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COB88 Estabilidade de Arcos segmentados de concreto armado / stability of precast concrete segmental arches
Humberto C. Lima Júnior, Paulo B. Gonçalves & Giuseppe B. Guimarães
Departamento de Engenharia Civil, PUC/Rio
Rua Marquês de São Vicente, 225 - Gávea, CEP: 22435-900 - Rio de Janeiro - RJ
Tel. (021)529-9325-Fax (021)511-1546- E-mail: [humberto, paulo, giuseppe]@civ.puc-rio.br
Segmental arch is a structure made of several straight segments of precast concrete, connected at points belonging to a curve in the form of an arch which circumscribes the structure. This work presents a study of the effects of height to span ratio, number of segments and initial geometric imperfections on the arch stability. The study was carried out with a computational model based on the finite element method. The model takes into account material and geometric non-linearities, and concrete cracking.
It was found that the optimal height to span ratio value is 0,3, the number of segments affects the behaviour of three-hinged arches and that geometric imperfections can drastically decrease the arch load capacity.
Keywords: segmental arch, reinforced concrete, stability, critical load, limit point and bifurcation point. arco segmentado, concreto armado, estabilidade, carga crítica.
COB179 FORMULAÇÃO LAGRANGEANA ATUALIZADA PARA ANÁLISE NÃO-LINEAR GEOMÉTRICA DE ESTRUTURAS RETICULADAS PLANAS VIA M.E.F. / UP DATE LAGRANGEAN FORMULATION TO ANALYSE GEOMETRIC NON-LINEAR PLANE FRAMED STRUCTURES THROUGH USING F.E.M.
Rogério de Oliveira Rodrigues1 & Wilson Sergio Venturini2
1Departamento de Engenharia Civil, Faculdade de Engenharia - UNESP/FEIS -
CEP 15.385-000 Ilha Solteira - S.P., Brasil - Av. Brasil Centro, 56
2Departamento de Estruturas, Escola de Engenharia de São Carlos - USP/EESC
CEP 13.560-250 São Carlos - S.P., Brasil - Av. Dr. Carlos Botelho, 1465
This work deals with up dated Lagrangean formulation to analyse geometric non-linear plane trusses and frames, using finite elements. The equilibrium is enforced at the actual position, allowing to compute internal efforts using the true displacement field. Appropriate shape functions are adopted to each type of element, giving therefore the corresponding normal strain component represented by the complete Green-Lagrange tensor. For the truss formulation, all terms are taken into account to derive the global stiffness matrix, while for frames, some terms of higher orders have been neglected. The Lagrangean formulation is used to write the equilibrium at the position giving the final tangent and secant incremental stiffness matrices. Static and dynamic numerical examples are shown to illustrate the accuracy of the proposed formulation.
Keywords: Structural analysis; Non-linear behaviour / Análise estrutural; Comportamento não-linear.
COB656 ANÁLISE ELASTO-PLÁSTICA DE LAJES UTILIZANDO O MÉTODO DOS ELEMENTOS FINITOS E PROGRAMAÇÃO MATEMÁTICA / ELASTO-PLASTIC ANALYSIS OF SLABS USING THE METHOD OF THE FINITE ELEMENTS AND MATHEMATICAL PROGRAMMING
Alexandre Miranda Mont’alverne1 & Luiz Eloy Vaz2
1 Departamento de Engenharia Civil, Pontifícia Universidade Católica do Rio de Janeiro (PUC-Rio), Rio de Janeiro, RJ, CEP 22453-900, Brasil. E-mail: miranda@tecgraf.puc-rio.br, miranda@civ.puc-rio.br
2 Departamento de Engenharia Civil, Pontifícia Universidade Católica do Rio de Janeiro (PUC-Rio), Rio de Janeiro, RJ, CEP 22453-900, Brasil. E-mail: eloy@civ.puc-rio.br
A elastoplastic analysis by non-linear Mathematical Programming is developed for thin and thick bending plates, under small deformations. The Finite Element Method is used to discretize the model. The equilibrium equations at the structural level are solved by a conventional Newton-Raphson technique. The elastoplastic constitutive problem is stated for stress variables at Gauss points of the discretized structure as a Mathematical Programming problem. The strength criteria proposed by Johansen and Velasco are used in this work. The tangent consistent matrix is used to update the elastoplastic stiffness matrix. A Newton-like interior point method is used to solve the Mathematical Programming problem.
