Página 1 dos resultados de 54 itens digitais encontrados em 0.005 segundos

R&D on control of vibrations under covicocepad during 2007-2008

Barros, R.C.; Baratta, A.; Corbi, O.; Braz César, M.T.; Corbi, I.; Bairrão, R.; Guerreiro, L.; Oliveira, C.; Magonette, G.
Fonte: Instituto Politécnico de Bragança Publicador: Instituto Politécnico de Bragança
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
46.21%
This paper provides information on the latest R&D within COVICOCEPAD project approved in the framework of Eurocores program. It addresses the use of TLD, base isolation devices, MR dampers and a hybrid technique using both devices together. Some results are provided associated with calibration of a MR damper at FEUP, as well as its inclusion in a small scale laboratory set-up with proper equations of motion of the controlled smart structure. An application of semi-active control technique to a bridge is outlined. Further remarks and details on future tests to be performed in LNEC shaking table, within COVICOCEPAD project, are provided.

Stone masonry buildings : shaking table testing and advanced methods of analysis

Lourenço, Paulo B.; Mendes, N.; Ramos, Luís F.; Scappaticci, T.; Yang, G.
Fonte: Universidade do Minho Publicador: Universidade do Minho
Tipo: Conferência ou Objeto de Conferência
Publicado em //2011 ENG
Relevância na Pesquisa
46.21%
The paper presents the main results of experimental tests concerning the reduction of the seismic vulnerability of stone masonry buildings with flexible floors. Two mock-ups (original condition and repaired) were tested in a 3D shaking table. The results show that the adopted measures are efficient. A set of non-linear static analyses (pushover) were considered, together with time integration analysis. The non-linear dynamic analyses reproduced the seismic behavior observed in the seismic tests. However, the pushover analyses did not simulate correctly all the failure mode of the structure and should be used with caution.

On the influence of masonry infills in concrete buildings

Leite, João C.; Lourenço, Paulo B.
Fonte: Universidade do Minho Publicador: Universidade do Minho
Tipo: Conferência ou Objeto de Conferência
Publicado em //2010 ENG
Relevância na Pesquisa
46.14%
The stresses induced in a structure by a seismic action have a low probability of occurrence and their magnitude is such that the structure is forced beyond the ultimate limit state. The effective standards in Portugal, and the ones that will be effective shortly, consider the possibility of a seismic action in all the territory, fact that has been neglect by designers and authorities in the last years. This new standard, Eurocode 8, Design of structures for earthquake resistance, defines new standards for infill walls, imposing the use of reinforcement but failing to give detailed information besides the type of reinforcement. Furthermore, the structural designer is the responsible for these non-structural elements. Therefore, with the goal of contributing to the creation of simple design rules for these infills, a shaking table test program of reinforced concrete frame buildings with infill walls, reinforced and unreinforced, will be carried out. Predeceasing these tests, different numerical simulations of the buildings were carried out, with two main objectives: i) understand the behavior of the structure when subjected to a seismic action, in order to more accurately define the experimental program; ii) using different computational programs and numerical elements to perform static non-linear analyses...

Shaking table tests of stone masonry buildings

Mendes, N.; Lourenço, Paulo B.; Costa, Alfredo Campos
Fonte: Universidade do Minho Publicador: Universidade do Minho
Tipo: Conferência ou Objeto de Conferência
Publicado em //2010 ENG
Relevância na Pesquisa
76.39%
This paper presents the main results of experimental tests concerning the reduction of the seismic vulnerability of stone masonry buildings with flexible floors. The tests were performed in the LNEC 3D shaking table by imposing artificial accelerograms in two horizontal uncorrelated orthogonal directions, triggering in-plane and out-of-plane response of two tested mock-ups; one in original condition and another repaired. The preliminary results show that adopted measures are efficient, allowing to improve the seismic performance of this building typology.

