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Proposta de método de referência aplicado a retrofitting de máquinas-ferramentas; Proposal for a reference method applied to the retrofitting of machine tools

Plotegher, Silvio Luiz
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 18/12/2012 PT
Relevância na Pesquisa
37.8%
A obsolescência das Máquinas-Ferramentas (MFs) é um processo natural de envelhecimento neste tipo de equipamento. Esse processo compreende uma série de degradações tecnológicas, os quais se instalam e ocorrem em toda estrutura física de uma MF, independentemente da tecnologia utilizada. As degradações podem, no entanto, ser resultantes de vários fatores, como uso, aplicação, regime de trabalho, dentre outros. Os aspectos tecnológicos ficam mais evidentes quando se analisam as máquinas a Comando Numérico Computadorizado (CNC). Por sua vez, o CNC é um equipamento que apresenta uma evolução constante, mas que muitas vezes não pode ser facilmente incorporado às máquinas já existentes sem um processo de retrofitting anteriormente definido. Um processo de retrofitting pode ser considerado como um processo que permite aplicar incrementos tecnológicos em uma MF. Mais recentemente, diversos estudos têm apresentado tendências que fazem uma ligação entre MFs e sustentabilidade, sem, no entanto, definir ou propor modelos. Estudar os aspectos do comportamento das MFs existentes e poder aplicar recursos das novas tecnologias pode contribuir para melhorar os aspectos de sua produtividade e, por conseguinte, contribuir para uma produção mais sustentável. No entanto...

Concrete retrofitting using metakaolin geopolymer mortars and CFRP

Vasconcelos, E.; Fernandes, S.; Aguiar, J. L. Barroso de; Torgal, Fernando Pacheco
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
Publicado em 20/04/2011 ENG
Relevância na Pesquisa
37.22%
This paper presents results about the use of metakaolin based geopolymers mortars for retrofitting purposes. Two main situations are addressed, the use of geopolymeric mortars as a repairing layer or as a binding agent to insure the adhesion between CFRP sheets and the concrete substrate. Several compositions of metakaolin geopolymer mortars were executed by varying the percentage of sand/binder mass ratio and the concentration of sodium hydroxide. It was found that metakaolin geopolymer mortars show a high mechanical resistance and a relevant adhesion to the concrete substrate. Although their adhesion strength is lower than the one present by commercial pre-pack repair mortars, they are very cost-effective (5 to 10 times less expensive). On the other hand, the adhesion strength between CFRP and geopolymer mortars proved to be lower than expected which could be due to the fact that the composition of the geopolymeric mortars was not optimized and also to the fact that the CFRP used was not prone to this kind of application.

A brief overview on the retrofitting possibilities of masonry infill walls

Fangueiro, Raúl; Cunha, Fernando Eduardo Macedo; Vasconcelos, Graça; Abreu, S.
Fonte: Universidade do Minho Publicador: Universidade do Minho
Tipo: Conferência ou Objeto de Conferência
Publicado em /11/2011 ENG
Relevância na Pesquisa
37.39%
This work presents a brief review on the seismic behavior on non-loadbearing masonry walls used as masonry infills. O Some examples of inefficient performance are shown based on information available of recent earthquakes. Additionally, a literature overview on the techniques for retrofitting existing masonry infills is provided. Finally, alternative braided reinforced composite materials are briefly described and pointed out as an alternative solution for retrofitting masonry infill walls.

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
37.22%
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...

