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Non-linear and hysteretic analysis of the behaviour of magnetorheological dampers

Braz-César, Manuel; Barros, Rui
Fonte: Saxe-Coburg Publications Publicador: Saxe-Coburg Publications
Tipo: Parte de Livro
ENG
Relevância na Pesquisa
25.73%
This chapter reviews the basic concept of MR fluids and provides insight into the magnetorheological.

Experimental behaviour and numerical analysis of dampers MR dampers

Braz-César, Manuel; Barros, Rui
Fonte: Instituto Politécnico de Bragança Publicador: Instituto Politécnico de Bragança
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
45.85%
This paper presents the results of an experimental and numerical analysis developed to study the non-linear hysteretic behavior of MR dampers. In the first section a brief review of the numerical models available to simulate their behavior will be presented. To obtain and analyze the hysteretic behavior of MR dampers, a device was experimentally tested under several input excitations. Based on the experimental results an identification procedure was carried out to determine the parameters that are necessary to develop a numerical model. Finally, results from experimental investigations and numerical analyses are summarized and compared.

Contribuição ao emprego da mecânica do dano para a análise do comportamento dinâmico não-linear de vigas em concreto armado; Contribution to the application of damage mechanics in non-linear dynamic behaviour analysis of reinforced concrete beams

Araújo, Francisco Adriano de
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 30/05/2003 PT
Relevância na Pesquisa
75.97%
O trabalho trata da formulação e implementação numérica de um modelo de dano para o concreto. O objetivo é o de reproduzir laços de histerese observados experimentalmente em diagramas de tensão-deformação uniaxiais quando, a partir de um certo nível de solicitação, e dano correspondente, passam-se a realizar ciclos de descarregamento e recarregamento. O modelo propõe que os laços de histerese resultam da dissipação conjunta decorrente do dano evolutivo e do fenômeno de fricção interna nas faces das fissuras. O fenômeno de fricção interna está relacionado à suposição de que as fissuras não se abrem simplesmente por separação formando faces com superfícies lisas, mas tendem a combinar modos de separação e deslizamento segundo superfícies com uma certa rugosidade. O deslizamento entre as faces das fissuras dá origem a uma deformação por escorregamento, assumida como responsável por um comportamento plástico com encruamento cinemático não-linear. A abordagem termodinâmica considerada no sentido de contemplar a danificação e a fricção interna leva à dedução de que a tensão total num ponto do meio com dano resulta dividida em uma parcela dita tensão elasto-danificada e em uma outra denominada tensão de escorregamento...

Influence of the joints stiffness in the monotonic and cyclic behaviour of traditional timber trusses. Assement of the efficaccy of different strengthenning techniques

Branco, Jorge M.
Fonte: Universidade do Minho Publicador: Universidade do Minho
Tipo: Tese de Doutorado
Publicado em 28/07/2008 POR
Relevância na Pesquisa
25.97%
Tese de Doutoramento em Engenharia Civil - Estruturas; Connections are the key element in the behaviour of traditional timber trusses. The overall behaviour and stresses distribution are function of connections strength and stiffness, in particular under non-symmetric loads and extreme events. In these situations, the connections are loaded well beyond their pseudo-elastic limit. Normally, traditional timber connections are assumed as hinges or rigid. However, even without any strengthening device, they have a significant rotational stiffness and may be better classified as semi-rigid and friction-based. It is the misunderstanding of the connections behaviour that normally leads to the replacement of old timber structures, instead of their retrofitting to satisfy safety. In order to better predict and understand the behaviour of timber structures, analytical models of connections are crucial. Semi-rigid models, using nonlinear laws and hysteretic rules, intend to represent the behaviour of timber structures with a comparable level of detail for all the structural components. In this thesis, structural analysis of some full-scale timber trusses is presented. After a primary survey an extensive experimental program, using fullscale connections investigating the monotonic and cyclic behaviours of traditional timber connections...