Solutions for infilled masonry buildings : shaking table tests

Leite, João C.; Lourenço, Paulo B.
Fonte: Universidade Federal de Santa Catarina (UFSC) Publicador: Universidade Federal de Santa Catarina (UFSC)
Tipo: Conferência ou Objeto de Conferência
Publicado em //2012 ENG
Relevância na Pesquisa
76.27%
Infilled masonry can be seen as an old research issue, but recent seismic activities, such as the 2009 Aquila earthquake in Italy, showed seismic engineers and structural designers that current infill solutions may not work as expected. In this seismic action, the analysis of the damages in buildings constructed in the last 20 years, designed according to modern standards, may lead to the worrying conclusion that the design Limit States were not fulfilled. Taking this into account, a research program was conducted as a partnership between the University of Minho, Portugal, and the National Laboratory for Civil Engineering (L.N.E.C.), Portugal, which included a shaking table experimental program. The objective of this program was to study the seismic behaviour of the most common infill solution in Portugal, the unreinforced double leaf clay brick masonry, and two reinforced solutions referenced in the standard Eurocode 8: i) single leaf clay brick with bed joint reinforcement, connected to the bounding frame; ii) single leaf clay brick with steel net in the plaster, connected to the bounding frame. The present paper details the first two tested solutions, along with the discussion of the results, focusing on the obtained collapse modes of the infills and the measured accelerations for those modes.

Experimental investigation on the seismic behaviour of new concrete block masonry buildings

Avila, Leonardo; Vasconcelos, Graça; Lourenço, Paulo B.
Fonte: Humberto Ramos Roman e Guilherme Aris Parsekian Publicador: Humberto Ramos Roman e Guilherme Aris Parsekian
Tipo: Conferência ou Objeto de Conferência
Publicado em /06/2012 ENG
Relevância na Pesquisa
46.21%
The present work deals with the experimental validation of a new structural solution for concrete block masonry buildings. Dynamic tests of two identical two-­story concrete block masonry models were performed on a shaking table in reduced scale 1:2, with focus on the global behavior. Both models were tested in the two orthogonal horizontal components with uncorrelated artificial accelerograms compatible with the elastic response spectrum defined by Eurocode 8. The first model was tested in reinforced conditions following the same code, while the second building was tested as an unreinforced solution. The identification of the dynamic properties using modal analysis (based on input-­output techniques) as well as the seismic evaluation of both buildings is presented. In the experimental tests, various input motions with incremental amplitude were implemented. The damage identification through stiffness degradation is studied. Furthermore, the experimental analysis encompasses parameters as the cracking patterns with consequence collapse mechanisms. In-­plane and out of plane behavior in terms of displacements and lateral drifts are discussed. Findings related to the global dynamic behavior and comparisons between the results of the two buildings are also presented.

Seismic assessment of ancient masonry buildings : shaking table tests and numerical analysis

Mendes, N.
Fonte: Universidade do Minho Publicador: Universidade do Minho
Tipo: Tese de Doutorado
Publicado em 21/12/2012 ENG
Relevância na Pesquisa
66.51%
Tese de doutoramento em Estruturas - Engenharia Civil; Ancient masonry buildings were built for many centuries taking into account only vertical static loads, without reference to any particular seismic code. The different types of masonry present common features that are directly related to the high seismic vulnerability of this type of buildings, such as the high specific mass, the low tensile strength, low to moderate shear strength and low ductility (brittle behaviour). Besides the material properties, the seismic behaviour of ancient masonry buildings depends on other factors, such as geometry of the structure, connection between orthogonal walls, connections between structural walls and floors, connections between walls and roof, foundation strength, stiffness of the floors and strength of the non-structural elements. The Portuguese housing stock consists of several building typologies in which some of them present construction features associated with poor seismic performance. Thus, it is necessary to intervene in these types of buildings with the purpose of reducing their seismic vulnerability. The “gaioleiro” buildings correspond to a Portuguese building typology, built between the 19th century and the beginning of the 20th century...

