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CFRP - Confined reinforced concrete elements subjected to cyclic compressive loading

Ferreira, Débora; Barros, Joaquim; Varma, Rajendra
Fonte: American Concrete Institute Publicador: American Concrete Institute
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
46.06%
The effectiveness of discrete and continuous CFRP wrapping arrangements for reinforced concrete (RC) short column subjected to monotonic and cyclic compressive loading is assessed in this work. The experimental program is composed of four series of RC columns with discrete wrapping arrangements and one series of full wrapped RC columns. Each series is composed of a monotonic and a cyclic test. Strain gauges were installed along the height of each column to measure the strain field in the CFRP during the test. The variation of the stiffness of the unloading and reloading branches of each loading cycle was determined. A constitutive model to simulate FRP-confined RC concrete elements subjected to cyclic compressive loading was developed and implemented into a computer program based on the finite element method. This model was appraised with the data obtained from the carried out experimental program.

Cyclic Fatigue Resistance of Rotary Nickel-Titanium Instruments Submitted to Nitrogen Ion Implantation

GAVINI, Giulio; PESSOA, Oscar Faciola; BARLETTA, Fernando Branco; VASCONCELLOS, M. A. Z.; CALDEIRA, Celso Luiz
Fonte: ELSEVIER SCIENCE INC Publicador: ELSEVIER SCIENCE INC
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
36.09%
Introduction: The aim of this study was to assess cyclic fatigue resistance in rotary nickel-titanium instruments submitted to nitrogen ion implantation by using a custom-made cyclic fatigue testing apparatus. Methods: Thirty K3 files, size #25, taper 0.04, were divided into 3 experimental groups as follows: group A, 12 files exposed to nitrogen ion implantation at a dose of 2.5 x 10(17) ions/cm(2), accelerating voltage of 200 kV, currents of 1 mu A/cm(2), 130 degrees C temperature, and vacuum conditions of 10 x 10(-6) torr for 6 hours; group B, 12 nonimplanted files; and group C, 6 files submitted to thermal annealing for 6 hours at 130 degrees C. One extra file was used for process control. All files were submitted to a cyclic fatigue test that was performed with an apparatus that allowed the instruments to rotate freely, simulating rotary instrumentation of a curved canal (40-degree, 5-mm radius curve). An electric motor handpiece was used with a contra-angle of 16:1 at an operating speed of 300 rpm and a torque of 2 N-cm. Time to failure was recorded with a stopwatch in seconds and subsequently converted to number of cycles to fracture. Data were analyzed with the Student t test (P < .05). Results: Ion-implanted instruments reached significantly higher cycle numbers before fracture (mean...

Desenvolvimento de máquina de movimentos cíclicos para testes biomecânicos ; Development of machine of cyclic movements for biomechanical tests

Marinheiro, Carlos Alberto
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 10/02/2003 PT
Relevância na Pesquisa
46.14%
O ser humano locomove-se utilizando-se do complexo sistema neuro-músculo-esquelético, o que lhe confere qualidade de vida. Partes do sistema esquelético são passíveis de tratamento ou mesmo de substituição pelo emprego de materiais estranhos ao corpo humano mas que provocam pequena reação biológica e necessitam ser dimensionados de modo a suportar toda tensão resultante do movimento humano. O objetivo deste trabalho foi desenvolver uma máquina de ensaio cíclico para testes biomecânicos, de implantes utilizados nas cirurgias de reconstrução ósteo-articular, utilizando tecnologia nacional. A máquina possui um sistema de acionamento por meio de um motor trifásico de 2 HP, 1800 rpm; um sistema de transmissão de cargas cíclicas utilizando um eixo excêntrico, que aciona um pistão, que promove o movimento de duas alavancas que transmitem a carga para os componentes a serem ensaiados. Há um inversor de freqüência para controle do número de ciclos do motor, um reservatório de soro fisiológico com um sistema que mantém o soro aquecido entre 36 e 38 ºC, e uma bomba hidráulica submersa que mantém o soro em constante movimentação. Foi feito um teste cíclico de fadiga de componente femoral de artroplastia de quadril...

"Resistência à fadiga cíclica flexural de instrumentos rotatórios de Ni-Ti em razão do uso e do torque"; Flexural cyclic fatigue resistance of NiTi rotatory instruments due to number of users and torque.