Numerical model to account for the influence of infill masonry on the RC structures behaviour

Varum, H.; Rodrigues, H.; Costa, A.
Fonte: Universidade de Aveiro Publicador: Universidade de Aveiro
Tipo: Conferência ou Objeto de Conferência
ENG
Relevância na Pesquisa
76%
It is a common misconception considers that masonry infill walls in structural RC buildings can only increase the overall lateral load capacity, and, therefore, must always be considered beneficial to seismic performance. Recent earthquakes have showed numerous examples of severe damages or collapses of buildings caused by structural response modification induced by the non-structural masonry partitions. From a state-of-the-art review of the available numerical models for the representation of the infill masonry behaviour in structural response, it was proposed an upgraded model. The proposed model is inspired on the equivalent bi-diagonal compression strut model, and considers the non-linear behaviour of the infill masonry subjected to cyclic loads. The model was implemented and calibrated in a non-linear dynamic computer code, VISUALANL. In this paper, it is presented the proposed model and the results of the calibration analyses are briefly introduced and discussed.

Biaxial seismic behaviour of reinforced concrete columns; Comportamento sísmico biaxial de pilares de betão armado

Rodrigues, Hugo Filipe Pinheiro
Fonte: Universidade de Aveiro Publicador: Universidade de Aveiro
Tipo: Tese de Doutorado
ENG
Relevância na Pesquisa
36.18%
A análise dos efeitos dos sismos mostra que a investigação em engenharia sísmica deve dar especial atenção à avaliação da vulnerabilidade das construções existentes, frequentemente desprovidas de adequada resistência sísmica tal como acontece em edifícios de betão armado (BA) de muitas cidades em países do sul da Europa, entre os quais Portugal. Sendo os pilares elementos estruturais fundamentais na resistência sísmica dos edifícios, deve ser dada especial atenção à sua resposta sob ações cíclicas. Acresce que o sismo é um tipo de ação cujos efeitos nos edifícios exige a consideração de duas componentes horizontais, o que tem exigências mais severas nos pilares comparativamente à ação unidirecional. Assim, esta tese centra-se na avaliação da resposta estrutural de pilares de betão armado sujeitos a ações cíclicas horizontais biaxiais, em três linhas principais. Em primeiro lugar desenvolveu-se uma campanha de ensaios para o estudo do comportamento cíclico uniaxial e biaxial de pilares de betão armado com esforço axial constante. Para tal foram construídas quatro séries de pilares retangulares de betão armado (24 no total) com diferentes características geométricas e quantidades de armadura longitudinal...

Simplified hysteretic model for the representation of the biaxial bending response of RC columns

Rodrigues, H.; Romão, X.; Andrade-Campos, A.; Varum, H.; Arêde, A.; Costa, A.
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
56.13%
The biaxial cyclic behaviour of reinforced concrete columns has been object of many experimental studies over the past years, and different modelling strategies have been proposed. In the present paper, a simplified hysteretic model is proposed for the representation of the non-linear response of reinforced concrete members subjected to biaxial bending combined with a constant axial load. The proposed model corresponds to an upgrade of an existing uniaxial hysteretic model, with piecewise linear behaviour, and adopts an interaction function based on the formulation of Bouc–Wen smooth hysteretic model. The proposed biaxial model requires the same type of information as the corresponding uniaxial model, and in order to couple the two loading directions a correcting term is applied to the response in each uniaxial direction. For the calibration of the proposed interaction function, optimisation techniques were used to adjust the required parameters. Finally, the validity of the simplified model is demonstrated through the simulation of the response of reinforced concrete columns tested under biaxial loading.

Simplified model for the non-linear behaviour representation of reinforced concrete columns under biaxial bending

Rodrigues, H.; Andrade-Campos, A.; Romão, X.; Arêde, A.; Varum, H.; Costa, A.
Fonte: Universidade de Aveiro Publicador: Universidade de Aveiro
Tipo: Conferência ou Objeto de Conferência
ENG
Relevância na Pesquisa
96.19%
In the present paper a simplified model is proposed for the force-deformation behaviour of reinforced concrete members under biaxial loading combined with axial force. The starting point for the model development was an existing fixed-length plastic hinge element model that accounts for the non-linear hysteretic behaviour at the element end-sections, characterized by trilinear moment-curvature laws. To take into account the section biaxial behaviour, the existing model was adopted for both orthogonal lateral directions and an interaction function was introduced to couple the hysteretic response of both directions. To calibrate the interaction function it were used numerical results, obtained from fibre models, and experimental results. For the parameters identification, non-linear optimization approaches were adopted, namely: the gradient based methods followed by the genetic, evolutionary and nature-inspired algorithms. Finally, the simplified non-linear model proposed is validated through the analytical simulation of biaxial test results carried out in full-scale reinforced concrete columns.

