Large amplitude vibration of thermo-electro-mechanically stressed FGM laminated plates

This paper presents a large amplitude vibration analysis of pre-stressed functionally graded material (FGM) laminated plates that are composed of a shear deformable functionally graded layer and two surface-mounted piezoelectric actuator layers. Nonlinear governing equations of motion are derived within the context of Reddy's higher-order shear deformation plate theory to account for transverse shear strain and rotary inertia. Due to the bending and stretching coupling effect, a nonlinear static problem is solved first to determine the initial stress state and pre-vibration deformations of the plate that is subjected to uniform temperature change, in-plane forces and applied actuator voltage. By adding an incremental dynamic state to the pre-vibration state, the differential equations that govern the nonlinear vibration behavior of pre-stressed FGM laminated plates are derived. A semi-analytical method that is based on one-dimensional differential quadrature and Galerkin technique is proposed to predict the large amplitude vibration behavior of the laminated rectangular plates with two opposite clamped edges. Linear vibration frequencies and nonlinear normalized frequencies are presented in both tabular and graphical forms, showing that the normalized frequency of the FGM laminated plate is very sensitive to vibration amplitude, out-of-plane boundary support, temperature change, in-plane compression and the side-to-thickness ratio. The CSCF and CFCF plates even change the inherent hard-spring characteristic to soft-spring behavior at large vibration amplitudes. (C) 2003 Elsevier B.V. All rights reserved.

Postbuckling of piezoelectric FGM plates subject to thermo-electro-mechanical loading

In this paper, we examine the postbuckling behavior of functionally graded material FGM rectangular plates that are integrated with surface-bonded piezoelectric actuators and are subjected to the combined action of uniform temperature change, in-plane forces, and constant applied actuator voltage. A Galerkin-differential quadrature iteration algorithm is proposed for solution of the non-linear partial differential governing equations. To account for the transverse shear strains, the Reddy higher-order shear deformation plate theory is employed. The bifurcation-type thermo-mechanical buckling of fully clamped plates, and the postbuckling behavior of plates with more general boundary conditions subject to various thermo-electro-mechanical loads, are discussed in detail. Parametric studies are also undertaken, and show the effects of applied actuator voltage, in-plane forces, volume fraction exponents, temperature change, and the character of boundary conditions on the buckling and postbuckling characteristics of the plates. (C) 2003 Elsevier Science Ltd. All rights reserved.

Theoretical and experimental studies of unbraced tubular trusses allowing for torsional stiffness

This paper describes the buckling phenomenon of a tubular truss with unsupported length through a full-scale test and presents a practical computational method for the design of the trusses allowing for the contribution of torsional stiffness against buckling, of which the effect has never been considered previously by others. The current practice for the design of a planar truss has largely been based on the linear elastic approach which cannot allow for the contribution of torsional stiffness and tension members in a structural system against buckling. The over-simplified analytical technique is unable to provide a realistic and an economical design to a structure. In this paper the stability theory is applied to the second-order analysis and design of the structural form, with detailed allowance for the instability and second-order effects in compliance with design code requirements. Finally, the paper demonstrates the application of the proposed method to the stability design of a commonly adopted truss system used in support of glass panels in which lateral bracing members are highly undesirable for economical and aesthetic reasons.

Unsaturated diffusivity functions for concrete derived from NMR images

Deterioration of concrete or reinforcing steel through excessive contaminant concentration is often the result of repeated wetting and drying cycles. At each cycle, the absorption of water carries new contaminants into the unsaturated concrete. Nuclear Magnetic Resonance (NMR) is used with large concrete samples to observe the shape of the wetting profile during a simple one-dimensional wetting process. The absorption of water by dry concrete is modelled by a nonlinear diffusion equation with the unsaturated hydraulic diffusivity being a strongly nonlinear function of the moisture content. Exponential and power functions are used for the hydraulic diffusivity and corresponding solutions of the diffusion equation adequately predict the shape of the experimental wetting profile. The shape parameters, describing the wetting profile, vary little between different blends and are relatively insensitive to subsequent re-wetting experiments allowing universal parameters to be suggested for these concretes.

