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Análise sísmica de pórticos planos com dissipadores metálicos de energia; Seismic analysis of plane frames with metallic yield dampers

Pari, David Miguel Chalco
Fonte: Universidade de Brasília Publicador: Universidade de Brasília
Tipo: Dissertação
POR
Relevância na Pesquisa
36.06%
Dissertação (mestrado)—Universidade de Brasília, Faculdade de Tecnologia, Departamento de Engenharia Civil e Ambiental, 2014.; No âmbito dos sistemas de dissipação de energia passiva para proteção sísmica de estruturas de edifícios, os dissipadores de energia metálicos têm sido comumente usados. O foco deste trabalho está em um desses dispositivos - o amortecedor ADAS (Added Damping And Stiffness). A análise das estruturas que empregam estes dispositivos requer a utilização de métodos de análise não linear. Este trabalho apresenta uma metodologia detalhada pararealizar a análise dinâmica tempo-história não linear de pórticos planos com amortecedores ADAS pelo método dos elementos finitos. Adicionalmente mostram-se: o modelo força deslocamento bilinear para o comportamento não linear histerético do dispositivo ADAS, o algoritmo return-mapping para integrar este modelo bilinear e a idealização em elementos finitos do dispositivo ADAS. Na metodologia proposta são utilizados conjuntamente o método de Newmark, o método de Newton-Raphson e o algoritmo return-mapping para obtera resposta da estrutura ao longo do tempo.A implementação computacional desta metodologia se materializa com a criação de um programa computacional capaz de realizar a análise acima mencionada. A eficiência da metodologia proposta e a validade do programa criado são avaliadas por meio de dois exemplos académicos...

Reducing the seismic vulnerability of cultural heritage buildings

Lourenço, Paulo B.; Roca, Pere; Modena, C.; Oliveira, Daniel V.
Fonte: Institute of Theoretical and Applied Mechanics of the Academy of Sciences of the Czech Republic (ITAM) Publicador: Institute of Theoretical and Applied Mechanics of the Academy of Sciences of the Czech Republic (ITAM)
Tipo: Conferência ou Objeto de Conferência
Publicado em //2006 ENG
Relevância na Pesquisa
36.06%
European-Indian Economic Cross Cultural Programme - contract n.º ALA-95-23-2003-077-122.

Ductile connection characterization regarding seismic retrofitting of masonry buildings

Carles, Tristan Hamilton
Fonte: Universidade do Minho Publicador: Universidade do Minho
Tipo: Dissertação de Mestrado
Publicado em //2012 ENG
Relevância na Pesquisa
36.37%
Dissertação de mestrado em Structural Analysis of Monuments and Historical Constructions; Anthropological reasons apart, earthquakes are one of the most devastating causes of damage to monuments and historical constructions, and, as a consequence, lead to significant cultural, human, and economical losses. Protection of such structures against seismic excitations is thus an important factor regarding life safety and the conservation of our historical heritage. Efficient connections between structural elements can highly reduce the seismic vulnerability of masonry buildings by enhancing the out of plane behaviour of the walls regarding lateral loads which are presented as the principal cause of failure in this type of structure. In spite of the importance of structural connections regarding the global behaviour of historical constructions under seismic actions, research in this field is almost nonexistent and needs to be developed. The objective of this thesis is to study the seismic response to a ductile connection used to connect tie-rods to masonry walls in the scope of seismic retrofitting of historical constructions and to analyse its behaviour in comparison to the behaviour of the other structural elements. In seismic vulnerability assessment...

