• 한국농공학회논문집
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• 제52권4호
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• pp.45-52
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• 2010

The purposes of this research are to analyze the internal settlement behavior of Concrete Faced Rockfill Dam (CFRD) typed 'D dam' and to evaluate the stability of the 'D dam' during dam construction using internal settlement measurements and results of numerical analysis. The field measurements were obtained during dam construction period. The numerical analysis was also carried out for the same construction period. The numerical analysis focused mainly on prediction of stress and displacement behavior of 'D dam' during dam construction stage using input parameters obtained from laboratory tests, i.e. large triaxial tests. The behavior of 'D dam' was evaluated to be stable from comparing the results of field measurements and numerical analysis. A simple empirical equation is also presented to predict final settlement at the completion of dam construction, using settlement measurement monitored during dam embankment.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2010년도 추계 학술발표회 2차
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• pp.171-180
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• 2010

In this study, applicability of software used to analyze the lateral deformations and its shape of braced cuts, executed to excavate the ground for constructing the underground structures, was assessed by performing field measurements and numerical analyses and their behaviors were also compared with results of previous studies. Three typical sections, located at the construction site where the subway was on the process of construction at Suwon city in Gyeonggido, were chosen and the data of field measurement at those sections were collected. Numerical analyses with FEM technique of using the software PLAXIS and elasto-plastic approach of using the software MIDAS were performed. In general, the deformed shapes of braced cut, obtained from numerical approaches, were in relatively good agreements with results from field measurements. For sections of A-A and B-B, measured values were greater than analyzed ones whereas they were in relatively good agreements in the section C-C. As results of comparing the values from the measurements and the estimations, they were found to be close to each other so that numerical approaches were assessed to be appropriate to estimate the lateral deformation. The numerical technique with FEM was preferred to use because it estimated closer to the measurements than the elasto-plastic approach.

• 대한원격탐사학회지
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• 제10권2호
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• pp.17-35
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• 1994

A semi-empirical model for microwave polarimetric radar backscattering from bare soil surfaces was developed using polarmetric radar measurements and the knowledge based on the theoretical and numerical solutions. The microwave polarimetric backscatter measurements were conducted for bare soil surfaces under a variety of roughness and moisture conditions at L-, C-, and X-band frequencies at incidence angles ranging from 10` to 70`. Since the accrate target parameters as well as the radar parameters are necessary for radar scattering modeling, a complete and accurate set of ground truth data were also collected using a laser profile meter and dielectric probes for each surface condition, from which accurate measurements were made of the rms height, correlation length, and dielectric constant. At first, the angular and spectral dependencies of the measured radar backscatter for a wide range of roughnesses and moisture conditions are examined. Then, the measured scattering behavior was tested using theoretical and numerical solutions. Based on the experimental observations and the theoretical and numerical solutions, a semi-empirical model was developed for backscattering coeffients in terms of the surface roughness parameters and the relative dielectric constant of the soil surface. The model was found to yield very good agreement with the backscattering measurements of this study as well as with independent measurements.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2001년도 봄 학술발표회 논문집
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• pp.33-40
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• 2001

In this research, the cracking of tunnel concrete lining was investigated and analyzed through long-term measurement and nonlinear numerical analysis. For one year after the casting of lining, the stresses and strains were measured by the sensors installed in hard rock tunnel lining. The measurements showed that only small stresses which were less than cracking stress occurred in every survey sections regardless of sensor directions. It could be induced that the external load applied to the lining was small or ignorable. Also, it was carried out short-term numerical analysis based on such site condition as ambient temperature, the- degree of overbreak and mold staying period. Long-term numerical analysis based on creep & shrinkage and nonlinear cracking was carried out. The output showed that construction condition and ambient environments could make the lining concrete crack without external loads. The cracks formed in this process does not indicate the structural instability of the tunnel.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2005년도 학술발표회(2)
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• pp.958-960
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• 2005

• Wind and Structures
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• 제32권4호
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• pp.371-391
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• 2021

Tornadoes are the most devastating meteorological natural hazards. Many empirical and theoretical numerical models of tornado vortex have been proposed, because it is difficult to carry out direct measurements of tornado velocity components. However, most of existing numerical models fail to explain the physical structure of tornado vortices. The present paper proposes a new empirical numerical model for a tornado vortex, and its load effects on a low-rise and a tall building are calculated and compared with those for existing numerical models. The velocity components of the proposed model show clear variations with radius and height, showing good agreement with the results of field measurements, wind tunnel experiments and computational fluid dynamics. Normal stresses in the columns of a low-rise building obtained from the proposed model show intermediate values when compared with those obtained from existing numerical models. Local forces on a tall building show clear variation with height and the largest local forces show similar values to most existing numerical models. Local forces increase with increasing turbulence intensity and are found to depend mainly on reference velocity Uref and moving velocity Umov. However, they collapse to one curve for the same normalized velocity Uref / Umov. The effects of reference radius and reference height are found to be small. Resultant fluctuating force of generalized forces obtained from the modified Rankine model is considered to be larger than those obtained from the proposed model. Fluctuating force increases as the integral length scale increases for the modified Rankine model, while they remain almost constant regardless of the integral length scale for the proposed model.

