• Structural Engineering and Mechanics
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• 제83권3호
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• pp.377-386
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• 2022

This paper considers dynamic impedance functions and presents a detailed analysis of the soil plasticity influence on the pile-group foundation dynamic response. A three-dimensional finite element model is proposed, and a calculation method considering the time domain is detailed for the nonlinear dynamic impedance functions. The soil mass is modeled as continuum elastoplastic solid using the Mohr-Coulomb shear failure criterion. The piles are modeled as continuum solids and the slab as a structural plate-type element. Quiet boundaries are implemented to avoid wave reflection on the boundaries. The model and method of analysis are validated by comparison with those published on literature. Numerical results are presented in terms of horizontal and vertical nonlinear dynamic impedances as a function of the shear soil parameters (cohesion and internal friction angle), pile spacing ratio and frequencies of the dynamic signal.

• Geomechanics and Engineering
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• 제32권6호
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• pp.553-566
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• 2023

A circular tank foundation resting on the ground and subjected to axisymmetric horizontal and vertical loads and moments is analyzed using the variational principles of mechanics. The circular foundation is assumed to behave as a Kirchhoff plate with in-plane and transverse displacements. The soil beneath the foundation is assumed to be a multi-layered continuum in which the horizontal and vertical displacements are expressed as products of separable functions. The differential equations of plate and soil displacements are obtained by minimizing the total potential energy of the plate-soil system and are solved using the finite element and finite difference methods following an iterative algorithm. Comparisons with the results of equivalent two-dimensional finite element analysis and other researchers establish the accuracy of the method.

• Structural Engineering and Mechanics
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• 제35권6호
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• pp.677-697
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• 2010

This paper focuses on geometrically non-linear static analysis of a simply supported beam made of hyperelastic material subjected to a non-follower transversal uniformly distributed load. As it is known, the line of action of follower forces is affected by the deformation of the elastic system on which they act and therefore such forces are non-conservative. The material of the beam is assumed as isotropic and hyperelastic. Two types of simply supported beams are considered which have the following boundary conditions: 1) There is a pin at left end and a roller at right end of the beam (pinned-rolled beam). 2) Both ends of the beam are supported by pins (pinned-pinned beam). In this study, finite element model of the beam is constructed by using total Lagrangian finite element model of two dimensional continuum for a twelve-node quadratic element. The considered highly non-linear problem is solved by using incremental displacement-based finite element method in conjunction with Newton-Raphson iteration method. In order to use the solution procedures of Newton-Raphson type, there is need to linearized equilibrium equations, which can be achieved through the linearization of the principle of virtual work in its continuum form. In the study, the effect of the large deflections and rotations on the displacements and the normal stress and the shear stress distributions through the thickness of the beam is investigated in detail. It is known that in the failure analysis, the most important quantities are the principal normal stresses and the maximum shear stress. Therefore these stresses are investigated in detail. The convergence studies are performed for various numbers of finite elements. The effects of the geometric non-linearity and pinned-pinned and pinned-rolled support conditions on the displacements and on the stresses are investigated. By using a twelve-node quadratic element, the free boundary conditions are satisfied and very good stress diagrams are obtained. Also, some of the results of the total Lagrangian finite element model of two dimensional continuum for a twelve-node quadratic element are compared with the results of SAP2000 packet program. Numerical results show that geometrical nonlinearity plays very important role in the static responses of the beam.

• Tunnel and Underground Space
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• 제29권5호
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• pp.318-331
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• 2019

A three-dimensional(3D) equivalent continuum modeling was performed to analyze hydraulic behavior of rock mass considering discontinuities by using DFN model and smeared fracture model. DFN model was generated by FLAC3D and smeared fracture model was applied by using FISH functions, which is built-in functions in FLAC3D, for equivalent continuum model of fractured rock mass. Comparative analysis with 3DEC, which is for discontinuum analysis, was conducted to verify reliability of equivalent continuum analysis by using FLAC3D. Similar results of hydraulic analysis under the same conditions could be achieved. Equivalent continuum analysis of fractured rock mass by using DFN model was implemented to compare with existing analytical methods for inflow into the tunnel.

• Selected Papers of The Society of Naval Architects of Korea
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• 제2권1호
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• pp.106-128
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• 1994

An elasto-plastic-damage constitutive model for ductile materials is proposed within the framework of a thermodynamic approach of continuum damage mechanics (CDM) in which internal irreversible thermodynamic changes of micro-structure of materials such as plastic deformation and damage evolution are considered as thermodynamic state variables. The new constitutive model can predict not only the elasto-plastic behaviors but also the sequential stiffness degradation process of ductile materials more rationally.

• Proceedings of the Korea Concrete Institute Conference
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• 한국콘크리트학회 2006년도 춘계 학술발표회 논문집(II)
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• pp.633-636
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• 2006

Impact damage modeling of concrete under high strain rate loading conditions is investigated. A phenomenological penetration model that can account for complicated impact and penetration process such as the rate and loading history response of concrete, the microstructure-penetration interaction etc. is discussed. Constitutive law compatible with Second Law of thermodynamics and coupled damage and plasticity modelling based on continuum damage mechanics are also examined. The purpose of this paper is preliminarily to study with respect to impact and penetration models for concrete before the development of that model.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 한국소성가공학회 1996년도 추계학술대회논문집
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• pp.131-138
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• 1996

A new yield criterion for metal powder compaction based on continuum mechanics has been proposed. It includes three parameters to characterize the geometrical hardening of powder compact and strain hardening of incompressible metal matrix. The elasto-plastic finite element method to describe compaction of metal powders has been formulated using the new yield criterion. The values of parameters in the yield criterion can be determined using cold isostatic pressing(CIP). The finite element method can simulate compaction behavior of various copper powders.

• Proceedings of the KIEE Conference
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• 대한전기학회 1990년도 하계학술대회 논문집
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• pp.19-22
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• 1990

In order to optimize systematically the shape of electromagnetic devices, two sensitivity analyses, one based on finite element method and the other based on variational formulae and material derivative in continuum mechanics, are proposed. These are applied to eddy current problem of time-varying field and verified these usefulness.

• Structural Engineering and Mechanics
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• 제41권1호
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• pp.67-81
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• 2012

Differential Quadrature Method (DQM) is a powerful method which can be used to solve numerical problems in the analysis of structural and dynamical systems. In this study the governing equation which represents the free vibration of coupled shear walls is solved using the DQM method. A one-dimensional model has been used in this study. At the end of study various examples are presented to verify the accuracy of the method.

• Coupled systems mechanics
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• 제6권4호
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• pp.399-415
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• 2017

This paper deals with the nonlinear static deflections of functionally graded (FG) porous under thermal effect. Material properties vary in both position-dependent and temperature-dependent. The considered nonlinear problem is solved by using Total Lagrangian finite element method within two-dimensional (2-D) continuum model in the Newton-Raphson iteration method. In numerical examples, the effects of material distribution, porosity parameters, temperature rising on the nonlinear large deflections of FG beams are presented and discussed with porosity effects. Also, the effects of the different porosity models on the FG beams are investigated in temperature rising.