• Steel and Composite Structures
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• 제24권6호
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• pp.659-670
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• 2017

In the present work, an analytical solution for the static analysis of laminated composites, functionally graded and sandwich singly and doubly curved panels on the rectangular plan-form, subjected to uniformly distributed transverse loading is presented. Mathematical formulation is based on the higher order shear deformation theory and principle of virtual work is applied to derive the equations of equilibrium subjected to small deformation. A solution methodology based on the fast converging finite double Chebyshev series is used to solve the linear partial differential equations along with the simply supported boundary condition. The effect of span to thickness ratio, radius of curvature to span ratio, stacking sequence, power index are investigated. The accuracy of the solution is checked by the convergence study of non-dimensional central deflection and moments. Present results are compared with those available in the literature.

• Bulletin of the Korean Chemical Society
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• 제8권2호
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• pp.122-126
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• 1987

Oribtal energies for AuH and AgH are calculated by an all-electron relativistic self-consistent-field method using Slater type basis functions. Major relativistic effects for AgH are spin-orbit splittings and those for AuH are large shifts in orbital energies in addition to spin-orbit splittings. Relativistic effects on orbital energies in AgH and AuH imply that changes in correlation energies for relativistic calculations of AuH will be significantly larger than those of AgH, providing partial explanation for the large discrepencies in equilibrium bond length and the dissociation energy between experiments and theoretical estimates for AuH. Large relativistic effects on orbital energies indicate that relativistic contributions should be included for the correct interpretation of ionization potentials for these molecules. Relativistic effects are also evident in dipole moments for these molecules.

• Structural Engineering and Mechanics
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• 제77권6호
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• pp.765-777
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• 2021

Recently, the plate bending analysis has been interpreted in terms of the tensor's components of curvatures and bending moments by presenting the conceptual perspectives of the Hydrostatic Method of Analysis (HM) and theoretical formulations that combine the continuum mechanics with the graphical statics analysis, the theory of thin orthotropic and isotropic plates, and the elasticity theory. In pursuance of uncovering a genuine formulation of the plate's flexural differential equations, that possess the general-covariance and coordinates-independency. This study had then, tackled various natural and structural problems in both solid and fluid branches of the continuum mechanics in a description of such theoretical and conceptual attainment in uncovering the dimensional independent diffeomorphism covariant partial differential laws.

• Bulletin of the Korean Chemical Society
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• 제23권12호
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• pp.1754-1758
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• 2002

Tetrathiafulvalene(TTF) reacts with $PdCl_2,Pd(NO_3)_2$ and $Pd(hfacac)_2$(hexafluoroacetylacetonate) in ethanol to give $(TTF)_{1.5}PdCl_2$ (1a), $(TTF)_3Pd(NO_3)_2$ (1b) and $(TTF)_4Pd(hfacas)_2$ nd (1c), respectively. $PdCl(TCNQ)_{2.5}{\cdot}CH_3OH(2a)$was obtained from the reaction of $PdCl_2$ with LiTCNQ in methanol via the partial replacement of $Cl^-$ in $PdCl_2$ by $TCNQ^-$anion, whereas the total substitution of the labile $NO_3^-$ in $Pd(NO_3)_2$ yielded pd(TCNQ)·$CH_3OH$ (2b). $Pd(hfacac)_2(TCNQ)_2\cdot3CH_3OH$ (2c) was obtained from $Pd(hfacac)_2$ and LiTCNQ in methanol. The prepared compounds were characterized by spectroscopic (IR, UV, XPS) methods and magnetic (EPR, magnetic susceptibility) studies. The powdered electrical conductivities (${\sigma}_{rt}$) of the prepared compounds at room temperature were about~$10^{-7}S{\cdot}cm^{-1}$. The effective magnetic moments were lass than the spin-only value of one unpaired electron and no EPR signals from Pd metal ions were observed in any of the compounds, indicating that the Pd ions were diamagnetic and the magnetic moments arose from$(TTF)_n$ or $(TCNQ)_n$ moieties. The experimental evidences revealed that the charge transfer had occurred form $(TTF)_n$ moiety to the central Pd metal ion in 1a, 1b and 1c. Thus the TTF donors were ions in 2a and 2b were diamagnetic Pd(II) oxidation state. In contrast, the Pd metal ion was oxidized to Pd(IV) state in 2c as a result of an addition of $TCNQ^-$anion to $Pd(hfacac)_2$ in methanol. The oxidation states of the Pd metal ions were confirmed using the x-ray photoelectron spectroscopy.

• 콘크리트학회논문집
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• 제23권2호
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• pp.177-184
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• 2011

이 연구에서는 PC 구조의 단부를 연속으로 연결한 MRS(multi-ribbed moment resisting slab) 구조에 대한 해석 및 설계법을 제안하고자 하였다. MRS 구조에서는 더블티 부재가 역티보 위에서 부모멘트 철근에 의해서 연속으로 설계되므로, 부모멘트 철근이 좁은 지역에 밀집되는 문제가 발생할 수 있다. 따라서 선형 및 비선형 해석을 통하여 모멘트 분포 메커니즘을 분석하여, 적절한 설계법을 제시하였다. 또한 이 연구와 병행하여 실시한 실험 연구의 결과를 비선형상세 해석을 통하여 분석하였다. 그리고 단부구속효과 및 모멘트 재분배에 관한 연구를 위하여 비선형 골조 해석을 선택하여 변수별 연구를 수행하였다. 해석을 위한 재질 및 단면의 특성은 함께 진행된 실험 연구의 결과로부터 얻어졌으며, 비선형 골조 해석을 위한 소성힌지는 균열 모멘트, 공칭 모멘트, 부재 연성도 등의 값으로 모델링되었다. 선형 및 비선형 해석의 결과로부터 단부 회전 스프링과 부모멘트재분재를 통하여 MRS 구조의 단부 모멘트는 상당한 크기로 감소시킬 수 있음을 알 수 있었다.

