• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2001년도 봄 학술발표회 논문집
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• pp.347-354
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• 2001

In this study, 3-D FEM analysis are carried out to investigate the effect of the corners and re-entrant corners which can't be analysed by 2-D analysis. The excavation shape is re-entrant type conditions. The wall displacement, earth pressure and effectiveness of the corner struts are investigated in the re-entrant case, The 3D analysis are peformed to evaluate the effect of various factors, such as re-entrant corner size, excavation depth, and presence of struts. The wall displacement and earth pressures are influenced the size of re-entrant corner. Therefore, the effect of re-entrant corner should be considered in the evaluation of the earth pressure and displacement of the corners. Finally, strut-support systems are not effective at the re-entrant corner.

• Wind and Structures
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• 제22권4호
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• pp.409-428
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• 2016

The mechanical and aerodynamic effect of building shape plays a dominate role in the pedestrian level wind environment. These effects have been presented in numerous studies and are available in many wind codes. However, most studies have focused on wind flow around conventional buildings and are limited to few wind directions. The present study investigated wind circulation in the re-entrant corners of cross-shaped high-rise buildings from various wind directions. The investigation focused on the pedestrian level wind environment in the re-entrant corners with different aspect ratios of building arrangements. Ninety cases of case study arrangements were evaluated using wind tunnel experimentation. The results show that for adequate wind circulation in the re-entrant corners, building orientations and separations play a critical role. Furthermore, in normal wind incident directions and at a high aspect ratio, poor wind flow was observed in the re-entrant corners. Moreover, it was noted that an optimized building orientation and aspect ratio significantly improved the wind flow in re-entrant corners and through passages. In addition, it was observed that oblique wind incident direction increased wind circulation in the re-entrant corners and through passages.

• Nuclear Engineering and Technology
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• 제31권2호
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• pp.214-225
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• 1999

An accurate method is presented for flexural vibrations of sectorial plates having simply supported-free and free-free radial edges, when the circular edge is either clamped or simply supported. The classical Ritz method is employed with two sets of admissible functions assumed for the transverse vibratory displacements. These sets consist of : (1) mathematically complete algebraic-trigonometric polynomials which gurantee convergence to exact frequencies as sufficient terms are retained, and (2) comer functions which account for the bending moment singularities at re-entrant comer of the radial edges having arbitrary edge conditions. Accurate (at least four significant figures) frequencies and normalized contours of the transverse vibratory displacement are presented for the spectra of corner angles [90$^{\circ}$, 180$^{\circ}$(semi-circular), 270$^{\circ}$, 300$^{\circ}$, 330$^{\circ}$, 350$^{\circ}$, 355$^{\circ}$, 360$^{\circ}$ (complete circular)] causing a re-entrant comer of the radial edges. Future solutions drawn from alternative numerical procedures and finite element techniques may be compared with these accurate results.

• Journal of applied mathematics & informatics
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• 제7권2호
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• pp.493-506
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• 2000

Recently the first author and his coworker report a new finite element method for the Poisson equations with homogeneous Dirichlet boundary conditions on a polygonal domain with one re-entrant angle [7], They use the well-known fact that the solution of such problem has a singular representation, deduced a well-posed new variational problem for a regular part of solution and an extraction formula for the so-called stress intensity factor using tow cut-off functions. They use Fredholm alternative an Garding's inequality to establish the well-posedness of the variational problem and finite element approximation, so there is a maximum bound for mesh h theoretically. although the numerical experiments shows the convergence for every reasonable h with reasonable size y imposing a restriction to the support of the extra cut-off function without using Garding's inequality. We also give error analysis with similar results.

• 한국강구조학회 논문집
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• 제10권4호통권37호
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• pp.601-613
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• 1998

본 논문은 부채꼴형 평판의 원형연단이 고정되어 있거나 또는 단순지지 되어 있을 때 요각 모서리의 응력 특이도를 고려하여 자유 진동해를 최초로 구한 연구이다. Ritz방법을 이용하여 수직진동변위를 두가지 적합함수식으로 가정하였다. 본 연구에서는 부채꼴형 각도의 범위에 따른 엄밀한 진동수 및 수직진동 변위의 전형적인 등고선을 제시하였다.

