• Title, Summary, Keyword: equilibrium path

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Energy approach for dynamic buckling of shallow fixed arches under step loading with infinite duration

  • Pi, Yong-Lin;Bradford, Mark Andrew;Qu, Weilian
    • Structural Engineering and Mechanics
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    • v.35 no.5
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    • pp.555-570
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    • 2010
  • Shallow fixed arches have a nonlinear primary equilibrium path with limit points and an unstable postbuckling equilibrium path, and they may also have bifurcation points at which equilibrium bifurcates from the nonlinear primary path to an unstable secondary equilibrium path. When a shallow fixed arch is subjected to a central step load, the load imparts kinetic energy to the arch and causes the arch to oscillate. When the load is sufficiently large, the oscillation of the arch may reach its unstable equilibrium path and the arch experiences an escaping-motion type of dynamic buckling. Nonlinear dynamic buckling of a two degree-of-freedom arch model is used to establish energy criteria for dynamic buckling of the conservative systems that have unstable primary and/or secondary equilibrium paths and then the energy criteria are applied to the dynamic buckling analysis of shallow fixed arches. The energy approach allows the dynamic buckling load to be determined without needing to solve the equations of motion.

Bypass, homotopy path and local iteration to compute the stability point

  • Fujii, Fumio;Okazawa, Shigenobu
    • Structural Engineering and Mechanics
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    • v.5 no.5
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    • pp.577-586
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    • 1997
  • In nonlinear finite element stability analysis of structures, the foremost necessary procedure is the computation to precisely locate a singular equilibrium point, at which the instability occurs. The present study describes global and local procedures for the computation of stability points including bifurcation points and limit points. The starting point, at which the procedure will be initiated, may be close to or arbitrarily far away from the target point. It may also be an equilibrium point or non-equilibrium point. Apart from the usual equilibrium path, bypass and homotopy path are proposed as the global path to the stability point. A local iterative method is necessary, when it is inspected that the computed path point is sufficiently close to the stability point.

A Traffic Equilibrium Model with Area-Based Non Additive Road Pricing Schemes (지역기반의 비가산성 도로통행료 부과에 따른 교통망 균형모형)

  • Jung, Jumlae
    • Journal of The Korean Society of Civil Engineers
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    • v.28 no.5D
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    • pp.649-654
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    • 2008
  • In the definition of non additive path, the sum of travel costs of links making up the path is not equal to the path cost. There are a variety of cases that non-additivity assumption does not hold in transportation fields. Nonetheless, traffic equilibrium models are generally built up on the fundamental hypothesis of additivity assumption. In this case traffic equilibrium models are only applicable within restrictive conditions of the path cost being linear functions of link cost. Area-wide road pricing is known as an example of realistic transportation situations, which violates such additivity assumption. Because travel fare is charged at the moment of driver's passing by exit gate while identified at entry gate, it may not be added linearly proportional to link costs. This research proposes a novel Wordrop type of traffic equilibrium model in terms of area-wide road pricing schemes. It introduces binary indicator variable for the sake of transforming non-additive path cost to additive. Since conventional shortest path and Frank-Wolfe algorithm can be applied without route enumeration and network representation is not required, it can be recognized more generalized model compared to the pre-proposed approaches. Theoretical proofs and case studies are demonstrated.

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An Equilibrium Diffusion Model of Demand and Supply of New Product and Empirical Analysis (신기술 제품의 확산에 관한 수요$\cdot$공급의 균형확산모형과 실증분석)

  • Ha, Tae-Jeong
    • Journal of Technology Innovation
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    • v.13 no.1
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    • pp.113-139
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    • 2005
  • The purpose of this study is to analyse the diffusion process of personal computer (PC) in Korea during the 1990's. To achieve the goal, five research steps have been done such as the literature survey of diffusion theory, set-up of theoretic equilibrium model of supply and demand, derivation of an equilibrium path using Hamiltonian, and empirical analysis. The empirical analysis has been performed based on that equilibrium path. The results can be summarized as follows : First, technological attribute of diffusing product influences the diffusion speed of Product. It has been proven that the size of the network has a significant effect on the diffusion of PC in empirical study Second, supply factors have an important role in the diffusion process. According to the empirical analysis, decreasing cost of production as a result of technological advance promotes the speed of diffusion. This point seems to be manifest theoretically, but existing empirical models have not included supply factors explicitly, Third, it has been found out that expectation of decreasing cost would influence the speed of diffusion negatively as expected ex ante. Theoretically this result is supported by arbitrage condition of purchasing timing.

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A dual approach to perform geometrically nonlinear analysis of plane truss structures

  • Habibi, AliReza;Bidmeshki, Shaahin
    • Steel and Composite Structures
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    • v.27 no.1
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    • pp.13-25
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    • 2018
  • The main objective of this study is to develop a dual approach for geometrically nonlinear finite element analysis of plane truss structures. The geometric nonlinearity is considered using the Total Lagrangian formulation. The nonlinear solution is obtained by introducing and minimizing an objective function subjected to displacement-type constraints. The proposed method can fully trace the whole equilibrium path of geometrically nonlinear plane truss structures not only before the limit point but also after it. No stiffness matrix is used in the main approach and the solution is acquired only based on the direct classical stress-strain formulations. As a result, produced errors caused by linearization and approximation of the main equilibrium equation will be eliminated. The suggested algorithm can predict both pre- and post-buckling behavior of the steel plane truss structures as well as any arbitrary point of equilibrium path. In addition, an equilibrium path with multiple limit points and snap-back phenomenon can be followed in this approach. To demonstrate the accuracy, efficiency and robustness of the proposed procedure, numerical results of the suggested approach are compared with theoretical solution, modified arc-length method, and those of reported in the literature.