Biaxial seismic behaviour of reinforced concrete columns

Rodrigues, H.; Varum, H.; Arêde, A.
Fonte: Universidade de Aveiro Publicador: Universidade de Aveiro
Tipo: Conferência ou Objeto de Conferência
ENG
Relevância na Pesquisa
55.96%
The present work focuses on the assessment of the structural response of RC columns under bidirectional horizontal loads in three main streamlines. First, an experimental testing campaign was performed on rectangular columns, for different types of loading. Subsequently, the tested columns were simulated with different non-linear modelling strategies. Finally, a simplified hysteretic model is proposed for the representation of the non-linear response of RC members subjected to biaxial bending.

Intertissue differences in the hysteretic behaviour of carnitine palmitoyltransferase in the presence of malonyl-CoA.

Lloyd, A C; Carpenter, C A; Saggerson, E D
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em 01/07/1986 EN
Relevância na Pesquisa
46.01%
In the presence of malonyl-CoA, the overt form of carnitine palmitoyltransferase (CPT1) in mitochondria from rat liver, kidney cortex, heart, skeletal muscle and brown adipose tissue shows non-linear time courses, suggesting hysteretic behaviour. The pattern of this hysteresis is similar in heart, skeletal muscle and brown adipose tissue, but the hysteretic behaviour of the enzyme in these three tissues differs markedly from that seen in liver and kidney.

THE VISCOELASTIC MOVING-CONTACT PROBLEM WITH INERTIAL EFFECTS INCLUDED

GOLDEN, J. M.; GRAHAM, G. A. C.
Fonte: Oxford University Press Publicador: Oxford University Press
Tipo: Artigo de Revista Científica Formato: text/html
EN
Relevância na Pesquisa
15.99%
A general integral equation is derived for the problem of a rigid punch moving across a viscoelastic half-space with inertial effects included. When the half-space is modelled as a standard linear solid, it is shown that the problem is formally equivalent to a non-inertial problem with the half-space response described by a continuous-spectrum viscoelastic function. The resulting integral equation is solved numerically. The pressure function and the coefficient of hysteretic friction are plotted for various materials. The discussion is restricted to punch velocities less than the lowest speed of Rayleigh waves in the material. The theory predicts that internal frictional losses, and therefore hysteretic friction, are low for large and small viscoelastic decay times. In some cases, this gives rise to a hump-shaped curve when hysteretic friction is plotted against velocity, just as for the non-inertial theory. However, because hysteretic friction always increases sharply as the lowest Rayleigh speed is approached, its behaviour as a function of velocity, for some material densities, may be monotonic.

Seismic fragility curves for un-reinforced masonry walls

Lumantarna, E.; Vaculik, J.; Griffith, M.; Lam, N.; Wilson, J.
Fonte: Australian Earthquake Engineering Society; Australia Publicador: Australian Earthquake Engineering Society; Australia
Tipo: Conference paper
Publicado em //2006 EN
Relevância na Pesquisa
35.8%
Quasi-static experiments have been carried out on unreinforced masonry (URM) wall specimens subject to two-way bending and a range of boundary conditions. The hysteretic behaviour so obtained from the experiments have been used to generate fragility curves which define the probability of the wall sustaining minor to severe damage in an earthquake based on different levels of ground motion intensity and boundary conditions of the wall. The calculation for the fragility curves involves the generation of filtered accelerograms which take into account a range of earthquake scenarios, site conditions and building types. The generated accelerograms have been used for input into non-linear time-history analyses for quantifying the amount of drift sustained by the URM walls in order that the level of damage can be ascertained.; Elisa Lumantarna, Jerry Vaculik, Mike Griffith, Nelson Lam and John Wilson

Dynamic response behaviour of unreinforced masonry walls subject to out of plane loading

