Structural Reanalysis Research Articles

Structural Optimization Based on Inversion Reduced-Basis Method

Efficiency and stability of forward problem are important in structural optimum design. A real-time algorithm, called inversion reduced-basis method (IRBM), is applied to solve the forward problem in this paper. IRBM is introduced theoretically. Taking a truck frame as an example, results computed from IRBM are obtained. In the optimization process, a modified micro-genetic algorithm (μGA) is adopted to get the global optimum. In the structural reanalysis, IRBM is used, which greatly shorten the design cycle and improve work efficiency.

Vibration reanalysis using frequency-shift combined approximations

In the structural dynamic optimization procedure, many repeated analyses are conducted to evaluate vibration performance of successively modified structural designs. A new procedure for structural vibration (or eigenproblem) reanalysis is developed based on iteration and inverse iteration method with frequency-shift and linear combination acceleration to reduce the high computational cost of structure reanalysis. With a suitable frequency-shift factor, the Frequency-Shift Combined Approximations (FSCA) method allows to calculate higher modes accurately. Three numerical examples are presented to demonstrate the accuracy of the proposed method. Excellent results can be obtained in cases where large modifications are made and higher modes are needed.

A simple approach to find optimal topology of a continuum with tension-only or compression-only material

The material-replacement method is presented to improve the efficiency of topology optimization of a continuum structure with tension-only or compression-only material. Traditionally, a structure with tension-only or compression-only material should be considered as nonlinear in finite element analysis and many times of reanalysis are required to obtain the accurate physical fields for the update of the design variables in optimization. To improve the efficiency of structural optimization, the material-replacement method is proposed, in which the original tension/compression only material is replaced with an isotropic material with the same effective elasticity. The method contents two major ideas. One is the structural reanalysis for nonlinearity of material is put into the global iteration of optimization. The other is that the local stiffness will be modified step by step according to the local stress state. Numerical results show the validity of the method.

DISCRETE SIZING OPTIMIZATION OF TRUSS STRUCTURES WITH A STRUCTURAL REANALYSIS TECHNIQUE AND AN ENUMERATION METHOD

This study proposes to apply a structural reanalysis technique to an enumeration method for global optimization of discrete truss structures. The optimization problem is to find the sectional areas which minimize the truss structural volume from a list of standard sections under the stress and deflection constraints. At first, to reduce the computational effort, a structural reanalysis equation is derived, in which large number of unknown degrees of freedom are reduced. Next, a numerical generation method of relaxed linear constraints is also presented to reduce the number of structural analyses and re-analyses. The procedure of the enhanced enumeration method with above-mentioned two techniques is presented. The proposed method is applied to three trusses and compared with the structural analyses of all combinations.

Updating the Craig–Bampton reduction basis for efficient structural reanalysis

AbstractA Combined Approximation (CA) based reanalysis technique is proposed for updating the static modes in a reduction basis which can be used for sizing optimization problems. Although the proposed technique is utilized under the framework of the Craig–Bampton (CB) method, it can be employed with any condensation procedure that involves the computation of the static modes. An automated update scheme is also presented that switches the proposed technique with the exact analysis when the computational efficiency is lost. Moreover, the Enriched Craig–Bampton (ECB) method is studied for the reanalysis of the normal modes. The ECB‐ and the CA‐based techniques are merged for efficient update of the CB reduction basis. An academic test problem is utilized for the demonstration of the introduced concepts. Copyright © 2010 John Wiley & Sons, Ltd.

From determining to emphasizing meanings: The adjectives of specificity

In the recent literature (Adamson, A lovely little example: Word order options and category shift in the premodifying string, John Benjamins, 2000; Paradis, Reinforcing adjectives: A cognitive semantic perspective on grammaticalisation, Mouton de Gruyter, 2000; Athanasiadou, Language Sciences 29: 554–565, 2007; Traugott, Journal of Historical Pragmatics 8: 295–309, 2007a, Cognitive Linguistics 18: 523–557, 2007b), the development of ‘emphasizing’ meanings by prenominal elements of the English NP is generally envisaged along a path leading from descriptive, propositional meaning to emphasizing meaning (e.g. from a complete sentence to complete nonsense ; cf. Paradis, Reinforcing adjectives: A cognitive semantic perspective on grammaticalisation, Mouton de Gruyter, 2000: 245). However, earlier Bolinger (Degree words, Mouton, 1972: 59, 60) had posited an alternative path for elements that also express determining meanings, i.e. from determining to emphasizing meaning (e.g. from the complete period to a complete fool ). This paper will assess these opposed claims about the origin of emphasizing uses by means of a data-based study of the development of two adjectives, particular and specific , that have descriptive, determining, as well as emphasizing uses. Reconstruction of the various meaning extensions and structural reanalyses that have affected the adjectives indicates that the now mostly neglected determining uses are an essential step in the subjectification process to emphasizing meanings and they can shed new light on both the chronology and the conceptual mechanisms involved in the syntactic-semantic shifts.

