• 한국지반공학회논문집
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• 제19권4호
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• pp.65-74
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• 2003

본 논문에서는 사면안정해석에 있어서의 유한요소법과 한계평형법의 결과를 나타내었다 해석의 타당성을 부여하기 위하여 유한요소법과 한계평형법에 의한 안전율을 비교하였으며, 각각의 방법에 의한 안전율이 잘 일치됨을 보여 전단강도감소기법을 사용한 유한요소해석이 사면안정해석에 있어서 효과적으로 사용될 수 있음을 확인하였다. 구성 법칙, 사면의 경사각, 흐름법칙, 그리고 유한요소망의 이산화에 따른 일련의 유한요소해석을 실시한 결과, 전단강도감소기법에 근거한 유한요소해석법은 안전율에 관하여 합리적인 결과를 제공할 수 있음을 확인하였고 유한요소해석결과는 구성법칙과 흐름법칙의 선택에 의해 상당한 영향을 받을 수 있음을 알 수 있다.

• 콘크리트학회논문집
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• 제17권6호
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• pp.1053-1064
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• 2005

The mechanical damage of concrete is normally attributed to the formation of microcracks and their propagation and coalescence into macroscopic cracks. This physical degradation is caused from progressive and hierarchical damage of the microstructure due to debonding and slip along bimaterial interfaces at the mesoscale. Their growth and coalescence leads to initiation of hairline discrete cracks at the mesoscale. Eventually, single or multiple major discrete cracks develop at the macroscale. In this paper, from this conceptual model of mechanical damage in concrete, the computational efforts were made in order to characterize physical cracks and how to quantify the damage of concrete materials within the laws of thermodynamics with the aid of interface element in traditional finite element methodology. One dimensional effective traction/jump constitutive interface law is introduced in order to accommodate the normal opening and tangential slips on the interfaces between different materials(adhesion) or similar materials(cohesion) in two and three dimensional problems. Mode I failure and mixed mode failure of various geometries and boundary conditions are discussed in the sense of crack propagation and their spent of fracture energy under monotonic displacement control.

• Structural Engineering and Mechanics
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• 제33권6호
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• pp.675-696
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• 2009

In this paper, a unified solution method is presented for the classical beam theory. In Strength of Materials approach, the geometry, material properties and load system are known and related with the unknowns of forces, moments, slopes and deformations by applying a classical differential analysis in addition to equilibrium, constitutive, and kinematic laws. All these relations are expressed in a unified formulation for the classical beam theory. In the special case of simple beams, a system of four linear ordinary differential equations of first order represents the general mechanical behaviour of a straight beam. These equations are solved using the numerical differential quadrature method (DQM). The application of DQM has the advantages of mathematical consistency and conceptual simplicity. The numerical procedure is simple and gives clear understanding. This systematic way of obtaining influence line, bending moment, shear force diagrams and deformed shape for the beams with geometric and load discontinuities has been discussed in this paper. Buckling loads and natural frequencies of any beam prismatic or non-prismatic with any type of support conditions can be evaluated with ease.

• 콘크리트학회논문집
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• 제16권4호
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• pp.501-509
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• 2004

제안된 모델은 FRP 구속 콘크리트에 대한 압축거동 예측을 위한 것이다. FRP로 구속된 콘크리트의 모델링을 위하여, 3축 응력상태의 콘크리트 아탄성 구성관계를 제시하였다. FRP 구속에 따른 콘크리트 강도 증진은 3축 응력공간의 파괴기준에 따라 결정되며, 이에 대응하는 최대 압축변형률은 본 연구에서 제안된 변형률 증진계수로부터 결정된다. 따라서, 기존의 모델들이 하중단계에 관계없이 구속조건이 초기부터 파괴까지 일정하게 고려되는 반면에, 제안된 모델은 FRP로 구속된 콘크리트의 구속현상을 하중단계에 의존적인 비선형 관계로 제시하였다. FRP 층은 2차원의 적층된 복합재료의 해석에 기초하여 모델링되었다. 개발된 해석모델은 증분법에 의한 압축거동실험에 대한 해석을 수행할 수 있도록 하였다. FRP로 구속된 콘크리트 실린더의 대한 여러 연구자들의 실험 결과와 본 예측모델을 비교한 결과, 제안된 모델은 축방향 변형 뿐만 아니라 횡방향 변형을 포함하여 FRP 층으로 인한 콘크리트의 구속효과의 증진에 관한 거동 특성들을 잘 예측해 주었다.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2008년도 춘계 학술발표회 초청강연 및 논문집
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• pp.1278-1289
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• 2008

Currently in increasing number of urban tunnels with small overburden are excavated according to the principle of the New Austrian Tunneling Method (NATM). Successful design, construction and maintenance of NATM tunnel in urban area demands prediction, control and monitoring of surface settlement, gradient and ground displacement with high accuracy. Use of measured displacement for parameter determination has been researched over the years, and one geotechnical engineering principle has been formed as back analysis. In this paper, back analysis of a ground deformational behavior involving nonlinear behavior is discussed. It is of primary importance to make reliable prediction of deformational behavior for shallow tunnels in soft ground. However, predictions made often prove to be incorrect due to complexity of constitutive law and other relevant factors. Back analysis therefore becomes more important, for it may be used to interpret measured displacement to derive nonlinear material characteristics. The paper shows some example in which a deformational mechanism is studied in the light of inhomogeneous distrubution of Young's module, from which a logic is derived to identify two different types of nonlinear constitutive relationships.