Connections and dissipative systems with early warning

Paganoni, S.; D’Ayala, D.; Miccoli, L.; Hračov, S.; Urushadze, S.; Wünsche, M.; Adami, C. E.; Vintzileou, E.; Moreira, S.; Oliveira, Daniel V.; James, P.; Cóias, Vítor
Fonte: Jerzy Jasieńko Publicador: Jerzy Jasieńko
Tipo: Conferência ou Objeto de Conferência
Publicado em /10/2012 ENG
Relevância na Pesquisa
36.06%
The global response of historic buildings is determined by the behaviour of the single structural elements as well as by their mutual connections. Consequently, in the last decades a number of technical solutions for the improvement of structural connections have been developed in response to the increasing demand in the field of the seismic protection of heritage assets. At the same time, the experimental assessment of structural strengthening techniques is a well established practice both in the scientific community and among commercial producers. It is therefore surprising how testing of connections is rarely performed and very few codes of practice deal with it. Additionally, the few existing experimental procedures for testing connections are neither standardised nor easily accessible to end users. Within the framework of the EU-funded NIKER project, Work Package 6 aims to address such technical gap through the development of procedures specific to the strengthening of structural connections of historic buildings.

Seismic-V : vernacular seismic culture in Portugal

Correia, M.; Carlos, G.; Rocha, S.; Lourenço, Paulo B.; Vasconcelos, Graça; Varum, Humberto
Fonte: Taylor and Francis Publicador: Taylor and Francis
Tipo: Conferência ou Objeto de Conferência
Publicado em //2014 ENG
Relevância na Pesquisa
36.34%
For a long time, reactive seismic retrofitting was focused on monumental heritage and very little on vernacular architecture. In the last years, there has been a growing interest on seismic resistant design and solutions and several research units emerged to produce important research in the scientific field. However, for some time, international focus to address earthquake-damaged buildings was on intrusive techniques and technological materials to retrofit monuments. This paper aims to explore how the research project SEISMIC-V intends to fill the gap regarding this critical research problem. The research will contribute to the awareness and protection of the local seismic culture. The project outcomes will provide data for the strengthening of seismic-resistant architectural components in in-use vernacular heritage.; Fundação para a Ciência e a Tecnologia (FCT)

Reforço sísmico de edifícios de habitação. Viabilidade da mitigação do risco; Seismic strengthening of residential buildings. Risk analysis and mitigation

Lamego, P.
Fonte: Universidade do Minho Publicador: Universidade do Minho
Tipo: Tese de Doutorado
Publicado em 24/02/2014 POR
Relevância na Pesquisa
36.41%
Uma das principais missões de um engenheiro civil é a garantia da segurança e protecção de pessoas e bens. Ora, é do conhecimento geral que Portugal Continental possui um historial de ocorrência de sismos de elevada intensidade e que, sempre que estes ocorrem, os danos observados são extremamente elevados. Ao mesmo tempo, verifica-se que parte do parque habitacional existente apresenta características que lhe conferem grande vulnerabilidade sísmica e que se tratam de edifícios já com alguma idade, necessitando de intervenção, tanto ao nível estrutural como ao não estrutural. Assim, surge a motivação para estudar a viabilidade da intervenção estrutural para a redução da vulnerabilidade sísmica deste edificado. Este trabalho constitui então um contributo para resolução do problema atrás mencionado, demonstrando-se de forma clara a necessidade de intervenção estrutural nas três tipologias construtivas analisadas, com a análise e verificação da vulnerabilidade sísmica dos edifícios e procedendo-se também a estudos de viabilidade económica e de desempenho do edificado. Simultaneamente, pretende-se que o mesmo seja entendido como uma ferramenta de auxílio aos técnicos especialistas na tomada de decisão. A análise da vulnerabilidade sísmica do edificado existente é realizada para cada uma das tipologias construtivas em estudo: edifícios com paredes em alvenaria de pedra e pavimentos em madeira...