Seismic analysis of a 2-storey log house

Branco, Jorge M.; Lourenço, Paulo B.; Aranha, C.
Fonte: Trans Tech Publications Publicador: Trans Tech Publications
Tipo: Artigo de Revista Científica
Publicado em //2013 ENG
Relevância na Pesquisa
46.14%
The current paper deals with the analysis of the results yielded by a series of tests performed to evaluate the seismic behaviour of a model log construction. The study was based on an experimental investigation performed to improve the existing knowledge on log houses subject to seismic events. The main part of the experimental work is based on a full scale shaking table test, conducted on a two-storey log house designed by the Portuguese company Rusticasa® in compliance with design rules for timber buildings. The test was performed by the University of Minho within the framework of the SERIES Project ‘Multi-storey timber buildings’ and was coordinated by the University of Trento, at LNEC, Lisbon, Portugal. The geometry of the specimen, the design of the test, the setup and the instrumentation layout are first presented in this paper. The test procedure was conducted in stages with maximum accelerations (bi-directional) of 0.07g, 0.28g and 0.5g. The experimental results of each test have been analyzed and the resultant values of inter-storey drift, wall slippage and uplift measurements, shear deformations and hold-down forces measured are presented. Most importantly, the dynamic properties (fundamental period and mode shapes) of the system have been determined.

Modal identification and stiffness degradation of concrete block masonry buildings

Avila, Leonardo; Lourenço, Paulo B.; Vasconcelos, Graça; Mendes, N.
Fonte: IOMAC 2013 Publicador: IOMAC 2013
Tipo: Conferência ou Objeto de Conferência
Publicado em //2013 ENG
Relevância na Pesquisa
56.21%
A new construction system for masonry buildings is analysed. Identification of modal parameters has been carried out in two structural solutions by using this system namely reinforced and unreinforced symmetric two-story concrete block masonry buildings. Experimental shaking table tests were developed on these buildings by incremental inputs. Traditional modal analysis by using low amplitude input motion was made before and after dynamic tests and stiffness degradation has been correlated. Mode shapes, mode frequencies, damping ratios and damage identification through the test are discussed.

Modern masonry structures and earthquakes : reinforced or unreinforced?

Lourenço, Paulo B.; Vasconcelos, Graça
Fonte: Universidade do Minho Publicador: Universidade do Minho
Tipo: Artigo de Revista Científica
Publicado em 02/12/2013 ENG
Relevância na Pesquisa
56.14%
The evolution of structural masonry is briefly reviewed, from old thrust line behavior to modern global behavior using shear walls. For modern structural masonry, the use of unreinforced, confined and reinforced masonry is addressed in seismic areas. A first focus is given to recent approaches towards the safety assessment of unreinforced masonry buildings and their performance in shaking table tests. Subsequently, building systems for modern masonry structures recently developed and tested at University of Minho are presented, one based on lightweight concrete blocks and another based on normal concrete blocks. The experimental and numerical work carried out is discussed and conclusions on the performance of the systems are given.

Development and experimental validation of building systems for masonry housing in seismic areas

Lourenço, Paulo B.; Vasconcelos, Graça; Avila, Leonardo
Fonte: CNIS Publicador: CNIS
Tipo: Artigo de Revista Científica
Publicado em //2013 ENG
Relevância na Pesquisa
56.14%
The evolution of structural masonry is briefly reviewed, from old thrust line behavior to modern global behavior using shear walls. For modern structural masonry, the use of unreinforced, confined and reinforced masonry is addressed in seismic areas. A first focus is given to recent approaches towards the safety assessment of unreinforced masonry buildings and their performance in shaking table tests. Subsequently, building systems for modern masonry structures recently developed and tested at University of Minho are presented, one based on lightweight concrete blocks and another based on normal concrete blocks. The experimental and numerical work carried out is discussed and conclusions on the performance of the systems are given.; La evolución de la mampostería estructural se revisa brevemente, del anterior comportamiento con líneas de empuje al comportamiento global moderno con muros de cortante. Para mampostería estructural moderna, su uso como no reforzada, confinada y reforzada se trata en zonas sísmicas. Un primer enfoque se da a los abordajes recientes hacia la evaluación de la seguridad de los edificios de mampostería no reforzada y su desempeño en pruebas en mesa sísmica. Posteriormente, los sistemas de construcción para estructuras de mampostería modernos recientemente desarrollados y probados en la Universidad de Minho se presentan...