Kawakami, Dirce Akemi Sacaguti
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 14/03/2007 PT
Relevância na Pesquisa
36.06%
O objetivo do presente estudo foi avaliar a resistência à fadiga cíclica flexural de instrumentos rotatórios de níquel-titânio de número 25, conicidade 0,04 e 25 mm de comprimento (K3, SybronEndo), submetidos a variados torques de acionamento e repetidos ciclos de usos em canais simulados, valendo-se de dispositivo apropriado para ensaios dinâmicos. Procurou-se determinar se, além do fator de variação número de uso, há influência relacionada com o torque e, ainda, a possibilidade de interação entre número de uso e torque. Valendo-se motor elétrico acionado à velocidade de 300 rpm foram instrumentados 320 canais simulados, utilizado-se 80 instrumentos divididos em 4 grupos com 20 espécimes cada, de acordo com os torques (0,5 Ncm, 1,0 Ncm, 2,0 Ncm e 6,0 Ncm) a que seriam submetidos. Cada grupo foi subdividido em 4 subgrupos com 5 espécimes, de acordo com o número de usos (1, 3, 5 e 7 ciclos de usos). Todos os instrumentos foram submetidos a ensaio de fadiga cíclica flexural que foi realizado num dispositivo que permitia ao instrumento girar livremente, reproduzindo a instrumentação rotatória num canal curvo (40º e raio de curvatura de 5 mm), simulando o movimento de pecking, onde o instrumento deslizava pelo sulco criado no anel de aço temperado. Foi utilizada peça de mão com contra-ângulo redutor de 16:1...

Implementação de ensaios de arrancamento cíclico de geossintéticos; Implementation of cyclic pull out tests of geosynthetics

Napa García, Gian Franco
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 30/03/2011 PT
Relevância na Pesquisa
46.28%
Os ensaios de arrancamento cíclicos são utilizados para avaliar o comportamento de sistemas de solo reforçado quando submetidos a carregamentos cíclicos, podendo ser aplicados na área de pavimentos reforçados com geossintéticos ou em comportamento sísmico de solos reforçados com geossintéticos. O comportamento de sistemas de solo reforçado submetidos a carregamentos cíclicos ainda não é bem compreendido. Em vista disso, equipamentos de arrancamento cíclicos de geossintéticos são desejáveis para o estudo deste comportamento. O equipamento de arrancamento de geossintéticos existente no laboratório de geossintéticos da Escola de Engenharia de São Carlos da Universidade de São Paulo foi modificado para a realização de ensaios de arrancamento cíclico de geossintéticos. Dois tipos de ensaios foram implementados para avaliar o comportamento cíclico de sistemas de solo reforçado com geogrelhas: o ensaio de módulo de cisalhamento de resiliência de interface solo-geogrelha, Gi, e o ensaio de resistência pós-ciclagem. Foram realizados 20 ensaios, entre ensaios de arrancamento monotônico, cíclicos e de testes, de geogrelhas. Foram avaliados dois sistemas, um deles de inclusão longa, de 510 mm de comprimento e 310 mm de largura; e o outro de inclusão curta...

Air-particle abrasion on zirconia ceramic using different protocols: Effects on biaxial flexural strength after cyclic loading, phase transformation and surface topography

