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RISS 인기검색어
- 검색키워드
- 저자 : Mejia-Nava, Rosa Adela (검색결과 5 건)
- 무료
- 기관 내 무료
- 유료
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Mejia-Nava, Rosa Adela,Ibrahimbegovic, Adnan,Lozano-Leal, Rogelio Techno-Press 2020 Coupled systems mechanics Vol.9 No.1
In this paper we study the control for nonlinear geometric instability problem of a deep or a shallow truss or yet a frame structure. All the structural models are built with geometrically exact truss and beam finite elements.The proposed models can successfully handle large overall motion under static or dynamic conservative load.The control strategy considers adding a damping from either friction device or viscous damper.This kind of control belong to well-known concept of passivity. Different examples are presented in order to illustrate the proposed theoretical developments.
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Viscoelastic behavior of concrete structures subject to earthquake
Mejia-Nava, Rosa Adela,Ibrahimbegovic, Adnan,Dominguez-Ramirez, Norberto,Flores-Mendez, Esteban Techno-Press 2021 Coupled systems mechanics Vol.10 No.3
This paper investigates an alternative way to the Raleigh formula to catch con- tributions of damping effects. Nowadays, thanks to the power of new software and effi- cient computational methods, there exist possibility to implement new analysis of damping through multiscale approach. The corresponding homogenization of a representative elemen-tal volume of concrete is used to calculate the effective properties of the composite, since energy dissipation properties such as viscoelasticity are not taken into account. At the end of this work, these methodologies are incorporated into a column of a building subject to seismic action. More precisely, with concrete as a composite material (aggregate+cement), we can use homogenization methods to calculate its effective properties by using the classical approach of a representative elemental volume. This can help to take into account properties of energy dissipation, such as produced by viscoelasticity. Finally, for illustration, the pro- posed methodology is applied to structural analysis of a column under the most unfavorable conditions in a building subject to earthquake action.
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Hajdo, Emina,Mejia-Nava, Rosa Adela,Imamovic, Ismar,Ibrahimbegovic, Adnan Techno-Press 2021 Coupled systems mechanics Vol.10 No.1
In this paper we deal with instability problems of structures under nonconservative loading. It is shown that such class of problems should be analyzed in dynamics framework. Next to analytic solutions, provided for several simple problems, we show how to obtain the numerical solutions to more complex problems in efficient manner by using the finite element method. In particular, the numerical solution is obtained by using a modified Euler-Bernoulli beam finite element that includes the von Karman (virtual) strain in order to capture linearized instabilities (or Euler buckling). We next generalize the numerical solution to instability problems that include shear deformation by using the Timoshenko beam finite element. The proposed numerical beam models are validated against the corresponding analytic solutions.
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Instability of (Heterogeneous) Euler beam: Deterministic vs. stochastic reduced model approach
Ibrahimbegovic, Adnan,Mejia-Nava, Rosa Adela,Hajdo, Emina,Limnios, Nikolaos Techno-Press 2022 Coupled systems mechanics Vol.11 No.2
In this paper we deal with classical instability problems of heterogeneous Euler beam under conservative loading. It is chosen as the model problem to systematically present several possible solution methods from simplest deterministic to more complex stochastic approach, both of which that can handle more complex engineering problems. We first present classical analytic solution along with rigorous definition of the classical Euler buckling problem starting from homogeneous beam with either simplified linearized theory or the most general geometrically exact beam theory. We then present the numerical solution to this problem by using reduced model constructed by discrete approximation based upon the weak form of the instability problem featuring von Karman (virtual) strain combined with the finite element method. We explain how such numerical approach can easily be adapted to solving instability problems much more complex than classical Euler's beam and in particular for heterogeneous beam, where analytic solution is not readily available. We finally present the stochastic approach making use of the Duffing oscillator, as the corresponding reduced model for heterogeneous Euler's beam within the dynamics framework. We show that such an approach allows computing probability density function quantifying all possible solutions to this instability problem. We conclude that increased computational cost of the stochastic framework is more than compensated by its ability to take into account beam material heterogeneities described in terms of fast oscillating stochastic process, which is typical of time evolution of internal variables describing plasticity and damage.
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Ibrahimbegovic, Adnan,Nava, Rosa Adela Mejia Techno-Press 2021 Coupled systems mechanics Vol.10 No.3
This study is aimed to develop a damping model to accurately predict vibration amplitude reduction for any size of structure. It is developed in the framework of multi-scale analysis, where different sources of energy dissipation at captured at material-scales (e.g.,scale of representative volume element). In particular, we illustrate details for concrete structures, where one needs different failure mechanisms like plasticity, damage and viscosity to represent different sources of dissipation are reproduce the typical hysteresis loops of concrete with both residual deformation and change of initial elastic response. The final step in proposed approach is to account for structure heterogeneities by allowing for variability of elasticity limit, which produces the same exponential (rather than linear decay) of vibration amplitudes, just as in the case of Rayleigh damping. However, contrary to Rayleigh damping calibration that can be done only on a single structure (and for a chosen frequency), the proposed approach can be adapted to any structure size and full interval of frequencies of interest. The price to pay is in terms of nonlinear analysis, which is here rendered very efficient by hybrid-stress formulation to uncouple different damage mechanisms and by using linear evolution equations for internal variables representing such mechanisms. The details illustrated for 1D and 3D concrete model can be easily adapted to other materials, such as steel, soils etc.
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