Decision making under epistemic uncertainty : an application to seismic design

Agarwal, Anna
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 92 leaves
ENG
Relevância na Pesquisa
36.47%
The problem of accounting for epistemic uncertainty in risk management decisions is conceptually straightforward, but is riddled with practical difficulties. Simple approximations are often used whereby future variations in epistemic uncertainty are ignored or worst-case scenarios are postulated. These strategies tend to produce sub-optimal decisions. We develop a framework based on Bayesian decision theory that accounts for the random temporal evolution of the epistemic uncertainty and minimum safety standards, and illustrate the effects of these factors for the case of optimal seismic design of buildings. Results show that when temporal fluctuations in the epistemic uncertainty and regulatory safety constraints are included, the optimal level of seismic protection exceeds the normative level at the time of construction. We do a sensitivity analysis concerning the repair and retrofit strategies that control the repair actions following earthquake damages and the amount of structural upgrading in the case of non-compliance with the safety standards. We see, that just like the optimal initial design system, upgrades should also be made conservatively to provide a margin of safety against future adverse changes in the epistemic uncertainty and regulations. The optimal degree of conservatism depends in a complex way on the cost of providing additional seismic protection...

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
36.49%
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...

Pre-Normative Research Needs to Achieve Improved Design Guidelines for Seismic Protection

PINTO VIEIRA ARTUR; TAUCER FABIO; DIMOVA Silvia
Fonte: OPOCE Publicador: OPOCE
Tipo: EUR - Scientific and Technical Research Reports Formato: Printed
ENG
Relevância na Pesquisa
46.19%
The document provides description of the pre-normative research needs to achieve improved design guidelines for seismic protection, research priorities and possible strategies for financing the research needs identified. The EU policy context is defined in the view of the Commission Recommendation to Member States on the implementation and use of the EN Eurocodes concerning the research needs to facilitate the integration into the Eurocodes of the latest developments in scientific and technological knowledge. The background activities which headed the preparation of the document, such as the organization and participation in relevant European workshops and projects, as well as consultations with experts in the field of Earthquake Engineering, are summarized. Two background documents which have been prepared as a consequence of these activities are summarized and analyzed. The research priorities are presented in terms of the necessary time span, effort and priority of to include the results of the research into the EN Eurocodes. Possible strategies for financing the identified research needs are discussed centering on the European Institutions, as these are the most concerned in benefiting from a research that needs to be undertaken at a European level...

Substructured Pseudodynamic and Cyclic Tests on a Seismic Protection System including Steel-Teflon Bearings and Fluid Viscous Devices

SORACE Stefano; TERENZI Gloria; MAGONETTE GEORGES; MOLINA RUIZ FRANCISCO JAVIER
Fonte: American Concrete Institute Publicador: American Concrete Institute
Tipo: Contributions to Conferences Formato: CD-ROM
ENG
Relevância na Pesquisa
46.36%
An experimental investigation was carried out on a base isolation system incorporating stainless steel-Teflon bearings, operating as sliders, and silicone fluid viscous spring-dampers. In this system, the dampers are connected to the base-floor of the isolated building to provide the desired passive control of superstructure response, as well as to guarantee its complete re-centring after 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 characterising the hysteretic response of the spring-dampers, the frictional behaviour of the steel-Teflon bearings, and the combined response of their assembly. The pseudodynamic test simulated the installation of the protection system at the base of a three-story steel frame structure. The results of the performed tests, as well as of relevant mechanical interpretation and numerical simulation analyses, are presented in this paper. Keywords: pseudodynamic tests; substructuring; cyclic tests; seismic protection; sliding bearings; fluid viscous devices; base isolation; supplemental damping.; JRC.G.5-European laboratory for structural assessment

