An analytical insight into the buckling paradox for circular cylindrical shells under axial and lateral loading

A large number of authors in the past have concluded that the flow theory of plasticity tends to overestimate significantly the buckling load for many problems of plates and shells in the plastic range, while the deformation theory generally provides much more accurate predictions and is consequently used in practical applications. Following previous numerical studies by the same authors focused on axially compressed cylinders, the present work presents an analytical investigation which comprises the broader and different case of nonproportional loading. The analytical results are discussed and compared with experimental and numerical findings and the reason for the apparent discrepancy on the basis of the so-called “buckling paradox” appears once again to lay in the overconstrained kinematics on the basis of the analytical and numerical approaches present in the literature

Numerical And Analytical Analyses Of High-Strength Steel Cellular Beams: A Discerning Approach

The behaviour of cellular beams made from normal and high strength steel with various geometries is investigated through a large number of finite element analyses and a simple mechanical model for the Web-Post Buckling (WPB) failure is developed and analysed in order to highlight the factors which influence its occurrence and development for both normal and High-Strength (HS) steels. The performed FE analyses and the proposed modelling, once calibrated, allow to shed some light on the characteristics of the phenomenon and to provide the basis of a reliable design method to predict shear buckling of web-post of cellular beams made both of mild and HS steel

Le sfide della teoria: una conversazione con Fiorenzo Iuliano

Fiorenzo Iuliano è ricercatore di Lingue e letterature angloamericane presso l'Università di Cagliari. I suoi ambiti di ricerca comprendono la letteratura americana contemporanea (romanzo, graphic novel, rapporti tra letteratura e musica, Studi Culturali negli USA), gli studi di genere e gli studi sulla corporeità e la teoria letteraria. Al momento sta lavorando a uno studio sulla costruzione del mito culturale della città di Seattle negli anni Novanta

A parallel Block Lanczos algorithm and its implementation for the evaluation of some eigenvalues of large sparse symmetric matrices on multicomputers

In the present work we describe HPEC (High Performance Eigenvalues Computation), a parallel software package for the evaluation of some eigenvalues of a large sparse symmetric matrix. It implements an efficient and portable Block Lanczos algorithm for distributed memory multicomputers. HPEC is based on basic linear algebra operations for sparse and dense matrices, some of which have been derived by ScaLAPACK library modules. Numerical experiments have been carried out to evaluate HPEC performance on a cluster of workstations with test matrices from Matrix Market and Higham’s collections. A comparison with a PARPACKroutine is also detailed. Finally, parallel performance is evaluated on random matrices, using standard parameters

Analytical evaluation of local effects in cylindrical shells testing and design

A simple analytical evaluation of apparently anomalous results from tests on circular cylindrical shells that have been observed in the past is provided on the basis of the classical Ritz ap­proach and modified Donnell relationships.Із використанням класичного підходу Рітца та модифікованих рівнянь Дон­нелла виконано просту аналітичну оцінку явно аномальних результатів, які отримані при випробуваннях круглих циліндричних оболонок.С использованием классического подхода Ритца и модифицированных уравнений Доннелла выполнена простая аналитическая оценка явно аномальных результатов, полученных при испытаниях круглых цилиндрических оболочек

Epidemiología de la infección hospitalaria por Pseudomonas aeruginosa multirresistente en niños quemados críticos

