Momentum Equation을 이용한 차로감소구간 교통류의Higher-Order Continuum 모형 개발

손영태,양충헌,박우신 대한교통학회 2002 大韓交通學會誌 Vol.20 No.2

The purpose of this study was to develop a improved high-order continuum model among ma- croscopic traffic flow models. This study was mainly performed for uninterrupted flow. In the first step, the proposed model described traffic flow at dropped lane. (no exits) It was possible to describe the traffic flow during short - term considering lane change. The proposed model was based on Payne's model. Our model was newly applied to uninterrupted traffic flow in consideration of geometry condition and driver behavior. It is possible to establish efficient control stra- tegies, simulation and assess the effects of geometric improvements using this model . This model was simulated with field data for the actual adaption The results of the model tests, traffic volume and density is suitably represented. we think that the results in the article can be led to predicting the situation in the near future. 본 연구는 거시적 교통류 모형 중 고차연속교통류모형(high-order continuum model)의 개발을 목적으로 한다. 이 모형은 연속류 구간을 대상으로 수행되었고, 그 첫 번째 단계로 유·출입 구간이 없는 차로감소구간에서의 교통류를 묘사하였다. 개발된 모형은 차로변경율을 고려하였으며, 짧은 구간에서, 단기간동안의 교통류 행태에 대한 묘사를 가능하도록 하였다.본 연구에서 개발된 모형은 우리나라 연속류 시설의 기하구조조건과 운전자들의 운전행태를 고려하여 우리나라 실정에 맞도록 새롭게 적용하였다. 이를 통해 장래에 연속류 시설에 대한 교통제어 전략 수립이나 운영 체계 개선과 같은 교통공학적 관리를 할 수 있을 것으로 기대된다.모형의 현장적용성을 알아보기 위해, 현장에서 관측한 자료를 가지고 모의실험을 하였다. 그 결과, 교통량, 밀도, 속도의 시간대별 변동을 비교적 충실히 구현해 낸 것으로 판단된다.본 논문은 2000년도 한국학술진흥재단의 선도연구자 지원 연구비에 의하여 수행(2000-041-E00603)되었으며, 이에 감사드립니다.

Static and dynamic analyses of a suspension bridge with three-dimensionally curved main cables using a continuum model

Gwon, Sun-Gil,Choi, Dong-Ho Elsevier 2018 ENGINEERING STRUCTURES Vol.161 No.-

<P><B>Abstract</B></P> <P>In this paper, a continuum model is proposed for static and dynamic analyses of a three-span suspension bridge with three-dimensionally curved main cables. To obtain equations of motion for this model, coupled differential equations are derived for vertical displacements of a main cable and a girder as well as lateral displacements of a main cable subjected to external loads. A compatibility equation of a three-dimensionally curved cable is also derived. Utilizing the Galerkin method, the equations of motion are obtained in matrix form. A case study bridge is used to verify the continuum model against a finite element model. Verification results show that, for distributed static loads on the girder and temperature changes in the main cable and the hangers and for dynamic moving loads on the girder, the continuum model can accurately determine static and dynamic responses, namely displacements, velocities, accelerations, bending moments, and shear forces of the girder and additional horizontal forces in the main cable.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A continuum model for a suspension bridge with three-dimensionally curved main cables is newly proposed. </LI> <LI> This model considers extensible hangers and a continuous girder as well as 3D cables. </LI> <LI> A case study bridge is used to verify this model against a finite element model. </LI> <LI> This model can accurately determine the static and dynamic responses of the bridge. </LI> </UL> </P>

Design and Kinematic Modeling of a Notch Continuum Manipulator for Laryngeal Surgery

Haodong Wang,Xiaolong Wang,Wenlong Yang,Zhijiang Du 제어·로봇·시스템학회 2020 International Journal of Control, Automation, and Vol.18 No.11

A notch continuum manipulator with a large cavity is presented. The continuum manipulator which is designed for laryngeal surgery is composed of guidewire discs and a Nitinol skeleton. The deformation of the continuum manipulator is superimposed by the flexible units, therefore its posture and driving force are coupled. Based on the small deformation cantilever beam theory, the mechanical model from the microscopic to the macroscopic is used to establish the mapping from the driving space to the joint space. The manipulator is assumed to be a multi-joint series robot. Based on the mechanical model, the mapping from the joint space to the Cartesian space is established by the Denavit-Hartenberg (D-H) method. The kinematics is established from the driving space to the Cartesian space. The proposed kinematic model is verified by a prototype. The experimental results show the validity of the model.

