• Wind and Structures
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• 제31권6호
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• pp.495-508
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• 2020

To investigate the structural behaviour of grouped tanks under wind loads, 2 problems need to be figured out, wind pressures on tank shells and critical loads of the shell under these pressure distribution patterns. Following the wind tunnel tests described in the companion paper, this paper firstly seeks to obtain wind loads on the external wall in a squarely-arranged cylindrical tank group by numerical simulation, considering various layouts. The outcomes demonstrate that the numerical method can provide similar results on wind pressures and better insights on grouping effects through extracted streamlines. Then, geometrically nonlinear analyses are performed using several selected potentially unfavourable wind pressure distributions. It is found that the critical load is controlled by limit point buckling when the tank is empty while excessive deformations when the tank is full. In particular, significant reductions of wind resistance are found on grouped full tanks compared to the isolated tank, considering both serviceability and ultimate limit state, which should receive special attention if the tank is expected to resist severe wind loads with the increase of liquid level.

• 전기학회논문지
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• 제59권3호
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• pp.531-535
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• 2010

345kV Incheon Thermal Power Plant Transmission Line Collapse Analysis and Countermeasures. The Typhoon Galmaegi which had been formed in July 15, 2008 diminished into a tropical cyclone and cooled the air above the West Sea. The cooled air colliding with the warm inland air caused a strong whirlwind at some places in the west seaside; the whirlwind battered the 345kV Incheon Thermal Power Plant Transmission Line to be collapsed. The resistance of transmission towers against wind pressure, one of the key elements in transmission line engineering, is designed to endure the pressure corresponding to the maximum instantaneous wind speed. Before the above accident happened, no transmission line has ever been collapsed by a whirlwind. So this paper is aimed to analyze causes that collapsed 345kV Incheon Thermal Power Plant transmission line and to introduce countermeasures.

• Wind and Structures
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• 제12권5호
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• pp.425-439
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• 2009

The expediency of revising universal rules for the combination of gravity and lateral actions of wind force-resisting steel structures recommended by the Standards EN 1990 and ASCE/SEI 7-05 is discussed. Extreme wind forces, gravity actions and their combinations for the limit state design of structures are considered. The effect of statistical uncertainties of extreme wind pressure and steel yield strength on the structural safety of beam-column joints of wind force-resisting multistory steel frames designed by the partial factor design (PFD) and the load and resistance factor design (LRFD) methods is demonstrated. The limit state criterion and the performance process of steel frame joints are presented and considered. Their long-term survival probability analysis is based on the unsophisticated method of transformed conditional probabilities. A numerical example illustrates some discrepancies in international design standards and the necessity to revise the rule of universal combinations of loads in wind and structural engineering.

• Wind and Structures
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• 제32권5호
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• pp.439-452
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• 2021

The concept of Performance objective assessment is extended to wind engineering. This approach applies using the Database-Assisted Design technique, relying on the aerodynamic database provided by the National Institute of Standards and Technology (NIST). A structural model of a low-rise building is analyzed to obtain influence coefficients for internal forces and displacements. Combining these coefficients with time histories of pressure coefficients on the envelope produces time histories of load effects on the structure, for example knee and ridge bending moments, and eave lateral drift. The peak values of such effects are represented by an extreme-value Type I Distribution, which allows the estimation of the gust wind speed leading to the mean hourly extreme loading that cause specific performance objective compromises. Firstly a fully correlated wind field over large tributary areas is assumed and then relaxed to utilize the denser pressure tap data available but with considerably more computational effort. The performance objectives are determined in accordance with the limit state load combinations given in the ASCE 7-16 provisions, particularly the Load and Resistance Factor Design (LRFD) method. The procedure is then repeated for several wind directions and different dominant opening scenarios to determine the cases that produce performance objective criteria. Comparisons with two approaches in ASCE 7 are made.

• Wind and Structures
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• 제16권6호
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• pp.579-601
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• 2013

Interference effects are of considerable concern for group hyperboloidal cooling towers, but evaluation methods and results are different from each other because of the insufficient understanding on the structure behavior. Therefore, the mechanical performance of hyperboloidal cooling tower shell under wind loads was illustrated according to some basic properties drawn from horizontal rings and cantilever beams. The hyperboloidal cooling tower shell can be regarded as the coupling of horizontal rings and meridian cantilever beams, and this perception is beneficial for understanding the mechanical performance under wind loads. Afterwards, the mean external latitude wind pressure distribution, CP(${\theta}$), was artificially adjusted to pursue the relationship between different CP(${\theta}$) and wind-induced responses. It was found that the maximum responses in hyperboloidal cooling tower shell are primarily dominated by the non-uniformity of CP(${\theta}$) but not the local pressure amplitude CP or overall resistance/drag coefficient CD. In all the internal forces, the maximum amplitude of meridian axial tension shows remarkable sensitivity to the variation of CP(${\theta}$) and it's also the controlling force in structure design, so it was selected as an indicator to evaluate the influence of CP(${\theta}$) on responses. Based on its sensitivity to different adjustment parameters of CP(${\theta}$), an comprehensive response influence factor, RIF, was deduced to assess the meridian axial tension for arbitrary CP(${\theta}$).