Vaculik, J.; Lumantarna, E.; Griffith, M.; Lam, N.; Wilson, J.
Fonte: AEES; Australia Publicador: AEES; Australia
Tipo: Conference paper
Publicado em //2007 EN
Relevância na Pesquisa
36.09%
Unreinforced masonry (URM) walls have been traditionally considered to possess very limited ductility and hence designed to behave in a linear elastic manner when subject to out of plane loading. This notion contradicts recent findings which have found significant displacement capacity of URM walls beyond their linear elastic limit. This paper presents an overview of recent research progress on URM walls subject to out of plane two-way bending. Parametric studies based on non-linear time history analyses have been undertaken to identify the displacement demand behaviour of URM walls. Hysteretic models used in the studies were representative of hysteretic behaviour observed from cyclic testings. Analytical simulations of URM walls using the representative hysteretic models have then been evaluated by comparison with the dynamic response of the walls recorded from shaking-table testings. The materials presented in this paper represent an important part of the research outcomes from a joint ARC Discovery research project undertaken between the University of Adelaide and the University of Melbourne.; http://www.aees.org.au/Proceedings/Proceedings.html; Jaroslav Vaculik, Elisa Lumantarna, Mike Griffith, Nelson Lam and John Wilson

A Procedure for the Approximate Calculation of the Stiffness and Energy Dissipation Characteristics of Piers for the Seismic DBD and Performance Evaluation of RC Bridges

PAULOTTO Carlo; AYALA Gustavo; TAUCER FABIO
Fonte: Sociedad Mexicana de Ingenieria Sismica Publicador: Sociedad Mexicana de Ingenieria Sismica
Tipo: Contributions to Conferences Formato: CD-ROM
ENG
Relevância na Pesquisa
25.88%
The stiffness and energy dissipation characteristics of RC rectangular hollow bridge piers are investigated using two different models for the sections: a continuous non-linear without energy dissipation derived from non-linear fibre analyses and an equivalent bilinear hysteretic derived from a non-linear model with energy dissipation due to pinching behaviour. Using the results obtained and the plastic hinge theory, an equivalent linear viscoelastic model with secant to yield stiffness and equivalent damping is defined. The implications of using these properties are discussed within the framework of the performance based seismic evaluation and design of RC bridges; JRC.G.5-European laboratory for structural assessment

Experimental Investigation on a Base Isolation System Incorporating Steel-Teflon Sliders and Pressurized Fluid Viscous Spring Dampers

SORACE Stefano; TERENZI Gloria; MAGONETTE GEORGES; MOLINA RUIZ FRANCISCO JAVIER
Fonte: JOHN WILEY & SONS LTD Publicador: JOHN WILEY & SONS LTD
Tipo: Articles in Journals Formato: Printed
ENG
Relevância na Pesquisa
25.78%
An experimental investigation on a base isolation system incorporating stainless steel¿Teflon bearings as sliders, and pressurized fluid viscous spring dampers, is presented in this paper. In the system examined, dampers are connected to the base floor of an isolated building to provide the desired passive control of response in the superstructure, as well as to guarantee that it re-centres completely after the termination of a seismic action. Two types of experiments were conducted: sinusoidal and random cyclic tests, and a pseudodynamic test in ¿substructured¿ configuration. The cyclic tests were aimed at characterizing what follows: the hysteretic and strain rate-dependent response of the considered highly non-linear spring dampers; the normal pressure- and strain-rate-dependent frictional behaviour of steel¿Teflon bearings, manufactured in compliance with the latest standards for this class of sliders; and the combined response of their assembly. The pseudodynamic test imulated the installation of the protection system at the base of a 2:3-scale three-storey steel frame structure, already tested in unprotected conditions by an earlier experimental campaign. Among other findings, the results of the performed tests, as well as of relevant mechanical interpretation and numerical simulation analyses...