Souza, Rodrigo O.A.; Valandro, Luiz F.; Melo, Renata M.; Machado, João P.B.; Bottino, Marco A.; Özcan, Mutlu
Fonte: Universidade Estadual Paulista Publicador: Universidade Estadual Paulista
Tipo: Artigo de Revista Científica Formato: 155-163
ENG
Relevância na Pesquisa
36.03%
This study evaluated the effect of different air-particle abrasion protocols on the biaxial flexural strength and structural stability of zirconia ceramics. Zirconia ceramic specimens (ISO 6872) (Lava, 3M ESPE) were obtained (N=336). The specimens (N=118, n=20 per group) were randomly assigned to one of the air-abrasion protocols: Gr1: Control (as-sintered); Gr2: 50 μm Al2O3 (2.5 bar); Gr3: 50 μm Al2O3 (3.5 bar); Gr4: 110 μm Al2O3(2.5 bar); Gr5: 110 μm Al2O3 (3.5 bar); Gr6: 30 μm SiO2 (2.5 bar) (CoJet); Gr7: 30 μm SiO2(3.5 bar); Gr8: 110 μm SiO2 (2.5 bar) (Rocatec Plus); and Gr9: 110 μm SiO2 (3.5 bar) (duration: 20 s, distance: 10 mm). While half of the specimens were tested immediately, the other half was subjected to cyclic loading in water (100,000 cycles; 50 N, 4 Hz, 37 °°C) prior to biaxial flexural strength test (ISO 6872). Phase transformation (t→m), relative amount of transformed monoclinic zirconia (FM), transformed zone depth (TZD) and surface roughness were measured. Particle type (p=0.2746), pressure (p=0.5084) and cyclic loading (p=0.1610) did not influence the flexural strength. Except for the air-abraded group with 110 μm Al2O3 at 3.5 bar, all air-abrasion protocols increased the biaxial flexural strength (MPa) (Controlnon-aged: 1030±153...

Estudo comparativo da resistência mecânica cíclica e linear entre placas pré-dobradas e dobradas manualmente para avanço maxilar em cirurgia ortognática; Comparative study of cyclic and linear mechanical resistance of prebent and manually bent plates used for maxillary advancement in orthognathic surgery

Andrezza Lauria de Moura
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 28/07/2014 PT
Relevância na Pesquisa
36.25%
O propósito no estudo foi avaliar comparativamente, através de teste de carregamento linear e cíclico, placas pré-dobradas e dobradas manualmente para avanço maxilar em cirurgia ortognática. Os grupos foram divididos em: Grupo I com placas pré-dobradas para avanço maxilar de 5mm, fixadas em blocos de poliuretano para o teste linear e blocos de alumínio para o teste cíclico; e grupo II, com placas dobradas manualmente simulando avanço maxilar de 5mm, fixadas em blocos de poliuretano e alumínio. Os testes de carregamento linear foram realizados com 8 amostras em cada grupo e com auxílio da máquina para ensaio universal mecânica Instron® 4411 até a falha do material. Já o teste cíclico foi realizado com 5 amostras em cada grupo através de uma máquina para ensaio universal Instron® E3000 e foram submetidas à carga de 12N a 120N, frequência de 3 Hz até a fratura da placa ou parafuso e com o número máximo de 500.000 ciclos. As médias e desvio padrão foram avaliadas através dos testes t-Student e Mann-Whitney em nível de significância de 5% para o teste linear e medianas através do teste Mann-Whitney para o teste cíclico. Os resultados do teste mecânico linear mostraram que não houve diferença estatística entre os grupos de placas pré-dobradas e dobradas manualmente...

CFRP - Confined reinforced concrete elements subjected to cyclic compressive loading

Barros, Joaquim A. O.; Ferreira, Débora R. S. M.; Varma, R. K.
Fonte: Universidade do Minho Publicador: Universidade do Minho
Tipo: Conferência ou Objeto de Conferência
Publicado em 08/06/2009 ENG
Relevância na Pesquisa
46.09%
The effectiveness of discrete and continuous CFRP wrapping arrangements for reinforced concrete (RC) short column subjected to monotonic and cyclic compressive loading is assessed in this work. The experimental program is composed of four series of RC columns with discrete wrapping arrangements and one series of full wrapped RC columns. Each series is composed of a monotonic and a cyclic test. Strain gauges were installed along the height of each column to measure the strain field in the CFRP during the test. The variation of the stiffness of the unloading and reloading branches of each loading cycle was determined. A constitutive model to simulate FRP-confined RC concrete elements subjected to cyclic compressive loading was developed and implemented into a computer program based on the finite element method. This model was appraised with the data obtained from the carried out experimental program.