El aumento de la prevalencia de Pseudomonas aeruginosa multirresistente ocasiona un desafío terapéutico constante en las Unidades de Cuidados Intensivos en general y de Quemados en particular. El presente trabajo epidemiológico reveló una tasa de infecciones hospitalarias de 18,91/1000 pacientes/día, con un total de 63 episodios. La tasa de bacteriemia asociada a vía venosa central (VVC) fue de 13,48/1000 días de uso de VVC, con una tasa de utilización del 80,6% y 19 episodios de bacteriemia. Los gérmenes más frecuentemente hallados en la infecciones hospitalarias fueron Pseudomonas aeruginosa, Fusarium spp y Acinetobacter spp (37,5%, 8,3% y 6,9%, respectivamente). Pseudomonas aeruginosa estuvo presente como microorganismo causal de infección hospitalaria en 27 casos, siendo multirresistente en todos y con sensibilidad exclusiva al colistin.Increasing prevalence of multiresistant Pseudomonas aeruginosa is a constant challenge in the Intensive Care Units in general and particularly those treating burned patients. This epidemiological research showed a rate of hospital infections of 18.91 for every 1000 day-patients (63 episodes). The average rate of bacteriemia associated with central venous route (VCV) was 13.48 per 1000 days using VCV. The use rate of VCV was 80.6% with a resulting 19 episodes of bacteriemia. The most frequently encountered germs of nosocomial infections were Pseudomonas aeruginosa, Acinetobacter spp and Fusarium spp (37.5%, 8.3% y 6.9%, respectively). Pseudomonas aeruginosa was found in 27 episodes as the etiology of infection being multidrugresistant in all cases with exclusive sensitivity to colistin

Some Considerations on the Behaviour of Bolted Stainless-Steel Beam-to-Column Connections: A Simplified Analytical Approach

Stainless-steel has proven to be a first-class material with unique mechanical properties for a variety of applications in the building and construction industry. High ductility, strain hardening, durability and aesthetic appeal are only a few of them. From a specific point of view, its nonlinear stress–strain behaviour appears capable of providing a significant increase in the rotational capacity of stainless-steel connections. This, in turn, may provide significant benefits for the overall response of a structure in terms of capacity and ductility. However, the bulk of the research on stainless-steel that has been published so far has mostly ignored the analysis of the deformation capabilities of the stainless-steel connections and has mostly focused on the structural response of individual members, such as beams or columns. For such a reason, the present study aims to contribute to the general understanding of the behaviour of stainless-steel connections from a conceptual, numerical and design standpoint. After a brief review of the available literature, the influence of the use of stainless-steel for column–beam connections is discussed from a theoretical standpoint. As a novel contribution, a different approach to compute the pseudo-plastic moment resistance that takes into account the post-elastic secant stiffness of the stainless-steel is proposed. Successively, a refined finite element model is employed to study the failure of stainless-steel column–beam connections. Finally, a critical assessment of the employment of carbon-steel-based design guidelines for stainless-steel connections provided by the Eurocode 3 design (EN 1993-1-8) is performed. The findings prove the need for the development of novel design approaches and more precise capacity models capable of capturing the actual stainless-steel joint response and their impact on the overall ductility and capacity of the whole structure

A numerical investigation into the plastic buckling of circular cylinders

It has been long known that finding a thoroughly good agreement with experimental results for the buckling loads of circular cylinders in the plastic range constitutes a very difficult task, beyond the same as well challenging problem in the elastic range. This paper attempts to contribute to the understanding of this issue by discussing a few numerical examples in comparison with some classical experimental results reported by Blachut et al. (1996) and Batterman (1965). It is shown that finite-element analyses grounded on the hypo-elasticity-based extension of small-strain theory of plasticity to geometrically nonlinear problems lead to good agreement with experimental results, although in some cases the sensitivity to the amount and shape of imperfection plays an important role, a fact which leaves open issues in terms of fully predictive capability of the computational models

On the elasto-plastic stability analysis of circular cylindrical shells

Copyright ©: SDSS'2016. The stability of thin circular shells under proportional and non-proportional loading, i.e. axial tensile stress and external pressure is extensively investigated. Two plasticity theories are considered; the flow and the deformation theory of plasticity. The results obtained confirm that under over-constrained kinematic assumptions the deformation theory tends to provides lower values of buckling pressure and the discrepancies in the results from the two plasticity theories increase with increasing thickness ratios, tensile stresses, boundary clamping E/σy and ratio

Editorial: Stability: A Current Overview

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