• Wind and Structures
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• 제20권2호
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• pp.349-361
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• 2015

Higher-mode vertical vortex-induced vibrations (VIV) have been observed on several steel box-girder suspension bridges where different vertical modes are selectively excited in turn with wind velocity in accordance with the Strouhal law. Understanding the relationship of VIV amplitudes for different modes of vibration is very important for wind-resistant design of long-span box-girder suspension bridges. In this study, the basic rectangular cross-section with side ratio of B/D=6 is used to investigate the effect of different modes on VIV amplitudes by section model tests. The section model is flexibly mounted in wind tunnel with a variety of spring constants for simulating different modes of vibration and the non-dimensional vertical amplitudes are determined as a function of reduced velocity U/fD. Two 'lock-in' ranges are observed at the same onset reduced velocities of approximately 4.8 and 9.4 for all cases. The second 'lock-in' range, which is induced by the conventional vortex shedding, consistently gives larger responses than the first one and the Sc-normalized maximum non-dimensional responses are almost the same for different spring constants. The first 'lock-in' range where the vibration frequency is approximately two times the vortex shedding frequency is probably a result of super-harmonic resonance or the "frequency demultiplication". The main conclusion drawn from the section model study, central to the higher-mode VIV of suspension bridges, is that the VIV amplitude for different modes is the same provided that the Sc number for these modes is identical.

• Wind and Structures
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• 제24권3호
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• pp.205-221
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• 2017

The unsteady flow field disturbance between the blades and tower is one of the primary factors affecting the aerodynamic performance of wind turbine. Based on the research object of a 3MW horizontal axis wind turbine which was developed independently by Nanjing University of Aeronautics and Astronautics, numerical simulation on the aerodynamic performance of wind turbine system in halt state with blades in different position was conducted using large eddy simulation (LES) method. Based on the 3D unsteady numerical simulation results in a total of eight conditions (determined by the relative position with the tower during the complete rotation process of the blade), the characteristics of wind pressure distributions of the wind turbine system and action mechanism of surrounding flow field were analysed. The effect of different position of blades on the aerodynamic performance of wind turbine in halt state as well as the disturbance effect was evaluated. Results of the study showed that the halt position of blades had significant effect on the wind pressure distribution of the wind turbine system as well as the characteristics of flow around. Relevant conclusions from this study provided reference for the wind-resistant design of large scale wind turbine system in different halt states.

• Smart Structures and Systems
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• 제25권1호
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• pp.81-96
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• 2020

Wind measurements were made on the Canton Tower at a height of 461 m above ground during the Typhoon Vincente, the wind-induced accelerations and displacements of the tower were recorded as well. Comparisons of measured wind parameters at upper level of atmospheric boundary layer with those adopted in wind tunnel testing were presented. The measured turbulence intensity can be smaller than the design value, indicating that the wind tunnel testing may underestimate the crosswind structural responses for certain lock-in velocity range of vortex shedding. Analyses of peak factors and power spectral density for acceleration response shows that the crosswind responses are a combination of gust-induced buffeting and vortex-induced vibrations in the certain range of wind directions. The identified modal frequencies and mode shapes from acceleration data are found to be in good agreement with existing experimental results and the prediction from the finite element model. The damping ratios increase with amplitude of vibration or equivalently wind velocity which may be attributed to aerodynamic damping. In addition, the natural frequencies determined from the measured displacement are very close to those determined from the acceleration data for the first two modes. Finally, the relation between displacement responses and wind speed/direction was investigated.

• 대한토목학회논문집
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• 제33권4호
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• pp.1271-1279
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• 2013

본 논문에서는 단기 관측자료를 활용하여 장대교량 현장의 기본풍속을 추정하는 방법에 대한 연구를 수행하였다. 기상관측소로부터 거리가 먼 장대교량의 내풍설계시 현장의 기본 풍속을 추정하기 위해 현장의 장기 풍속자료를 통계처리하는 것이 필요하다. 현장에 풍관측탑을 설치하고 단기간의 풍관측 자료를 확보하였고 선형회귀분석 및 MCP 방법을 이용하여 인근 기상관측소와의 상관관계를 분석하였다. 기상관측소의 장기풍자료를 지형보정을 한 후 상관관계식에 의해 현장의 장기 풍속자료를 얻었고 풍속자료의 극치 확률분포 분석에 의해 기본풍속 산정을 할 수 있었다. 연구결과에서는 선형회귀분석의 방법이 MCP 방법에 비해 풍속을 낮게 추정하고 있으며, 향후 여러 현장에서 일련의 상관관계 분석을 수행한다면 종합적으로 두 방법에 의한 기본풍속 산정의 차이를 보다 명확히 보여줄 것이다. 또한, 장기자료의 질 관리가 풍속추정에 매우 중요하다는 것을 보여주고 있다.

• Wind and Structures
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• 제18권4호
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• pp.443-456
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• 2014

A popular modern architectural form for tall buildings is two (or more) towers which are structurally linked through such features as a shared podium or sky-bridges. The fundamental features of the wind loading and the structural links of such buildings can be studied by measuring load components on the individual unlinked towers along with their correlations. This paper describes application of dual high frequency force balance (DHFFB) in a wind tunnel study of the base wind loading exerted on generic tall twin buildings in close proximity. Light models of two identical generic tall buildings of square plan were mounted on DHFFB and the base wind loading exerted on the buildings was simultaneously acquired. The effects of the relative positions of the buildings on the correlations and coherences involving loading components on each building and on the two buildings were investigated. For some relative positions, the effects of the building proximity on the wind loading were significant and the loading was markedly different from that exerted on single buildings. In addition, the correlations between the loadings on the two buildings were high. These effects have potential to significantly impact, for example, the modally-coupled resonant responses of the buildings to the aerodynamic excitations. The presented results were not meant to be recommended for direct application in wind resistant design of tall twin buildings. They were intended to show that wind loading on tall buildings in close proximity is significantly different from that on single buildings and that it can be conveniently mapped using DHFFB.