The cyclic triaxial test as tool to quantify coarse non-conventional materials response

Araújo, Nuno Faria; Correia, A. Gomes
Fonte: Centro para a Valorização de Resíduos (CVR), Campus de Azurém, Guimarães, Portugal Publicador: Centro para a Valorização de Resíduos (CVR), Campus de Azurém, Guimarães, Portugal
Tipo: Conferência ou Objeto de Conferência
Publicado em //2011 ENG
Relevância na Pesquisa
36.17%
Sustainable waste management requires efficient dealing to protect landfill and reduce waste deposits. For that it becomes necessary to improve material characterization, using performance based tests, to estimate waste reuse as construction material. Several mechanical tests exist which make possible to use numerical tools to estimate reversible and irreversible behaviour of non-conventional coarse material, as industrial waste. From the available tests, the large-scale cyclic triaxial test is commonly used since it is the simple one to implement and allows the study of the irreversible behaviour, an import factor for materials to be used in roadway and railway infrastructures. The large-scale cyclic triaxial test is an equipment that exists on several important laboratories, in Europe, USA and Asia. This paper describes a large cyclic triaxial test facility developed at Centre for Waste Valorisation (Campus of University of Minho), able to study coarse aggregates/waste materials with grain size particles up to 50 mm.

Influence of infill on the cyclic behaviour of traditional half-timbered walls

Poletti, Elisa; Vasconcelos, Graça; Oliveira, Daniel V.
Fonte: BTCM 2013 Publicador: BTCM 2013
Tipo: Conferência ou Objeto de Conferência
Publicado em //2013 ENG
Relevância na Pesquisa
45.93%
Half-timbered buildings represent an important historical heritage in many countries. They are diffused in various regions for different reasons, such as availability of materials, to lighten a structure, low cost and the strength they offer, and as a construction element able to resist seismic actions. This latter issue is the research topic analysed here, as half-timbered buildings have been specifically used in reconstruction plans as earthquake-resistant buildings in many countries, such as Portugal, India, Greece, etc. The aim of this paper is to study the behaviour under cyclic loading of such half-timbered walls, with typical connections, materials and geometries encountered in existing buildings. Traditionally, different types of infill could be applied to half-timbered walls depending on the country, namely brick masonry, rubble masonry, hay, mud, etc. The focus of this paper is to study and compare the seismic behaviour of the walls considering two different infill typologies, as well as the possibility of having no infill, i.e. considering only the timber frame. Cyclic test were performed on traditional walls and their behaviour was studied in terms of ultimate capacity, deformability, energy dissipation and stiffness.; Fundação para a Ciência e a Tecnologia (FCT)

Numerical modelling of the cyclic behaviour of RC elements built with plain reinforcing bars

Melo, José; Fernandes, Catarina; Varum, Humberto; Rodrigues, Hugo; Costa, Aníbal; Arêde, António
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
46.06%
The bond-slip mechanism is one of the features that significantly controls the response as well as damage evolution of reinforced concrete structures when subjected to severe cyclic loadings, such as those induced by earthquakes. Its effect is particularly important in structures built with plain reinforcing bars. For a rigorous simulation of the response of existing RC structures, built mainly with plain bars, the bond-slip mechanism should be considered. However, the majority of the available concrete-steel bond numerical models were developed and calibrated for elements with deformed reinforcing bars. Moreover, the available experimental data on the cyclic behaviour of RC elements built with plain bars is still limited. In this framework, the objective of the present paper is to calibrate a numerical model based on results of a cyclic test performed on a two-span RC beam built with plain bars, which was collected from an existing structure. The numerical modelling was carried out with the nonlinear OpenSees software platform. Particular awareness was devoted to the bond-slip mechanism. The numerical results obtained with the calibrated nonlinear model are presented and compared with the experimental results. The consideration of the bond-slip effect in the numerical model was fundamental to achieve a good agreement between the numerical simulation and the test results. (C) 2010 Elsevier Ltd. All rights reserved.; FCT - SFRH/BD/62110/2009; FCT - SFRH/BD/27406/2006; FCT - SFRH/BD/63032/2009; FCT - SFRH/BSAB/939/2009