• 한국전산응용수학회:학술대회논문집
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• 한국전산응용수학회 2003년도 KSCAM 학술발표회 프로그램 및 초록집
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• pp.9-9
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• 2003

Let $\Omega$ be a bounded, open, and polygonal domain in $R^2$ with re-entrant corners. We consider the following Partial Differential Equations: $$(I-\nabla\nabla\cdot+\nabla^{\bot}\nabla\times)u\;=\;f\;in\;\Omega$$, $$n\cdotu\;0\;0\;on\;{\Gamma}_{N}$$, $${\nabla}{\times}u\;=\;0\;on\;{\Gamma}_{N}$$, $$\tau{\cdot}u\;=\;0\;on\;{\Gamma}_{D}$$, $$\nabla{\cdot}u\;=\;0\;on\;{\Gamma}_{D}$$ where the symbol $\nabla\cdot$ and $\nabla$ stand for the divergence and gradient operators, respectively; $f{\in}L^2(\Omega)^2$ is a given vector function, $\partial\Omega=\Gamma_{D}\cup\Gamma_{N}$ is the partition of the boundary of $\Omega$; nis the outward unit vector normal to the boundary and $\tau$represents the unit vector tangent to the boundary oriented counterclockwise. For simplicity, assume that both $\Gamma_{D}$ and $\Gamma_{N}$ are nonempty. Denote the curl operator in $R^2$ by $$\nabla\times\;=\;(-{\partial}_2,{\partial}_1$$ and its formal adjoint by $${\nabla}^{\bot}\;=\;({-{\partial}_1}^{{\partial}_2}$$ Consider a weak formulation(WF): Find $u\;\in\;V$ such that $$a(u,v):=(u,v)+(\nabla{\cdot}u,\nabla{\cdot}v)+(\nabla{\times}u,\nabla{\times}V)=(f,v),\;A\;v{\in}V$$. (2) We assume there is only one singular corner. There are many methods to deal with the domain singularities. We introduce them shortly and we suggest a new Finite Element Methods by using Singular representation for the solution.

• 콘크리트학회논문집
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• 제13권1호
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• pp.46-53
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• 2001

본 연구에서는 PCI 방법으로 설계한 직사각형보의 댑 전단거동을 구명키 위해 실물 크기의 두 개의 보 네 개의 댑단부에 대하여 실험하였다. 적용된 설계 활하중 500kgf/$m^2$은 주차장, 1,200kgf/$m^2$은 매장을 위한 국내설계기준이다. 보의 하단폭은 5층 정도의 매장 또는 주차장건물의 하부 기둥크기와 동일하게 60cm로 하였고, 댑의 깊이는 PCI에서 허용하는 최대치 내에서 하부 플랜지높이의 절반을 적용하였다. 대상 실물 실험체는 PCI 설계에 충분히 만족하도록 설계하였으나, 네 개의 실험체중 활하중 1200kgf/$m^2$를 위한 두 개의 실험체는 사용하중이전에 초기균열이 발생되었고 예측강도에 훨씬 못 미치는 하중에서 니브의 수직 전단파괴에 의하여 종국파괴되었다. 니브 수직전단파괴를 일으킨 활하중 1200kgf/$m^2$실험체의 최종 파괴강도는 77.22tonf과 78.36tonf으로 PCI의 81.9tonf과 ACI의 65.62tonf 사이 값으로 ACI의 예측식에 상회하나 PCI 제안 값에 미달하여 발생하였으므로 ACI제안 방식이 안전적인 측면을 고려할 때 더 합리적인 것으로 사료된다. 모든 하중-변형률곡선에서 걸이철근(Ash)의 변형률이 항복변형률에 도달할 정도로 가장 두드러졌다. 강도를 개선하기 위하여 추가적인 경사 걸이 철근이 필요한 것으로 판단된다.