Spatial Planning and Earthquake Protection in Greece

DANDOULAKI Miranta
Fonte: Centro Comum de Pesquisa da Comissão Européia Publicador: Centro Comum de Pesquisa da Comissão Européia
Tipo: PhD Theses Formato: Printed
GRE
Relevância na Pesquisa
26.4%
The thesis examines earthquake protection in Greece as a multi-disciplinary and multi-sectoral undertaking, focussing on its relationship with spatial planning. One relevant point is examination of the hypothesis of ¿disaster as window of opportunity¿ for comprehensive reconstruction. Cornerstone of the thesis is the study of the theoretical discussion on hazards and disasters together with international policies and practices. Then earthquake protection in Greece comes into focus. Consequently spatial planning in Greece and its links with earthquake protection is examined. To supplement the written sources, research on the role of professional cultures has been carried out through semi-structured interviews with selected informants from the disciplines of civil engineering, geosciences and urban/regional planning. Finally, starting from the reconstruction of Kalamata after the 1986 earthquakes, which is a reference case for earthquake reconstruction in Greece, there is investigation of how under certain preconditions earthquake disaster can function as catalyst for broader multi-sectoral and multi-disciplinary approaches to reconstruction. Examination of earthquake protection policies in Greece in the period 1975-2005 reveals the predominant role of state policies. Earthquake protection was a national priority in preceding decades. Gradually knowledge and experience were acquired and a system was developed to deal with every phase of a disaster. The key feature of earthquake protection in Greece has been a focus on the building and its owner. Notwithstanding the positive results it has yielded...

Modeling, analysis, and comparative study of several seismic passive protective systems for structures

Wan, Yaming
Fonte: Universidade Rice Publicador: Universidade Rice
ENG
Relevância na Pesquisa
36.16%
This thesis is concerned with passive control systems for seismic protection of building structures, with special emphasis on elastomeric bearings, viscous dampers and tuned mass dampers. Both mathematical modeling and earthquake response analysis techniques are presented for this class of problems. Earthquake response simulations are carried out for a six-story L-shaped building equipped with these protective systems and subjected to three real earthquake ground excitations, namely the El Centro 1940, Orion Blvd 1971 and Capitola 1989 earthquake records. Both deterministic and stochastic earthquake ground excitations are considered. The performance and effectiveness of these passive protective systems are studied mainly in the time domain with some considerations of the frequency domain. Based on all analyses performed and for the particular building structure considered, it is found that base isolation is very effective in reducing the seismic structural response, especially if it exhibits a nonlinear hysteretic behavior, since in addition to decoupling the frame structure from the ground motion, it dissipates the earthquake input energy through hysteretic action. Tuned-mass damping is less effective than viscous damping in reducing the structural response to earthquake excitations. The results also show that the characteristics of the earthquake ground excitation represent a very important factor which influences the performance of the three passive earthquake protective systems studied herein...

Seismic response control of structures using novel adaptive passive and semi-active variable stiffness and negative stiffness devices

Pasala, Dharma Theja
Fonte: Universidade Rice Publicador: Universidade Rice
ENG
Relevância na Pesquisa
46.16%
Current seismic design practice promotes inelastic response in order to reduce the design forces. By allowing the structure to yield while increasing the ductility of the structure, the global forces can be kept within the limited bounds dictated by the yield strength. However, during severe earthquakes, the structures undergo significant inelastic deformations leading to stiffness and strength degradation, increased interstory drifts, and damage with residual drift. The research presented in this thesis has three components that seek to address these challenges. To prevent the inelastic effects observed in yielding systems, a new concept “apparent weakening” is proposed and verified through shake table studies in this thesis. “Apparent weakening” is introduced in the structural system using a complementary “adaptive negative stiffness device” (NSD) that mimics "yielding” of the global system thus attracting it away from the main structural system. Unlike the concept of weakening and damping, where the main structural system strength is reduced, the new system does not alter the original structural system, but produces effects compatible with an early yielding. Response reduction using NSD is achieved in a two step sequence. First the NSD...