• 한국융합학회논문지
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• 제11권9호
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• pp.175-180
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• 2020

본 연구에서는 화물 운송 차량들을 모델링하였고 화물 운송 차량의 화물칸 및 윈드 디플렉터의 유무에 따른 유동해석을 수행하였다. Model A, B, C 모두, 100km/hr의 운행 속도를 기준으로 하여, 모델 형상의 윗부분에서 58m/에서 59m/s 사이로 가장 높은 유동 속도가 나타났다. Model A, B, C 세 모델들 모두 모델 형상의 앞부분에서 652Pa에서 671Pa사이에 공기저항의 압력이 가장 높게 나타났다. Model A의 최대 압력은 Model B 및 C에 비하여, 작게 나타나서, 속도에 대한 유동 저항이 가장 적게 작용한 것으로 사료된다. 따라서 Model A가 유류비 측면에서 공기 저항에 대한 유리한 조건을 가짐을 알 수 있다. Model C는 화물칸에서 급격하게 유동저항이 발생하는 Model B와 달리 유선형 형상의 윈드 디플렉터를 타고 공기가 조금 더 원활하게 흐르는 것을 확인할 수 있다. 따라서 각진 형상보다 유선형의 형상에서 공기저항 측면에서는 더 유리하다고 사료된다. 트럭 화물칸 및 윈드 디플렉터에 따른 운행중 공기흐름에 대한 해석 연구 결과를 적용함으로서, 본 연구가 실제적인 효율적인 설계와 미적인 융합에 적합하다고 보인다.

• Wind and Structures
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• 제25권5호
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• pp.433-457
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• 2017

As a novel typical wind-sensitive structure, the wind load and wind-induced structural behaviors of super-large straight-cone cooling towers are in an urgent need to be addressed and studied. A super large straight-cone steel cooling tower (189 m high, the highest in Asia) that is under construction in Shanxi Power Plant in China was taken as an example, for which four finite element models corresponding to four structural types: the main drum; main drum + stiffening rings; main drum + stiffening rings + auxiliary rings (auxiliary rings are hinged with the main drum and the ground respectively); and main drum + stiffening rings + auxiliary rings (auxiliary rings are fixed onto the main drum and the ground respectively), were established to compare and analyze the dynamic properties and force transferring paths of different models. After that, CFD method was used to conduct numerical simulation of flow field and mean wind load around the cooling tower. Through field measurements and wind tunnel tests at home and abroad, the reliability of using CFD method for numerical simulation was confirmed. On the basis of this, the surface flow and trail characteristics of the tower at different heights were derived and the wind pressure distribution curves for the internal and external surfaces at different heights of the tower were studied. Finally, based on the calculation results of wind-induced responses of the four models, the effects of stiffening rings, auxiliary rings, and different connecting modes on the dynamic properties and wind-induced responses of the tower structure were derived and analyzed; meanwhile, the effect mechanism of internal suction on such kind of cooling tower was discussed. The study results could provide references to the structure selection and wind resistance design of such type of steel cooling towers.

• Wind and Structures
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• 제26권2호
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• pp.75-87
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• 2018

A large number of low-rise buildings experienced serious roof covering failures under strong wind while few suffered structural damage. Clay and concrete tiles are two main kinds of roof covering. For the tile roof system, few researches were carried out based on Finite Element (FE) analysis due to the difficulty in the simulation of the interface between the tiles and the roof sheathing (the bonding materials, foam or mortar). In this paper, the FE analysis of a single clay or concrete tile with foam-set or mortar-set were built with the interface simulated by the equivalent nonlinear springs based on the mechanical uplift and displacement tests, and they were expanded into the whole roof. A detailed wind tunnel test was carried out at Tongji University to acquire the wind loads on these two kinds of roof tiles, and then the test data were fed into the FE analysis. For the purpose of validation and calibration, the results of FE analysis were compared with the full-scale performance ofthe tile roofs under simulated strong wind impact through one-of-a-kind Wall of Wind (WoW) apparatus at Florida International University. The results are consistent with the WoW test that the roof of concrete tiles with mortar-set provided the highest resistance, and the material defects or improper construction practices are the key factors to induce the roof tiles' failure. Meanwhile, the staggered setting of concrete tiles would help develop an interlocking mechanism between the tiles and increase their resistance.

• 한국안전학회지
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• 제16권4호
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• pp.1-6
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• 2001

An experimental study was carried out to investigate the emission characteristics of LP gas burner for the Practical combustion conditions including fm voltage, inlet area, gas Pressure, emission resistance, duct length and height. The result shows that CO is almost remains constant for the emission fan voltage, but significantly increases with the reduction rate of air inlet, up to 3000ppm at 50% of reduction rate. Also, the variation of gas pressure has no effect to CO of gas boiler due to its governor which controls gas pressure secondly, but it gives an rapid increase of CO for the gas range. The emission resistance test shows that CO is suddenly increased with the reduction rate of emission duct above 70% and main burner is stopped at 90%. The reverse wind test shows that CO is suddenly increased with the air velocity above 7m/s and main burner is stopped at 9m/s. The more horizontal length of emission duct is long and the vertical height is low, CO is infinitesimally increased.

• 한국건축시공학회지
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• 제16권2호
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• pp.125-131
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• 2016

도심지 건물의 증가는 친환경 공간에 대한 요구를 발생시키고, 이에 따라 옥상 및 인공지반 녹화의 보급이 급속히 증가되고 있다. 본 연구는 녹화시스템의 보급 확대를 위해 공법의 단순화, 일체화, 프리훼브화 개념을 적용, 연속 토양층 형성 박스 유닛형 녹화시스템을 개발하고, 이 시스템의 주요 성능으로 부착성, 내풍성, 단열성을 평가하여 적용 가능성을 검토하였다. 부착성 및 내풍성 시험결과, 설계 풍압 및 풍속과 비교하면 100m 높이의 건물에 설치해도 안전한 것을 확인하였고, 단열성 평가를 위해 120일간 측정한 내부 온도의 변화를 분석한 결과, 개발 시스템이 연속된 토양층을 형성하여 기존 유닛박스 시스템보다 주간은 17%, 야간은 45% 우수한 단열성능을 보여 주었다.