• 터널과지하공간
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• 제26권6호
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• pp.493-507
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• 2016

본 연구에서는 축소모형실험을 통해 석회암 공동 상부에 존재하는 구조물 기초의 안정성을 검토하였다. 공동의 형상은 단축장축비율 1/3인 타원형으로 가정하고, 공동의 심도, 위치, 경사, 크기, 개수를 변화시킨 5가지 그룹, 12개 모형들을 실험하였다. 실험결과로서 모형별 균열개시압력, 최대압력, 변형거동, 파괴양상, 침하곡선을 구하였으며, 공동의 제반 조건들이 기초의 안정성에 어떠한 영향을 미치는지를 알아보았다. 무공동 모형은 전단파괴를 보였으나, 공동 포함 모형들은 관입파괴만 발생한 경우, 전단파괴와 관입파괴가 함께 발생한 경우, 전단파괴가 이중으로 발생한 경우 등의 다소 복잡한 파괴형식을 보였다. 공동의 심도가 작을수록, 크기가 클수록, 개수가 많을수록 기초의 안정성은 감소하였다. 공동의 일부가 기초저면의 직하부에 놓일 때는 부등침하가 관찰되었고, 공동들의 분포상태에 따라 침하곡선은 다른 형태를 보였다.

• Steel and Composite Structures
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• 제17권4호
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• pp.453-470
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• 2014

This article is the result of an investigation on the influence of a Pasternak elastic foundation on the stability of exponentially graded (EG) cylindrical shells under hydrostatic pressure, based on the first-order shear deformation theory (FOSDT) considering the shear stresses. The shear stresses shape function is distributed parabolic manner through the shell thickness. The governing equations of EG orthotropic cylindrical shells resting on the Pasternak elastic foundation on the basis of FOSDT are derived in the framework of Donnell-type shell theory. The novelty of present work is to achieve closed-form solutions for critical hydrostatic pressures of EG orthotropic cylindrical shells resting on Pasternak elastic foundation based on FOSDT. The expressions for critical hydrostatic pressures of EG orthotropic cylindrical shells with and without an elastic foundation based on CST are obtained, in special cases. Finally, the effects of Pasternak foundation, shear stresses, orthotropy and heterogeneity on critical hydrostatic pressures, based on FOSDT are investigated.

• Computers and Concrete
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• 제26권1호
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• pp.53-62
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• 2020

Concrete is the most widely used substance in construction industry, so it's been required to improve its quality using new technologies. Nowadays, nanotechnology offers new frontiers for improving construction materials. In this paper, we study the stability analysis of the Single Walled Carbon Nanotubes (SWCNT) reinforced concrete cylindrical shell embedded in elastic foundation using the Donnell cylindrical shell theory. In this regard, we propose a new explicit analytical formula of the critical buckling load which takes into account the distribution of SWCNT reinforcement through the thickness of the concrete shell using the U, X, O and V forms and the elastic foundation using Winkler and Pasternak models. The rule of mixture is used to calculate the effective properties of the reinforced concrete cylindrical shell. The influence of diverse parameters on the stability behavior of the reinforced concrete shell is also discussed.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2007년도 정기 학술대회 논문집
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• pp.127-132
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• 2007

This paper has the object of investigating dynamic stability of opening thick plates on Pasternak foundation by means of finite element method and providing Kinematic design data for mat of building structures. Finite element analysis of Tapered Thick plate is done by use of rectangular finite element with 8-nodes. In order to analysis plate which is supported on Pasternak foundation. the Winkler foundation parameter is varied with $10^2$, $10^3$ and the shear foundation parameter is 5, 10. The ratio of force to critical load is applied as 0.4, 0.6, respectively. This paper analyzed varying Tapered Ratio and Concentrated Mass.

• 한국건축시공학회지
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• 제9권5호
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• pp.95-101
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• 2009

최근 건축물의 고층화에 따라 양중 계획의 중요성이 증대되고 있다. 타워크레인은 중요한 양중 장비로서의 역할을 수행하고 있으나, 구조적 안전사고 발생 시 그 피해가 매우 크므로 철저한 안정성검토가 선행되어야 한다. 타워크레인은 구조적 안정성을 확보하기 위해 횡지지 보강과 독립기초 및 파일기초 설계 등 안정성확보에 대한 고려가 매우 중요하며, 그 중 현장의 특수한 상황으로 인해 지내력 확보가 곤란하거나 더 이상 기초 사이즈를 증가시킬 수 없을 때 파일기초를 사용한다. 파일기초를 사용할 경우 독립기초 사용 시 보다 더 많은 안정성 검토 항목을 고려 해야하므로 체계적이고 철저한 검토가 필요하다. 본 연구는 파일기초 설계 시 파일기초의 기본적인 안정성 확보 뿐 만 아니라 최소의 비용 발생을 위한 최적설계 알고리즘 개발이 목적이며, 파일기초를 사용하는 고정식 트롤리타입의 타워크레인으로 연구 범위를 제한하여 진행한다. 타워크레인 파일 기초의 안정성 검토 항목과 절차, 최적설계에 관한 연구 결과물을 토대로 관련 업무 담당자의 업무 효율성을 향상 시킬 수 있을 뿐 아니라 파일 기초 설계에 투입되는 시간 및 비용의 절감효과를 기대 할 수 있다.