Full-scale experimental testing of retrofitting techniques in Portuguese “Pombalino” traditional timber frame walls

Poletti, Elisa; Vasconcelos, Graça; Jorge, Marco
Fonte: Taylor & Francis Publicador: Taylor & Francis
Tipo: Artigo de Revista Científica
Publicado em 25/11/2014 ENG
Relevância na Pesquisa
37.5%
Traditional timber frame walls are constructive elements representative of different timber frame buildings that are well known as one of the most efficient seismic resistant structures in the world. Timber frame walls were also used in the reconstruction of buildings of the old town of Lisbon after the earthquake of 1755 aiming at improving their seismic global behaviour. As it is important to preserve these structures, a better knowledge about their behaviour under seismic actions is important and can give some indications about possible retrofitting techniques to be used to improve the seismic performance. Due to the great rehabilitation effort currently carried out in many countries, a better understanding of retrofitting techniques is also needed. Therefore, this paper aims at providing a study on possible retrofitting techniques adopting traditional solutions such as bolts and steel plates. Static cyclic tests have been performed on retrofitted traditional timber frame walls in order to study their seismic performance. The experimental results showed the overall good seismic performance of steel plates and the more ductile behaviour of retrofitted timber frame walls with bolts.; Fundação para a Ciência e a Tecnologia (FCT)

Experimental assessment and retrofit of full-scale models of existing RC frames

Pinto, A. V.; Varum, H.; Molina, J.
Fonte: Universidade de Aveiro Publicador: Universidade de Aveiro
Tipo: Conferência ou Objeto de Conferência
ENG
Relevância na Pesquisa
27.5%
PSD tests on two full-scale models of existing non-seismic resisting RC frame structures are described. The testing program covered several aspects, namely assessment of seismic performance of existing frames without and with infill panels, retrofitting of the bare frame using Selective Retrofitting techniques, strengthening of the infill panels using shotcrete and retrofitting of the frame using K-bracing with shear-link dissipators. The main results from the tests are summarized and discussed and the conclusions are drawn. The tests on the bare frame have shown how vulnerable are existing structures constructed in the 60’s and the beneficial effects of infill panels were confirmed from the tests on the infilled frame. Important improvements, in terms of seismic performance, were achieved by the retrofitting of the frames. However, it was also confirmed that strengthening of the existing infill panels in poorly detailed frames may lead to dangerous ‘local’ failures, such as the shear out of the external columns.

Seismic analyses of a R/C building: study of a retrofitting solution

Varum, H.; Pinto, A. V.; Coelho, E.; Carvalho, E. C.
Fonte: Universidade de Aveiro Publicador: Universidade de Aveiro
Tipo: Conferência ou Objeto de Conferência
ENG
Relevância na Pesquisa
37.22%
The preliminary experimental results from the tests on a 4-storey R/C frame structure are presented and discussed. The full-scale model is representative of the common practice of 40~50 years ago in most south European countries. Special attention is devoted to the study of a retrofitting solution based on bracing and rubber dissipaters, which intends to increase stiffness and damping reducing consequently the earthquake deformation demands.

Seismic analyses of a R/C building: study of a retrofitting solution

Pinto, A. V.; Varum, H.; Coelho, E.; Carvalho, E. C.
Fonte: Universidade de Aveiro Publicador: Universidade de Aveiro
Tipo: Parte de Livro
ENG
Relevância na Pesquisa
37.22%
The preliminary experimental results from the tests on a 4-storey R/C frame structure are presented and discussed. The full-scale model is representative of the common practice of 40~50 years ago in most south European countries. Special attention is devoted to the study of a retrofitting solution based on bracing and rubber dissipaters, which intends to increase stiffness and damping reducing consequently the earthquake deformation demands.

Performance evaluation of retrofitting strategies for non-seismically designed RC buildings using steel braces

