Redesign of marine structures by perturbation

Kim, Jong-Hyun; Bernitsas, Michael M.

doi:10.1016/0951-8339(88)90004-4

Cited by 12 publications

(15 citation statements)

References 15 publications

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“…be the fractional change in property e, where p properties of elements, or groups of elements, are allowed to change. Such properties may be mass, bending stiffness, torsional stiffness, etc., 17 or geometric properties like linear dimensions of a beam cross section, 18 plate thickness, 23 and tube internal and external diameters. 20 Several elements may be linked together in one group to ensure that they remain identical in UM.…”

Section: Correlation Variablesmentioning

confidence: 99%

“…That code is about 20,500 Fortran 77 commands and was initially developed to solve the problem of structural redesign. 23 Currently, it also solves the problem of model correlation described in this paper and the problem of redundancy and failure mode identification. RESTRUCT may accept any kind of stiffness and mass matrices produced by a special or general purpose FE code, including MSC/NASTRAN.…”

Section: Computer Implementationmentioning

confidence: 99%

“…They perform, however, a FEA by MSC/NASTRAN at each increment. Kim and Bernitsas 23 introduced static deflections as redesign objectives along with modal measurements. Other approaches to redesign have been developed by Hafka and Prasad 24 and Haug et al 25 The problem of model correlation by perturbation is defined in Sec.…”

Section: Introductionmentioning

confidence: 99%

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Structural model correlation using large admissible perturbations incognate space

Bernitsas

Tawekal

1991

AIAA Journal

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A nonlinear perturbation method is developed to solve the problem of correlating a finite element model (FEM) to a structure for which an incomplete set of natural frequencies and mode shapes and/or some static deflections have been measured. The solution algorithm can handle differences between FEM and structure, in design variables and response, as large as 100-300%, depending on the scale of the structure and correlation measures. This is achieved incrementally by making inadmissible predictions, identifying the modal cognate space relevant to the correlation measures, and making admissible corrections in the cognate space. The developed computer code postprocesses results of the FEM modal and/or static analyses of the initial model only. No additional finite element analysis is required. Lagrange multipliers reveal the dominant correlation requirements and the active admissible cognate subspace. Depending on the number of correlation variables and measures, an optimal, a unique, or an inadmissible minimal error solution may be produced. Beam and offshore tower examples are used to test the algorithm and investigate conflicting requirements, definition of admissible cognate space, limits of allowable differences between FEM and structure, accuracy, and cost of the nonlinear perturbation method.

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Section: Correlation Variablesmentioning

confidence: 99%

Section: Computer Implementationmentioning

confidence: 99%

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Structural model correlation using large admissible perturbations incognate space

Bernitsas

Tawekal

1991

AIAA Journal

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“…Hoff and Bernitsas (1985) introduced static and modal dynamic redesign. These two objectives were integrated by Kim and Bernitsas (1990) for redesign, satisfying both objectives simultaneously. Bernitsas and Tawekal (1991) solved the problem of model calibration by LEAP in a cognate space.…”

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confidence: 99%

Topology redesign for performance by large admissible perturbations

Miao

Bernitsas

2006

Struct Multidisc Optim

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A methodology is developed for optimal structural topology design subject to several performance constraints. Eight-node solid elements are used to model the initial structure, which is a uniform solid block satisfying the boundary conditions and subjected to external loading. The Young modulus of each solid element or group of elements is used as redesign variable. A minimum change function is used as an optimality criterion. Performance constraints include static displacements, natural frequencies, forced response amplitudes, and static stresses. These constraints are treated by the large admissible perturbation methodology which makes it possible to achieve the performance objectives incrementally without trial and error or repetitive finite element analyses for changes in the order of 100-300%. Thus, the optimal topology is reached in about four to five iterations, where each iteration includes one finite element analysis and setting of an upper limit for the value of the modulus of elasticity to produce a manufacturable structure. Several numerical applications are presented using three different benchmark structures to demonstrate the methodology and the impact of performance constraints on the generated topology. Keywords Topology • Performance • Optimization • Structural redesign • Large admissible perturbations 1 Background The goal of structure optimization is to improve the performance of any given objective set in a structural environment

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“…(P3) If % < np the problem is overdetermined and even a mapping cannot be established. This is the case for a plate element of unit length and thickness t, where A' = t' = (1 + a,)t = (1 + at)A(25) I' -t'3 --(1 + tZt)3/3 ~--(1 + at)31(26) 1212…”

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confidence: 99%

Invariant and consistent redundancy by large admissible perturbations

1992

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ABSTRQCT Structural perturbation theory has been developed over the past 16 years to relate two structural states modeled by the same Finite Element (FE) model but described by di$erent values of the design variables. Relating an intact/ damaged (initial) structure to a limit state structure produces the reserve/ residual redundancy. Invariant and consistent redundancy, redundancy functions, and injective mappings are defined and related to the design variables. General perturbation equations are derived to relate the two states andproducefailuresuflaceequations. Individual andjointfailurepoints are identtfied and redundancy is computed without linearization of failure surfaces, enumeration of failure paths, trial and error, or repeated FE Analyses (FEAs). This is achieved by large admissible perturbations using a prediction-correction algorithm and postprocessing FEA results of the initial structure only. The latter may dtferfiom the limit state structure in sti&ess, mass, geometry, or response by as much as 1 &I-300% depending on the size of the FE model. Structural perturbation theory treats discrete and continuous structures as the FE method does: modeling of the structure as a simpltjkd system of components is not needed. To introduce this new approach to redundancy, modal dynamic and stank deflection failure criteria are used in the elastic range. Numerical applications on a beam, a small, and a large o$shore tower are used to test the method. Future developments and impact to design are discussed as the new methodology introduces an alternative to systems reliabiliry and stochastic FE.

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Redesign of marine structures by perturbation

Cited by 12 publications

References 15 publications

Structural model correlation using large admissible perturbations incognate space

Structural model correlation using large admissible perturbations incognate space

Topology redesign for performance by large admissible perturbations

Invariant and consistent redundancy by large admissible perturbations

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