• Geomechanics and Engineering
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• 제36권4호
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• pp.355-366
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• 2024

The original elastoplastic Hardening Soil model is formulated actually partly under hexagonal pyramidal Mohr-Coulomb failure criterion, and can be only used in specific stress paths. It must be completely generalized under Mohr-Coulomb criterion before its usage in engineering practice. A set of generalized constitutive equations under this criterion, including shear and volumetric yield surfaces and hardening laws, is proposed for Hardening Soil model in principal stress space. On the other hand, a Mohr-Coulumb type yield surface in principal stress space comprises six corners and an apex that make singularity for the normal integration approach of constitutive equations. With respect to the isotropic nature of the material, a technique for processing these singularities by means of Koiter's rule, along with a transforming approach between both stress spaces for both stress tensor and consistent stiffness matrix based on spectral decomposition method, is introduced to provide such an approach for developing generalized Hardening Soil model in finite element analysis code ABAQUS. The implemented model is verified in comparison with the results after the original simulations of oedometer and triaxial tests by means of this model, for volumetric and shear hardenings respectively. Results from the simulation of oedometer test show similar shape of primary loading curve to the original one, while maximum vertical strain is a little overestimated for about 0.5% probably due to the selection of relationships for cap parameters. In simulation of triaxial test, the stress-strain and dilation curves are both in very good agreement with the original curves as well as test data.

• 한국항해항만학회지
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• 제46권2호
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• pp.99-109
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• 2022

A report released by the Chinese Maritime Court found that the natural environment and other objective factors have greatly reduced the risk of ship collision accidents with the advancement of technologies. However, collisions between merchant ships and fishing boats occur frequently along the coast during fishing seasons, which should be highly valued. International conventions and domestic legislation in China comprise detailed laws with respect to ship collisions, but the theory of ship collision infringement needs to be improved, enriched, and developed. Meanwhile, the development of the tort liability law provides theoretical support for ship collision infringement. As far as China's ship tort legal system is concerned, the research on ship collision tort damage compensation is relatively extensive, and the constitutive elements and causality of ship collision tort liability have also been studied in depth. The purpose of this paper is to explore the domestic legislation applicable to disputes related to ship collisions in China. As these laws are unclear on the resolution of disputes resulting from ship collisions, significant attention has been focused on the final judgments by the Supreme Court of China (SPC), as well as the judicial judgments set by the Maritime Court of China.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2002년도 가을 학술발표회 논문집
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• pp.167-172
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• 2002

Nonlinear analysis of the reinforced concrete beam subjected to torsion is presented. Seventeen equations involving seventeen variables are derived from the equilibrium equation, compatibility equation, and the material constitutive laws to solve the torsion problem. Newton method was used to solve the nonlinear simultaneous equations and efficient algorithms are proposed. Present model covers the behavior of reinforced concrete beam under pure torsion from service load range to ultimate stage. Tensile resistance of concrete after cracking is appropriately considered. The softened concrete truss model and the average stress-strain relations of concrete and steel are used. To verify the validity of Present model, the nominal torsional moment strengths according to ACI-99 code and the ultimate torsional moment by present model are compared to experimental torsional strengths of 55 test specimens found in literature. The ultimate torsional moment strengths by the present model show good results.

• International Journal of Concrete Structures and Materials
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• 제9권2호
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• pp.255-266
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• 2015

A strut-and-tie based method intended for determining the load-carrying capacity of reinforced concrete (RC) corbels is presented in this paper. In addition to the normal strut-and-tie force equilibrium requirements, the proposed model is based on secant stiffness formulation, incorporating strain compatibility and constitutive laws of cracked RC. The proposed method evaluates the load-carrying capacity as limited by the failure modes associated with nodal crushing, yielding of the longitudinal principal reinforcement, as well as crushing or splitting of the diagonal strut. Load-carrying capacity predictions obtained from the proposed analysis method are in a better agreement with corbel test results of a comprehensive database, comprising 455 test results, compiled from the available literature, than other existing models for corbels. This method is illustrated to provide more accurate estimates of behaviour and capacity than the shear-friction based approach implemented by the ACI 318-11, the strut-and-tie provisions in different codes (American, Australian, Canadian, Eurocode and New Zealand).

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1993년도 추계학술대회 논문집
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• pp.22-27
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• 1993

The finite element method is applied to analyze the mechanism of metal cutting. This paper introduces some effects, such constitutive deformation laws of workpiece material, friction of tool-chip contact interfaces, tool rake angles and also simulate the cutting process, chip formation and geometry, tool-chip contact, reaction force of tool, cutting temperature. Under the usual [lane strain assumption, quasi-static analysis were performed with variation of tool-chip interface friction coefficients and rake angles. In this analysis, various cutting speeds and depth of cut are adopted. Some cutting parameters are affected to cutting force, plastic deformation of chip, shear plane angle, chip thickness and tool-chip contact length and reaction forces on tool. Cutting temperature and Thermal behavior. Several aspects of the metal cutting process predicted by the finite element analysis provide information about tool shape design and optimal cutting conditions.