Varum, H.; Teixeira-Dias, F.; Marques, P.; Pinto, A.; Bhatti, A.
Fonte: Springer Verlag Publicador: Springer Verlag
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
27.39%
Recent major earthquakes around the world have evidenced that research in earthquake engineering must be directed to the vulnerability assessment of existing constructions lacking appropriate seismic resisting characteristics. Their retrofit or replacement should be made in order to reduce vulnerability, and consequent risk, to currently accepted levels. In this work, the efficiency of ductile steel eccentrically-braced systems in the seismic retrofitting of existing reinforced concrete (RC) buildings is studied. The retrofit technique studied consists in a bracing system with an energy dissipation device, designed to dissipate energy by shear deformation. The numerical model was calibrated with cyclic test results on a full-scale structure. The models used for the RC frame and masonry represent their real behavior and influence in the global structural response. The steel bracing system was modeled with strut rigid elements. The model for the energy dissipater device reproduces rigorously the behavior of the shear-link observed in the cyclic tests, namely in terms of shear, drift and energy dissipation. With the calibrated numerical model, a series of non-linear dynamic analyses were performed, for different earthquake input motions...

The use of attached-sunspaces in retrofitting design: the case of residential buildings in Portugal

Aelenei, Daniel; Leal, Hugo de Azevedo; Aelenei, Laura
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
Publicado em //2014 ENG
Relevância na Pesquisa
37.22%
This study addresses the energetic performance of an attached-sunspace applied to an existing residential building in Portugal. Four configurations (two attached, one integrated and one partially integrated) are studied in six different climatic zones. In addition other key parameters are considered such as ventilation (with or without natural ventilation), shading devices (one external and two internal configurations), number of glazed surface layers (single glazed and double glazed) and orientation (South, East and West). The thermal performance analysis, carried out using a dynamic simulation code, proved that energy savings for retrofitting design can be very important and that in climates with warm summers the risk of overheating can be considerably diminished through an accurate analysis based on modeling.

A performance-based approach to retrofitting unreinforced masonry structures for seismic loads; Performance-based approach to retrofitting URM structures for seismic loads

Bouchard, Keith M. (Keith Michael)
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 59, [47] leaves
ENG
Relevância na Pesquisa
27.39%
The structural inadequacy of existing unreinforced masonry (URM) buildings to resist possible seismic loading is a serious problem in many parts of the United States, including the Northeast and Midwest. The fact that many of these buildings are deemed historic structures or house critical facilities, like firehouses, emphasizes the need for an effective retrofitting program. The Federal Emergency Management Agency published a performance-based design code - FEMA 356 - in 2000 to use for analyzing and retrofitting existing structures. This code includes procedures for URM buildings. This paper applies these performance-based analysis procedures to a URM shear wall and compares the results to a modified analysis proposed by researchers. The wall is then rehabilitated using two common retrofit methods and again analyzed using the code. Recommendations are made for practicing engineers when evaluating URM structures for seismic loads.; by Keith M. Bouchard.; Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2007.; Includes bibliographical references (leaves 58-59).

Retrofitting of RC slabs against explosive loads

Wu, C.; Oehlers, D.; Xia, S.
Fonte: Tianjin University; China Publicador: Tianjin University; China
Tipo: Conference paper
Publicado em //2006 EN
Relevância na Pesquisa
27.59%
With the increase of terrorist bomb attacks on buildings, there is a need to develop advanced retrofitting techniques to strengthen structures against blast loads. Currently, several guidelines including an Australian version for retrofitting reinforced concrete (RC) structures are available for the design of retrofitting systems against seismic and monotonic loads using steel or fibre reinforced polymer (FRP) plates that can be either adhesively bonded to the surface or near surface mounted to the concrete cover. However, none of these guidelines provide advice suitable for retrofitting structures subjected to blast loads. In this paper, numerical models are used to simulate the performance of retrofitted RC slabs subjected to blast loads. Airblast pressure distributions on the surface of the slabs estimated in a previous study are used as input in the analysis. A material damage model developed previously for concrete and an elastoplastic model for steel bars are employed in this research for modelling reinforced concrete behaviour due to explosive loads. The material models and blast loading are coded into a finite element computer program LS-DYNA3D to do the analysis.With the numerical model, parametric studies are conducted to investigate RC slabs retrofitted by either externally bonded or near-surface mounted plates or GFRP sheets subjected to blast loads. Discussion is made on the effectiveness of the retrofitting system for RC slabs against blast loads.; http://202.113.13.67/colleges/civil/lzx/Welcome.html; http://scholar.ilib.cn/A-tianjdxxb-e2006z1018.html

Numerical simulation of strengthened unreinforced masonry (URM) walls by new retrofitting technologies for blast loading.