Cyclic behavior of a two-span RC beam built with plain reinforcing bars

Fernandes, Catarina; Melo, José; Varum, Humberto; Costa, Aníbal
Fonte: Budapest University of Technology and Economics Publicador: Budapest University of Technology and Economics
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
46.06%
Reinforced concrete structural elements lacking appropriate seismic detailing and built with plain reinforcing bars, and subjected to cyclic loads like the ones induced by earthquakes, are particularly sensitive to the bond-slip mechanism. Though, existing studies on the cyclic behavior of RC structures generally refer to elements with deformed bars. As a result, the behavior of elements with plain bars is not yet fully understood. In this framework, the cyclic behavior of a two-span RC beam built with plain reinforcing bars, collected from an ancient building structure, was investigated. The support and loading conditions observed in-situ were simulated in the test setup. The beam displayed a flexural failure and the damage was concentrated in three short plastic hinges. The poor damage distribution evidences the effects of the bar slippage mechanism on the beam behavior; FCT - SFRH/BD/27406/2006; FCT - SFRH/BD/62110/2009

Cyclic behaviour of RC elements with plain reinforcing bars; Comportamento cíclico de elementos de betão armado com armadura lisa

Fernandes, Catarina Alexandra Louro
Fonte: Universidade de Aveiro Publicador: Universidade de Aveiro
Tipo: Tese de Doutorado
ENG
Relevância na Pesquisa
36.02%
O comportamento cíclico das estruturas de betão armado é fortemente condicionado pelo mecanismo de aderência entre o betão e o aço. O escorregamento relativo entre os dois materiais, resultante da degradação progressiva da aderência em elementos solicitados por ações cíclicas, é uma causa frequente de danos graves e até do colapso de estruturas devido à ocorrência de sismos. Entre as estruturas existentes de betão armado que foram dimensionadas e construídas antes da entrada em vigor dos regulamentos sísmicos atuais, muitas foram construídas com armadura lisa, e portanto, possuem fracas propriedades de aderência. A informação disponível na literatura sobre o comportamento cíclico de elementos estruturais de betão armado com armadura lisa é reduzida e a influência das propriedades da aderência associadas a este tipo de armadura no comportamento cíclico das estruturas existentes não se encontra ainda devidamente estudada. O objectivo principal desta tese foi estudar a influência do escorregamento na resposta cíclica de elementos estruturais de betão armado com armadura lisa. Foram realizados ensaios cíclicos em elementos do tipo nó viga-pilar, construídos à escala real, representativos de ligações interiores em edifícios existentes sem pormenorização específica para resistir às ações sísmicas. Para comparação...

Investigation of cold rolled steel gusset plates under cyclic load when varying the unsupported length-thickness ratio; Practice Periodical on Structural Design and Construction

Nuñez-Moreno, Federico Alejandro; Ruiz, Daniel; Castelblanco, Carlos; Uribe, Nicolás
Fonte: Pontifícia Universidade Javeriana Publicador: Pontifícia Universidade Javeriana
Formato: 48-53
Relevância na Pesquisa
36.03%
17; This article is an investigation of buckling of cold-rolled gusset plates subjected to cyclic axial load for various unsupported length-to-thickness ratios (L/e). A total of twelve specimens were tested and their respective time-to-failure (in terms of the number of cycles) were measured. Using the data obtained, the dependence of time-to-failure on the ratio L/e was investigated. The dependence of time-to-failure on the L/e ratio is important and can be rationalized via an equation through analyses and test results. Such an equation will especially be helpful in design and can be used, along with other requirements, for the selection of an appropriate size for a gusset plate. The paper draws conclusions based on the limited test results and discusses the importance of L/e and cyclic loads in design of gusset plates in bridges.

Biomechanische Testung der femoralen Pressfit-Technik beim Ersatz des vorderen Kreuzbandes mittels Patellarsehne; Biomechanical test of the femoral pressfit technique in ACL replacement using a patellar tendon graft

