• Wind and Structures
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• 제36권4호
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• pp.263-275
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• 2023

As a new kind of construction facility for high rise buildings, the integral steel platform scaffold system (ISPS) consisting of the steel skeleton and suspended scaffold faces high wind during the construction procedure. The lattice structure type and existence of core tubes both make it difficult to estimate the wind load and calculate the wind-induced responses. In this study, an aeroelastic model with a geometry scale ratio of 1:25 based on the ISPS for Shanghai Tower, with the representative square profile, is manufactured and then tested in a wind tunnel. The first mode of the prototype ISPS is a torsional one with a frequency of only 0.68 Hz, and the model survives under extreme wind speed up to 50 m/s. The static wind load and wind vibration factors are derived based on the test result and supplementary finite element analysis, offering a reference for the following ISPS design. The spacer at the bottom of the suspended scaffold is suggested to be long enough to touch the core tube in the initial status to prevent the collision. Besides, aerodynamic wind loads and cross-wind loads are suggested to be included in the structural design of the ISPS.

• Wind and Structures
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• 제38권5호
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• pp.367-379
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• 2024

Compared with traditional transmission towers, T-shaped angle towers have long cross-arms and are specially used for ultrahigh-voltage direct-current (UHVDC) transmission. Nevertheless, the wind loads of T-shaped towers have not received much attention in previous studies. Consequently, a series of wind tunnel tests on the T-shaped towers featuring cross-arms of varying lengths were conducted using the high-frequency force balance (HFFB) technique. The test results reveal that the T-shaped tower's drag coefficients nearly remain constant at different testing velocities, demonstrating that Reynolds number effects are negligible in the test range of 1.26 × 10⁴-2.30 × 10⁴. The maximum values of the longitudinal base shear and torsion of the T-shaped tower are reached at 15° and 25° of wind incidence, respectively. In the yaw angle, the crosswind coefficients of the tower body are quite small, whereas those of the cross-arms are significant, and as a result, the assumption in some load codes (such as ASCE 74-2020, IEC 60826-2017 and EN 50341-1:2012) that the resultant force direction is the same as the wind direction may be inappropriate for the cross-arm situation. The fitting formulas for the wind load-distribution factors of the tower body and cross-arms are developed, respectively, which would greatly facilitate the determination of the wind loads on T-shaped angle towers.

• Wind and Structures
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• 제38권3호
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• pp.161-170
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• 2024

In recent years, there have been an increasing number of experimental studies showing the need to include robustness criteria in the design process to develop complex active control designs for practical implementation. The paper investigates the crosswind aerodynamic parameters after the blocking phase of a two-dimensional square cross-section structure by measuring the response in wind tunnel tests under light wind flow conditions. To improve the accuracy of the results, the interpolation of the experimental curves in the time domain and the analytical responses were numerically optimized to finalize the results. Due to this combined effect, the three aerodynamic parameters decrease with increasing wind speed and asymptotically affect the upper branch constants. This means that the aerodynamic parameters along the density distribution are minimal. Taylor series are utilized to describe the fuzzy nonlinear plant and derive the stability analysis using polynomial function for analyzing the aerodynamic parameters and numerical simulations. Due to it will yield intricate terms to ensure stability criterion, therefore we aim to avoid kinds issues by proposing a polynomial homogeneous framework and utilizing Euler's functions for homogeneous systems. Finally, we solve the problem of stabilization under the consideration by SOS (sum of squares) and assign its fuzzy controller based on the feasibility of demonstration of a nonlinear system as an example.

• Wind and Structures
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• 제38권4호
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• pp.277-293
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• 2024

The recorded thunderstorm winds at a point contain tri-directional components. The probabilistic characteristics of such recorded winds in terms of instantaneous mean wind speed and direction, and the probability distribution and the time-frequency dependent crossed and non-crossed power spectral density functions for the high-frequency fluctuating wind components are unclear. In the present study, we analyze the recorded tri-directional thunderstorm wind components by separating the recorded winds in terms of low-frequency time-varying mean wind speed and high-frequency fluctuating wind components in the alongwind direction and two orthogonal crosswind directions. We determine the time-varying mean wind speed and direction defined by azimuth and elevation angles, and analyze the spectra of high-frequency wind components in three orthogonal directions using continuous wavelet transforms. Additionally, we evaluate the coherence between each pair of fluctuating winds. Based on the analysis results, we develop empirical spectral models and lagged coherence models for the tri-directional fluctuating wind components, and we indicate that the fluctuating wind components can be treated as Gaussian. We show how they can be used to generate time histories of the tri-directional thunderstorm winds.

• Wind and Structures
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• 제38권6호
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• pp.411-425
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• 2024

To investigate the optimal aerodynamic parameters of wind barriers for the T-beam of high-speed railway (HSR) bridge and the wind field of the wind barrier-train-bridge system, the three-component forces of the system and the wind pressure on the vehicle surface were tested and analyzed through the sectional model wind test. The effects of wind velocity, with/without wind barrier, the height of wind barrier, and the air permeability of the wind barrier on the aerodynamic characteristics of the train-bridge system are discussed. Additionally, a CFD numerical model is constructed to evaluate the wind environment of the bridge surface with/without the wind barrier, and the impact of wind barrier on the running safety of vehicles are analyzed. Comprehensively considering the running safety of the train and the wind-resistant stability of the bridge, it is more appropriate to set the wind barrier height H as 3.5 m and the porosity 𝛽 as 30% respectively.