Shaking table testing of an existing masonry building : assessment and improvement of the seismic performance

Mendes, N.; Lourenço, Paulo B.; Costa, Alfredo Campos
Fonte: John Wiley & Sons Publicador: John Wiley & Sons
Tipo: Artigo de Revista Científica
Publicado em //2014 ENG
Relevância na Pesquisa
66.39%
This paper aims to assess and improve the seismic performance of an existing masonry building with flexible floors, representative of a Portuguese building typology—‘gaioleiro’ buildings. The study involved seismic tests and dynamic identification tests of two models (nonstrengthened and strengthened) in the shaking table. Each model was subjected to several seismic tests with increasing amplitude. . Before the first test and after each seismic test, the dynamic identification of the model was carried out, aiming at obtaining their seismic vulnerability curves based on a damage indicator obtained from the decrease of the frequencies of the modes. In the strengthened model, steel elements were used to improve the connection between walls and floors, together with ties in the upper stories. The results show that adopted strengthening technique is effective for reducing the seismic vulnerability of ‘gaioleiro’ buildings, namely for improving the out-of-plane behavior of the facades.

Experimental and numerical analysis of the seismic performance of concrete block masonry buildings

Velez, Leonardo Avila; Vasconcelos, Graça; Lourenço, Paulo B.
Fonte: Universidade do Minho Publicador: Universidade do Minho
Tipo: Conferência ou Objeto de Conferência
Publicado em 25/11/2014 ENG
Relevância na Pesquisa
56.25%
The increase in housing demand and the construction cost of the necessary houses for its satisfaction have motivated the study of economical and efficient solutions aiming at developing new construction methods. A new solution for the construction of residential houses is presented. Dynamic seismic tests by using a shaking table were performed on two masonry buildings. The first experimental model incorporates steel reinforcement according to the Eurocodes, while the second was tested as an unreinforced solution. A numerical model for the unreinforced solution was prepared by using macro-modelling approach. Five non-linear phased dynamic analyses with time integration representing the same seismic amplitude tests implemented during the experimental campaign were made. In terms of experimental results, the quantitative parameters for both models and the crack patterns are presented. Comparisons between the experimental results and those from the numerical simulations are also presented.; Portuguese Agency of Innovation (ADI).

Analysis on Two Typical Landslide Hazard Phenomena in The Wenchuan Earthquake by Field Investigations and Shaking Table Tests

Yang, Changwei; Zhang, Jianjing; Liu, Feicheng; Bi, Junwei; Jun, Zhang
Fonte: MDPI Publicador: MDPI
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
66.21%
Based on our field investigations of landslide hazards in the Wenchuan earthquake, some findings can be reported: (1) the multi-aspect terrain facing empty isolated mountains and thin ridges reacted intensely to the earthquake and was seriously damaged; (2) the slope angles of most landslides was larger than 45°. Considering the above disaster phenomena, the reasons are analyzed based on shaking table tests of one-sided, two-sided and four-sided slopes. The analysis results show that: (1) the amplifications of the peak accelerations of four-sided slopes is stronger than that of the two-sided slopes, while that of the one-sided slope is the weakest, which can indirectly explain the phenomena that the damage is most serious; (2) the amplifications of the peak accelerations gradually increase as the slope angles increase, and there are two inflection points which are the point where the slope angle is 45° and where the slope angle is 50°, respectively, which can explain the seismic phenomenon whereby landslide hazards mainly occur on the slopes whose slope angle is bigger than 45°. The amplification along the slope strike direction is basically consistent, and the step is smooth.