Dynamic stability of elastomeric seismic isolation bearings and seismic protection using enhanced adaptive negative stiffness system

Vemuru, Venkata
Fonte: Universidade Rice Publicador: Universidade Rice
Relevância na Pesquisa
66.43%
In this study the issue of stability of elastomeric bearings subjected to extreme dynamic loading is studied in detail and response reduction strategies in structures both fixed base and base-isolated structures using a negative stiffness device (NSD) are evaluated. For response reduction, the composite response spectrum approach is utilized to provide a comprehensive representation of the trade-offs associated with each choice of design strategies. A comprehensive database of strong ground motion is used to study the suitability of NSD for seismic protection. The spectral characteristics of all the ground motions selected are identified using a mathematical model and the characteristics of the ground motion that affect the structural assembly and the response reduction strategies considered are evaluated. The results of the study are organized based on the identified characteristics of ground motion to demonstrate the effectiveness of the negative stiffness device for response reduction. The analytical study takes into account both linear fixed base structures as well as base-isolated structures equipped with linear and nonlinear dampers. For stability of elastomeric bearings, detailed analytical models that capture the nonlinear behavior of the bearings under extreme axial loads and horizontal displacements are developed...

Places of fear and attachment. How Azoreans perceive seismic and volcanic risk.

Rego, Isabel Estrela; Arroz, Ana Margarida Moura
Fonte: GJCPP Editorial Board Publicador: GJCPP Editorial Board
Tipo: Artigo de Revista Científica
Publicado em /12/2012 ENG
Relevância na Pesquisa
36.27%
Copyright © 2012 Global Journal of Community Psychology Practice by GJCPP Editorial Board is licensed under a Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported License.; Earthquakes and volcanic eruptions have been regular phenomena in the Azores. In spite of the knowledge already gathered by local historians and earth sciences researchers, there are no scientific data on the socio- cultural dimensions of volcanic and seismic risks. A research project on risk perception of natural hazards (TOPOI METUS) is now being carried out in order to study the social cosmographies of seismic and volcanic hazard. Based on data produced along fourteen in-depth extensive interviews conducted in five of the nine islands of the archipelago, this presentation focuses on preliminary findings of perceptions regarding seismic and volcanic risk profiles, patrimonial and economic vulnerability to those risks, and risk management (i.e. information and actions taken before a crisis, and during the response and recovery phases of a disaster situation). Exploratory results show that people living in the most vulnerable areas insist in staying there, even when they are aware of the dangerousness involved in it. To uncover the apparently irrational reasons beneath these options will allow understanding some of the barriers encountered by risk managers engaged in the minimization of destructive impacts of those natural hazards. Knowing that people both 'put themselves in the Hands of God' and highly identify with the patrimonial history of their living place may help to develop knowledge to more fully inform civil protection/defence policies. Results may also allow reconceptualising the variable "identification with the local" in the scope of risk perception.

Social Housing Protection

Soluciones Integrales de Reduccion de Vibracioness a; Mauricio Bulnes Bulnes Carrasco
Fonte: Corporação de Fomento da Produção Publicador: Corporação de Fomento da Produção
Tipo: Proyecto
Publicado em 29/08/2011
Relevância na Pesquisa
36.19%
This project focuses on developing seismic solutions for social and public housing that will contribute to improve their safety; Globally comercialize a new seismic protection for low income household; Corporación de Fomento de la Producción

Integrated seismic and cone penetration test observations at a distressed earthen levee: Marrero, Louisiana, U.S.A.

Vera Sommer, Emilio Eduardo; Hicks, Jason; Lorenzo, Juan M.
Fonte: Elsevier Publicador: Elsevier
Tipo: Artículo de revista
EN
Relevância na Pesquisa
26.36%
Artículo de publicación ISI; Seismic refraction velocity-versus depthmodels can complement our understanding of natural soils beneath flood protection levees at locations between geotechnical sites. Levee failures in New Orleans in 2005 are attributable in part to poor understanding of sediments between geotechnical sites. To a first order, subsurface fluvial–deltaic facies in the lower Mississippi delta plain correlate with general geotechnical properties of water content and cohesive strength, but are too laterally variable to be easily predicted from geotechnical sites spaced 100 mapart. An artificial earthen levee, suitable for seismic investigation, lies ~15 km S of the city of New Orleans, Louisiana. Values of shear-wave velocity (VSH) versus depth (0–20 m) are derived by forward-ray-trace models of seismic refraction arrivals which match key boundaries identified at (geotechnical) cone-penetration testing sites, spaced at 300 m apart. In particular, a 100-m section along the levee crest shows continuous cracks which are as much as 10 cm wide, and 30 cm deep at their northern end. Cracking may relate to high strain, induced by variable near-surface subsidence of organic-rich sediments. Topographic cross-sections across the levee show variable differential subsidence of 1–2 m. Based on effective medium theory...