Banzhaf, Maike
Fonte: Universidade de Tubinga Publicador: Universidade de Tubinga
Tipo: Dissertação
DE_DE
Relevância na Pesquisa
36.03%
In der vorliegenden Arbeit wurde die femorale Pressfit- Technik beim Ersatz des vorderen Kreuzbandes mittels Patellarsehne unter Variation der Knochenblocklänge und der Einbringwinkel untersucht. Material und Methode: An 41 Schweinepräparaten wurde aus der Patella ein Knochenblock mit anhängender Patellarsehne entnommen. Bei der Hälfte der Präparate wurde die Länge der totalen Verblockungsstrecke auf 5 mm verkürzt. Bei der anderen Hälfte wurde der Knochenblock so bearbeitet, dass eine totale Verblockungsstrecke von 10 mm Länge bestand. Die Knochenblöcke mit 9,4 mm Durchmesser wurden in einen 0,4 mm kleineren Bohrkanal am Schweinefemur, der entweder parallel zur Femurachse (0°- Verblockung) oder in 60° zur Femurachse angelegt worden war, eingestößelt. Die Präparate wurden in einer Halterung befestigt und in eine Materialtestungsmaschine eingespannt. Sie wurden zunächst über 200 Zyklen jeweils um 2 mm gedehnt und wieder entlastet und anschließend einem Zugversuch bis zum Versagen unterzogen. Ergebnisse: Alle Präparate durchliefen die zyklische Testung unbeschadet. Die Maximalkraftwerte betrugen bei 0° und 10 mm Verblockungsstreckenlänge durchschnittlich 276 N, bei 0° und 5 mm 222 N, bei 60° und 10 mm 601 N und bei 60° und 5 mm 574 N. Unter Berücksichtigung eines Ausreißers bestand im t- Test ein signifikanter Unterschied zwischen den Maximalkraftergebnissen bei den Gruppen mit 0°- Verblockung und 5 bzw. 10 mm Verblockungsstreckenlänge (p = 0...

Experimental investigation for constitutive modeling of fine sand under cyclic loading using hollow cylinder specimens

Sun, Yuanhui
Fonte: Universidade Rice Publicador: Universidade Rice
Tipo: Thesis; Text Formato: 223 p.; application/pdf
ENG
Relevância na Pesquisa
36.25%
An experimental program for the understanding of the behavior of fine cohesionless soil under monotonic and cyclic loading and for the development and refinement of constitutive models has been undertaken. An experimental program for both loose and dense saturated fine Ottawa Silica sands under monotonic loading using both solid and hollow cylinder specimens has been conducted. The failure surfaces have been established from twenty drained monotonic load tests. Results were found in good agreement with the failure surfaces incorporated in Lade's constitutive model. The soil behavior and deformation characteristics under undrained conditions have been investigated under a cyclic experimental program for loose sand. Results indicated that the circular rotation of principal stress axes with a constant amplitude deviator stress, as well as the stress direction reversals have significant effects on the rate of pore water pressure buildup, the triggering of a liquefaction flow failure in contractive sand and the rate of accumulation of deformation. The rate of excess pore water pressure buildup is faster during a cyclic test with circular rotation of principal stress axes than during a cyclic triaxial shear test or a cyclic torsional shear test having same amplitude of shear stress. The rate is faster during a cyclic triaxial extension test than in a cyclic triaxial compression test or a cyclic torsional simple shear test with the same amplitude of shear stress. The deformation and significant pore water pressures are developed during the first cycle and more remarkably during the last cycle. The pore water pressures (and mean effective stress reduction) and developed fast when the stress path reaches the failure surface which was established in monotonic load tests. The pore water pressure and deformation increase fast in the case of shear stress reversal. The pore water pressure buildup and mean effective stress reduction are more pronounced during extension loading than in compression loading. Moreover...

EXPERIMENTAL RESPONSE OF A PILE IN SAND UNDER STATIC AND CYCLIC LATERAL LOADS

Oghabi, PEGAH
Fonte: Quens University Publicador: Quens University
Tipo: Tese de Doutorado
EN; EN
Relevância na Pesquisa
36.17%
Piles are engineering structures which are subjected to axial and lateral loading. In this dissertation, pile load tests were performed on a full-scale fabricated pile to understand lateral pile responses under static and cyclic loading. The experiments were performed on a fabricated test pile at the Geo-Engineering Laboratory at Queen's University. Dry loose Olimag Synthetic Olivine sand was used as the test soil. Instrumentation including axial strain gauges, null sensors (earth pressure sensors) and string potentiometers were used to monitor pile responses throughout the tests. What differentiates the current study from previous investigations is direct measurements of lateral earth pressure on a test pile using those null sensors with conventional measurements of curvature and deformation. The null sensors of Talesnick (2005) have ‘infinite stiffness’ and calibration that is almost independent of the soil type, soil condition and stress history, qualities that make the sensor superior to other commercially available sensors. The initial pile response under static loading was examined. Previous laterally loaded pile test programs have utilized curvature measurements to infer moments, and differentiation of moments to determine lateral forces. Comparisons with the directly measured pressures confirmed the effectiveness of differentiated moments. To understand offshore structures...