Constitutive modelling of cork-polyurethane gel composites

Antunes, Paulo Jorge da Rocha Soares
Fonte: Universidade do Minho Publicador: Universidade do Minho
Tipo: Tese de Doutorado
Publicado em 06/07/2009 ENG
Relevância na Pesquisa
16.13%
Tese de doutoramento em Engenharia de Polímeros (ramo de conhecimento em Ciência de Materiais Poliméricos); The CPGC - Cork-Polyurethane Gel Composite is a rubber-like material produced by ACC-Amorim Cork Composites. The non-conventional combination of cork with polyurethane gel results in a composite material with particular mechanical characteristics that must be clearly understanded for potentiate new applications or optimize products already produced with CPGC. The application of CPGC in products such as comfort enhancement devices and vibration damping or other applications, must be supported by Computer Aided Enginnering (CAE) tools, that can predict the mechanical response of the CPGC and its adequability for particular loading case scenarios. The mechanical behaviour of the CPGC was evaluated from experimental tests conducted at di erent temperatures, that furnished crucial information for the constitutive modelling procedure. From the experimental tests was possible to conclude that CPGC is mechanically characterized by a nonlinear elastic behaviour at large deformations (hyperelastic behaviour) and a dissipative behaviour evidenced by the hysteretic e ect that occurs during loading-unloading cycles. The nonlinear elastic behaviour was modelled by hyperelastic constitutive models based on phenomenological strain energy functions what enabled a structured framework for CPGC's material modelling. A new methodology for modelling hysteretic cycles and consequent material heat build-up...

Synchronized charge oscillations in correlated electron systems

Shukla, Nikhil; Parihar, Abhinav; Freeman, Eugene; Paik, Hanjong; Stone, Greg; Narayanan, Vijaykrishnan; Wen, Haidan; Cai, Zhonghou; Gopalan, Venkatraman; Engel-Herbert, Roman; Schlom, Darrell G.; Raychowdhury, Arijit; Datta, Suman
Fonte: Nature Publishing Group Publicador: Nature Publishing Group
Tipo: Artigo de Revista Científica
Publicado em 14/05/2014 EN
Relevância na Pesquisa
25.92%
Strongly correlated phases exhibit collective carrier dynamics that if properly harnessed can enable novel functionalities and applications. In this article, we investigate the phenomenon of electrical oscillations in a prototypical MIT system, vanadium dioxide (VO2). We show that the key to such oscillatory behaviour is the ability to induce and stabilize a non-hysteretic and spontaneously reversible phase transition using a negative feedback mechanism. Further, we investigate the synchronization and coupling dynamics of such VO2 based relaxation oscillators and show, via experiment and simulation, that this coupled oscillator system exhibits rich non-linear dynamics including charge oscillations that are synchronized in both frequency and phase. Our approach of harnessing a non-hysteretic reversible phase transition region is applicable to other correlated systems exhibiting metal-insulator transitions and can be a potential candidate for oscillator based non-Boolean computing.

Modelling strong seismic ground motion: three-dimensional loading path versus wavefield polarization

D'Avila, Maria Paola Santisi; Lenti, Luca; Semblat, Jean-François
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 08/08/2013
Relevância na Pesquisa
46.03%
Seismic waves due to strong earthquakes propagating in surficial soil layers may both reduce soil stiffness and increase the energy dissipation into the soil. To investigate seismic wave amplification in such cases, past studies have been devoted to one-directional shear wave propagation in a soil column (1D-propagation) considering one motion component only (1C-polarization). Three independent purely 1C computations may be performed ('1D-1C' approach) and directly superimposed in the case of weak motions (linear behaviour). This research aims at studying local site effects by considering seismic wave propagation in a 1-D soil profile accounting for the influence of the 3-D loading path and non-linear hysteretic behaviour of the soil. In the proposed '1D-3C' approach, the three components (3C-polarization) of the incident wave are simultaneously propagated into a horizontal multilayered soil. A 3-D non-linear constitutive relation for the soil is implemented in the framework of the Finite Element Method in the time domain. The complex rheology of soils is modelled by mean of a multisurface cyclic plasticity model of the Masing-Prandtl-Ishlinskii-Iwan type. The great advantage of this choice is that the only data needed to describe the model is the modulus reduction curve. A parametric study is carried out to characterize the changes in the seismic motion of the surficial layers due to both incident wavefield properties and soil non-linearities. The numerical simulations show a seismic response depending on several parameters such as polarization of seismic waves...