A Development of Analytical Strategies for Elastic Bifurcation Buckling of the Spatial Structures (공간구조물의 탄성 분기좌굴해석을 위한 수치해석 이론 개발)

  • Lee, Kyung Soo;Han, Sang Eul
    • Journal of Korean Society of Steel Construction
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    • v.21 no.6
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    • pp.563-574
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    • 2009
  • This paper briefly describes the fundamental strategies--path-tracing, pin-pointing, and path-switching--in the computational elastic bifurcation theory of geometrically non-linear single-load-parameter conservative elastic spatial structures. The stability points in the non-linear elasticity may be classified into limit points and bifurcation points. For the limit points, the path tracing scheme that successively computes the regular equilibrium points on the equilibrium path, and the pinpointing scheme that precisely locates the singular equilibrium points were sufficient for the computational stability analysis. For the bifurcation points, however, a specific procedure for path-switching was also necessary to detect the branching paths to be traced in the post-buckling region. After the introduction, a general theory of elastic stability based on the energy concept was given. Then path tracing, an indirect method of detecting multiple bifurcation points, and path switching strategies were described. Next, some numerical examples of bifurcation analysis were carried out for a trussed stardome, and a pin-supported plane circular arch was described. Finally, concluding remarks were given.

Mathematical Modeling for Traffic Flow (교통흐름의 수학적 모형)

  • Lee, Seong-Cheol
    • Journal of the Korea Safety Management & Science
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    • v.13 no.1
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    • pp.127-131
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    • 2011
  • Even if there are no causing factors such as car crash and road works, traffic congestion come from traffic growth on the road. In this case, estimation of traffic flow helps find the solution of traffic congestion problem. In this paper, we present a optimization model which used on traffic equilibrium problem and studied the problem of inverting shortest path sets for complex traffic system. And we also develop pivotal decomposition algorithm for reliability function of complex traffic system. Several examples are illustrated.

Composite Control for Inverted Pendulum System

  • Kwon, Yo-Han;Kim, Beom-Soo;Lee, Sang-Yup;Lim, Myo-Taeg
    • Transactions on Control, Automation and Systems Engineering
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    • v.4 no.1
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    • pp.84-91
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    • 2002
  • A new composite control method for a carriage balancing single inverted pendulum system is proposed and applied to swing up the pendulum and to stabilize it under the state constraint. The target inverted pendulum system has an extremely limited length of the cart(below 16cm). The proposed swing-up controller comprises a sliding mode control algorithm and an optimal control algorithm based on two regions: the region near the inverted unstable equilibrium position and the rest of the state space including the downward stable equilibrium position. The sliding mode controller uses a switching control action to converge along the specified path(hyperplane) derived from energy equation from a state around the path to desired state(standing position). An optimal control method is also used to guarantee the stability at unstable equilibrium position. Compared with the reported controllers, it is simpler and easier to implement. Experimental results are given to show the effectiveness of this controller.

Nash equilibrium-based geometric pattern formation control for nonholonomic mobile robots

  • Lee, Seung-Mok;Kim, Hanguen;Lee, Serin;Myung, Hyun
    • Advances in robotics research
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    • v.1 no.1
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    • pp.41-59
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    • 2014
  • This paper deals with the problem of steering a group of mobile robots along a reference path while maintaining a desired geometric formation. To solve this problem, the overall formation is decomposed into numerous geometric patterns composed of pairs of robots, and the state of the geometric patterns is defined. A control algorithm for the problem is proposed based on the Nash equilibrium strategies incorporating receding horizon control (RHC), also known as model predictive control (MPC). Each robot calculates a control input over a finite prediction horizon and transmits this control input to its neighbor. Considering the motion of the other robots in the prediction horizon, each robot calculates the optimal control strategy to achieve its goals: tracking a reference path and maintaining a desired formation. The performance of the proposed algorithm is validated using numerical simulations.

Nonlinear Viscoelastic Analysis of Reticulated Spatial Truss Composed of Composite Materials (복합재료 그물형 공간 트러스의 점탄성적 비선형 해석)

  • Han, Sung Cheon;Chang, Suk Yoon
    • Journal of Korean Society of Steel Construction
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    • v.13 no.6
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    • pp.661-672
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    • 2001
  • The present study is concerned with the arc-length method in the investigation of the large deflection behavior of spatial structures with composite materials. This study should be able to trace the main equilibrium path by automatically varying the arc-length size of individual solution steps with the variation of the curvature of the nonlinear equilibrium path. A quasi-elastic method is used for the solution for viscoelastic analysis of the reticulated spatial structures. Elastic modulus of composite materials is defined by micro mechanical materials modeling method and nonlinear equilibrium path is traced with various load types. To demonstrate the effectiveness of the present strategies, numerical examples of reticulated spatial truss is given and compared with solutions using other methods.

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