• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2007년 가을학술발표회
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• pp.305-316
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• 2007

Free field ground motion during earthquake is significantly affected by the local soil conditions and it is essential for the seismic design to perform the site specific ground response analysis. So, Round Robin Test (RRT) on ground response analysis was performed for three sites in Korea. A total of 12 teams presented the results of ground response analysis with used input soil properties based on own judgement. In this paper, the results of one dimensional equivalent linear analysis presented by 11 teams were compared to evaluate the effect of input soil properties on ground response analysis. Additionally, 4 influence factors on ground response analysis, that is shear wave velocity of soil layer, nonlinear dynamic deformational characteristics, bedrock depth and bedrock velocity were studied for assumed simple soil conditions.

• Structural Engineering and Mechanics
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• 제58권6호
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• pp.1021-1044
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• 2016

Different versions of a damage index (DI) along with a formulation to find the number of cycles at failure due to fatigue, applicable to reinforced concrete (RC) structures are presented. These are based on an energetic analysis method and applicable to both global and local levels. The required data can be found either from the numerical simulation of structures or from the experimental tests. A computer program has been developed to simulate numerically the nonlinear behavior of RC columns under cyclic loading. The proposed DI gives a regular distribution of structural damages up to failure and is validated by the results of the tests carried out on RC columns subjected to cyclic loading. In general, the local and global damage indices give approximately similar results, while each of them has its own advantages. The advantage of the implicit version of DI is that, it allows the comparison of the results with those of the monotonic loading case, while the explicit version makes it possible to estimate the number of loading cycles at failure due to fatigue, and the advantage of the simplified version is that; the monotonic loading data is not needed for the cyclic loading case.

• Advances in concrete construction
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• 제8권2호
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• pp.77-90
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• 2019

This paper aims to investigate vibration frequency decrease (vibration period elongation) of reinforced concrete (RC) structure with unreinforced infill wall and reinforced infill wall exposed to progressively increased artificial earthquake load on shaking table. For this purpose, two shaking table experiments were selected as a case study. Shaking table experiments were carried on 1:1 scaled prototype one bay one storey RC structure with infill walls. The purpose of this shaking table experiment sequence is to assess local behavior and progressive collapse mechanism. Frequency decrease and eigen-vector evolution are directly related to in-plane and out-of-plane bearing capacities of infill wall enclosure with reinforced concrete frame. Firstly, frequency decrease-damage relationship was evaluated on the base of experiment results. Then, frequency decrease and stiffness degradation were evaluated with applied Peak Ground Acceleration (PGA) by considering strength deterioration. Lastly, eigenvector evolution-local damage and eigenvector evolution-frequency decrease relationship was investigated. Five modes were considered while evaluating damage and frequency decrease of the tested specimens. The relationship between frequency decrease, stiffness degradation and damage level were presented while comparing with Unreinforced Brick Infill (URB) and Reinforced Infill wall with Bed Joint Reinforcement (BJR) on the base of natural vibration frequency.

• Structural Engineering and Mechanics
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• 제60권6호
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• pp.953-977
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• 2016

Modern performance-based design methods require ways to determine the factual behavior of structures subjected to earthquakes. Drift ratio demands are important measures of structural and/or nonstructural damage of the structures in performance-based design. In this study, global drift ratio and interstory drift ratio demands, obtained by nonlinear time history analysis of three generic RC frames using code-compatible ground motion record sets, are statistically evaluated. Several ground motion record sets compatible with elastic design spectra defined for the local soil classes in Turkish Earthquake Code are used for the analyses. Variation of the drift ratio demands obtained from ground motion records in the sets and difference between the mean of drift ratio demands calculated for ground motion sets are evaluated. The results of the study indicate that i) variation of maximum drift ratio demands in the sets were high; ii) different drift ratio demands are calculated using different ground motion record sets although they are compatible with the same design spectra; iii) the effect of variability due to random causes on the total variability of drift ratio demands is much larger than the effect of variability due to differences between the mean of ground motion record sets; iv) global and interstory drift ratio demands obtained for different ground motion record sets can be accepted as simply random samples of the same population at %95 confidence level. The results are valid for all the generic frames and local soil classes considered in this study.

