• Wind and Structures
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• v.4 no.1
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• pp.31-44
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• 2001

Mean concentrations of ammonia gas released as a tracer from an isolated low-rise building have been measured and predicted. Predictions were calculated using computational fluid dynamics (CFD) and two dispersion models: a diffusion model and a Lagrangian particle tracking technique. Explicit account was taken of the natural variation of wind direction by a technique based on the weighted summation of individual steady state wind direction results according to the probability density function of the wind direction. The results indicated that at distances >3 building heights downstream the weighted predictions from either model are satisfactory but that in the near wake the diffusion model is less successful. Weighted solutions give significantly improved predictions over unweighted results. Lack of plume spread is identified as the main cause of inaccuracies in predictions and this is linked to inadequate resolution of flow features and mixing in the CFD model. Further work on non-steady state simulation of wake flows for dispersion studies is recommended.

• Wind and Structures
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• v.30 no.1
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• pp.1-13
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• 2020

The loss prediction and assessment during extreme events such as wind hazards is always crucial for the group low-rise residential buildings. This paper analyses the effect of variation in building density on wind-induced loss for low-rise buildings and proposes a loss assessment method consequently. It is based on the damage matrices of the building envelope structures and the main load-bearing structure, which includes the influence factors such as structure type, preservation degree, building density, and interaction between different envelope components. Accordingly, based on field investigation and engineering experience, this study establishes a relevant building direct economic loss assessment model. Finally, the authors develop the Typhoon Disaster Management System to apply this loss assessment methodology to practice.

• 한국태양에너지학회:학술대회논문집
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• 2008.04a
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• pp.184-189
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• 2008

These days, Apartment is altered oversized and high-rise through construction techniques development. Also, the cost of cooling and heating load would be expected by balcony expansion into inner space caused by legalization. In specially, HVAC systems of high-rise residential building almost apply to pre-existence techniques of middle and low residential building except for consideration and methods of the air inflow minimization into indoor through mechanical ventilation is used in ventilation system. From these cause, window systems of high-rise apartments stands high in estimation of components. Thus, purpose of this study is to make a comparative study through difference of window systems.

• Journal of the Earthquake Engineering Society of Korea
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• v.25 no.5
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• pp.201-211
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• 2021

The Ministry of the Interior and Safety in Korea developed seismic fragility function for various building types in 2009. Damage states for most building types were determined by structural analyses of sample models and foreign references because actual cases damaged by earthquakes rarely exist in Korea. Low-rise, piloti-type buildings showed severe damage by brittle failure in columns due to insufficient stirrup details in the 2017 Pohang earthquake. Therefore, it is necessary to improve damage state criteria for piloti-type buildings by consulting actual outcomes from the earthquake. An analytical approach was conducted by developing analysis models of sample buildings reflecting insufficient stirrup details of columns to accomplish the purpose. The result showed that current spectral displacements of damage states for piloti-type buildings might be too large to estimate actual fragility. When the brittle behavior observed in the earthquake is reflected in the analysis model, one-fourth through one-sixth of current spectral displacements of damage states may be appropriate for existing low-rise, piloti-type buildings.

• Wind and Structures
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• v.36 no.6
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• pp.393-404
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• 2023

Skewness and kurtosis are important higher-order statistics for simulating non-Gaussian wind pressure series on low-rise buildings, but their predictions are less studied in comparison with those of the low order statistics as mean and rms. The distribution gradients of skewness and kurtosis on roofs are evidently higher than those of mean and rms, which increases their prediction difficulty. The conventional artificial neural networks (ANNs) used for predicting mean and rms show unsatisfactory accuracy in predicting skewness and kurtosis owing to the limited capacity of shallow learning of ANNs. In this work, the deep neural networks (DNNs) model with the ability of deep learning is introduced to predict the skewness and kurtosis on a low-rise building. For obtaining the optimal generalization of the DNNs model, the hyper parameters are automatically determined by Bayesian Optimization (BO). Moreover, for providing a benchmark for future studies on predicting higher order statistics, the data sets for training and testing the DNNs model are extracted from the internationally open NIST-UWO database, and the prediction errors of all taps are comprehensively quantified by various error metrices. The results show that the prediction accuracy in this study is apparently better than that in the literature, since the correlation coefficient between the predicted and experimental results is 0.99 and 0.75 in this paper and the literature respectively. In the untrained cornering wind direction, the distributions of skewness and kurtosis are well captured by DNNs on the whole building including the roof corner with strong non-normality, and the correlation coefficients between the predicted and experimental results are 0.99 and 0.95 for skewness and kurtosis respectively.

