those at mid-depth. Properties in through-thickness direction are similar to those at mid-depth in the horizontal direction. The cyclic performance at different locations of a given plate is similar within the range of strain amplitude studied. However, when damage parameters identified from monotonic tensile tests are included in the numerical simulation of cyclic loading tests, damage is found accumulating faster at mid-depth than close to outer surface.

• Wind and Structures
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• 제25권6호
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• pp.551-567
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• 2017

Studies of unsymmetrical blade H-Darrieus rotors at low wind speeds in terms of starting time, static torque, and power performances for different blade parameters: thickness-to-chord (t/c), camber position, and solidity are scarce. However these are required for knowing insights of rotor performances to obtain some design guidelines for the selection of these rotors. Here, an attempt is made to quantify the effects of these blade parameters on the performances of three different H-Darrieus rotors at various low wind streams. Different blade profiles, namely S815, EN0005 (both unsymmetrical), and NACA 0018 (symmetrical blade for comparison) are considered. The rotors are investigated rigorously in a centrifugal blower apparatus. Firstly the dynamic and static performances of the rotors are evaluated to determine the best performing rotor and their optimum solidity. Generalised performance equations are developed based on selected blade parameters which are validated for the unsymmetrical rotors. Further, the starting time is quantified with respect to the rotor inertia to determine the suitable range of inertia that helps the unsymmetrical blade rotor to self-start earlier than the symmetrical one. This study can work as a benchmark for the selection of optimum blade parameters while designing an unsymmetrical blade rotor at low wind speeds.

• Wind and Structures
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• 제20권5호
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• pp.683-699
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• 2015

Lighting poles and antenna masts are typically high, slender and light structures. Moreover, they are often characterized by distributed eccentricities that make very complex their shape. Experience teaches that this structural type frequently suffers severe damage and even collapses due to wind actions. To understand and interpret the aerodynamic and aeroelastic behavior of lighting poles and antenna masts, this paper presents the results of static and aeroelastic wind tunnel tests carried out on a complex prismatic element representing a segment of the shaft of such structures. Static tests are aimed at determining the aerodynamic coefficients and the Strouhal number of the test element cross-section; the former are used to evaluate the critical conditions for galloping occurrence based on quasi-steady theory; the latter provides the critical conditions for vortex-induced vibrations. Aeroelastic tests are aimed at reproducing the real behavior of the test element and at verifying the validity and reliability of quasi-steady theory. The galloping hysteresis phenomenon is identified through aeroelastic experiments conducted on increasing and decreasing the mean wind velocity.

• 국제강구조저널
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• 제18권4호
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• pp.1431-1439
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• 2018

For floating buildings may fl oat on the water for a long time, they are constantly affected by various environmental loads such as wind and wave loads. In this study to find the wave effect on the floating building, five models are designed using steel moment resisting frame. It is assumed that the lower part of the floating building is a reinforced concrete pontoon, while the upper part is a three-story steel frame. To analyze floating buildings affected by wind and wave loads, hydro-dynamic and substructure analysis are performed. As input loads, this study set limits that the mean wind velocity is 35 m/s and the significant wave height is 0.5 m for the residential building. From the hydrodynamic analysis, the time-history acceleration of building is obtained and transformed into a base ground input for a substructure analysis of the superstructure of the building. Finally the mean of the maximum from 30 dynamic analysis of the floating buildings are used to be compared with the results of the same model on the ground. It was shown that the dynamic results with wind and wave loads are not always lesser than the static results which are calculated with static equivalent wind load for a building that is located on the ground.

• Wind and Structures
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• 제4권5호
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• pp.383-398
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• 2001

The paper describes the results of the monitoring of an elevated steel water-tank with unusual shape, 85 m high and 40 m wide. The research was carried out analysing both the static and dynamic behaviour under wind actions. The instruments used (some of which were employed for the first time for this project) are described and the data processing procedures are discussed. Comparison between the experimental results and those obtained through a numerical model gives interesting information both on the structural behaviour and on the characterisation of wind actions.