Keywords: Lajes de Concreto Armado, Método dos Elementos Finitos, Análise Elasto-Plástica, Programação Matemática / Slabs of Reinforced Concrete, Method of the Finite Elements, Elasto-Plastic Analysis. Mathematical Programming.
COB657 ANÁLISE ESTÁTICA DE VIGAS LAMINADAS ORTOTRÓPICAS PELO MÉTODO DOS ELEMENTOS FINITOS/STATIC ANALISYS OF ORTHOTROPIC BEAMS BY FINITE ELEMENT METHOD
Amir Elias Abdalla Kurban, Anderson Dolinski Campos & Humberto Lima Soriano
1 - Departamento de Engenharia de Fortificação e Construção, IME, R J, Brasil, amir@aquarius.ime.eb.br
2 - Departamento de Engenharia Mecânica, PEM, COPPE/UFRJ, R J, Brasil
3 - DME, EE/UFRJ e PEC,COPPE/UFRJ, R J, Brasil
This paper presents a finite element formulation of multilayered orthotropic beams for static analysis. This formulation is developed based on a transverse shear deformation theory which accounts piecewise linear distribution across the interfaces between the layers of the displacement u and satisfies the contact conditions at the interfaces. The element is quite versatile and it can be used to analyse not only thin beams with negligible shear deformation but also thick beams and beams of sandwich construction in which shear effect is important. Numerical examples are worked out to complete the theoretical formulation.
Keywords: FEM, orthotropic beams, vigas ortotrópicas, multilayered beams, vigas laminadas
COB661 ANÁLISE DE UM BANCO VEICULAR SUJEITO A GRANDES DEFORMAÇÕES POR COLISÃO / ANALYSIS OF VEHICULAR SEAT SUBMITED TO LARGE DEFORMATIONS BY COLISION
Mauro Speranza Neto1, Fernando Ribeiro da Silva2 e Jorge Dias Lage3
1Departamento de Engenharia Mecânica - PUC-Rio - E-mail: msn@mec.puc-rio.br
2Departamento de Engeharia Mecânica e de Materiais - IME - E-mail: d4fernan@epq.ime.eb.br
3Instituto Tecnológico - PUC-Rio - E-mail: jlage@venus.rdc.puc-rio.br
This work presents an analysis of a vehicle seat under dynamic load, during a colision. From the deformated seat after the colision, we determine the probable vehicle velocity just before the acident, using simple models, system dynamic tools and some engineering analysis procedures. We describe our methodology and discuss our analysis showing the most important results.
Keywords: Análise Dinâmica, Colisão de Veículos, Método dos Elementos Finitos, Simulação Dinâmica.
Dynamic Analysis, Vehicle Colisions, Finite Element Methods, Dynamic Simulation.
COB831 STRESS STIFFENING EFFECTS ON LAMINATED TIMOSHENKO BEAMS WITH PIEZOELECTRIC ACTUATORS
Donatus C. D. Oguamanan
University of Toronto- Institute for Aerospace Studies, 4925 Dufferin St., Downsview, Ont., Canada M3H 5T6
Sérgio Frascino Müller de Almeida
Instituto Tecnológico de Aeronáutica - Div. Enga Mecânica-Aeronáutica,
12228-900 São José dos Campos - SP - E-mail: frascino@mec.ita.cta.br
Jorn S. Hansen
University of Toronto- Institute for Aerospace Studies, 4925 Dufferin St., Downsview, Ont., Canada M3H 5T6
The effectiveness of using piezoelectric elements to control the mechanical performance of laminated structures by inducing favorable in-plane stresses is investigated. A finite element formulation is presented for the analysis of laminated Timoshenko beams with an arbitrary number of piezoelectric actuators and/or sensors placed along the length of the beam. Von Kàrmàn non-linear strain-displacement relations are used and ideal linear behavior is assumed for the piezoelectric actuation. It is shown that with proper boundary conditions the piezoelectric actuators induce in-plane stresses that may significantly affect the mechanical behavior of the beam. It is shown that the stress stiffening is more pronounced for slender beams. A configuration with a piezoelectric actuator at the top of a slender beam and a sensor at the bottom is analyzed. It is demonstrated that neglecting the stress stiffening effects may lead to large errors in both the static and dynamic analyses of this widely used configuration. Further, the stiffness of the beam can be electrically tuned to a desired value with interesting applications in active structures.