Artificial Seismic Shadow Zone by Acoustic Metamaterials

Kim, Sang-Hoon; Das, Mukunda P.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
26.51%
We developed a new method of earthquakeproof engineering to create an artificial seismic shadow zone using acoustic metamaterials. By designing huge empty boxes with a few side-holes corresponding to the resonance frequencies of seismic waves and burying them around the buildings that we want to protect, the velocity of the seismic wave becomes imaginary. The meta-barrier composed of many meta-boxes attenuates the seismic waves, which reduces the amplitude of the wave exponentially by dissipating the seismic energy. This is a mechanical method of converting the seismic energy into sound and heat. We estimated the sound level generated from a seismic wave. This method of area protection differs from the point protection of conventional seismic design, including the traditional cloaking method. The meta-barrier creates a seismic shadow zone, protecting all the buildings within the zone. The seismic shadow zone is tested by computer simulation and compared with a normal barrier.; Comment: 4 pages, 3 figures

Seismic auxetic metamaterials as novel earthquake protections

Ungureanu, Bogdan; Achaoui, Younes; Enoch, Stefan; Brûlé, Stéphane; Guenneau, Sébastien
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 29/10/2015
Relevância na Pesquisa
26.34%
We propose that wave propagation through a class of elastodynamic metamaterials opens unprecedented avenues in seismic wave protection based on spectral properties of auxetic metamaterials. The elastic parameters of these metamaterials, like the Poisson ratio {\nu}, bulk modulus B, shear modulus G, or the mass density \r{ho}0, are known to exhibit negative values in elastic stop bands. We show here that the propagation of seismic waves with different frequencies can be influenced by a meter scale version of auxetic metamaterials buried in the soil. More precisely, we numerically examine and illustrate the markedly different behaviors between the propagation of seismic waves through a continuum isotropic elastic medium (concrete) and our seismic auxetic metamaterials utilized here like a foundation of the building one would like to protect. This novel class of seismic metamaterials opens band gaps at frequencies compatible with seismic waves when they are designed appropriately, what makes them interesting candidates for seismic isolation structures.

New Finite Element Models and Seismic Analyses of the Telescopes at WM Keck Observatory

Kan, Frank W.; Sarawit, Andrew T.; Callahan, Shawn P.; Pollard, Mike L.
Fonte: Society of Photo-Optical Instrumentation Engineers Publicador: Society of Photo-Optical Instrumentation Engineers
Tipo: Book Section; PeerReviewed Formato: application/pdf
Publicado em 22/07/2014
Relevância na Pesquisa
26.34%
On 15 October 2006 a large earthquake damaged both telescopes at Keck observatory resulting in weeks of observing downtime. A significant portion of the downtime was attributed to recovery efforts repairing damage to telescope bearing journals, radial pad support structures and encoder subsystems. Inadequate damping and strength in the seismic restraint design and the lack of break-away features on the azimuth radial pads are key design deficiencies. In May, 2011 a feasibility study was conducted to review several options to enhance the protection of the telescopes with the goal to minimize the time to bring the telescopes back into operation after a large seismic event. At that time it was determined that new finite element models of the telescope structures were required to better understand the telescope responses to design earthquakes required by local governing building codes and the USGS seismic data collected at the site on 15 October 2006. These models were verified by comparing the calculated natural frequencies from the models to the measured frequencies obtained from the servo identification study and comparing the time history responses of the telescopes to the October 2006 seismic data to the actual observed damages. The results of two finite element methods...