INNOVATIVE TECHNOLOGIES FOR THE VIBRATION CONTROL OF EQUIPMENT IN CRITICAL FACILITIES

REGGIO, ANNA
Fonte: La Sapienza Universidade de Roma Publicador: La Sapienza Universidade de Roma
Tipo: Tese de Doutorado
EN
Relevância na Pesquisa
66.21%
The present thesis settles in the framework of the dynamic modelling, seismic mitigation and permanent health monitoring of equipment in critical facilities. The main objective is to assess the feasibility and the effectiveness of innovative mitigation Technologies including: the passive isolation of a single equipment (equipment isolation systems); the passive isolation of a raised floor, on which a group of several equipment is anchored (isolated raised-floor systems); a non-conventional Tuned Mass Damper (TMD), realized by converting a large mass already present on the structure, e.g. the mass of an equipment, into a tuned mass, in order to reduce the structural response. The area of research is believed to have the potential for a wide application, since a still limited number of authors has addressed the theoretical and technical issues associated with the seismic design and protection of equipment. As a result, international seismic codes and standards also appear to be inadequate in this regard. Furthermore, the proposed technologies give the opportunity of addressing topics of significant scientific interest: the analysis of the dynamic interaction between an equipment and its supporting structure, generally neglected in current Literature and seismic codes; the definition of reduced-order generalized models...

Apparent Damping Induced by Spurious Pitching in Shaking-Table Testing

MOLINA RUIZ FRANCISCO JAVIER; MAGONETTE GEORGES; VIACCOZ BERNARD; GERADIN MICHEL
Fonte: JOHN WILEY & SONS LTD Publicador: JOHN WILEY & SONS LTD
Tipo: Articles in Journals Formato: Printed
ENG
Relevância na Pesquisa
46.45%
A seismic shaking-table test performed on a one-storey steel frame with an 8 ton RC floor slab was reproduced on a similar specimen by means of the pseudo-dynamic (PsD) method. A satisfactory agreement of the results could only be achieved after recalibration of the theoretical mass in the PsD equation and proper inclusion in the PsD test input of the horizontal and pitching accelerations measured on the table. In the shaking-table test, the spurious pitching motion produced a significant increase in the apparent damping that could be estimated as a function of the pitching dynamic flexibility of the system. Dynamic and PsD snap-back tests were also performed to provide an additional check of the reliability of the PsD method. The spurious pitching motion of the shaking table should always be measured during the tests and reported as a mean to increase the reliability and usefulness of the results.; JRC.G.5-European laboratory for structural assessment

SEISMIC PERFORMANCE OF GEOSYNTHETIC-SOIL RETAINING WALL STRUCTURES

Zarnani, Saman
Fonte: Quens University Publicador: Quens University
Tipo: Tese de Doutorado
EN; EN
Relevância na Pesquisa
56.48%
Vertical inclusions of expanded polystyrene (EPS) placed behind rigid retaining walls were investigated as geofoam seismic buffers to reduce earthquake-induced loads. A numerical model was developed using the program FLAC and the model validated against 1-g shaking table test results of EPS geofoam seismic buffer models. Two constitutive models for the component materials were examined: elastic-perfectly plastic with Mohr-Coulomb (M-C) failure criterion and non-linear hysteresis damping model with equivalent linear method (ELM) approach. It was judged that the M-C model was sufficiently accurate for practical purposes. The mechanical property of interest to attenuate dynamic loads using a seismic buffer was the buffer stiffness defined as K = E/t (E = buffer elastic modulus, t = buffer thickness). For the range of parameters investigated in this study, K ≤ 50 MN/m3 was observed to be the practical range for the optimal design of these systems. Parametric numerical analyses were performed to generate design charts that can be used for the preliminary design of these systems. A new high capacity shaking table facility was constructed at RMC that can be used to study the seismic performance of earth structures. Reduced-scale models of geosynthetic reinforced soil (GRS) walls were built on this shaking table and then subjected to simulated earthquake loading conditions. In some shaking table tests...

