• Structural Engineering and Mechanics
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• 제26권3호
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• pp.231-250
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• 2007

The influence of masonry infills with eccentric openings on the seismic performance of reinforced concrete (r/c) frames that were designed in accordance with current code provisions are investigated. Eight 1/3-scale, single-story, single-bay frame specimens were tested under cyclic horizontal loading up to a drift level of 4%. In all examined cases the shear strength of columns was higher than the cracking shear strength of solid infill. The parameters investigated include the shape and the location of the opening. Assessment of the behavior of the frames is also attempted, based on the observed failure modes, strength, stiffness, ductility, energy dissipation capacity and degradation from cycling loading. Based on these results there can be deduced that masonry infills with eccentrically located openings has been proven to be beneficial to the seismic capacity of the bare r/c frames in terms of strength, stiffness, ductility and energy dissipation. The location of the opening must be as near to the edge of the infill as possible in order to provide an improvement in the performance of the infilled frame.

• Wind and Structures
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• 제18권1호
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• pp.57-67
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• 2014

For a building with a dominant windward wall opening, the wind-induced internal pressure response can be described by a second-order non-linear differential equation. However, there are two ill-defined parameters in the governing equation: the inertial coefficient $C_I$ and the loss coefficient $C_L$. Lack of knowledge of these two parameters restricts the practical use of the governing equation. This study was primarily focused on finding an accurate reference value for $C_I$, and the paper presents a systematic investigation of the factors influencing the inertial coefficient for a wind-tunnel model building including: opening configuration and location, wind speed and direction, approaching flow turbulence, the model material, and the installation method. A numerical model was used to simulate the volume deformation under internal pressure, and to predict the bulk modulus of an experimental model. In considering the structural flexibility, an alternative approach was proposed to ensure accurate internal volume distortions, so that similarity of internal pressure responses between model-scale and full-scale building was maintained. The research showed 0.8 to be a reasonable standard value for the inertial coefficient.

• 한국수자원학회논문집
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• 제55권9호
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• pp.701-705
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• 2022

이상기후로 가뭄이 빈번해짐에 따라 수자원 시설의 가뭄대응력 산정에 대한 필요성이 커지고 있다. 이를 위해서는 신뢰할 수 있는 갈수빈도 유입량 추정 연구가 선행되어야 한다. 본 연구는 기존 K-water의 가뭄 빈도유입량 추정방법인 누가차분법의 세 가지 한계, 즉 음의 값과 역전현상, 그리고 평년 이상으로 과대 산정되는 문제의 발생조건에 대해 각각 2변수 log-normal 분포와 Gumbel 분포를 적용하여 이론적 고찰을 실시하였다. 그 결과, 음의 값은 누가 과정에서 scale parameter보다 location parameter의 변화가 커지는 경우 발생함을 확인하였고, 역전현상 및 평년보다 큰 가뭄유입량은 누가 과정에서 표준편차가 감소하는 경우 발생하는 것으로 분석되었다.

• Structural Engineering and Mechanics
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• 제82권6호
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• pp.747-756
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• 2022

This study presents the nonlinear free and forced vibrations of a cracked atomic force microscopy (AFM) cantilever by using the modified couple stress. The cracked section of the AFM cantilever is considered and modeled as rotational spring. In the frame work of Euler-Bernoulli beam theory, Von-Karman type of geometric nonlinear equation and the modified couple stress theory, the nonlinear equation of motion for the cracked AFM is derived by Hamilton's principle and then discretized by using the Galerkin's method. The semi-inverse method is utilized for analysis nonlinear free oscillation of the system. Then the method of multiple scale is employed to investigate primary resonance of the system. Some numerical examples are presented to illustrate the effects of some parameters such as depth of the crack, length scale parameter, Tip-Mass, the magnitude and the location of the external excitation force on the nonlinear free and forced vibration behavior of the system.

• Journal of the Korean Data and Information Science Society
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• 제25권6호
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• pp.1581-1589
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• 2014

In this paper, we consider maximum likelihood estimators of the location and scale parameters for the half-logistic distribution when samples are multiply Type I hybrid censored. The scale parameter is estimated by approximate maximum likelihood estimation methods using two different Taylor series expansion types ($\hat{\sigma}_I$, $\hat{\sigma}_{II}$). We compare the estimators in the sense of the root mean square error (RMSE). The simulation procedure is repeated 10,000 times for the sample size n=20 and 40 and various censored schemes. The approximate MLE of the second type is better than that of the first type in the sense of the RMSE. Further an illustrative example with the real data is presented.

