Determination of optimal placements of sensors/actuators in large structures is a difficult job as large number of possible combinations leads to a very high computational time and storage. Therefore, this kind of optimization problem demands a parallel implementation of the optimization schemes. Island model genetic algorithm (GA) being inherently parallel has been used for searching optimal placements of collocated sensors/actuators. Numerical simulations have been done for determination of optimal placements of collocated PZT sensors and actuators in smart fiber reinforced shell structures using island model parallel GA (IMPGA) in conjunction with electro-mechanical finite element analysis with an objective of maximizing the controllability index. It has been observed that the present IMPGA-based formulation (due to its migration scheme) not only makes it possible to determine optimal sensors/actuators locations for large structures but also leads to a better solution at a much reduced and achievable computational time. Results from scalability analysis also show that the efficacy of the present method of using IMPGA for determination of optimal sensors/actuators location based on FEA will be more pronounced when actually used for real life problems requiring large number of sensors and actuators.
Nonlinear seismic analysis is becoming increasingly significant to grasp the performance of structures under earthquake. A nonlinear finite element model of existing bridge at Karad, India, including the bridge structure, pile groups, and the supporting foundation soil, is developed under 2D and 3D conditions in Gid (a pre and postprocessor software). The computational model is analyzed using Parallel OpenSees. OpenSees is open source software for carrying out earthquake engineering simulations, developed by Pacific Earthquake Engineering Research Centre, USA. The earthquake simulations were carried out using C-DAC's high performance computing facilities. The ground motion selection and modification technique-predicting median interstory drift response of building, ground motions are selected by M and R and scaling to Sa(T1), is used for seismic response of combined large scale soil-structure interaction of Karad bridge. The idealized model properly represents the actual geometry; boundary conditions, gravity loads and mass distribution. Nonlinear modeling and analysis allows more accurate determination of stresses, strains, deformations and forces of critical components. The present work involves the effects of specially varying input excitation (earthquakes) at an existing bridge site. A nonlinear finite element model of this bridge site including the bridge structure, pile group and supporting foundation soil is developed in 2D plane strain conditions and in 3D 20 noded brick element. Carefully calibrated nonlinear stress-strain models are employed for both bridge and soil materials, in order to realistically reproduce actual site conditions. Seismic input motions are defined as forces using the boundary layer force method (zero length element approach). The earthquake simulation of bridge structure includes large scale interaction between structure-foundation-soil system and deformations at various locations of the bridge. The results include deformations at base of piers and at various spans of the bridge. Performing the bridge simulation on C-DAC's Param Yuva facility results in accuracy and saving in computing efforts.
To accurately predict the critical loads on shell structures, it is essential to carry out non-linear analysis. Within the framework of the non-linear theory of shells, a solution method is introduced to investigate the shell stability, the stable pre-and postbuckling states and the in¯uence of initial imperfections on critical loads. At the solution of non-linear equations by iterative methods a problem of convergence near critical points exists. To get over these diculties an iterative method was constructed on the basis of added-viscosity technique, which relies on introducing additional terms into the relationship between the strains and stresses. The spatial problem was solved by the ®nite element method. The ®nite element formulation has been developed and implemented on parallel processing computers. The eective use of these computers is demonstrated with the case study of analysis of a cylindrical panel.Keywords: domain decomposition technique; ®nite element method; iterative solver; message passing interface (MPI); non-linear stability analysis; parallel processing.Reference to this article should be made as follows: Yakushev, V.L. and Shah, M.S. (2005) Simulation of non-linear stability analysis in thin-walled structures on parallel computers',
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