• 한국구조물진단유지관리공학회 논문집
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• 제13권6호통권58호
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• pp.183-191
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• 2009

본 연구에서는 지진시 nailed-soil 굴착벽체의 안전율과 거동특성에 대하여 제시하였다. 시간이력해석을 이용하여 정적하중과 지진하중을 받는 nailed-soil 굴착벽체 전면부의 수평변위, 축력, 전단력, 모멘트를 해석하였다. Dawson과 Roth가 제안한 전단강도 감소기법에 바탕을 둔 안전율을 지진시 nailed-soil 굴착벽체의 안전율 계산에 사용하였다. 제안된 방법에 의한 안전율을 기존의 연구에서 산정된 안전율과 비교하여 그 타당성을 확인하였다.

• Structural Engineering and Mechanics
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• 제64권1호
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• pp.109-120
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• 2017

The behavior of moment resistant steel structures depends on both the beam-column connections and columns foundations connections. Obviously, if the connections can meet the adequate ductility and resistance against lateral loads, the seismic capacity of these structures will be linked practically to the performance of these connections. The shape memory alloys (SMAs) have been most recently used as a means of energy dissipation in buildings. The main approach adopted by researchers in the use of such alloys is firstly bracing, and secondly connecting the beams to columns. Additionally, the behavior of these alloys is modeled in software applications rarely involving equivalent torsional springs and column-foundation connections. This paper attempts to introduce the shape memory alloys and their applications in steel structural connections, proposing a new steel column-foundation connection, not merely a theoretical model but practically a realistic and applicable model in structures. Moreover, it entails the same functionality as macro modeling software based on real behavior, which can use different materials to establish a connection between the columns and foundations. In this paper, the suggested steel column-foundation connection was introduced. Moreover, exploring the seismic dynamic behavior under cyclic loading protocols and the famous earthquake records with different materials such as steel and interconnection equipment by superelastic shape memory alloys have been investigated. Then, the results were compared to demonstrate that such connections are ideal against the seismic behavior and energy dissipation.

• 한국산학기술학회논문지
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• 제13권9호
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• pp.4294-4301
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• 2012

본 연구는 내진설계 되지 않은 학교시설물 중 다수를 차지하는 1980년도 표준설계 도면(건설부 공고 제130호, 1980년 10월 28일)에 의하여 건설된 국내에 현존하는 4층 모멘트 연성골조의 학교건물을 대상으로 이력모델의 특성과 지진파의 특성에 따라 표준학교건물의 비탄성지진거동을 분석하고자 한다. El-centro지진은 주파수 성분과 강진지속시간의 특성에 의하여 표준학교건물의 단변방향 층전단력, 층간변위비, 층변위 응답에 매우 큰 영향을 미치며 특히 수정다케다모델 선택시 응답의 차이가 매우 크게 나타남을 알 수 있다. 층전단력의 경우 최대 46%, 층간변위비의 경우 최대 70%, 층변위의 경우 최대 59%의 편차를 보인다. Santa Monica지진은 장변방향의 응답에서 이력모델별 편차가 더 크게 나타났으며, 층전단력은 최대 59%, 층간변위비는 최대 65%, 층변위는 최대 50%의 편차를 보였다. 이는 장변방향의 고유주기가 단변방향에 비하여 크기 때문에 1초이상의 주기성분이 많은 Santa Monica지진의 특성에 의한 것으로 판단된다. Taft지진은 이력모델에 따른 층간변위비와 층변위 응답의 편차가 가장 적은 것으로 나타났으며, 층간변위비는 최대 15%, 층변위는 최대 5%의 편차를 보여 변위응답에 있어서 이력모델에 가장 의존도가 적은 결과를 얻을 수 있을 것으로 판단 된다.