• 한국소음진동공학회논문집
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• 제21권8호
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• pp.698-707
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• 2011

이 연구는 유한요소법을 이용하여 집중질량을 갖고 비균질한 지반에 놓은 변단변 후판 구조물에 대한 동적 안정해석이다. 해석을 위하여 유한요소법을 이용하여 해당구조물의 고유진동수와 좌굴하중을 구하여 기존해와 비교하여 프로그램을 검증하였다. 비균질 Pasternak 지반에 놓인 변단면으로 집중질량을 갖는후판의 동적안정 해석을 통하여 판의 불안정 영역이 결정된다. 무차원 Winkler 지반강성은 100, 1000을 적용하였고, 무차원 전단지반강성은 5로 하였다. 그리고 변단면율은 0.25, 1.0, 집중질량비는 0.25, 1.0 그리고 면내응력은 $0.4{\sigma}_{cr}$을 적용하여 해석하였다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 춘계학술대회논문집A
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• pp.596-601
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• 2000

The paper presents free vibration and stability analyses of a non-uniform Timoshenko beam resting on a two-parameter elastic soil. The soil parameters can vary along the spat and is assumed to be two-parameter model including the effects of both transverse shear deformation and elastic foundation Governing equations related to the vibration and the stability of the beam are derived from Hamilton's principle, and the resulting eigen-value problems can be solved to give natural frequencies and critical force by finite element method. Numerical results for both vibration and stability of beams under an axial force are presented and compared with other available solutions. Finally, vibration frequencies, mode shapes and critical forces are investigated for various thickness ratios, shear foundation parameter, Winkler foundation parameter and boundary conditions of tapered Timoshenko beams.

• Architectural research
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• 제20권3호
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• pp.65-73
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• 2018

The restoration of foundations supporting the immense load of the stone pagoda at Mireuksa Temple Site prioritizes securing its structural stability. But so far, rammed earth construction is still not easy to determine the structural stability. This paper aims to emphasize that a scientific experimental study was conducted on a rammed earth construction, to identify its methodology and obtain objective data about structural stability of the foundation work. An experimental study fabricated specimens from the soil that had been removed during the excavation survey, determined the allowable bearing capacity through plate load tests, and compared the results with the predicted stress after reassembly of the stone pagoda to estimate the structural stability. Then, the repair method was selected based on the experimental study result. The evaluation method of the restoration of foundations consisted of an examination of the allowable bearing capacity and settlement. The allowable bearing of the reinforced foundation was more than twice the contact pressure under the stacked stones of the pagoda. The possibility of settlement of the rammed earth foundation soil layer during the pagoda assembly is expected to be very low because the settlement amount of the reformed soil layer is less than half of the settlement of the stabilized existing soil layer.

• Smart Structures and Systems
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• 제23권3호
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• pp.215-225
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• 2019

In the present paper, the nonlocal strain gradient refined model is used to study the thermal stability of sandwich nanoplates integrated with piezoelectric layers for the first time. The influence of Kerr elastic foundation is also studied. The present model incorporates two small-scale coefficients to examine the size-dependent thermal stability response. Elastic properties of nanoplate made of functionally graded materials (FGMs) are supposed to vary through the thickness direction and are estimated employing a modified power-law rule in which the porosity with even type of distribution is approximated. The governing differential equations of embedded sandwich piezoelectric porous nanoplates under hygrothermal loading are derived through Hamilton's principle where the Galerkin method is applied to solve the stability problem of the nanoplates with simply-supported edges. It is indicated that the thermal stability characteristics of the porous nanoplates are obviously influenced by the porosity volume fraction and material variation, nonlocal parameter, strain gradient parameter, geometry of the nanoplate, external voltage, temperature and humidity variations, and elastic foundation parameters.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2001년도 춘계학술대회 논문집
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• pp.228-233
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• 2001

In this case study, under conideration of field situations, such as increase of water level, height increment of the marine structure, dredging and backfill, the stability analysis of sliding and lateral flow of the marine structure in OOOharbor was carried out, and foundation reinforcement methods was presented. based on the results of site investigation, the stability analysis of slope sliding and lateral flow was performed as following. In section BH-1, 2, the analysis was performed in two cases that the marine structure was heightened and filled, and not heightened and filled. In section BH-1, 4, heightened and filled. The analysis results showed that the stabilities of slope sliding and lateral flow in section BH-1, 2, 3, 4 were unstable. After additional reinforcements with Deep Mortar Pile, the stabilities in section BH-1, 2, 3, 4 were evaluated as efficiently large.