• 한국농공학회지
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• 제42권5호
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• pp.144-150
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• 2000

This study dealt with the comparison of lateral baring capacity for vertical PHC pile between predicted and measured values driven in weathered granite soils to build world cup gymnasium in Kwangju area. Recently, the calculation of horizontal bearing capacity of piles foundation has been considered very important for earthquake or wind resistant design in Korea. During this study , Matlock & Reese, Broms and Chang's methods were selected in prediction of lateral resistant of PHC piles. As for case study, the prediction values were compared with 5 measured ones based on ASTM. The result showed that prediction values proposed by Matlock & Reese , Chang and Broms were smaller that real values. Three proposed methods by Matlock & Reese and Chang based on lateral deflection and Broms by ultimated lateral resistance turned out valid in view of engineering practice.

• 생물환경조절학회지
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• 제10권3호
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• pp.148-154
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• 2001

본 연구에서는 1-2W형 플라스틱피복 파이프 온실의 내풍성을 증대시키기 위하여 형상 및 직경이 서로 다른 말뚝에 대하여 인발저항력을 검토하였다. 그 결과 민말뚝의 경우, 인발하중이 증가함에 따라 인발저항력은 증가하지만, 대부분의 경우 인발변위가 발생한 직후의 하중단계에서 극한인발저항력에 도달하였다. 그러나 주름말뚝의 경우는 인발변위가 발생한 이후에도 실험을 종료할 때까지 인발저항력의 증감이 반복되는 경향을 나타내었다. 그리고 기초의 형상, 직경 및 매입깊이에 따라 극한인발저항력은 다르지만, 본 실험의 경우 직경과 매입깊이에 관계없이 극한인발저항력은 주름말뚝이 민말뚝보다 약 2배 정도 크게 나타났다. 단위면적당 극한인발저항력은 매입깊이가 깊어질수록 증가하지만, 직경이 커지면 감소하였다. 실험 대상지역의 설계풍속(26.9m.s$^{-1}$)을 고려하면, 민말뚝은 매입깊이에 관계없이 기초의 인발저항력이 부족하였고, 주름말뚝의 경우은 대부분의 실험조건에서 충분한 것으로 나타났다.

• 한국지리정보학회지
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• 제18권3호
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• pp.1-10
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• 2015

급격한 도시팽창 및 각종 산업시설의 밀집화는 도심지역의 지형지물 변화에 많은 영향을 주게된다. 건물의 고층화가 진행되더라도 기존에 그 지역에 존재하던 주택 및 공업단지와 같은 저층건물과 혼재하게 되며, 이는 건물의 설계풍속 산정 시 중요한 요소인 지표면조도를 산정함에 있어 설계자에게 혼란을 주고 있다. 이러한 문제점을 해결하기 위해 본 연구는 지리정보를 이용하여 지표면조도를 산정하였다. 각 나라 건축구조기준 규정을 참고하여 연구범위 내 건물의 높이에 따라 지표면조도의 구분 방안을 제시하였으며, 1:5,000 수치지형도 자료 및 GIS를 활용하여 지표면조도를 산정하였다. 이는 설계자의 주관에 따라 지표면조도가 산정되는 기존의 문제점을 해결하고 보다 합리적인 내풍설계에 기여할 것으로 기대된다.

• Wind and Structures
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• 제27권2호
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• pp.137-147
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• 2018

Heavy damages to properties with attendant losses were frequently caused by tornadoes in recent years. This natural hazard is one of the most destructive wind events that must be fully studied and well understood in order to keep the safety of structures and infrastructure facilities. On June 23, 2016, a severe tornado, which is an Enhanced Fujita (EF) 4 storm, occurred in the rim of a coastal city named as Yancheng in China. Numerous low-rise buildings as well as facilities (e.g., transmission towers) were destroyed or damaged. In this paper, damages to structures and infrastructure facilities by the severe tornado are reviewed. The collapses of residential buildings, industrial structures and other infrastructure facilities are described. With an overview of the damages, various possible mechanisms of the collapse are then discussed and utilized to reveal the initiation of the damage to various facilities. It is hoped that this paper can provide a concise but comprehensive reference for the researchers and engineers to help understand the tornado effects on structures and expose the vulnerabilities that need to be improved in current wind-resistant design practices.

• 한국태양에너지학회:학술대회논문집
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• 한국태양에너지학회 2012년도 춘계학술발표대회 논문집
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• pp.331-336
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• 2012

Nowaday the conventional solar collector material prices are rising up because of pricy metal material over the world. The solar collector is too expensive to recycle to save the earth. Advanced polymer research is founded a high thermal resistant polymer and also it has high sun energy transmission. It also has cheaper material and easy manufacturing process, compare with conventional solar collector material. This paper is focussing on glazing simulation of polymer solar collector against wind pressure. The modeling geometry of polymer solar glazing are purposed by single layer, double layer hollow, zig-zag and tower. A simulation by using the Finite Volume was conducted to get Factor of Safety (FoS). The purpose of this paper is to find the best polymer glazing design, which can be as reference for the solar collector company to build Polymer. Hope fully new model of polymer solar collector has cheap, light, high sun energy transmitter, easy to be made and strong against wind force characteristics.