A numerical investigation into the plastic buckling paradox for circular cylindrical shells under axial compression

It is widely accepted that for many buckling problems of plates and shells in the plastic range the flow theory of plasticity leads to a significant overestimation of the buckling stress while the deformation theory provides much more accurate predictions and is therefore generally recommended for use in practical applications. The present work aims to contribute to further understanding of the seeming differences between these two theories with particular regards to circular cylindrical shells subjected to axial compression. A clearer understanding of the two theories is established using accurate numerical examples and comparisons with some widely cited accurate physical test results. It is found that, contrary to common perception, by using a geometrically nonlinear finite element formulation with carefully determined and validated constitutive laws very good agreement between numerical and test results can be obtained in the case of the physically more sound flow theory of plasticity. The reasons underlying the apparent buckling paradox found in the literature regarding the application of deformation and flow theories and the different conclusions reached in this work are investigated and discussed in detail. © 2014 Elsevier Ltd

Optimal design and optimal control of structures undergoing finite rotations and elastic deformations

In this work we deal with the optimal design and optimal control of structures undergoing large rotations. In other words, we show how to find the corresponding initial configuration and the corresponding set of multiple load parameters in order to recover a desired deformed configuration or some desirable features of the deformed configuration as specified more precisely by the objective or cost function. The model problem chosen to illustrate the proposed optimal design and optimal control methodologies is the one of geometrically exact beam. First, we present a non-standard formulation of the optimal design and optimal control problems, relying on the method of Lagrange multipliers in order to make the mechanics state variables independent from either design or control variables and thus provide the most general basis for developing the best possible solution procedure. Two different solution procedures are then explored, one based on the diffuse approximation of response function and gradient method and the other one based on genetic algorithm. A number of numerical examples are given in order to illustrate both the advantages and potential drawbacks of each of the presented procedures.Comment: 35 pages, 11 figure

Avian Influenza (H5N1) Susceptibility and Receptors in Dogs

Inoculation of influenza (H5N1) into beagles resulted in virus excretion and rapid seroconversion with no disease. Binding studies that used labeled influenza (H5N1) showed virus attachment to higher and lower respiratory tract tissues. Thus, dogs that are subclinically infected with influenza (H5N1) may contribute to virus spread

A PC-BASED SYSTEM FOR MAINTENANCE MANAGEMENT OF BUILDINGS: GENERAL DESCRIPTION

ABSTRACT Europe's rich culture in wooden buildings are rapidly degrading due to environmental impact, wrong conservation techniques and lack of resources and technological tools for appropriate conservation. These issues were addressed in the former EU-project ENV4-CT95-0110 Wood-Assess , which has been finalised . In a new EU-project MMWood (ENV4-CT-98-0796) a PC-based system for maintenance management of buildings has been developed. The project had the following objectives: To develop and validate for the SMEs an integrated Maintenance Management system for historic buildings, adapted to the needs and purposes of various user group levels. Based on the Wood-Assess concept and results the modular GIS (Geographical Information System) based system, MMWood, will specifically contain • A documentation system for outer and inner parts of buildings and components, • Soft-and hardware tools for the building inspection in the course of maintenance tasks, • An environmental risk factor assessment module, • A standardized maintenance assessment module, • A cost and maintenance planning module. Main developments from the Wood-Assess project are the inclusion of the maintenance management phase, extension of the damage atlas to include also adjoining materials in wood constructions, rendering, brick and natural stone, and a fully integrated field inspection system, allowing the user to import/export all background and recorded data between the field inspection and the total maintenance management system. In this paper some of the main results of the project are given with much of the emphasis on presenting the PC-based application, and its use in some practical examples. Detailed results from the environmental risk factor assessment module and the standardised maintenance assessment module will be given in separate papers to this Congress