Automatización del equipo de simulación sísmica uniaxial del laboratorio de estructuras; Automation of the Uniaxial Earthquake Simulator in the Structures Laboratory

Bernal Ruiz, Nestor Mauricio; Carrillo, Julián; Aponte, Jorge
Fonte: Universidad Militar Nueva Granada; Facultad de Ingeniería; Ingeniería en Mecatrónica Publicador: Universidad Militar Nueva Granada; Facultad de Ingeniería; Ingeniería en Mecatrónica
Tipo: bachelorThesis; Trabajo de grado Formato: pdf; pdf
SPA
Relevância na Pesquisa
46.33%
Las consecuencias catastróficas de los sismos ocurridos en el mundo durante los últimos años han incentivado estudios experimentales para evaluar los efectos sísmicos sobre las estructuras. En este trabajo se presentan los resultados del diseño de una mesa vibratoria uniaxial neumática, para ensayos de estructuras a escala reducida. La mesa es capaz de simular los efectos sísmicos en estructuras con peso máximo de 10 kN. El informe está dividido en tres secciones principales. En la primera sección se presenta la evaluación del problema, una revisión de la literatura y la recolección de datos disponibles. En la segunda sección se evalúan diferentes propuestas de diseño con base al análisis de montaje, movimiento y cimentación, y se desarrolla el diseño correspondiente. En esta etapa se eligieron los elementos mecánicos que permiten el movimiento de la mesa, luego se validó el desempeño del sistema a partir de herramientas de simulación de elementos finitos (FEA), y finalmente, se realizó la automatización de la mesa por medio de la selección de componentes neumáticos y un control on-off con sistema de lazo abierto, realizando pruebas y simulaciones. En la tercera sección se presentan las conclusiones del proyecto y las recomendaciones para futuros trabajos. La utilidad de esta mesa vibratoria...

EVALUATION OF MASS-RIG SYSTEMS FOR SHAKING TABLE EXPERIMENTS

CARRILLO,JULIAN; GONZALEZ,GIOVANNI; LLANO,LUIS
Fonte: DYNA Publicador: DYNA
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/12/2012 EN
Relevância na Pesquisa
66.39%
Shaking tables are experimental tools to assess the behavior of structures and nonstructural components under characteristic seismic vibrations. Because of the size and weight limitations of the tables, testing reduced-scale models or testing only the main structural components are normally necessary. In these cases, to comply with modeling requirements, large amount of extra-mass should be added to the specimen. This paper reviews and discusses the mass-rig systems for shaking table testing. The advantages and drawbacks of each system are critically compared. To avoid the risk of lateral instability of models and to maintain the weight of test specimens within table payload, external devices for transmitting the inertial forces to the models have become a preferred choice when tests are performed using small- or medium-size shaking tables.

DEFORMATION ANALYSIS OF CONCRETE WALLS UNDER SHAKING TABLE EXCITATIONS

CARRILLO,JULIAN; ALCOCER,SERGIO M.; GONZÁLEZ,GIOVANNI
Fonte: DYNA Publicador: DYNA
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/08/2012 EN
Relevância na Pesquisa
86.39%
Deformation analysis of structural elements is a valuable tool for researching the relationship of lateral force versus shear, sliding and flexural deformations, to assess the strength mechanism of failure mode, to assign suitable values of lateral stiffness, to estimate the contribution of steel reinforcement to strength and displacement capacities, to calibrate analytical models, and to propose appropriate parameters for performance-based seismic design. An experimental and analytical study was conducted to assess the components of deformation of low-rise reinforced concrete walls. The experimental program included shaking table tests of 6 low-rise concrete walls. The method and the instrumentation schemes to allow accurate assessment of the three components of deformations for squat walls and walls with openings are proposed. It was found that the proposed method produce consistent results for the tests evaluated.