Geometric nonlinear analysis of thin plates by a refined nonlinear non-conforming triangular plate element

Based on the refined non-conforming element method for geometric nonlinear analysis, a refined nonlinear non-conforming triangular plate element is constructed using the Total Lagrangian (T.L.) and the Updated Lagrangian (U.L.) approach. The refined nonlinear non-conforming triangular plate element is based on the Allman's triangular plane element with drilling degrees of freedom [1] and the refined non-conforming triangular plate element RT9 [2]. The element is used to analyze the geometric nonlinear behavior of plates and the numerical examples show that the refined non-conforming triangular plate element by the T.L. and U.L. approach can give satisfactory results. The computed results obtained from the T.L. and U.L. approach for the same numerical examples are somewhat different and the reasons for the difference of the computed results are given in detail in this paper. © 2003 Elsevier Science Ltd. All rights reserved.

Dynamic stability of laminated FGM plates based on higher-order shear deformation theory

This paper conducts a dynamic stability analysis of symmetrically laminated FGM rectangular plates with general out-of-plane supporting conditions, subjected to a uniaxial periodic in-plane load and undergoing uniform temperature change. Theoretical formulations are based on Reddy's third-order shear deformation plate theory, and account for the temperature dependence of material properties. A semi-analytical Galerkin-differential quadrature approach is employed to convert the governing equations into a linear system of Mathieu-Hill equations from which the boundary points on the unstable regions are determined by Bolotin's method. Free vibration and bifurcation buckling are also discussed as subset problems. Numerical results are presented in both dimensionless tabular and graphical forms for laminated plates with FGM layers made of silicon nitride and stainless steel. The influences of various parameters such as material composition, layer thickness ratio, temperature change, static load level, boundary constraints on the dynamic stability, buckling and vibration frequencies are examined in detail through parametric studies.

Projecto de estabilidade da Escola Superior de Enfermagem Artur Ravara

O presente trabalho, refere-se ao projecto de estabilidade, em betão armado e pré-esforçado, da Escola Superior de Enfermagem Artur Ravara, situada na zona da EXPO em Lisboa. O edifício apresenta-se com uma implantação em “L”, tendo como dimensões máximas 38,50m x 54,80m e desenvolve-se em altura por quatro pisos, dos quais, dois são enterrados. A estrutura do edifício em causa, apresenta duas juntas de dilatação, por forma a tornar desprezáveis os efeitos devidos à retracção e diminuição de temperatura, dividindo o edifício em três blocos. As suas fundações são indirectas, constituídas por estacas moldadas no terreno e respectivos maciços de encabeçamento. As lajes são fungiformes aligeiradas de moldes perdidos, de modo a permitir vencer maiores vãos, que variam entre os 6,60m e os 10,00m, e permitindo também maior rapidez de execução e maior economia. As consolas de 3,50m de vão, em laje maciça, são suportadas por vigas pré-esforçadas de secção variável. Para o cálculo automático da estrutura e da obtenção dos respectivos desenhos das armaduras, foi utilizado o programa de cálculo automático, Tricalc 7.1. O conteúdo do projecto em questão, sendo de carácter académico, não corresponde à versão real, à qual não se teve acesso. O dimensionamento das fundações, devido à fraca resistência dos solos e o dimensionamento da estrutura, devido à geometria e dimensões do edifício, permitiram enfrentar desafios interessantes. Tais desafios, deram possibilidade de enriquecer bastante os conhecimentos sobre a engenharia de estruturas.

Dimensionamento de um pavilhão industrial misto com fundações indirectas

Trabalho de Projecto para obtenção do grau de Mestre em Engenharia Civil Perfil Estruturas

Smart object for 3D interaction

This paper reports on the creation of an interface for 3D virtual environments, computer-aided design applications or computer games. Standard computer interfaces are bound to 2D surfaces, e.g., computer mouses, keyboards, touch pads or touch screens. The Smart Object is intended to provide the user with a 3D interface by using sensors that register movement (inertial measurement unit), touch (touch screen) and voice (microphone). The design and development process as well as the tests and results are presented in this paper. The Smart Object was developed by a team of four third-year engineering students from diverse scientific backgrounds and nationalities during one semester.