Assessment of overlay masonry strengthening system under in-plane monotonic and cyclic loading using the diagonal tensile test

Almeida, João Alberto Pinheiro Pereira; Pereira, E. N. B.; Barros, Joaquim A. O.
Fonte: Universidade do Minho Publicador: Universidade do Minho
Tipo: Artigo de Revista Científica
Publicado em //2015 ENG
Relevância na Pesquisa
36.06%
The development of novel strengthening techniques to address the seismic vulnerability of masonry elements is gradually leading to simpler, faster and more effective strengthening strategies. In particular, the use of fabric reinforced cementitious matrix systems is considered of great potential, given the increase of ductility achieved with simple and economic strengthening procedures. To assess the effectiveness of these strengthening systems, and considering that the seismic action is involved, one important component of the structural behaviour is the in-plane cyclic response. In this work is discussed the applicability of the diagonal tensile test for the assessment of the cyclic response of strengthened masonry. The results obtained allowed to assess the contribution of the strengthening system to the increase of the load carrying capacity of masonry elements, as well as to evaluate the damage evolution and the stiffness degradation mechanisms developing under cyclic loading.; This research was carried in the framework of InoTec, Innovative material of ultra-high 16 ductility for the rehabilitation of the built patrimony, funded by COMPETE/QREN/FEDER 17 (NORTE-07-0202-FEDER-023024). InoTec project is promoted by CiviTest company 18 and University of Minho. S&P Clever Reinforcement Ibérica is gratefully acknowledged 19 for providing the materials used in the strengthening of the masonry specimens.

Cyclic load testing for integrity evaluation of prestressed concrete girders

Barrios F.; Ziehl P.H.
Fonte: Universidade de Medellín Publicador: Universidade de Medellín
Tipo: Article; info:eu-repo/semantics/article
ENG
Relevância na Pesquisa
36.11%
This study is focused on the performance and validation of the 24-hour load test (24h LT) method and the cyclic load test (CLT) method as applied to full-scale lightweight and normalweight self-consolidating prestressed concrete girders. This study examines data obtained from the four-point loading tests of six full-scale T-girders and applies the current criteria from these methodologies to evaluate the presence of damage and structural integrity. The experimental results indicate that the recovery criteria of the 24h LT method were insensitive to damage and hence did not provide a satisfactory integrity assessment of the members. Also, the permanency and repeatability criteria of the CLT were insensitive to damage for the girders studied. The global integrity parameter (GIP) based on the deviation from linearity criterion from the CLT is proposed for the quantitative assessment of the level of damage in prestressed concrete girders, and the results indicate good correlation with the experimental data. © 2012, American Concrete Institute.

The effect of brushing motion on the cyclic fatigue of rotary nickel titanium instruments

Gambarini,Gianluca; Tucci,Eugenio; Bedini,Rossella; Pecci,Raffaella; Galli,Massimo; Milana,Valerio; De Luca,Massimo; Testarelli,Luca
Fonte: Istituto Superiore di Sanità Publicador: Istituto Superiore di Sanità
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/12/2010 EN
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36.08%
The goal of the study is to evaluate if the use of rotary nickel-titanium (RNT) instruments, as Hedstroem files, is safe. Twelve twisted files (TF) RNT instruments size 06-25 were selected and randomly divided in 2 groups of 6 instruments each. Group A (new instruments) were used as control. Group B (test) instruments were clinically used only as Hedstroem files in a canal that had been previously instrumented to the working length with other 06-25 RNT instruments. Group B instruments were used only in the straight portion of the canal (1 minute at 1000 rpm). A cyclic fatigue test was performed for each instrument of groups. Data were statistically analyzed (Student's t-test). Results showed no significant difference (P > 0.05) between groups A and B. Data confirmed that the use of TF instruments as Hedstroem files is a safe procedure. Cross section images and volumes of the same instrument, before and after cyclic fatigue testing, have been obtained by means of microtomographic analysis to evaluate possible microstructure alterations.