• Computers and Concrete
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• 제22권6호
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• pp.527-538
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• 2018

Buckling of longitudinal bars is a brittle failure mechanism, often recorded in reinforced concrete (RC) structures after an earthquake. Studies in the literature highlights that it often occurs when steel is in the post elastic range, by inducing a modification of the engineered stress-strain law of steel in compression. A proper evaluation of this effect is of fundamental importance for correctly evaluating capacity and ductility of structures. Significant errors can be obtained in terms of ultimate bending moment and curvature ductility of an RC section if these effects are not accounted, as well as incorrect evaluations are achieved by non-linear static analyses. This paper presents a numerical investigation aiming to evaluate the engineered stress-strain law of reinforcing steel in compression, including second order effects. Non-linear FE analyses are performed under the assumption of local buckling. A role of key parameters is evaluated, making difference between steel with strain hardening or with perfectly plastic behaviour. Comparisons with experimental data available in the literature confirm the accuracy of the achieved results and make it possible to formulate recommendations for design purposes. Finally, comparisons are made with analytical formulations available in the literature and based on obtained results, a modification of the stress-strain law model of Dhakal and Maekawa (2002) is proposed for fitting the numerical predictions.

• Structural Engineering and Mechanics
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• 제80권6호
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• pp.737-747
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• 2021

The objective of seismic resilience is to maintain or rapidly restore the function of a building after an earthquake. An efficient tilt mechanism at the member level is crucial for the restoration of the main structure function; however, the damage resistance of the members should be the main focus. In this study, through a comparison with the classical Flamant theory of local loading in the elastic half-space, an elastomechanical solution for the axial-stress distribution of a reinforced-concrete (RC) rocking column was derived. Furthermore, assuming that the lateral displacement of the rocking column is determined by the contact surface rotation angle of the column end and bending and shear deformation of the column body, the load-lateral displacement mechanical model of the RC rocking column was established and validated through a comparison with finite-element simulation results. The axial-compression ratio and column-end strength were analyzed, and the results indicated that on the premise of column damage resistance, simply increasing the axial-compression ratio increases the lateral loading capacity of the column but is ineffective for improving the lateral-displacement capacity. The lateral loading and displacement of the column are significantly improved as the strength of the column end material increases. Therefore, it is feasible to improve the working performance of RC rocking columns via local reinforcement of the column end.

• Geomechanics and Engineering
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• 제36권5호
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• pp.455-464
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• 2024

Seismic movements have varying effects on structures based on characteristics of local site. During an earthquake, weak soils are susceptible to damage due to amplified wave amplitudes. Soil-structure interaction issue has garnered increased attention in Türkiye, after devastating earthquakes in Kocaeli Gölcük (1999), Izmir (2020), Kahramanmaraş Pazarcık and Elbistan (2023). Consequently, liquefaction potential has been investigated in detail for different regions of Türkiye, mainly with available field test results. Çankırı, a city located close to North Anatolian Fault, is mainly built on alluvium, which is prone to liquefaction. However, no study on liquefaction hazard has been conducted thus far. In this study, groundwater level map, SPT map, and liquefaction risk map have been generated using Geographical Information System (GIS) for the Buğday Pazarı District of Çankırı province. Site investigations studies previously performed for 47 parcels (76 boreholes) were used within the scope of this study. The liquefaction assessment was conducted using Seed and Idriss's (1971) simplified method and the visualization of areas susceptible to liquefaction risk has been accomplished. The results of this study have been compared with the City Council's precautionary map which is currently in use. As a result of this study, it is recommended that minimum depth of boreholes in the region should be at least 30m and adequate number of laboratory tests particularly in liquefiable areas should be performed. Another important recommendation for the region is that detailed investigation should be performed by local authorities since findings of this study differ from currently used precautionary map.