The European Project Semester at ISEP: the challenge of educating global engineers

Current engineering education challenges require approaches that promote scientific, technical, design and complementary skills while fostering autonomy, innovation and responsibility. The European Project Semester (EPS) at Instituto Superior de Engenharia do Porto (ISEP) (EPS@ISEP) is a one semester project-based learning programme (30 European Credit Transfer Units (ECTU)) for engineering students from diverse scientific backgrounds and nationalities that intends to address these goals. The students, organised in multidisciplinary and multicultural teams, are challenged to solve real multidisciplinary problems during one semester. The EPS package, although on project development (20 ECTU), includes a series of complementary seminars aimed at fostering soft, project-related and engineering transversal skills (10 ECTU). Hence, the students enrolled in this programme improve their transversal skills and learn, together and with the team of supervisors, subjects distinct from their core training. This paper presents the structure, implementation and results of the EPS@ISEP that was created in 2011 to apply the best engineering practices and promote internationalisation and engineering education innovation at ISEP.

Dimensionamento de um edifício misto de ensacagem a construir numa instalação industrial

Trabalho de Projeto para obtenção do grau de Mestre em Engenharia Civil Estruturas

Análise sobre a Escolha do Curso e Instituição dos Estudantes da Área de Engenharia

Todos os anos ingressam nas universidades portuguesas milhares de estudantes provenientes do concurso nacional de acesso ao ensino superior. Estes estudantes são alocados de acordo com a sua nota de candidatura e as suas preferências a um par estabelecimento-curso. Apesar das estatísticas oficiais fornecidas pelo Ministério da Ciência, Tecnologia e Ensino Superior (MCTES), nem sempre é possível retirar os indicadores relevantes para uma boa tomada de decisão por parte das Universidades sobre os cursos e vagas a oferecer. Este trabalho procura avaliar os fatores que irão influenciar os estudantes na sua escolha por um par estabelecimento-curso assim como compreender as diferentes variáveis que estão relacionadas com essa mesma atribuição de influência. Baseou-se num estudo empírico, observacional através da aplicação de questionário, com o respetivo estudo estatístico. Os resultados mostraram uma relação em maior número entre os fatores estudados e o género. Permitiram ainda concluir que os fatores prestígio da instituição, empregabilidade e desenvolvimento intelectual são os mais valorizados pelos estudantes.

Full analysis of suspension geometry and chassis performance of Formula Student racing car

Formula Student events gather engineering students, who compete, designing, building and racing single-seater cars. The team of ISEP is working on its first car that soon will take part in this competition. This work aims to analyze the current design’s chassis, focusing on suspension geometry and frame’s performance. After analyzing results of the tests planned suggestions, that can be taken into consideration during design process of next cars will be presented. As the car has not been tested yet this work can also be helpful to explain its performance on the track later.

CDIO and the European Project Semester: a match for capstone projects?

The CDIO Initiative is an open innovative educational framework for engineering graduation degrees set in the context of Conceiving – Designing – Implementing – Operating real-world systems and products, which is embraced by a network of worldwide universities, the CDIO collaborators. A CDIO compliant engineering degree programme typically includes a capstone module on the final semester. Its purpose is to expose students to problems of a greater dimension and complexity than those faced throughout the degree programme as well as to put them in contact with the so-called real world, in opposition to the academic world. However, even in the CDIO context, there are barriers that separate engineering capstone students from the real world context of an engineering professional: (i) limited interaction with experts from diverse scientific areas; (ii) reduced cultural and scientific diversity within the teams; and (iii) lack of a project supportive framework to foster the complementary technical and non-technical skills required in an engineering professional. To address these shortcomings, we propose the adoption of the European Project Semester (EPS) framework, a one semester student centred international capstone programme offered by a group of European engineering schools (the EPS Providers) as part of their student exchange programme portfolio. The EPS package is organised around a central module – the EPS project – and a set of complementary supportive modules. Project proposals refer to open multidisciplinary real world problems and supervision becomes coaching. The students are organised in teams, grouping individuals from diverse academic backgrounds and nationalities, and each team is fully responsible for conducting its project. EPS complies with the CDIO directives on Design-Implement experiences and provides an integrated framework for undertaking capstone projects, which is focussed on multicultural and multidisciplinary teamwork, problem-solving, communication, creativity, leadership, entrepreneurship, ethical reasoning and global contextual analysis. As a result, we recommend the adoption of the EPS within CDIO capstone modules for the benefit of engineering students.