Continuum modeling of deformation and aggregation of red blood cells

Yoon, D.,You, D. Pergamon Press ; Elsevier Science Ltd 2016 Journal of biomechanics Vol.49 No.11

In order to gain better understanding for rheology of an isolated red blood cell (RBC) and a group of multiple RBCs, new continuum models for describing mechanical properties of cellular structures of an RBC and inter-cellular interactions among multiple RBCs are developed. The viscous property of an RBC membrane, which characterizes dynamic behaviors of an RBC under stress loading and unloading processes, is determined using a generalized Maxwell model. The present model is capable of predicting stress relaxation and stress-strain hysteresis, of which prediction is not possible using the commonly used Kelvin-Voigt model. Nonlinear elasticity of an RBC is determined using the Yeoh hyperelastic material model in a framework of continuum mechanics using finite-element approximation. A novel method to model inter-cellular interactions among multiple adjacent RBCs is also developed. Unlike the previous modeling approaches for aggregation of RBCs, where interaction energy for aggregation is curve-fitted using a Morse-type potential function, the interaction energy is analytically determined. The present aggregation model, therefore, allows us to predict various effects of physical parameters such as the osmotic pressure, the thickness of a glycocalyx layer, the penetration depth, and the permittivity, on the depletion and electrostatic energy among RBCs. Simulations for elongation and recovery deformation of an RBC and for aggregation of multiple RBCs are conducted to evaluate the efficacy of the present continuum modeling methods.

Prediction of settlement influence factors for laterally loaded short piles by using a continuum-based soil model

J. Ryue,K. Baik,J. Lee 대한기계학회 2020 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.34 No.3

An existing continuum-based model for a laterally loaded pile embedded in layered soil is developed for long piles in which the vertical deformation of soil is neglected. However, the model is unsuitable for short piles, such as large-diameter caissons and suction buckets, because the soil will have considerable vertical deflections. Thus, this study attempts to modify the existing continuum-based model for laterally loaded long piles, and the aim is to render the model applicable for short piles with large diameters. Two resisting moments are added to the model: A moment on the base of the pile and a moment due to the vertical shear stress of the soil surrounding the pile. The modified continuum-based model is examined in terms of settlement influence factors and validated with the model with finite element (FE) analysis. Our linear static analysis found that the proposed modified continuum-based model is in good agreement with the FE method for short and long piles.

A modified replacement beam for analyzing building structures with damping systems

Hadi Moghadasi Faridani,Antonio Capsoni 국제구조공학회 2016 Structural Engineering and Mechanics, An Int'l Jou Vol.58 No.5

This paper assesses efficiency of the continuum method as the idealized system of building structures. A modified Coupled Two-Beam (CTB) model equipped with classical and non-classical damping has been proposed and solved analytically. In this system, complementary (non-classical) damping models composed of bending and shear mechanisms have been defined. A spatial shear damping model which is non-homogeneously distributed has been adopted in the CTB formulation and used to equivalently model passive dampers, viscous and viscoelastic devices, embedded in building systems. The application of continuum-based models for the dynamic analysis of shear wall systems has been further discussed. A reference example has been numerically analyzed to evaluate the efficiency of the presented CTB, and the optimization problems of the shear damping have been finally ascertained using local and global performance indices. The results reveal the superior performance of non-classical damping models against the classical damping. They show that the critical position of the first modal rotation in the CTB is reliable as the optimum placement of the shear damping. The results also prove the good efficiency of such a continuum model, in addition to its simplicity, for the fast estimation of dynamic responses and damping optimization issues in building systems.