• Wind and Structures
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• 제27권4호
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• pp.255-267
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• 2018

This paper investigated the wind-snow flow around the bogie region of a high-speed train under crosswinds using a coupled numerical method of the unsteady Realizable $k-{\varepsilon}$ turbulence model and discrete phase model (DPM). The flow features around the bogie region were discussed and the influence of bogie fairing height on the snow accumulation on the bogie was also analyzed. Here the high-speed train was running at a speed of 200 km/h in a natural environment with the crosswind speed of 15 m/s. The mesh resolution and methodology for CFD analysis were validated against wind tunnel experiments. The results show that large negative pressure occurs locally on the bottom of wheels, electric motors, gear covers, while the positive pressure occurs locally on those windward surfaces. The airflow travels through the complex bogie and flows towards the rear bogie plate, causing a backflow in the upper space of the bogie region. The snow particles mainly accumulate on the wheels, electric motors, windward sides of gear covers, side fairings and back plate of the bogie. Longer side fairings increase the snow accumulation on the bogie, especially on the back plate, side fairings and brake clamps. However, the fairing height shows little impact on snow accumulation on the upper region of the bogie. Compared to short side fairings, a full length side fairing model contributes to more than two times of snow accumulation on the brake clamps, and more than 20% on the whole bogie.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2008년도 추계학술대회 논문집
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• pp.416-421
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• 2008

최근 세계 각국의 고속열차들은 속도 향상 측면에서 비약적인 발전을 보이고 있으며, 국내에서도 2007년부터 '차세대 고속철도 기술개발 사업'을 통해 최고속도 400km/h급의 고속열차 개발을 진행 중에 있다. 고속열차의 주행속도가 증가함에 따라 이전에는 제기되지 않았던 공기저항, 공력소음 문제, 열차의 교행 및 측풍에 의해 발생하는 압력변동, 터널출구에서 발생하는 미기압파 등의 문제들이 대두되고 있으며 이와 같은 문제들은 열차의 고속화를 제약하는 요인이 된다. 특히, 고속열차의 전두부 형상은 이러한 공기역학적 문제들과 밀접하게 연결되어 있으며, 팬터그래프의 소음 및 안정적인 집전 성능 확보 등도 속도 향상을 위해 반드시 고려해야하는 사항이다. 본 논문에서는 고속열차의 속도향상 노력의 일환으로 진행되고 있는 '공력해석 향상 기술'의 연구 내용과 더불어, 터널 미기압파 저감을 위한 전두부 형상 최적화 결과와 팬터그래프 공력성능 향상을 위한 강건 최적화 결과를 소개한다.

• Wind and Structures
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• 제34권5호
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• pp.407-419
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• 2022

Many factors should be considered by architects and designers for designing a tall building. Wind load is one of these important factors that govern the design of tall building structures and can become a serious challenge when buildings tend to be built very tall and slender. On the other hand, through the initial stages of a design process, choosing the design geometry greatly affects the wind-induced forces on a tall building. With this respect, geometric shapes with 3-fold rotational symmetry are one of the applied plan shapes in tall buildings. This study, therefore, aims to investigate the aerodynamic characteristics of 8 different geometrical shapes using Computational Fluid Dynamics (CFD) by measuring the drag and lift forces. A case study approach was conducted in which different building shape models have the same total gross area and the same height of 300 meters. The simulation was an incompressible transient flow that ran 1700 timesteps (85 seconds on the real-time scale). The results show a great difference between wind-induced force performance of buildings with different plan shapes. Generally, it is stated that the shapes with the same area, but with smaller perimeters, are better choices for reducing the drag force on buildings. Applying the lift force, the results show that the buildings with plan shapes that have rounded corners act better in crosswind flow while, those with sharp corners induce larger forces in the same direction. This study delivers more analytical understanding of building shapes and their behavior against the wind force through the parametric modelling.

• Journal of Radiation Protection and Research
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• 제28권4호
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• pp.311-319
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• 2003

본 연구는 격자형 가우시안 플룸모형을 Matlab언어를 이용하여 구축한 후, 영광원자력시설의 부지에서 시행된 추적자 확산실험자료를 이용하여 예측력을 평가하였다. 풍하방향으로는 20km까지 10m간격으로 격자를 구분하였으며, 풍하방향에 수직인 지표방향은 방출점을 중심으로 상하 5km를 각각 10m 간격으로 구분하여 $1,990{\times}1,000{\times}1$의 격자망으로 구성하였다. 실험당시의 대기안정도는 P-G방법에 의해 B등급으로 나타났으며 이를 이용하여 각 격자의 농도예측을 수행하였다. 반경 3km의 A-line의 경우가 반경 8km근방의 B-line에 비해 격자형 가우시안 모형의 예측력이 뛰어난 것으로 나타났으며, 방출점에서 거리가 멀어질수록 P-G방법에 의한 확산폭의 산정은 모형의 예측력을 떨어뜨리는 것으로 나타났다. 모형의 예측력을 향상시키기 위하여 P-G 방법에 의한 확산폭인 sigma y 및 sigma z를 선형계획법을 이용하여 수정하였다. 수정된 확산인자를 적용한 결과 3km와 8km 모두 모형의 예측력이 향상됨을 확인할 수 있었다. 향후 추적자 확산실험 데이터의 축적을 통해 기상조건에 따른 확산인자에 대한 경험식을 개발한다면 격자형 가우시안 모델이 원자력시설에서의 대기질 환경영향평가에 유용하게 쓰일 수 있을 것으로 기대된다.