• Fire Science and Engineering
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• v.13 no.4
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• pp.61-67
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• 1999

• International Journal of High-Rise Buildings
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• v.8 no.4
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• pp.313-324
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• 2019

This paper presents the analysis of wind speeds data measured on top of three neighboring high-rise buildings close to a beach in Xiamen city, China, during Typhoon "Usagi" 2013. Wind tunnel simulation was carried out to validate the field measurement results. Turbulence intensity, turbulence integral scale, power spectrum and cross correlation of recorded wind speed were studied in details. The low frequency trend component of the typhoon speed was also discussed. The field measurement results show turbulence intensity has strong dependence to the wind speed, upwind terrain and even the relative location to the Typhoon center. The low frequency fluctuation could severely affect the characteristics of wind. Cross correlation of the measured wind speeds on different buildings also showed some dependence on the upwind terrain roughness. After typhoon made landfall, the spatial correlation of wind speeds became weak with the coherence attenuating quickly in frequency domain.

• International Journal of High-Rise Buildings
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• v.11 no.4
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• pp.321-329
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• 2022

High-rise buildings constructed adjacent to low-rise structures experience frequent damage caused by the associated strong wind. This study aimed to implement a standard evaluation of the wind environment and airflow characteristics around high-rise apartment blocks using wind tunnel tests (WTT) and computational fluid dynamics (CFD) simulations. The correlation coefficient between the CFD and wind tunnel results ranged between 0.6-0.8. Correlations below 0.8 were due to differences in the wake flow area range generated behind the target building according to wind direction angle and the effect of the surrounding buildings. In addition, a difference was observed between the average velocity ratio of the wake flow wind measured by the WTT and by the CFD analysis. The wind velocity values of the CFD analysis were therefore compensated, and, consequently, the correlations for most wind angles increased.

• Korean Journal of Environment and Ecology
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• v.34 no.5
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• pp.466-482
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• 2020

This study used 3D computational fluid dynamics (CFD) in the ENVI-met program to investigate how particulate matters (PM) generated on roads disperse through adjacent urban neighborhoods according to the urban development pattern. An urban area centered on a six-lane road in the vicinity of Miryang City Hall in Gyeongnam Province was selected to simulate the effect of the green space and building height on the PM concentration. The ENVI-met model considered the presence of green space and different building heights (high/low) on both sides of the road to examine the dispersion of PM. The result showed that the area of high-rise buildings and green space had the lowest PM concentration dispersed to the adjacent area, followed by the area of high-rise buildings and no green space. In contrast, the PM concentration remained relatively high for low-rise buildings, regardless of the green space. The reason for the low PM concentration in the area with high-rise buildings was a strong building wind, which caused PM to disperse to the outside, lowering the PM concentration quickly. These results indicate that the PM can disperse faster, and the PM concentration remains low in the urban neighborhood. On the other hand, green space had no significant effect on reducing PM in the urban neighborhood. In particular, when there are low-rise buildings on both sides of the road, the green space has no effect on the PM concentration in the urban neighborhood. Since this study considered only the case of PM emitted from the road, future studies should investigate other factors to figure out the dispersion model of PM and conduct on-site experiments.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.253-256
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• 2008

The objective of this study is to evaluate the seismic weakness of existing nonseismic low-rise piloti-type apartment buildings which have the irregularities of weak story, soft story, and torsion simultaneously. A prototype 4-story RC building was selected, analyzed using linear dynamic procedure and finally evaluated according to the acceptance criteria of FEM356. This building satisfies the criteria.