• 설비공학논문집
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• 제15권1호
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• pp.19-24
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• 2003

The objectives of this paper are to develop a new method of wettability mea-surement and to study the effect of surface roughness on the wettability in a $H_2O$/LiBr falling film absorber. Two absorber tubes with micro-scale roughness and a bare tube are tested in a falling film absorber installed in a test rig. Inlet solution temperature, concentration and mass flow rate are considered as key parameters. A new method is proposed to estimate the wettability of a tube by measuring a minimum mass flow rate to wet the tube completely. The wettability for the structured surfaces was higher than that for the bare tube. The wettability decreased linearly along the vertical location. The wettability increased with increasing the solution temperature and the solution mass flow rate. The experimental correlations of the wettability for the bare and the micro-hatched tubes were developed with error bands of$\pm20%\;and\;\pm10%$, respectively. This work can be used in the design of absorbers with micro-scale roughness.

• 품질경영학회지
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• 제29권3호
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• pp.49-65
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• 2001

This paper presents new compromise ALT plan which is applied to situations that true relationship between stress and parameters is not known exactly. The assumed failure distribution of this study is one of location-scale family, i. e., exponential, Weibull, and lognormal distributions which have been ones of the popular choices of failure distributions. The method of applying the stress is constant, and the censoring mechanism is Type I censoring. Compared with existing compromise plans under true simple linear model in terms of statistical efficiency, the efficiency of new compromise plan is better than the corresponding other compromise ones in most cases. For case when true model is quadratic, this plan can be used without any severe loss in statistical efficiency. The proposed new compromise ALT plan is illustrated with a numerical example and sensitivity analyses are conducted to study effects of pre-estimates of design parameters.

• Structural Engineering and Mechanics
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• 제89권1호
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• pp.61-75
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• 2024

Strengthening of hollow structural sections using through-bolts is a cost-effective and straightforward approach. It's a versatile method that can be applied during both design and service phases, serving as a non-disruptive and budget-friendly retrofitting solution. Existing research on axially loaded hollow sections T-joints has demonstrated that this technique can amplify the joint strength by 50%, where single bolt could enhance the strength of the joint by 35%. However, there's a gap in understanding their use for K-joints. As the behavior of K-joints is more complex, and they are widely existent in structures, this study aims to bridge that gap by conducting comprehensive parametric study using finite element analysis. Numerical investigation was conducted to evaluate the effect of through bolts on K-joints focusing on using single through bolt to achieve most of the strengthening effect. A full-scale parametric model was developed to investigate the effect of various geometric parameters of the joint. This study concluded the existence of optimal bolt location to achieve the highest strength gain for the joint. Moreover, a rigorous statistical analysis was conducted on the data to propose design equations to predict optimal bolt location and the corresponding strength gain implementing the verified by finite element models.

• 한국음향학회지
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• 제34권2호
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• pp.146-156
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• 2015

본 연구는 흡음재와 확산체의 적용위치가 소공연장의 음향성능에 미치는 영향에 대하여 알아보았다. 서울의 대학로의 2000년 이후 개관한 36곳의 공연장의 평균크기로 소공연장의 표준모델을 설정하여 연구를 진행하였다. 본 연구에서는 마감재 적용유효면적이 가장 작은 뒷벽을 기준으로 마감재의 적용면적을 산출하고, 마감재의 적용위치별 음향성능 변화를 분석하기 위하여 천장, 측벽의 적용위치를 전반부, 중반부, 후반부로 구분하여 총 8가지의 경우를 만들어, 1/10 축소모형실험을 진행하였다. 사용된 음향지표는 잔향시간(Reverberation Time, RT), 초기감쇠시간(Early Decay Time, EDT), 음악명료도(Clarity, C80), 음성명료도(Definition, D50), 음성전달지수(Speech Transmission Index, STI)를 이용하였다. 실험결과 마감재의 적용위치 변화는 소리의 울림에 양과 관련된 음향인자인 잔향시간, 초기감쇠시간 은 최소 변화 감지폭에 의한 (Just Noticeable Difference, JND) 평가시 변화가 뚜렷하게 나타났고, 소리의 명료도와 관련된 인자인 음악명료도, 음성명료도, 음성전달지수는 변화가 거의 없는 것으로 나타났다. 짧은 잔향시간을 얻고자 하는 경우 흡음재와 확산체 적용시 모두 측벽부분을 통한 잔향시간 조절이 가장 효과적이며, 측벽 전반부가 가장 짧은 잔향시간을 얻을 수 있는 위치인 것으로 나타났다.

• 콘크리트학회지
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• 제6권6호
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• pp.180-189
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• 1994

철근콘크리트 구조물의 손상을 진동반응특성치의 변화를 측정한 자료로부터 예측할 수 있는 실용적인 방법론이 제시되었다. 먼저, 구조물에 발생한 손상의 위치를 구조물 모드형상의 변화로부터 결정할 수 있는 알고리즘이 요약되었다. 다음으로, 실물크기 1/3 촉소 건조된 철근콘크리트 구조물을 사용한 실험에서 알고리즘을 이용하여 손상의 위치를 예측하였다. 이 실험과정에는 손상발생 전$\cdot$후의 소수의 진동반응특성치가 사용되었다. 구조물의 손상을 예측한 결과로부터 알고리즘이 손상을 정확하게 발견하는 것으로 판명되었다.