Prediction of anisotropic material behavior based on multiresolution continuum mechanics in consideration of a characteristic length scale

Dockjin Lee,장윤석,최재붕,김문기 대한기계학회 2012 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.26 No.9

New advanced materials have received more attention from many scientists and engineers because of their outstanding chemical, electrical,thermal, optical, and mechanical properties. Since the design of advanced material by experiments requires high cost and time,numerical approaches have always been of great interest. In this paper, finite element analysis of anisotropic material behavior has been carried out based on a multiresolution continuum theory. Gurson-Tvergaard-Needleman (GTN) damage model has been applied as a constitutive model at macroscale. Effects of plastic anisotropy on deformation behavior are assessed using Hill’s 48 yield function for anisotropic material and von Mises yield function for isotropic material, respectively. The material parameters for both isotropic and anisotropic damage models have systematically been determined from microstructure through unit cell modeling. The newly proposed linear approximation of local velocity gradient resolved the underdetermined problem of the previous homogenization process. Anisotropic material behaviors of a tensile specimen have been investigated by the proposed multiresolution continuum theory.

DFN 매질에 대한 등가연속체 유동모델의 적용 가능성 평가에 관한 연구

이다혜(Dahye Lee),엄정기(Jeong-Gi Um) 한국암반공학회 2017 터널과지하공간 Vol.27 No.5

본 연구는 다양한 기하학적 속성을 갖는 총 72개의 DFN 블록에 대하여 DFN 유동모델과 등가의 수리상수를 사용한 연속체 모델을 각각 적용하여 두 결과 간의 상관성을 분석하였다. DFN을 연속체로 가정한 이론적 블록수리전도도와 DFN 유동모델로 산정한 블록수리전도도 사이의 상대오차(ER)가 0.2 이하인 DFN 조건에서 두 접근법 사이에 강한 선형 관계를 이루며 두 결과가 거의 일치하는 것으로 평가되었다. DFN 매질에 대한 연속체 유동해석의 현장적용 가능성을 검토하기 위하여 다양한 DFN 조건을 갖는 지중 원형공동에서의 지하수 유입에 대한 모의 수치실험이 총 48회 수행되었다. 일정한 수리간극의 DFN 매질에 대한 등가연속체 유동모델은 유효한 것으로 평가되었지만 수리간극 변화로 인하여 이방성이 증대되면 DFN 유동모델에 의한 결과에 비하여 과대평가될 가능성이 높다. The correlation analysis between the results obtained from DFN flow model and equivalent continuum flow model were conducted on total of 72 DFN blocks having various fracture geometry and domain size. A strong linear relation seems to exist between the two approaches under condition that normalized relative error for continuum behavior (ER) is less than 0.2, and the results from both methods are found to almost identical. To explore the field applicability of equivalent continuum flow model in DFN media, a total of 48 numerical schemes related to inflow of underground circular openings were implemented under various DFN configurations. The equivalent continuum flow model in DFN media with a constant hydraulic aperture was evaluated as valid. However, as the anisotropy increases due to variation of the hydraulic aperture, the results are likely to be overestimated compare to the DFN flow model.