Structural reanalysis for a modified structure

Structural reanalysis aims to determine the variations in the displacement of a structure due to the addition or deletion of elements without solving the full degrees of freedom. The iterations change the design parameters at each step and utilize the factorization of the stiffness matrix of the initial design. This study develops a new reanalysis method to determine the additional forces that act on the initial structure and the displacements of the modified structure. It utilizes the compatibility conditions at the interfaces between the initial structure and the added or deleted members as static constraints, and applies the generalized inverse method to describe the static behavior of the constrained structure. The structural elements that are added may be statically stable substructures or floating members that possess rigid-body freedom. Examples are included to show the effectiveness of the proposed method.

Analysis/Test Correlation of Multiple Configurations Structures

The Sequential Quadratic Programming is applied to solve the problem of Analysis/Test correlation of structures with multiple configurations in this study. The proposed approaches are the extension of the conventional optimum design methods by considering the objective function and constraints from several configurations simultaneously. A general purpose program utilizing MSC/NASTRAN finite element analysis software for structural analysis was developed to implement the optimum design procedures. In order to improve the computational efficiency, the reduced order modal space method is applied for structural reanalysis and sensitivity calculation.

The status of subject–object reanalyses in the language comprehension architecture

This paper examines the hypothesis that grammatical function reanalyses in simple sentences should not be treated as phrase structure revisions, but rather as increased costs in “linking” an argument from a syntactic to a semantic representation. To this end, we investigated whether subject–object reanalyses in German verb-final sentences can be associated with an electrophysiological processing signature that is distinct from the response typically engendered by structure-affecting reanalyses (the P600). We hypothesized that the previously observed heterogeneous ERP component pattern for subject-object reanalyses in German might be due to task- or strategy-related interactions between the critical processing mechanisms and the experimental environment. In order to minimize specific task influences, Experiment 1 therefore embedded subject–object ambiguities into short stories (presented auditorily). Constructions with dative and accusative objects both showed a biphasic N400-late positivity pattern for disambiguation towards an object-initial structure. These results thus contrast with previous findings, in showing that there is no principled difference in the component pattern for the two types of structures. This conclusion was confirmed by the results of Experiment 2, which presented the identical accusative sentences from Experiment 1 in isolation using two different tasks (comprehension vs. acceptability) and again revealed N400-late positivity responses. From the overall data pattern, we conclude that the N400 is a robust correlate of grammatical function reanalysis that occurs independently of any lexical factors and, consequently, that grammatical function reanalysis is functionally distinct from phrase structure reanalysis.

Damage identification in skeletal structures using the virtual distortion method in frequency domain

The paper is a continuation of research on the application of a structural reanalysis method—the virtual distortion method—to structural health monitoring. The first approach, formulated previously in the time domain, suffered from a considerable numerical cost. In order to reduce it, this paper presents an alternative approach, formulated in the frequency domain thanks to the assumption of using harmonic excitation (quasi-static problem). The hardware devices supposed to collect structural responses are piezoelectric patch sensors. The software tool for damage identification solves a nonlinear least squares optimization problem by employing analytically derived sensitivities. Strains are the analyzed quantities, contributing to the objective function. Considerations are restricted to skeletal structures and a simplified dynamic problem with no damping. Effectiveness of the frequency-domain identification is demonstrated in numerical examples. Experimental verification is envisaged.

Optimal design of adaptive structures: Part I. Remodeling for impact reception

The paper (written in two parts) is devoted to the presentation of numerical tools, based on the so-called virtual distortion method (VDM) for fast structural reanalysis and to the application of this tools for optimal design of adaptive structures exposed to impact loads. The first paper deals with fast modifications of the material distribution (coupled stiffness and mass redistribution) in dynamically loaded structures, which allows their optimal remodeling, e.g., to minimize average deflections. The VDM-based approach allows analytical sensitivity determination, which is very helpful in efficient implementation of the optimization procedure, utilized to solve the defined remodeling problem. The presented methodology is illustrated with a numerical example of truss–beam structure exposed to random impact loads.

