• Geomechanics and Engineering
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• 제16권4호
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• pp.341-353
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• 2018

A reinforced concrete pedestrian tunnel is constructed under a four-track surface railway. Heavy rainfall and soil exposure to drying lead to soil with different water content throughout the year. A railway is an open utility that is subject to rainfall without control on the quantity of the water on it and when there is a tunnel under a railway, the water content of the soil around the tunnel is very influential. This research shows the effects of change of water content in the soil around a pedestrian tunnel under a four-track surface railway. The pedestrian tunnel and the soil block around the tunnel are modeled in 3D by the FEM and are studied under the vibrations induced by the moving trains on the four-track surface railway for different soil water contents and the effects of the soil water content on the dynamic behavior of the tunnel and the surrounding soil are demonstrated.

• Wind and Structures
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• 제9권6호
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• pp.473-492
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• 2006

This paper presents numerical results of pedestrian-level wind environment around the base of a row of tall buildings by CFD. Four configurations of building arrangement are computed including a single square tall building. Computed results of pedestrian-level wind flow patterns and wind speeds are compared to previous wind tunnel measurement data to enable an assessment of CFD predictions. The CFD model uses the finite-volume method with RNG $k-{\varepsilon}$ model for turbulence closure. It is found that the numerical results can reproduce key features of pedestrian-level wind environment such as corner streams around corners of upwind building, sheltered zones behind buildings and channeled high-speed flow through a building gap. However, there are some differences between CFD results and wind tunnel data in the wind speed distribution and locations of highest wind speeds inside the corner streams. In locations of high ground-level wind speeds, CFD values match wind tunnel data within ${\pm}10%$.

• 조명전기설비학회논문지
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• 제23권9호
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• pp.6-16
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• 2009

최근 거리상의 이점에 의해 도심 터널에 보행로의 추가 설치가 늘어남에 따라 터널 내 환경이 문제가 되고 있다. 그러므로 본 연구는 도심 터널 보행로의 조도 및 불쾌글레어를 측정하여 실제 보행자가 느끼는 빛 환경에 대한 실태조사를 실시하였다. 조도와 불쾌글레어의 물리적인 측정은 동작구에 위치한 'S터널'을 대상으로 야간과 주간으로 구분하여 실시되었다. 또한 실제 보행자가 느끼는 주관적 반응을 알아보기 위해 밝기와 불쾌 글레어에 대한 설문조사를 실시하였다. 조사 결과, 보행자는 야간보다 주간에 보행로를 어둡게 느끼는 것으로 나타났으며, 불쾌글레어 지수는 야간의 경우 더 높게 나타남을 알 수 있었다. 본 연구의 결과는 서울시에서 실시하고 있는 '터널보행로 환경개선 사업'에 있어 조명환경 개선을 위한 기초자료로 사용될 수 있을 것이라 생각된다.

• 한국방사선학회논문지
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• 제14권4호
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• pp.385-390
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• 2020

외부의 환경적인 요인은 인간 건강에 많은 영향을 준다. 특히 요즘시대에 가장 중요한 맹점은 미세먼지이다. 미세먼지는 인간의 호흡기를 통해 흡입되면 폐 속에 깊이 침투되기 때문에 다양한 건강 문제를 발생시킨다. 우리의 생활주변 환경에서는 자동차와 사람이 통행할 수 있는 터널을 쉽게 볼 수 있다. 이번 연구에서는 서울 및 경기도 내의 보행 가능한 터널 7개를 무작위로 선정하여 터널 내부의 먼지 량과 비산 방사선량을 측정하여 먼지 량과 방사선량의 상관관계를 알아보고자 하였다. 측정방법은 날씨가 좋은날 (미세먼지수준: 0~30 ㎍/㎥)과 보통날 (미세먼지수준: 0~80 ㎍/㎥)을 선택하여 터널내부의 먼지 량과 방사선량을 각각이 측정하였다. 측정 결과는 미세먼지 수준이 적은 날 즉, 날씨가 좋은 날은 보행터널 중심에서 10-20 % 먼지가 증가되었으며 미세먼지의 수준이 보통인 날은 터널 초입보다는 터널 중심에서 20-30 % 의 먼지가 증가되는 결과를 얻었다. 반면에 방사선량의 터널 측정결과는 날씨에 의존하지 않고 터널 초입보다는 터널 중심에서 10-20 % 방사선량이 증가가 되는 것으로 측정되었다. 결론적으로 사람이 오랜 시간터널에 머무를 경우에는 비산 먼지와 비산 방사선에 주의를 기울여야한다. 따라서 빈번하게 일반인이 터널보행 시에 본인의 건강을 위해 PM2.5 이하의 필터 마스크 착용을 권고한다.

• Wind and Structures
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• 제5권2_3_4호
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• pp.151-164
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• 2002

Predictions of the pedestrian level wind speeds for the downtown area of Auckland that have been obtained by wind tunnel and computational fluid dynamic (CFD) modelling are presented. The wind tunnel method involves the observation of erosion patterns as the wind speed is progressively increased. The computational solutions are mean flow calculations, which were obtained by using the finite volume code PHOENICS and the $k-{\varepsilon}$ turbulence model. The results for a variety of wind directions are compared, and it is observed that while the patterns are similar there are noticeable differences. A possible explanation for these differences arises because the tunnel prediction technique is sensitivity to gust wind speeds while the CFD method predicts mean wind speeds. It is shown that in many cases the computational model indicates high mean wind speeds near the corner of a building while the erosion patterns are consistent with eddies being shed from the edge of the building and swept downstream.