• 한국산학기술학회논문지
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• 제12권2호
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• pp.944-951
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• 2011

본 논문은 ADCP 계측기기 부근에서 음향학적인 그리고 ADCP 계기로 인해 발생하는 흐름의 교란에 기인한 속도 오차에 대한 원인들을 실험 및 수치모의를 통해 고찰한다. 실험실에서의 연구는 선박에 탑재되지 않은 독립된 ADCP에 대해 수행하였고, 수평 및 수직면에서 ADCP에 의해 유발되는 흐름 교란은 ADV를 이용하여 관측하였다. 그리고 ADCP와 ADV의 동시적 측정이 ADCP계측에 있어 추가적인 계측기기 부근의 영향들을 고려하기 위해 수행되었다. 수치모의는 ADCP가 선박에 탑재되었을 때 ADCP 계기 부근에 발생하는 잠재적인 오차에 대해 연구하기 위해 설계되었다. 수치해석 기법 사용된 LES (Large Eddy Simulation)는 선박에 탑재된 ADCP에 작용하는 항력과 계기와 선박의 막음효과에 의해 발생하는 흐름의 교란의 크기와 범위를 모의하였다. 결과로 ADCP에 의해 관측된 속도는 계측기기 하단의 제한된 범위 내에서 일정 정도 오차를 보였고 교란되지 않은 하천의 흐름 조건에 따라 오차가 실질적으로 다르게 나타났다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 1997년도 춘계학술대회논문집; 경주코오롱호텔; 22-23 May 1997
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• pp.669-674
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• 1997

A sound field in a reverberation room is analyzed by using numerical methods and the SPL distributions are compared to the measurements. In numerical predictions, the BEM is employed in the low frequency range, while sound ray tracing method is used for the high frequency range. In the BEM analysis, the surfaces of the empty reverberation room are assumed as rigid boundaries and the damping coefficients are estimated from the measured absorption coefficient. The comparisons with measurements for 100Hz shows good agreement. In the sound ray tracing analysis, the predicted energy decay are in excellent agreements with theoretical results. It is shown that the energy absorption by air damping plays an important role as frequency becomes higher.

• Wind and Structures
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• 제3권2호
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• pp.73-81
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• 2000

Snowdrifts around buildings can cause serious problems when formed on undesirable places. The formation of snowdrifts is highly connected to the wind pattern around the building, and the wind pattern is again dependent on the building design. The shear stress on the surface and snowdrifting around different buildings are investigated through CFD analysis and compared to measurements. The computations of shear stress shows local minima in the same areas as snowdrifts are formed. The snowdrifting computations utilises a drift-flux model where a fluid with snow properties is allowed to drift through a fluid with air properties. An apparent dynamic viscosity of the snow/air mixture is defined and used as a threshold criterion for snowdrifting. The results from the snowdrifting computations show increased snow density where snowdrifts are expected, and are in agreement with previous large-scale snowdrift measurements. The results show that computational fluid dynamics can be a tool for planning building design in snowdrifting areas.

• Steel and Composite Structures
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• 제22권3호
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• pp.647-662
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• 2016

This study aims to monitor the variation of modal frequencies of steel buildings during their construction sequence. In this respect, construction of a steel building is followed by vibration based measurements. The monitored building is a three-story educational building within a building group whose structural system consists of steel moment resisting steel frames and eccentric braces. Five different acceleration measurements in two perpendicular directions are taken on five different construction stages, starting from the erection of the columns and beams ending with the completion of the construction. The recorded measurements are transferred into frequency domain and the dominant frequencies for each case have been determined. The change in the dominant frequencies is evaluated with the existing construction stages and performed constructional works between the stages. The last measurement, performed on the building in service, revealed the first two dominant frequencies as mutual in X and Y direction, showing that these dynamic modes are torsional modes. This result is investigated by numerical analysis performed with finite element model of the building constructed for design purpose. Lower frequencies and different mode shapes are determined from numerical analysis. The reason of lower frequencies is discussed and the vibration survey is extended to determine the effects of an adjacent building. The results showed that the building is in strong relation with an adjoining building in spite of a designed construction joint.