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Ibrahimbegovic, Adnan,Hajdo, Emina,Dolarevic, Samir Techno-Press 2013 Coupled systems mechanics Vol.2 No.4
In this work we propose a novel procedure for direct computation of buckling loads for extreme mechanical or thermomechanical conditions. The procedure efficiency is built upon the von Karmann strain measure providing the special format of the tangent stiffness matrix, leading to a general linear eigenvalue problem for critical load multiplier estimates. The proposal is illustrated on a number of validation examples, along with more complex examples of interest for practical applications. The comparison is also made against a more complex computational procedure based upon the finite strain elasticity, as well as against a more refined model using the frame elements. All these results confirm a very satisfying performance of the proposed methodology.
Special issue on multiscale computations for solids and fluids
Ibrahimbegovic, Adnan Techno-Press 2018 Coupled systems mechanics Vol.7 No.1
This special issue contains selected papers first presented in a short format at the $3^{rd}$ International Conference ECCOMAS MSF 2017-Multiscale Computations for Solids and Fluids, organized in Slovenian capital Ljubljana, September 20-22, 2017.
Special issue on multiscale computations for solids and fluids
Ibrahimbegovic, Adnan Techno-Press 2021 Coupled systems mechanics Vol.10 No.6
This special issue contains selected papers first presented in a short format at the 5th International Conference ECCOMAS MSF 2019-Multiscale Computations for Solids and Fluids, organized in Dalmatian capital Split, Croatia, June 30-July 2, 2021.
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.
Ibrahimbegovic, Adnan,Boujelben, Abir Techno-Press 2018 Coupled systems mechanics Vol.7 No.2
In order to reduce the dependency on fossil fuels, a policy to increase the production capacity of wind turbine is set up. This can be achieved with increasing the dimensions of offshore wind turbine blades. However, this increase in size implies serious problems of stability and durability. Considering the cost of large turbines and financial consequences of their premature failure, it is imperative to carry out numerical simulations over long periods. Here, an energy-conserving time-stepping scheme is proposed in order to ensure the satisfying computation of long-term response. The proposed scheme is implemented for three-dimensional solid based on Biot strain measures, which is used for modeling flexible blades. The simulations are performed at full spatial scale. For reliable design process, the wind loads should be represented as realistically as possible, including the fluid-structure interaction (FSI) dynamic effects on wind turbine blades. However, full-scale 3D FSI simulations for long-term wind loading remain of prohibitive computation cost. Thus, the model to quantify the wind loads proposed here is a simple, but not too simple to be representative for preliminary design studies.
Special Issue on computational methods in engineering (CILAMCE 2018 - Paris/Compiegne)
Ibrahimbegovic, Adnan,Pimenta, Paulo M. Techno-Press 2019 Coupled systems mechanics Vol.8 No.2
This special issue contains selected papers first presented in a short format at the Congress CILAMCE 2018 ($39^{th}$ Ibero-Latin American Congress on Computational Methods in Engineering) held in Paris and in $Compi{\grave{e}}gne$, France, from 11 to 14 November 2018.
Special issue ACSM20: Advances in coupled systems mechanics 2020
Ibrahimbegovic, Adnan Techno-Press 2021 Coupled systems mechanics Vol.10 No.3
This special issue contains selected papers first presented in a short format at ACSM20 (Advances in Coupled Systems Mechanics) held at the Global Education Center for Engineers (GECE) in Seoul, Korea, August 25~29, 2020. ACSM20 was regrouped with 11 other International Conferences, all placed within the framework of The 2020 World Congress on Advances in Civil, Environmental, & Materials Research (ACEM20)/The 2020 Structures Congress (Structures20).
Ibrahimbegovic, Adnan,Kassiotis, Christophe,Niekamp, Rainer Techno-Press 2016 Coupled systems mechanics Vol.5 No.2
An efficient and general numerical strategy for fluid-structure interaction problems is presented where either the fluid or the structure part are represented by nonlinear models. This partitioned strategy is implemented under the form of code coupling that allows to (re)-use previous made developments in a more general multi-physics context. This strategy and its numerical implementation is verified on classical fluid-structure interaction benchmarks, and then applied to the impact of tsunamis waves on submerged structures.
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.
Special issue on multiscale computations for solids and fluids
Ibrahimbegovic, Adnan Techno-Press 2020 Coupled systems mechanics Vol.9 No.1
This special issue contains selected papers first presented in a short format at the 4th International Conference ECCOMAS MSF 2019 - Multiscale Computations for Solids and Fluids, organized in Bosnian capital Sarajevo, September 18-20, 2019.