• Wind and Structures
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• 제18권6호
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• pp.651-668
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• 2014

Wind tunnel tests are conducted to investigate the wind loads on vertical fixed-roof cylindrical tanks with a very low aspect ratio of 0.275, which is a typical ratio for practical tanks with a volume of $100,000m^3$. Both the flat-roof tank and the dome-roof tank are investigated in present study. The first four moments of the measured wind pressure, including the mean and normalized deviation pressure, kurtosis and skewness of the pressure signal, are obtained to study the feature of the wind loads. It is shown that the wind loads are closely related to the behavior of flow around the structure. For either tank, the mean wind pressures on the cylinder are positive on the windward area and negative on the sides and the wake area, and the mean wind pressures on the whole roof are negative. The roof configurations have no considerable influence on the mean pressure distributions of cylindrical wall in general. Highly non-Gaussian feature is found in either tank. Conditional sampling technique, envelope method, and the proper orthogonal decomposition (POD) analysis are employed to investigate the characteristics of wind loads on the cylinder in more detail. It is shown that the patterns of wind pressure obtained from conditional sampling are similar to the mean pressure patterns.An instantaneous pressure coefficient can present a wide range from the maximum value to the minimum value. The quasi-steady assumption is not valid for structures considered in this paper according to the POD analysis.

• 한국터널지하공간학회 논문집
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• 제12권6호
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• pp.443-450
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• 2010

NATM 터널의 콘크리트라이닝은 국내 도입 초기에는 내장재로서 고려되었으나, 최근에는 구조재로서의 역할로 고려되고 있다. 따라서 설계 시 여러 가지 하중을 고려해야 하며, 그중에서도 지반이완하중은 콘크리트라이닝의 두께 및 철근보강유무를 결정하는 주요 하중이다. 도심지 지하철터널에서는 한계평형이론식 Terzaghi 암반분류 등을 사용하여 비교적 높은 이완하중을 적용하여 설계하고 있다. 본 연구에서는 이완하중 산정식들에 대해 검토하고 이완하중 산정법에 따른 구조계산을 수행하여 콘크리트라이닝의 거동을 파악하고자 한다.

• Wind and Structures
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• 제38권3호
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• pp.203-214
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• 2024

Large-span cantilevered roof represents a unique type of structure that is vulnerable to wind loads. Inspired by the need to maximumly reducing the rooftop wind loads, this study examined the feasibility of positioning vented slots on the leading edge, and the effectiveness of such aerodynamic mitigation measures are assessed via both physical and numerical simulations. The reliability of numerical simulation was evaluated via comparisons with the wind tunnel tests. The results indicated that, the variation of venting hole arrangement can cause significant change in the rooftop wind load characteristics. For the cases involved in this study, the maximum reduction of mean and peak wind suction coefficients are found to be 9% and 8% as compared to the original circular slot without venting holes. In addition, the effect of slot shape is also evident. It was shown that the triangular shaped slot tends to increase the wind suction near the leading edge, whereas the hexagonal and octagonal shaped slots are found to decrease the wind suction. In particular, with the installation of octagonal shaped slot, the maximum reduction of wind suction coefficients near the leading edge reaches up to 31% as compared to the circular shaped slot, while the maximum reduction of mean wind suction coefficients is about 30%.

• Wind and Structures
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• 제13권1호
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• pp.83-94
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• 2010

Wind tunnel measurements on T-shaped free-standing walls and inclined free-standing walls have been carried out. Mean net pressure coefficients have been derived and compared with previous research. It was observed that the high loads at the free ends are differently distributed than those derived from the pressure coefficients for free-standing walls in EN 1991-1-4. In addition net pressure coefficients based on extreme value analysis have been obtained. The lack of correlation of the wind induced pressures at windward and leeward side result in lower values for the net pressure coefficients when based on extreme value analysis. The results of this wind tunnel study have been included in Dutch guidelines for noise barriers.

• Wind and Structures
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• 제21권5호
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• pp.505-521
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• 2015

A general approach of aerodynamic optimization of tall buildings is presented in this paper, focusing on how to best compromise wind issues with other design aspects in the most efficient manner. The given approach is reinforced by establishing an empirical method that can quickly assess the across-wind loads and accelerations as a function of building frequencies, building dimensions, aspect ratios, depth-to-width ratios, and site exposures. Effects of corner modifications, including chamfered corner and recessed corner, can also be assessed in early design stages. Further, to assess the effectiveness of optimization by tapering, stepping or twisting building elevations, the authors introduce a method that takes use of sectional aerodynamic data derived from a simple wind tunnel pressure testing to estimate reductions on overall wind loads and accelerations for various optimization options, including tapering, stepping, twisting and/or their combinations. The advantage of the method is to considerably reduce the amount of wind tunnel testing efforts and speed up the process in finding the optimized building configurations.

