• Earthquakes and Structures
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• 제25권2호
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• pp.99-112
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• 2023

This paper investigates the influences of Soil-Structure Interaction (SSI) on the seismic behavior of two-dimensional reinforced concrete moment-resisting frames subjected to Far-Field Ground Motion (FFGM) and Near-Field Ground Motion (NFGM). For this purpose, the nonlinear modeling of 7, 10, and 15-story reinforced concrete moment resisting frames were developed in Open Systems for Earthquake Engineering Simulation (OpenSees) software. Effects of SSI were studied by simulating Beam on Nonlinear Winkler Foundation (BNWF) and the soil type as homogenous medium-dense. Generally, the building resistance to seismic loads can be explained in terms of Incremental Dynamic Analysis (IDA); therefore, IDA curves are presented in this study. For comparison, the fragility evaluation is subjected to NFGM and FFGM as proposed by Quantification of Building Seismic Performance Factors (FEMA P-695). The seismic performance of Reinforced Concrete (RC) buildings with fixed and flexible foundations was evaluated to assess the probability of collapse. The results of this paper demonstrate that SSI and NFGM have significantly influenced the probability of failure of the RC frames. In particular, the flexible-base RC buildings experience higher Spectral acceleration (Sa) compared to the fixed-base ones subjected to FFGM and NFGM.

• 한국농공학회지
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• 제36권4호
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• pp.73-86
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• 1994

Ths paper was aimed to investigate the effect of reinforcement for the deformation characteristics of clayey foundation. Among numerous improvement method of foundation, only geotextil-reinforced foundation and foundation with both geotextile and sand mat which were 2-dimensional model clayey foundations were selected for load test in order to obtain fundamental results in analizing the behavior of the foundation with geotextile. To scrutinize the behavior characteristics and effect of reinforcement, the model foundations were constructed with various conditions on the location of layout of geotextile, the number of layouts and the depth of sand mat As for the technique of the numerical analysis elasto-plastic constitutive model for clayey soil, beam element for geotextile and elastic model for sand were respectively employed. Interface element was introduced for the block between materials with different rigidity. Observed values and numerical results were compared with satisfactory correspondence, which proved that the numercial technique developed in this paper was available.

• 한국지반공학회논문집
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• 제21권7호
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• pp.21-29
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• 2005

본 논문에서는 압축성이 큰 지반 위에 시공되는 지오그리드 보강 계단형 블록식 보강토 옹벽의 거동 특성에 관한 내용을 다루었다. 대상옹벽으로는 2단으로 시공되는 높이 lOrn의 블록식 보강토 옹벽을 고려하였으며 압축성이 큰 지반위에 시공되는 경우를 고려하였다. 본 연구는 검증된 유한요소해석 모델을 사용하여 수행되었으며 기초지반의 침하가 옹벽의 변위 및 보강재 유발 인장력에 미치는 영향을 집중적으로 다루었다. 연구결과 시공중 발생하는 기초지반의 과다 침하는 옹벽의 변위 뿐 아니라 보강재 유발 인장력 또한 현저히 증가시켜 내·외적 안정성에 지대한 영향을 미치는 것으로 나타났다. 본 논문에서는 연구결과와 아울러 실무적 관점에서의 고려사항 을 기술하였다.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2000년도 토목섬유 특별세미나
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• pp.61-69
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• 2000

It is not easy to find a good soil condition due to the shortage of suitable land for construction work. The earth structure and buildings can be constructed over the soft soil. The soft soil must be treated either using the reinforcement element or dewatering. Most of land reclamation projects are being implemented along the south coast or west coast of the Korean Peninsula. The soils in these areas are covered with the soft marine clay, so soil and site improvement is the most important things to do. Pile foundation at the bottom of embankment can be constructed either in the soft ground or in the soil contaminated area. The purpose of this research is to develop "geogrid-reinforced piled embankment method" to prevent the differential settlement and increase the bearing capacity of soil. In this study, the effectiveness of the geogrid-reinforcement was studied by varying the space between piles and reinforcement conditions. Also, the geotechnical engineering properties of the embankment material and foundation soil were determined through the laboratory tests as well as the field tests. As a result, the site that the pile-spacing S = 3b with geogrid reinforcement is the most effective to reduce the differential settlement and increase load bearing capacity.

• Structural Engineering and Mechanics
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• 제31권1호
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• pp.75-91
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• 2009

It is known that retaining walls were severely damaged as well in the most recent earthquakes having occurred in the countries in the active seismic belts of the world. This damage can be ascribed to the calculation methods used for the designs of retaining walls in the event of their constructions and employment having been accurately carried out. Generally simplified pseudo-static methods are used in the analysis of retaining walls with analytical methods and soil-structure interaction are not considered. In view of these circumstances, in this article by taking soil interaction into consideration, linear and nonlinear behaviours of retaining walls are analyzed with the assistance of LUSAS which is one of the structural analysis programs. This investigations are carried out per LUSAS which employs the finite element method as to the Erzincan (1992) Earthquake North-South component and the obtained findings are compared with the ones obtained from the method suggested in Eurocode-8, which is still effective today, and Mononobe-Okabe method. Not only do the obtained results indicate the distribution and magnitude of soil pressures are depend on the filling soil but on the foundation soil as well and nonlinear effects should be considered in designs of these walls.