Keywords: Piezoelectric, finite elements, stress stiffening, vibration.
COB832 AXISYMMETRIC ACTUATION OF COMPOSITE CYLINDRICAL SHELLS WITH PIEZOELECTRIC RINGS
Alfredo Rocha de Faria
University of Toronto- Institute for Aerospace Studies
4925 Dufferin St., Downsview, Ont., Canada M3H 5T6 E-mail: faria@bach.utias.utoronto.ca
Sérgio Frascino Müller de Almeida
Instituto Tecnológico de Aeronáutica - Div. Enga Mecânica-Aeronáutica
12228-900 São José dos Campos - SP - E-mail: frascino@mec.ita.cta.br
Axisymmetric static and frequency analyses of anisotropic cylindrical shells with one and two perfectly bonded ring piezoactuators are performed. The shell is assumed to be linear elastic and made of laminated composite materials. The electroelastic constitutive relations for the piezoelectric materials are also assumed to be linear. A simple closed-form solution of the equilibrium equations is obtained for the case of a infinite shell with one or two actuators. The finite element method with class C1 continuity elements is then applied to obtain the stiffness and mass matrices required for the static and dynamic analyses of arbitrary cylindrical shells with piezoelectric actuators. Good agreement is reached between the analytical solution found and the numerical procedure implemented. Results indicate that the maximum normalized displacement and its location vary according to the actuator length. Furthermore, a frequency analysis is carried on in a broad range of frequencies to investigate the effect of mass properties on the response of a simply supported cylindrical shell.
Keywords: Cylindrical Shell, Piezoelectric Actuation, Composite Materials.
COB837 INFLUÊNCIA DO AMORTECIMENTO INTERNO EM PLACAS SOB AÇÃO DE CARREGAMENTO NÃO CONSERVATIVO / INTERNAL DAMPING IN PLATE WITH NON CONSERVATIVE LOAD
Jánes Landre Júnior
Departamento de Engenharia Mecânica, IPUC - PUC-Minas - Belo Horizonte, CEP30.535-610 Belo Horizonte, Brasil
In the present work, that deals with the dynamic analysis of plates by using the finite elements method, there were used commun elements for structures in bending.In order to work the structures of plates under the action of follower forces and internal damping, it was necessary study plate problems with different boundary conditions, so that loss of stability could be studied. This study proves the destabilizing effect of low internal damping coefficients at plates, for this used graphs and tables for different critical loads values.
Keywords: Structural Vibration, Plate, Non-Conservative Load / Vibração de Estruturas, Placas, Cargas Não Conservativas.
COB1357 INFLUÊNCIA DAS JUNTAS SEMI-RÍGIDAS NO COMPORTAMENTO DINÂMICO DE PÓRTICOS PLANOS / INFLUENCE OF SEMI-RIGID CONNECTIONS ON THE DYNAMIC BEHAVIOUR OF PLANE FRAMES
Carmen Lucia Sahlit & Milton Soares Filho
Departamento de Engenharia Civil, Faculdade de Tecnologia - Universidade de Brasília -
70910-900, Brasília, DF, Brasil - E-mail: lucbbran@rudah.com.br / miltonsf@guarany.cpd.unb.br
The behaviour of framed structures with semi-rigid connections subjected to dynamic loads is studied. Attention is given to the effect of joint flexibility on the natural frequencies and corresponding mode shapes, as well as on the dynamic displacements and generalised stresses. The flexible connections are represented by zero-length rotational springs with linear moment-rotation relationship. The mass and stiffness matrices are developed as the sum of the conventional finite element matrices and correction matrices which incorporate the flexibility of the end joints. The problem of forced vibrations is then solved by means of the modal superposition method or, alternatively, by numerical integration of the motion equations. Numerical results are presented and it is shown that the consideration of semi-rigid connections alters significantly the dynamic behaviour of the structure.
Keywords: Estrutura reticulada, conexão semi-rígida, resposta dinâmica, análise de vibrações. / Framed structure, semi-rigid connection, dynamic response, vibration analysis.