• Computers and Concrete
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• 제21권6호
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• pp.717-726
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• 2018

Concrete pipelines are the most efficient and safe means for gas and oil transportation over a long distance. The use of nano materials and nono-engineering can be considered for enhancing concrete pipelines properties. the tests show that $SiO_2$ nanoparticles can improve the mechanical behavior of concrete. Moreover, severe hazard for pipelines is seismic ground motion. Over the years, scientists have attempted to understand pipe behavior against earthquake most frequently via numerical modeling and simulation. Therefore, in this paper, the dynamic response of underwater nanocomposite submerged pipeline conveying fluid is studied. The structure is subjected to the dynamic loads caused by earthquake and the governing equations of the system are derived using mathematical model via Classic shell theory and Hamilton's principle. Navier-Stokes equation is employed to calculate the force due to the fluid in the pipe. As well, the effect of external fluid is modeled with an external force. Mori-Tanaka approach is used to estimate the equivalent material properties of the nanocomposite. 1978 Tabas earthquake in Iran is considered for modelling seismic load. The dynamic displacement of the structure is extracted using differential quadrature method (DQM) and Newmark method. The effects of different parameters such as $SiO_2$ nanoparticles volume percent, boundary conditions, thickness to radius ratios, length to radius ratios, internal and external fluid pressure and earthquake intensity are discussed on the seismic response of the structure. From results obtained in this paper, it can be found that the dynamic response of the pipe is increased in the presence of internal and external fluid. Furthermore, the use of $SiO_2$ nanoparticles in concrete pipeline reduces the displacement of the structure during an earthquake.

• Structural Engineering and Mechanics
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• 제59권4호
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• pp.719-737
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• 2016

The present study investigated the earthquake behavior of R/C structures considering the vertical earthquake motion with the help of a comparative study. For this aim, the linear time-history analyses of a high-rise R/C structure designed according to TSC-2007 requirements were conducted including and excluding the vertical earthquake motion. Earthquake records used in the analyses were selected based on the ratio of vertical peak acceleration to horizontal peak acceleration (V/H). The frequency-domain analyses of the earthquake records were also performed to compare the dominant frequency of the records with that of the structure. Based on the results obtained from the time-history analyses under the earthquake loading with (H+V) and without the vertical earthquake motion (H), the value of the overturning moment and the top-story vertical displacement were found to relatively increase when considering the vertical earthquake motion. The base shear force was also affected by this motion; however, its increase was lower compared to the overturning moment and the top-story vertical displacement. The other two parameters, the top-story lateral displacement and the top-story rotation angle, barely changed under H and H+V loading cases. Modal damping ratios and their variations in horizontal and vertical directions were also estimated using response acceleration records. No significant change in the horizontal damping ratio was observed whereas the vertical modal damping ratio noticeably increased under H+V loading. The results obtained from this study indicate that the desired structural earthquake performance cannot be provided under H+V loading due to the excessive increase in the overturning moment, and that the vertical damping ratio should be estimated considering the vertical earthquake motion.

• 콘크리트학회논문집
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• 제20권5호
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• pp.643-651
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• 2008

본 연구의 목적은 면진장치 설계 절차 체계화에 따른 면진건물의 응답특성을 사용지진 기록에 따라 평가하는데 있다. 이를 위한 대상 건물은 면진에 적합한 기초 면진 적용한 20층 주거 건물로, 지진기록 사용에 따른 응답특성을 평가하였다. 그 결과 면진건물의 시간이력해석을 위한 지진파의 선정은 응답 결과에 많은 차이가 발생할 수 있으므로 관련기준의 제정이 필요한 것으로 판단된다. 본 연구에서 제안한 지진기록을 이용한 면진구조물의 시간이력해석 결과, 면진층 변위, 층간변위비, 면진장치의 거동이 적절한 것으로 평가되었다. 결론적으로 본 연구에서 제안한 지진기록 및 면진장치 선정 결과, 설계된 면진건물의 지진저항 성능이 우수함을 확인할 수 있었다.

• Earthquakes and Structures
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• 제10권4호
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• pp.757-768
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• 2016

In the past decades, effect of near field earthquake on the historical monuments has attracted the attention of researchers. So, many analyses in this regard have been presented. Tunnels as vital arteries play an important role in management after the earthquake crisis. However, digging tunnels and seismic effects of earthquake on the historical monuments have always been a challenge between engineers and historical supporters. So, in a case study, effect of near field earthquake on the historical monument was investigated. For this research, Finite Element Analysis (FEM) in soil environment and soil-structure interaction was used. In Plaxis 2D software, different accelerograms of near field earthquake were applied to the geometric definition. Analysis validations were performed based on the previous numerical studies. Creating a nonlinear relationship with space parameter, time, angular and numerical model outputs was of practical and critical importance. Hence, artificial Neural Network (ANN) was used and two linear layers and Tansig function were considered. Accuracy of the results was approved by the appropriate statistical test. Results of the study showed that buildings near and far from the tunnel had a special seismic behavior. Scattering of seismic waves on the underground tunnels on the adjacent buildings was influenced by their distance from the tunnel. Finally, a static test expressed optimal convergence of neural network and Plaxis.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2004년도 춘계학술발표회
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• pp.245-252
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• 2004