• Geomechanics and Engineering
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• 제9권1호
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• pp.39-55
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• 2015

Usually the analyses of structures are carried out by assuming the base of structures to be fixed. However, the soil beneath foundation alters the earthquake loading and varies the response of structure. Hence, it is not realistic to analyze structures by considering it to be fixed. The importance of soil-structure interaction was realized from the past failures of massive structures by neglecting the effect of soil in seismic analysis. The analysis of massive structures requires soil flexibility to be considered to avoid failure and ensure safety. Present study, considers the seismic behavior of multi-storey reinforced concrete narrow and wide buildings of various heights with and without shear wall supported on raft foundation incorporating the effect of soil flexibility. Analysis of the three dimensional models of six different shear wall positions founded on four different soils has been carried out using finite element software LS DYNA. The study investigates the differences in spectral acceleration coefficient (Sa/g), base shear and storey shear obtained following the seismic provisions of Indian standard code IS: 1893 (2002) (IS) and International building code IBC: 2012 (IBC). The base shear values obtained as per IBC provisions are higher than IS values.

• 한국지반환경공학회 논문집
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• 제2권2호
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• pp.41-50
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• 2001

본 연구에서는 수위상승, 호안구조물의 증고 및 배면 준설투기 등 외적조건에 따른 ${\bigcirc}{\bigcirc}$항 호안구조물의 활동 및 측방유동에 대한 안정성 검토를 실시하고 기초보강 방안을 제시하였다. 안정성 검토를 위해 지반조사, 기본물성시험, 역학실험 및 화학성분분석을 실시하였고, 지반물성치는 주상개량체의 경우 지반개량 개념을 적용하였으며, 구조물 배면 준설매립의 경우는 단계별매립에 의한 영향을 고려하여 결정하였다. 안정성 검토는 기시공된 상태로 증고하지 않고 매립하였을 경우와 기시공된 상태로 증고하여 매립하였을 경우로 구분하여 실시하였다. 해석 결과 두가지 경우 모두 활동과 측방유동에 대해 불안정한 것으로 판단되어 기시공공법과 동일한 방법인 심층몰탈파일에 의한 추가보강을 실시할 경우에 대하여 그 안정성을 검토한 결과 안정하였다. 따라서 본 현장에 대한 기초보강공법으로써 심층몰탈파일을 제시하였다.

• Geomechanics and Engineering
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• 제10권4호
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• pp.405-422
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• 2016

The paper deals with the results of the laboratory cyclic plate load tests performed on the reinforced soft clay beds. The performances of the clay bed reinforced with geocells and geocells with additional basal geogrid cases are compared with the performance of the unreinforced clay beds. From the cyclic plate load test results, the coefficient of elastic uniform compression ($C_u$) was calculated for the different cases. The $C_u$ value was found to increase in the presence of geocell reinforcement. The maximum increase in the $C_u$ value was observed in the case of the clay bed reinforced with the combination of geocell and geogrid. In addition, 3 times increase in the strain modulus, 10 times increase in the bearing capacity, 8 times increase in the stiffness and 90% reduction in the settlement was observed in the presence of the geocell and geogrid. Based on the laboratory test results, a hypothetical case of a prototype foundation subjected to cyclic load was analyzed. The results revealed that the natural frequency of the foundation-soil system increases by 4 times and the amplitude of the vibration reduces by 92% in the presence of the geocells and the geogrids.

• 한국지반공학회논문집
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• 제22권8호
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• pp.33-42
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• 2006

연성벽체인 보강토옹벽은 변형을 허용하므로 연약지반 상에 구축될 경우 뒤채움재와 연약지반의 변형이 수렴될 때까지 경과시간에 따라 벽체에 작용하는 토압과 옹벽내에 작용하는 보강재의 인장력은 변하나, 이들을 장기간에 걸쳐 계측 및 분석한 사례는 거의 없다. 본 연구에서는 얕은 층의 연약지반상에 실물보강토옹벽을 구축하여 보강재의 변형, 토압, 간극수압 등을 약 16개월 동안 계측 및 분석하였다. 스트레인 게이지를 사용하여 보강재의 변형을 계측하였으며, 특히 부직포의 변형 계측에 스트레인 게이지를 적용하는 새로운 방법을 제안하였다. 대부분의 보강재 변형은 옹벽구축 후로부터 한 달 이내에 발생하고, 약 16개월 동안 계측된 부직포, 직포, 지오그리드에서의 최대변형률은 6.05, 2.92, 2.33%로 나타났다. 보강토옹벽 내에서 간극수압은 무시할 수 있으나, 벽면에서의 수평토압은 옹벽의 저부와 상부에서 정지토압보다 크게 나타났다.

• 한국지반신소재학회논문집
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• 제2권1호
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• pp.15-25
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• 2003

계단식 보강토 옹벽의 거동 특성을 파악하기 위하여 계단식 보강토 옹벽을 시험 시공하였으며, 수평변위와 보강재에 발생한 변형률을 중심으로 계측을 실시하였다. 특히 수평변위와 보강재 유발 변형률을 장기간 계측함으로써 계절변화에 따른 영향을 평가하였으며, 강우가 보강토 옹벽에 미치는 영향, 연약지반에서의 거동특성 등등에 초점을 맞춰 계측하여 분석을 실시하였다. 본 논문에서는 계단식 보강토 옹벽 시공 중에 발생하는 수평변위 및 보강재 유발변형률을 중심으로 분석하였고, 그 결과 상단옹벽 시공으로 인한 하단옹벽의 수평변위 및 보강재 유발 변형률은 상당히 많은 영향을 받고 있는 것으로 조사되었다.