• 한국강구조학회 논문집
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• 제22권3호
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• pp.241-251
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• 2010

본 논문에서는 등분포 하중을 받는 등방성 환형 섹터판의 지배방정식에 대한 새로운 해석적 해가 3차원 극좌표계에서 개발된다. 4차의 편미분방정식 형태를 가지는 지배방정식은 레비 타입 시리즈 해에 대한 가정과 그 후속적인 수학적 처리를 통해 4차의 상미분방정식으로 전환된다. 전환된 상미분방정식의 특성방정식에 대한 실수 영역 및 복소수 영역의 해를 해석적으로 구한 후 제차 및 비제차 방정식의 각 해의 조합으로 최종적인 지배방정식의 해가 완성된다. 개발된 해의 수렴성 및 정확성을 보여주기 위해 다양한 경계조건 및 내부 중심 각도를 가지는 판에 대한 예제 해석을 수행하였고 그 결과를 다른 해석적 연구결과와 비교하였다. 또한 개발된 해의 정확성을 확인하기 위하여 유한요소 프로그램인 ABAQUS를 이용한 탄성해석을 추가로 수행하여 그 결과를 비교하였다. 제안된 해로부터 결정된 환형 섹터판의 변위 및 모멘트 값은 여타의 해석적 및 수치적 접근방법으로 구한 값들과 비교해 본 결과 매우 높은 수준에서 일치하고 있음이 확인되었다.

• Computers and Concrete
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• 제15권4호
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• pp.687-707
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• 2015

A finite element computer code for short-term analysis of steel-concrete composite structures is extended to study long-term effects under service loads, in the present work. Long-term effects are important in engineering design because they influence stress and strain distribution of the structural system and therefore contribute to the increment of deflections in these structures. For creep analysis, a rheological model based on a Kelvin chain, with elements placed in series, was employed. The parameters of the Kelvin chain were obtained using Dirichlet series. Creep and shrinkage models, proposed by the CEB FIP 90, were used. The shear-lag phenomenon that takes place at the concrete slab is usually neglected or not properly taken into account in the formulation of beam-column finite elements. Therefore, in this work, a three-dimensional numerical model based on the assemblage of shell finite elements for representing the steel beam and the concrete slab is used. Stud shear connectors are represented for special beam-column elements to simulate the partial interaction at the slab-beam interface. The two-dimensional representation of the concrete slab permits to capture the non-uniform shear stress distribution in the horizontal plane of the slab due to shear-lag phenomenon. The model is validated with experimental results of two full-scale continuous composite beams previously studied by other authors. Results are given in terms of displacements, bending moments and cracking patterns in order to shown the influence of long-term effects in the structural response and also the potentiality of the present numerical code.

• 한국강구조학회 논문집
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• 제19권4호
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• pp.395-402
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• 2007

허용응력설계법과 강도설계법으로 설계된 강합성 플레이트 보강형과 콘크리트 보강형으로 구성된 장대교량인 복합사장교의 확률적 위험도 평가를 수행하였다. 최대 축력, 전단력 및 정 부모멘트 발생단면에 기초한 위험단면에 대해 AFOSM 알고리즘과 시뮬레이션기법을 사용하여 케이블, 주탑, 보강형 및 강-콘크리트 접합부의 요소신뢰성을 평가하였다. 체계신뢰성해석을 위해, 케이블, 주탑 및 콘트리트와 강합성 보강형으로 구성된 복합사장교의 시스템을 조합 파괴모드로 모델링하였으며, 이를 통해 전체 구조시스템의 파괴확률과 신뢰성지수를 산출하였다. 본 연구를 통해 복합사장교의 거동특성에 기초한 파괴모드를 제안하였고 위험도평가 방법으로서 부분 ETA기법의 효용성을 확인하였다.

• Structural Engineering and Mechanics
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• 제20권6호
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• pp.727-745
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• 2005

The present study is an experimental investigation into the behaviour of high strength concrete square short columns subjected to biaxial bending moments and strengthened by GFRP laminates. The main objectives of the study are: to evaluate the improvement in the structural performance of HSC short square columns subjected to small biaxial eccentricity when strengthened by externally applied FRP laminates, and to investigate the optimum arrangement and amount of FRP laminates to achieve potential enhancement in structural performance especially ductility. The parameters considered in this study are: number of FRP layers and arrangement of wraps. The load eccentricity is kept corresponding to e/t = 0.125 in two perpendicular directions to the columns principal axes, and the wraps are applied in single or double layers (partial or full wrapping). In the present work, test results of five full scale concrete columns are presented and discussed. The study has shown that FRP wraps can be used successfully to enhance the ductility of HSC columns subjected to biaxial bending by 300%.

• 대한기계학회논문집A
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• 제24권8호
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• pp.2100-2107
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• 2000

The wavelet theory is relatively a new development and now acquires popularity and much interest in many areas including mathematics and engineering. This work presents an adaptive wavelet method for a numerical solution of partial differential equations in a collocation sense. Due to the multi-resolution nature of wavelets, an adaptive strategy can be easily realized it is easy to add or delete the wavelet coefficients as resolution levels progress. Typical wavelet-collocation methods use interpolating wavelets having no vanishing moment, but we propose a new wavelet-collocation method on modified interpolating wavelets having 2 vanishing moments. The use of the modified interpolating wavelets obtained by the lifting scheme requires a smaller number of wavelet coefficients as well as a smaller condition number of system matrices. The latter property makes a preconditioned conjugate gradient solver more useful for efficient analysis.