When some enormous earthquake hazards broke out in the neighboring Japan and Taiwan, many Korean earthquake engineers thought that seismic guidelines must be adjusted safely and economically to consider the moderate earthquake characteristics. In the present aseismic guideline for liquefaction potential assessment, a simplified method using SPT-N value and a detail method based on the dynamic lab-tests were introduced. However, it is said that these methods based on the equivalent stress concept to simplify an irregular earthquake are not reliable to simulate the kaleidoscopical characteristics of earthquake loading correctly. Especially, even though various data from the dynamic lab-test can be obtained, only two data, a maximum cyclic load and a number of cycle at an initial liquefaction are used to determine the soil resistance strength in the detailed method. In this study, a new assessment of liquefaction potential is proposed and verified. In the proposed assessment, various data from dynamic lab-tests are used to determine the unique soil resistance characteristic and a site specific analysis is introduced to analyze the irregular earthquake time history itself. Also, it is found that the proposed assessment is reasonable because it is devised to reflect the changeable soil behavior under dynamic loadings resulted from the generation and development of excess pore water pressure.

• KCI Concrete Journal
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• 제11권3호
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• pp.153-164
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• 1999

The objective of this research is to observe the actual response of a low-rise nonseismic moment-resisting masonry-infilled reinforced concrete frame subjected to varied levels of earthquake ground motions. The reduction scale for the model was determined as 1 : 5 considering the capacity of the shaking table to be used. This model was, then, subjected to the shaking table motions simulating Taft N2IE component earthquake ground motion, whose peak ground acceleration(PGA) was modified to 0.12g, 0.2g, 0.3g, and 0.4g. The g1oba1 behavior and failure mode were observed. The lateral accelerations and displacements at each story and local deformations at the critical portions of the structure were measured. Before and after each earthquake simulation test, free vibration tests and white noise tests were performed to find the changes in the natural period of the model. When the results of the masonry-infilled frame are compared with those of the bare frame, it can be recognized that masonry infills contribute to the large increase in the stiffness and strength of the g1oba1 structure whereas it also accompanies the increase of earthquake inertia forces. However, it is judged that masonry infills may be beneficial to the performance of the structure since the rate of increase in strength appears to be greater than that of the induced earthquake inertia forces.

• 한국해안·해양공학회논문집
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• 제31권6호
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• pp.386-394
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• 2019

본 연구에서는 2017년 11월 15일에 포항에서 발생한 규모 5.4의 지진으로 인하여 영일만항의 케이슨식 안벽 및 배후지에서 지반내에 발생된 과잉간극수압으로 유발된 침하와 수평변위를 지반배수조건(즉 비배수조건과 배수조건)에 따라 해석하였다. 일반적으로 비배수조건에서 지진응답해석을 실시하는데 본 연구에서는 배수조건 해석을 실시하여 지진 시 생기는 변위와 지진 이후에 과잉간극수압이 소산하면서 발생하는 추가적인 변위의 결과를 산정하였다. 지진 이후의 결과는 비배수조건의 해석에서는 알 수 없는 부분이다. 두 결과에 대한 비교 분석을 통해 지반배수조건에 따라 구조물과 지반의 거동 차이를 분명하게 확인하였다. 특히 배수조건의 해석 결과에서 지진이후 과잉간극수압 소산에 따른 추가적인 변위가 분명하게 발생하는 것으로 나타났다. 이것은 지진응답해석에서 지반배수조건에 따른 두 해석결과의 차이가 존재하는 것을 보여주는 것으로 지반과 구조물의 거동을 더 명확하게 해석하기 위해서는 배수조건에 대한 해석도 필요하다는 것을 나타내는 것이다.