구성방정식에 따른 고무 분기점 거동 비교 연구

박문식(Moon Shik Park),송승(Seung Song) 대한기계학회 2010 大韓機械學會論文集A Vol.34 No.6

설계 또는 해석을 위해 고무를 모델링할 때, 쓸 수 있는 구성방정식이 너무 많음으로 말미암아 종종 당황하거나 수수께끼 같은 일을 경험할 때가 있다. 어떤 모델들은 몇 개의 재료상수만을 갖지만 또 다른 모델들은 많은 수의 재료상수를 갖는다. 연구자들은 광범위한 실험데이터를 준비하여 신중하게 피팅을 하여야 한다. 본 논문에서는 먼저 8배 정도까지 큰 신장 영역에 대해 대표적인 고무재료의 구성방정식들을 비교해 보았다. 대부분의 공학적 응용에서처럼 상대적으로 변형이 적은 경우에는 연속체기반모델 또는 체인분자모델이 유사하게 쓰일 수 있지만, 대부분 생체적 거동에서 볼 수 있는 큰 변형의 경우에는 체인분자모델들이 더 유용함을 알 수 있었다. 구성방정식에 따른 분기점의 존재 여부를 알아보기 위하여 트렐로어 패치와 원통형 막대풍선에 대한 분기점 해석을 이론적 및 수치적으로 수행하였다. 키슬리의 조건식으로부터 트렐로어 패치에서의 분기점은 연속체기반 모델에서는 존재하였으나 체인분자모델에서는 존재하지 않음을 보였다. 원통형 막대풍선은 축신장 허용의 경계조건에 대해서는 모든 모델들이 분기점 거동을 보여주었다. 따라서 고무의 분기점 거동을 구하고자 할 때는 분기점의 존재유무 자체가 재료모델의 선정에 의존적이라 할 수 있다. Modeling of rubber for design or analysis often requires confusing or complex work because there are a large number of constitutive models to be considered. Some models have few material constants, while others have many. Researchers have to prepare and fit extensive experimental data with caution and discretion. In this paper, we first compared some typical rubber models in which deformation was carried out by stretching up to around eight times the original size. We conclude that continuum-based models and chain molecular models can be used in the study of the small deformation in most engineering applications, but chain molecular models are preferred in the study of the large deformations in most biomaterial applications. As discrimination problems, Treloar's patch and cylindrical balloon stick are tested theoretically and numerically for studying bifurcation. In the case of Treloar's patch, by using the Kearsley's equation, we show that bifurcation exists for continuum-based models but not for chain molecular models. Both models show bifurcation in the cylindrical balloon stick. Therefore, in the analysis of the bifurcation of rubber showed that its existence also depends on the constitutive model selected.

채굴적 상부 지표침하 특성에 관한 모형실험 연구

김종우,안영균,송원경 한국자원공학회 2011 한국자원공학회지 Vol.48 No.3

본 연구에서는 지하 채굴적이 존재하는 지반에서의 지표침하 특성을 조사하기 위하여 주문진산 모래로 제작한 연속체 지반 모형과 정육면체 석고블록들로 제작한 불연속체 지반 모형에 대해 채굴적 붕락 모형실험을 실시하였다. 채굴적의 심도와 규모를 달리하는 수많은 실험모형들을 제작하였는데, 특히 블록상의 암반을 모델링한 불연속체 지반모형에 대해서는 블록의 크기와 불연속면의 경사를 달리하여 제작하였다. 연속체 모형은 골형 침하를 나타낸 반면에 불연속체 모형은 블록간의 미끄러짐과 전도로 인해 함몰형 침하를 나타내었으며, 모든 모형에서 채굴적의 심도가 작을수록, 채굴적의 규모가 클수록 침하량은 증가하였다. 불연속체 모형의 침하는 채굴적의 규모가 작은 경우에는 연속체 모형에 비해 작았으나, 채굴적의 규모가 클 경우에는 이와 반대되는 경향도 나타났으며, 암석블록의 크기와 경사는 침하에 큰 영향을 미치는 주요 파라미터임을 알 수 있었다. In order to investigate the surface subsidence behavior by underground opening, physical model tests simulating sudden collapse of opening were performed. The physical models considered in this study were both the continuous and discontinuous ground models, where the modelling materials were sand and cubic plaster blocks respectively. Two kinds of models were also subdivided into many models with different depths and volumes of underground openings. In particular, the discontinuous ground models simulating blocky rock mass were manufactured with different block sizes and inclinations. As results, the continuous models showed trough subsidence whereas the discontinuous models showed sinkhole subsidence through falling down and sliding between individual blocks. As the opening depths were smaller and the opening volumes were larger, surface subsidence proved to be larger in all of models. Subsidences of the discontinuous models were smaller than those of continuous ones in case that opening volumes were relatively small. The size and inclination of rock blocks turned out to be one of the main parameters of subsidence occurring in discontinuous rock mass.