Modal reanalysis methods for structural large topological modifications with added degrees of freedom and non-classical damping

This paper presents two new methods for modal reanalysis of structures considering large topological modifications with added degrees of freedom. Firstly, a quite simple and efficient approximate method with the improved dynamic condensation, the Kirsch approximation and the decoupling mass orthogonality is proposed for reanalysis of real modes; then, a high-quality method which is comprised of complex eigensubspace condensation technique and Rayleigh-quotient inverse iteration is proposed for reanalysis of complex modes of structural large topological modifications. The convergence of iterative improvement will be achieved after only two or three cycles. Four numerical examples illustrate that the proposed methods are quite effective with high precision.

Efficient non‐linear reanalysis of skeletal structures using combined approximations

AbstractNon‐linear reanalysis of large‐scale structures usually involves much computational effort, because the set of non‐linear equations must be solved repeatedly during the solution process. Various approximations that are often used for linear reanalysis are not sufficiently accurate for non‐linear problems. In this study, solution procedures based on the combined approximations approach are developed and compared in terms of efficiency and accuracy. Various path‐independent non‐linear analysis and reanalysis problems are considered, including material non‐linearity, geometric non‐linearity and buckling analysis. Numerical examples demonstrate the effectiveness of the procedures presented. It is shown that in various cases accurate results can be achieved efficiently. Copyright © 2007 John Wiley & Sons, Ltd.

As far as individuals with conduction aphasia understood these sentences were ungrammatical: Garden path in conduction aphasia

Background: Recent studies have indicated that working memory is not a unitary resource and that different types of working memory are used for different types of linguistic processing: syntactic, semantic, and phonological. Phonological working memory was found to support the comprehension of sentences that require re‐access to the word‐form of a word that appeared earlier in the sentence. The research was supported by a research grant from the National Institute for Psychobiology in Israel (Friedmann 2004‐5‐2b), and by the Joint German–Israeli Research Program grant (Friedmann GR‐01791). We thank Irena Botwinik‐Rotem, Tali Siloni, and Michal Biran for discussions of this study. Aims: This study explored the relation between phonological working memory and sentence comprehension by testing the comprehension of garden path sentences in individuals with conduction aphasia who have very limited phonological working memory. Our prediction was that if phonological working memory limitation hampers word‐form reactivation, only the comprehension of garden paths that require word‐form reactivation will be impaired, whereas garden paths that require only structural reanalysis will be better preserved. Methods & Procedures: Five individuals with conduction aphasia and 15 matched controls participated in working memory tests and a garden path comprehension test. The phonological working memory assessment included a battery of 10 tests, which showed that four of the individuals, who had input conduction aphasia, had very limited phonological working memory, and one individual, with output conduction aphasia, had unimpaired working memory. The comprehension study included 60 garden path sentences of three types: structural garden paths, which require only structural reanalysis, lexical garden paths, which require lexical re‐access in addition to structural reanalysis, and optional‐complement garden paths, which require re‐access to the lexical‐syntactic frame of the verb in addition to the structural reanalysis. Outcomes & Results: The main result was that the individuals with input conduction aphasia showed different degrees of impairment in different types of garden path sentences. The lexical garden paths were exceptionally hard for them, with a mere 10% correct, and significantly more difficult than the structural garden paths. The individual with output conduction aphasia whose working memory was intact comprehended the lexical garden paths similarly to the normal controls. Conclusions: These findings indicate that phonological working memory impairment only affects the comprehension of sentences that require phonological, word‐form re‐access. The type of sentence and the type of processing it requires should be taken into account when trying to predict the effect of working memory limitation on a patient's ability to understand sentences. Whereas individuals with input conduction aphasia can understand complex syntactic structures well, they have considerable difficulties understanding sentences that also require re‐access to a word‐form.

Virtual surgery simulation for medical training using multi‐resolution organ models

Real-time simulation of organ deformation is one of the biggest challenges in virtual surgery, due to the conflicting requirements of real-time interactivity and simulation realism. In this paper we propose a method to overcome this challenge by introducing a multi-resolution modelling technique. In our approach a reasonably coarse global model is locally enhanced, using a mesh subdivision and smoothing algorithm. The global model is based on a discretization of the boundary integral representation of three-dimensional deformable objects. Local refinements are provided at the tool-tissue interaction region by a local subdivision technique. As an example, we have developed a deformable human kidney model generated from the Visible Human Dataset, with tissue properties determined from in vivo animal experiments. A mixed reality laparoscopic surgical training system has been developed, using an abdominal mannequin and force feedback devices. The use of precomputation and structural re-analysis techniques results in a very rapid computation procedure. Validation of the simulator is in progress.