• Wind and Structures
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• 제30권3호
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• pp.317-323
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• 2020

A novel approach is presented to improve dynamic responses of a pedestrian bridge by utilizing decorative wind chimes. Through wind tunnel tests, it was verified that wind chimes can provide stabilization effects against flutter instability, especially at positive or negative wind angles of attack. At zero degrees of angle of attack, the wind chimes can change the flutter pattern from rapid divergence to gradual divergence. The decorative wind chimes can also provide damping effects to suppress the lateral sway motion of the bridge caused by pedestrian footfalls and wind forces. For this purpose, the swing frequency of the wind chimes should be about the same as the structural frequency, which can be achieved by adjusting the swing length of the wind chimes. The mass and the swing damping level are other two important and mutually interactive parameters in addition to the swing length. In general, 3% to 5% swing damping is necessary to achieve favorite results. In the study case, the equivalent damping level of the entire system can be increased from originally assumed 1% up to 5% by using optimized wind chimes.

• Wind and Structures
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• 제9권2호
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• pp.147-158
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• 2006

The purpose of this paper is to find a more accurate method to evaluate pedestrian wind by computational fluid dynamics approach. Previous computational fluid dynamics studies of wind environmental problems were mostly performed by simplified models, which only use simple geometric shapes, such as cubes and cylinders, to represent buildings and structures. However, to have more accurate and complete evaluation results, various shapes of blocking objects, such as trees, should also be taken into consideration. The aerodynamic effects of these various shapes of objects can decrease wind velocity and increase turbulence intensity. Previous studies simply omitted the errors generated from these various shapes of blocking objects. Adding real geometrical trees to the numerical models makes the calculating domain of CFD very complicated due to geometry generation and grid meshing problems. In this case the function of Porous Media Condition can solve the problem by adding trees into numerical models without increasing the mesh grids. The comparison results between numerical and wind tunnel model are close if the parameters of porous media condition are well adjusted.

• Wind and Structures
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• 제11권1호
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• pp.51-70
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• 2008

CFD is applied to evaluate pedestrian wind comfort at outdoor platforms in a high-rise apartment building. Model validation is focused on generic building sub-configurations that are obtained by decomposition of the actual complex building geometry. The comfort study is performed during the design stage, which allows structural design changes to be made for wind comfort improvement. Preliminary simulations are performed to determine the effect of different design modifications. A full wind comfort assessment study is conducted for the final design. Structural remedial measures for this building, aimed at reducing pressure short-circuiting, appear to be successful in bringing the discomfort probability estimates down to acceptable levels. Finally, the importance of one of the main sources of uncertainty in this type of wind comfort studies is illustrated. It is shown that the uncertainty about the terrain roughness classification can strongly influence the outcome of wind comfort studies and can lead to wrong decisions. This problem is present to the same extent in both wind tunnel and CFD wind comfort studies when applying the same particular procedure for terrain relation contributions as used in this paper.

• 대한토목학회논문집
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• 제39권2호
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• pp.287-296
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• 2019

최근 지자체들이 경쟁하듯이 건설하고 있는 장경간 케이블 보도교(일명 출렁다리)는 공원 시설로 인식되어 제대로 된 검토와 설계 없이 진행되는 경우가 있다. 케이블 보도교는 기존 도로 현수교보다 훨씬 유연한 특성으로 인하여 내풍안정성 확보는 반드시 필요하며, 오히려 더 기존의 도로교보다 다양한 관점에서 상세하게 검토되어야 한다. 이에 본 연구에서는 케이블 보도교의 내풍 특성을 파악하고, 고유진동수를 추정할 수 있는 추정식을 제시하였다. 또한 경간장에 따른 플러터 풍속 추정에 대한 추세선을 제시하여 평판 거더 보도교의 내풍안정성 확보의 어려움과 그 한계를 제시하였다. 그리고 풍동실험을 통해 바닥 데크 그레이팅 적용 비율 변화를 통해 내풍안정성을 만족하는 단면을 제시하였다. 본 연구에서 제시한 방법은 향후 세장 케이블 보도교 계획시 기초 자료로 활용할 수 있을 것으로 판단된다.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2008년도 정기 학술대회
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• pp.402-409
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• 2008

Wind loads and environments in realistic situations surrounded by neighboring buildings may be considerably different from those in idealized or simplified situations such as codes and standards. Interference effects of change in wind passage of a building group on wind loads and wind environments are reviewed. Wind-induced interference effects depend mainly on the building geometry and arrangement of these structures, their orientation and upstream terrain conditions. The most important factor among them may be the arrangement of building structures which can change the wind direction directly. Interference effects regarding wind loads are discussed with examples of window damages by typhoon and of pressure measurements in the boundary layer wind tunnel. Wind environment problems are also discussed, specially underlined on pedestrian comfort and safety. Various evaluation techniques or standards of wind environment are introduced. The change of wind velocity between the panel-type apartment buildings is examined, depending on the distance each other.