• 대한건축학회논문집:구조계
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• 제35권7호
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• pp.157-164
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• 2019

The wind tunnel test makes it possible to predict the wind loads for the wind resistant design. There are many methods to evaluate wind loads from data obtained from the wind tunnel test and these methods have advantages and disadvantages. In this study, two of these methods were analyzed and compared. One is the wind load evaluation method by fluctuating displacement and the other is the wind load evaluation method considering vertical profile of fluctuating wind force. The former method is evaluated as the sum of the mean wind load of the average wind force and the maximum value of the fluctuating wind load. The latter method is evaluated as the sum of the mean wind load and maximum value of the background wind load, and the maximum value of the resonant wind load. Two methods were applied to the wind tunnel test to compare the evaluated wind loads according to the two methods, with a maximum difference of about 1.2 times. The wind load evaluated by the method considering vertical profile of the fluctuating wind force (VPFWF) was larger than the wind load evaluated by the method by fluctuating displacement (FD). Especially, the difference of the wind load according to the two methods is large in the lower part of the building and the wind load is reversed at a specific height of the building. VPFWF of evaluating resonant wind loads and background wind loads separately is more reasonable.

• Geomechanics and Engineering
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• 제15권3호
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• pp.911-917
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• 2018

This paper concerns a numerical investigation on the effect of construction sequence on three-arch (3-Arch) tunnel behavior. A three-arch tunnel section adopted in a railway tunnel construction site was considered in this study. A calibrated 3D finite element model was used to conduct a parametric study on a variety of construction scenarios. The results of analyses were examined in terms of tunnel and ground surface settlements, shotcrete lining stresses, loads and stresses developed in center column in relation to the tunnel construction sequence. In particular, the effect of the side tunnel construction sequence on the structural performance of the center structure was fully examined. The results indicated that the load, thus stress, in the center structure can be smaller when excavating two side tunnels from opposite direction than excavating in the same direction. Also revealed was that no face lagging distance between the two side tunnels impose less ground load to the center structure. Fundamental governing mechanism of three-arch tunnel behavior is also discussed based on the results.

• 한국터널지하공간학회 논문집
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• 제5권3호
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• pp.261-268
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• 2003

Terzaghi 터널 토압 산정식은 현재에 있어서도 보수적인 입장에서 터널 토압을 산정하는 지침으로 실무에서 활용되고 있다. 본 연구에서는 Terzaghi 터널 토압 모델을 성층 경사형 지반으로 확장하여 새로운 터널 토압 산정식을 유도하였으며 새롭게 유도된 터널 토압식을 이용하여 Terzaghi 터널 토압 산정식에 대한 재검토를 실시하였다.

• Wind and Structures
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• 제5권2_3_4호
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• pp.347-358
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• 2002

Mean surface pressures and overall wind loads on hemispherical domes immersed in a boundary layer were obtained by numerical simulation. The effects of alternative turbulence models, Reynolds Number and surface roughness were examined and compared with earlier studies. Surface pressures on dual hemispherical domes were also calculated for three wind orientations ($0^{\circ}$, $45^{\circ}$, and $90^{\circ}$) to evaluate flow field interactions. Calculated values were compared to wind-tunnel measurements made in equivalent flow conditions.

• Wind and Structures
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• 제14권4호
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• pp.321-335
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• 2011

The vulnerability of roofing components of contemporary houses built in cyclonic regions of Australia is assessed for increasing wind speeds. The wind loads and the component strengths are treated as random variables with their probability distributions derived from available data, testing, structural analysis and experience. Design details including types of structural components of houses are obtained from surveying houses and analyzing engineering drawings. Wind load statistics on different areas of the roof are obtained by wind tunnel model studies and compared with Australian/New Zealand Standard, AS/NZS 1170.2. Reliability methods are used for calculating the vulnerability of roofing components independently over the roof. Cladding and batten fixings near the windward gable edge are found to experience larger negative pressures than prescribed in AS/NZS 1170.2, and are most vulnerable to failure.