Efficient Dynamic Reanalysis of Structures

The combined approximations approach, developed originally for linear static reanalysis, is used for dynamic reanalysis of structures. The approach is based on the integration of several concepts and methods, including series expansion, reduced basis, matrix factorization, and Gram-Schmidt orthogonalizations. The advantage is that efficient local approximations and accurate global approximations are combined to achieve an effective solution procedure. Considering modal analysis, the computational effort involved in reanalysis is significantly reduced. However, the accuracy of the higher mode shapes might be insufficient. A procedure intended to improve the accuracy of the results is developed. A reduced eigenproblem is introduced, and a method for determining the basis vectors is presented. Improved basis vectors, using the concepts of shifts and Gram-Schmidt orthogonalizations, are developed, and eigenproblem reanalysis by combined approximations using inverse iteration with shifts is introduced. Numerical examples demonstrate the quality of the results. It is shown that high accuracy is achieved efficiently for various types of changes in the structure.

AN EQUALITY CONSTRAINED LEAST SQUARES APPROACH TO THE STRUCTURAL REANALYSIS

An efficient method for reanalysis of a damaged structures is presented. Perturbation analysis for the equality constrained least squares problem is adapted to handle structural reanalysis, and related theoretical and numerical results are presented.

A preconditioned conjugate gradient approach to structural reanalysis for general layout modifications

AbstractThis paper presents a preconditioned conjugate gradient approach to structural static reanalysis for general layout modifications. It is suitable for all types of layout modifications, including the general case in which some original members and nodes are deleted and other new members and nodes are added concurrently. The approach is based on the preconditioned conjugate gradient technique. The preconditioner is constructed, and an efficient implementation for applying the preconditioner is presented, which requires the factorization of the stiffness matrix corresponding to the newly added degrees of freedom only. In particular, the approach can adaptively monitor the accuracy of approximate solutions. Numerical examples show that the condition number of the preconditioned matrix is remarkably reduced. Therefore, the fast convergence and accurate results can be achieved by the approach. Copyright © 2006 John Wiley & Sons, Ltd.

Efficient procedures for repeated calculations of the structural response using combined approximations

Efficient procedures for repeated calculations of the response of large-scale structures that involve numerous repeated analyses are presented. These procedures are based on the combined approximations approach, which is further developed to improve both the efficiency of the calculations and the accuracy of the results. The procedures are suitable for linear, nonlinear, static, and dynamic reanalysis problems, and they can be used to improve the efficiency of response surface calculations. It is shown that the procedures presented provide accurate approximations and may significantly reduce the computational effort involved in reanalysis of large-scale structures. This might prove useful in various design and optimization problems.

Crystal Structures of Expressed Non-polymerizable Monomeric Actin in the ADP and ATP States

Actin filament growth and disassembly, as well as affinity for actin-binding proteins, is mediated by the nucleotide-bound state of the component actin monomers. The structural differences between ATP-actin and ADP-actin, however, remain controversial. We expressed a cytoplasmic actin in Sf9 cells, which was rendered non-polymerizable by virtue of two point mutations in subdomain 4 (A204E/P243K). This homogeneous monomer, called AP-actin, was crystallized in the absence of toxins, binding proteins, or chemical modification, with ATP or ADP at the active site. The two surface mutations do not perturb the structure. Significant differences between the two states are confined to the active site region and sensor loop. The active site cleft remains closed in both states. Minor structural shifts propagate from the active site toward subdomain 2, but dissipate before reaching the DNase binding loop (D-loop), which remains disordered in both the ADP and ATP states. This result contrasts with previous structures of actin made monomeric by modification with tetramethylrhodamine, which show formation of an alpha-helix at the distal end of the D-loop in the ADP-bound but not the ATP-bound form (Otterbein, L. R., Graceffa, P., and Dominguez, R. (2001) Science 293, 708-711). Our reanalysis of the TMR-modified actin structures suggests that the nucleotide-dependent formation of the D-loop helix may result from signal propagation through crystal packing interactions. Whereas the observed nucleotide-dependent changes in the structure present significantly different surfaces on the exterior of the actin monomer, current models of the actin filament lack any actin-actin interactions that involve the region of these key structural changes.