Su, Yu
Fonte: Universidade de Adelaide Publicador: Universidade de Adelaide
Tipo: Tese de Doutorado
Publicado em //2009
Relevância na Pesquisa
37.59%
Terrorism has become a serious threat in the world, with bomb attacks carried out both inside and outside buildings. There are already many unreinforced masonry buildings in existence, and some of them are historical buildings. However, they do not perform well under blast loading. Aiming on protecting masonry buildings, retrofitting techniques were developed. Some experimental work on studying the effect of retrofitted URM walls has been done in recent years; however, these tests usually cost a significant amount of time and funds. Because of this, numerical simulation has become a good alternative, and can be used to study the behaviour of masonry structures, and predict the outcomes of experimental tests. This project was carried out to find efficient retrofitting technique under blast loading by developing numerical material models. It was based on experimental research of strengthening URM walls by using retrofitting technologies under out-of-plane loading at the University of Adelaide. The numerical models can be applied to study large-scaled structures under static loading, and the research work is then extended to the field of blast loading. Aiming on deriving efficient material models, homogenization technology was introduced to this research. Fifty cases of numerical analysis on masonry basic cell were conducted to derive equivalent orthotropic material properties. To study the increasing capability in strength and ductility of retrofitted URM walls...

Analysis of retrofitted RC beam with fixed end supports against blast loads

Wu, C.; Cheng, W.; Oehlers, D.
Fonte: Trans Tech Publications Publicador: Trans Tech Publications
Tipo: Artigo de Revista Científica
Publicado em //2009 EN
Relevância na Pesquisa
27.59%
Currently, there are adequate guidelines available for FRP retrofitting RC structures against static and seismic loads. However, there is still limited information on retrofitting RC structures against short-duration dynamic loading effects such as blast loading. Due to the increasing threat of terrorism in recent years, retrofitting of RC structures against blast loading is of paramount importance in structural engineering. In this paper, a dynamic model that is based on single-degree-of-freedom (SDOF) approach is developed for the analysis of the response of retrofitted fixed end supported RC slabs subjected to blast loads. A previously validated layered capacity analysis method is used to determine the yielded and ultimate blast resistant capacity of a cross-section of a RC slab which allows varying strain rates with time along the depth of the member. The corresponding deflections are determined by plastic hinge analysis. To simplify the calculation process, a tri-linear resistance-deflection function which consists of elastic, elasto-plastic and plastic region for fixed end supported RC slabs is converted to an equivalent bilinear function. This developed model can adequately predict the retrofitted members’ response to blast loading. It is then is used to conduct a parametric study to optimise the retrofitting of RC slabs subjected to blast loading by varying the quantity...

Performance evaluation of retrofitting strategies for non-seismically designed RC buildings using steel braces

VARUM Humberto; TEIXEIRA-DIAS Filipe; MARQUES Paulo; PINTO VIEIRA Artur; QADIR-BHATTI Abdul
Fonte: SPRINGER Publicador: SPRINGER
Tipo: Articles in Journals Formato: Online
ENG
Relevância na Pesquisa
27.39%
Recent major earthquakes around the world have evidenced that research in earthquake engineering must be directed to the vulnerability assessment of existing constructions lacking appropriate seismic resisting characteristics. Their retrofit or replacement should be made in order to reduce vulnerability, and consequent risk, to currently accepted levels. In this work, the efficiency of ductile steel eccentrically-braced systems in the seismic retrofitting of existing reinforced concrete (RC) buildings is studied. The retrofit technique studied consists in a bracing system with an energy dissipation device, designed to dissipate energy by shear deformation. The numerical model was calibrated with cyclic test results on a full-scale structure. The models used for the RC frame and masonry represent their real behavior and influence in the global structural response. The steel bracing system was modeled with strut rigid elements. The model for the energy dissipater device reproduces rigorously the behavior of the shear-link observed in the cyclic tests, namely in terms of shear, drift and energy dissipation. With the calibrated numerical model, a series of non-linear dynamic analyses were performed, for different earthquake input motions...