• 지질공학
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• 제25권2호
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• pp.201-213
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• 2015

지진지반운동 증폭을 야기하는 부지효과는 지하 토사 조건과 구조뿐만 아니라 지표 지형에 의해 지대한 영향을 받는다. 그럼에도 불구하고 국내에서는 최근 수십 년에 걸쳐 주로 지질 및 토사 조건과 관련된 부지고유 지진응답 연구들이 대부분을 차지해 왔으며, 이러한 국부 지질 효과는 잘 정립되어 현행 국내 내진설계기준들에 반영되고 있다. 이 연구에서는 현행 국내 내진설계기준에서는 고려되고 있지 않은 지표 지형효과 평가의 일환으로, 세 가지 다른 경사각 조건의 유한요소 지반 모델링을 통한 이차원 지진 부지응답 해석을 수행하였다. 이차원 유한요소 해석 결과인 최대 지반가속도와 가속도 응답스펙트럼을 추가적으로 수행한 일차원 유한요소 해석 결과와 비교하였다. 최대 지반가속도와 스펙트럴가속도는 대부분의 사면상부 영역에서 지형효과로 인해 이차원이 일차원 해석에 비해 크게 나타났다.

• 한국지구과학회지
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• 제29권6호
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• pp.506-519
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• 2008

이 연구에서는 과학탐구공동체 구성을 위한 잠재적인 학습 자료로서 자연사박물관의 전시물의 교육적 잠재성을 탐색해보고자 한다. 과학 탐구공동체는 과학적 지식의 습득과 과학 방법의 학습으로 연결되는 과학실습의 한 형태로 제안하였다. 공동체 학습은 주변에서 접하게 되는 과학-기술-사회적인 이슈들을 통해 이루어질 수 있다. 자연사 박물관 전시가 이러한 사회과학적인 이슈들을 포함하고 있다면 이는 자연사박물관의 과학탐구공동체로의 가능성에 대해 고려해 볼 수 있음을 전제로 하였다. 이런 맥락에서 본 연구는 자연사박물관 전시의 사회과학적 학습 자료 잠재성을 탐색하였다. 구체적으로 사회과학적 소재로서 적용 가능한 지진' 학습의 과학탐구공동체 구현을 위해, 첫째 미국 뉴욕시의 미국 자연사박물관과 워싱턴 D.C.의 스미소니언 미국국립자연사박물관의 지진 관련 전시물과 지구과학 교육과정과의 연관성을 분석하였다. 둘째, 두 박물관의 관계자와 인터뷰하여 이와 관련한 박물관의 교육적 의도와 노력을 알아보았다. 마지막으로 과학탐구공동체 구현을 위한 주제와 관련된 자연사 박물관 전시물의 특징을 탐색적으로 분석하였다. 이 연구에서 조사한 박물관의 전시는 교육과정과 관련하여 사회과학적 소재인 '지진'의 다양하고 실제적인 사례와 사건에 관한 풍부한 자료를 제공하고 있었다. 대상 박물관은 지역적 흥미와 사회과학적 이슈와의 연관성에 초점을 맞추어 박물관의 교육적 목적을 달성하고자 했음을 알았다. 지진이란 주제를 관람객에게 적절하도록 하기 위해 전시특성에 있어 원자료나 상호작용적 매체를 이용하여 살아있는 경험의 전달을 강조되고 있음을 알아내었다.

• 한국지구과학회지
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• 제26권3호
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• pp.268-275
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• 2005

대표적인 엘니뇨 지수인 태평양 Nino 해역의 표층 수온을 예측하기 위해 비선형 통계모델 중의 하나인 신경망 기법을 적용하였다. 신경망 모델 학습 과정의 입력 자료로 1951년부터 1993년까지의 태평양 해역$(120^{\circ}\;E,\;20^{\circ}\;S-20^{\circ}\;N)$ NCEP/NCAR의 재분석 표층 수온 편차의 경험적 직교함수 7개 주모드를 사용하였고, 그 중 1994년부터 2003년까지의 10년 결과를 분석하였다. 모든 해역에서의 9개월까지의 신경망 모델의 예측력은 비교적 우수하였으며, 특히 1997년과 1998년의 강한 엘니뇨의 발달 및 소멸도 잘 예측함을 확인할 수 있었다. 해역별로는 Nino3 지역의 예측성능이 가장 높았으며, 9개월 이후부터는 그 예측력이 급격히 감소하였다. 한편 지역적인 영향이 커 예측력이 낮은 동태평양 연안의 Nino1+2 지역은 9개월 이후에도 예측력의 감소가 관찰되지 않았다.