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1、【仓储物流工程师仓储物流工程师, ,国电联合动力技术有限公司国电联合动力技术有限公司】前程无忧前程无忧.solid and fluid mechanics. For many of these problems least-squares principles offer many theoretical and computational advantages in the implementation of the corresponding finite element model that are not present in the traditional weak form Gal
2、erkin finite element model. For instance, the use of least-squares principles leads to a variational unconstrained minimization problem where compatibility conditions between approximation spaces never arise. Furthermore, the resulting linear algebraic problem will have a symmetric positive definite
3、 coefficient matrix, allowing the use of robust and fast iterative methods for its solution. We find that the use of high p-levels is beneficial in least-squares based finite element models and present guidelines to follow when a low p-level numerical solution is sought. Numerical examples in the co
4、ntext of incompressible and compressible viscous fluid flows, plate bending, and shear-deformable shells are presented to demonstrate the merits of the formulations.Article Outline1. Introduction2. An abstract least-squares formulation2.1. Notation2.2. The abstract problem2.3. L2 least-squares formu
5、lation2.3.1. Spacetime coupled formulation2.3.2. Spacetime decoupled formulation2.4. The variational problem2.5. The finite element model2.6. Norm-equivalence and its implications2.7. A least-squares collocation formulation3. Viscous incompressible and compressible fluid flows3.1. Governing equation
6、s3.2. Kovasznay flow3.3. Compressible flow past a NACA0012 airfoil4. Plates and shells4.1. Governing equations4.2. Simply supported circular plate4.3. Barrel vault5. Summary and concluding remarksReferences Purchase 154 Finite element modelling and updating of a lively footbridge: The complete proce
7、ss Original Research ArticleJournal of Sound and Vibration, Volume 301, Issues 1-2, 20 March 2007, Pages 126-145Stana ?ivanovi?, Aleksandar Pavic, Paul ReynoldsClose preview | Related articles | Related reference work articles AbstractAbstract | Figures/TablesFigures/Tables | ReferencesReferencesAbs
8、tractThe finite element (FE) model updating technology was originally developed in the aerospace and mechanical engineering disciplines to automatically update numerical models of structures to match their experimentally measured counterparts. The process of updating identifies the drawbacks in the
9、FE modelling and the updated FE model could be used to produce more reliable results in further dynamic analysis. In the last decade, the updating technology has been introduced into civil structural engineering. It can serve as an advanced tool for getting reliable modal properties of large structu
10、res. The updating process has four key phases: initial FE modelling, modal testing, manual model tuning and automatic updating (conducted using specialist software). However, the published literature does not connect well these phases, although this is crucial when implementing the updating technolo
11、gy. This paper therefore aims to clarify the importance of this linking and to describe the complete model updating process as applicable in civil structural engineering. The complete process consisting the four phases is outlined and brief theory is presented as appropriate. Then, the procedure is
12、implemented on a lively steel box girder footbridge. It was found that even a very detailed initial FE model underestimated the natural frequencies of all seven experimentally identified modes of vibration, with the maximum error being almost 30%. Manual FE model tuning by trial and error found that
13、 flexible supports in the longitudinal direction should be introduced at the girder ends to improve correlation between the measured and FE-calculated modes. This significantly reduced the maximum frequency error to only 4%. It was demonstrated that only then could the FE model be automatically upda
14、ted in a meaningful way. The automatic updating was successfully conducted by updating 22 uncertain structural parameters. Finally, a physical interpretation of all parameter changes is discussed. This interpretation is often missing in the published literature. It was found that the composite slabs
15、 were less stiff than originally assumed and that the asphalt layer contributed considerably to the deck stiffness.Article Outline1. Introduction2. Background review2.1. Finite element model updating2.2. Basic theory used in FE model updating2.3. Applications in civil structural engineering3. Descri
16、ption of test footbridge structure4. Initial FE modelling, modal testing and model tuning4.1. Initial finite element modelling4.2. Modal testing4.3. FE model tuning5. Automatic model updating5.1. Target response selection5.2. Parameter selection5.3. Formal updating and its results6. Discussion7. ConclusionsAcknowledgementsReferences Purchase 155 Strength prediction of multi-layer plain weave textile composites using the direct micromechanics method Original Research Articl