New European Technical Rules for the Assessment and Retrofitting of Existing Structures.

LUECHINGER Paul; FISCHER Juerg; CHRYSOSTOMOU Christis; DIETEREN Gerrie; LANDON Francois; LEIVESTAD Steinar; MALAKATAS Nikolaos; MANCINI Giuseppe; MARKOVA Jana; MATTHEWS Stewart; NOLAN Thomas; NUTI Camillo; OSMANI Evelyne; RONNOW Gert; SCHNELL Juergen; TAN
Fonte: Publications Office of the European Union Publicador: Publications Office of the European Union
Tipo: EUR - Scientific and Technical Research Reports Formato: Online
ENG
Relevância na Pesquisa
27.39%
The consideration of sustainability aspects in the construction sector jointly with considerable economic interests have been the main impulse to include the work item of assessment and retrofitting of existing structures in the Mandate M/515 with a high priority. The new European technical rules will be developed using the existing organization of CEN/TC250. The present report has been worked out in the frame of CEN/TC250/WG2 activities. The report encompasses:  Part I introduces the policy framework and the CEN/TC250 initiative.  Part II is a collation of the different existing National regulations and standards in Europe with regard to existing structures.  Part III gives a prospect for CEN guidance for the assessment and retrofitting of existing structures. Having in mind the stepwise procedure for preparation of CEN Technical Documents, the contents of Part III is broader, covers more aspects, and includes more information than the normative technical recommendations. In particular, key issues are identified that require resolution and a summary of different national perspectives is provided rather than seeking to resolve all difficult technical issues during the first work step. The report presents scientific and technical background intended to stimulate debate and serves as a basis for further work to achieve a harmonized European view on the assessment and retrofitting of existing structures.; JRC.G.4-European laboratory for structural assessment

Retrofitting of interior RC beam–column joints using CFRP strengthened SHCC: Cast-in-place solution

Esmaeeli, Esmaeel; Barros, Joaquim A. O.; Sena-Cruz, José; Fasan, Luca; Li Prizzi, Fabio Raimondo; Melo, José; Varum, Humberto
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
Publicado em /04/2015 ENG
Relevância na Pesquisa
37.39%
The effectiveness of a repair strategy, for damaged RC beam–column joints, that combines strain hardening cementitious composite (SHCC) and laminates of carbon fiber reinforced polymers (CFRP laminates) is assessed in the present work. According to this technique, the existing concrete cover in the joint zone of the frame is replaced by a self-compacting SHCC. This thin layer of SHCC is reinforced with CFRP laminates that are bonded into the saw cut grooves. Two full-scale severely damaged interior RC beam–column joints were retrofitted using two different configurations of this technique: (i) applying the strengthening system to only the front and rear faces of the specimen; (ii) jacketing all sides of the elements of the specimen with the strengthening system. The effectiveness of these retrofitting configurations is assessed and compared by evaluating experimentally the hysteretic response, the dissipated energy, the degradation of secant stiffness, the displacement ductility and the failure modes of each repaired specimen, and also using the values of these indicators obtained in the virgin state of the specimens. This comparison revealed that the adopted retrofitting strategies can restore and even enhance the performance of this type of structural elements...

Factors influencing the retrofitting of existing office buildings using Adelaide, South Australia as a case study

Bruce, T.; Zuo, J.; Rameezdeen, R.; Pullen, S.
Fonte: Emerald Group Publishing Publicador: Emerald Group Publishing
Tipo: Artigo de Revista Científica
Publicado em //2015 EN
Relevância na Pesquisa
37.59%
Purpose – The purpose of this paper is to explore the barriers preventing investment in the re-use of low-grade multi-storey building stock in order to identify attributes that determine whether an existing building is suitable for retrofitting. Design/methodology/approach – Semi-structured interviews were undertaken with key industry practitioners to investigate existing practices and barriers facing low-grade building retrofits and what “ideal” multi-storey building features represent a successful investment opportunity. Findings – The findings showed that tenant commitment is necessary before any project goes ahead and that there exist many barriers influencing the investment decision. These include: high levels of asbestos found in existing buildings; changes in the National Construction Code necessitating enhanced fire safety and disability access; heritage listing; lack of awareness; overestimation of costs involved on simple and effective energy efficiency upgrades and change in tenant demands towards modern and efficient open plan offices. Many low-grade structures are privately owned inherited assets where the owners lack the expertise and capital to undertake retrofitting effectively. Research limitations/implications – The study is focused on the Adelaide CBD in South Australia but the findings are relevant to other Australian cities. Practical implications – There is room in the market for more positive and influential schemes such as the Green Building Fund that encourage more energy efficiency upgrading of these buildings. Social implications – The greater occurrence of retrofitting and re-use of older buildings...

Retrofitting the domestic built environment: investigating household perspectives towards energy efficiency technologies and behaviour

Pelenur, Marcos
Fonte: University of Cambridge; Department of Engineering Publicador: University of Cambridge; Department of Engineering
Tipo: Thesis; doctoral; PhD
EN
Relevância na Pesquisa
37.39%
Retrofitting the UK domestic built environment presents an excellent opportunity to improve its energy performance. However, retrofitting homes is a complex challenge conflated by multiple factors. Due to this complexity, a shortfall exists between the full potential and realised adoption of energy efficiency measures in the UK, a phenomenon termed the ?Energy Efficiency Gap?. While a number of technical or economic factors may help explain this gap, difficult to quantify factors, such as social motivations, barriers, and viewpoints towards energy are also significant and often under-emphasised in public policy. As such, in order to improve the understanding of the Energy Efficiency Gap and the uptake of future retrofit initiatives, this research adopted a socio-technical approach that considered social and technical retrofit factors together. Specifically, this research collected data from interviews, questionnaires, and a Q Study in the cities of Manchester and Cardiff, alongside a questionnaire that measured energy efficiency technology and behaviour preferences. An original contribution to knowledge was using the data to empirically identify motivations and barriers to adopting energy efficient technologies, as well as identifying household viewpoints towards energy use and linking them to retrofit technology and energy efficiency behaviour preferences. As a result of this research...

Modelling the feasibility of retrofitting hydropower to existing South African dams

van Vuuren,SJ; Blersch,CL; van Dijk,M
Fonte: Water SA Publicador: Water SA
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2011 EN
Relevância na Pesquisa
37.22%
An investigation was carried out with the primary objective of ascertaining whether it is possible to develop a model for determining the feasibility of retrofitting hydropower to existing dams in South Africa. The need for such a model is primarily due to the growing importance of small-scale hydropower projects resulting from the global shift towards renewable energy and the South African energy crisis, the increased price of energy and the introduction of feed-in tariffs for renewables. The model is intended for engineers, typically working on behalf of a client who would like a simple first order assessment of feasibility. It therefore takes all technical, environmental, social and financial considerations into account in order to provide a recommendation on whether or not a project would be feasible. Achieving the primary objective required an in-depth study of the theory and literature related to the current electricity situation in South Africa as well as all the different components and considerations of hydropower projects. This theoretical knowledge could then be utilised to develop a computer model which combines the most important considerations into a cohesive whole in order to make a recommendation on feasibility. The accuracy and applicability of the model could then be ascertained through testing...