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Contribuição ao estudo da instabilidade lateral de vigas pré-moldadas ; On the lateral stability of precast concrete beams

Lima, Maria Cristina Vidigal de
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 26/02/2002 PT
Relevância na Pesquisa
16.46%
A verificação da estabilidade lateral de vigas pré-moldadas merece maior atenção em vigas longas e delgadas, especialmente durante as fases transitórias, como o içamento e o transporte, e também quando se leva em conta a deformabilidade das ligações temporárias. Apresenta-se nesta tese, um estado da arte sobre o problema da instabilidade lateral em vigas pré-moldadas, a fim de situar este trabalho no contexto técnico atual, bem como estudos anteriores relacionados à torção pura e quando associada a outras solicitações. Alguns modelos numéricos foram implementados computacionalmente a fim de simular o comportamento não-linear físico de vigas de concreto armado e protendido sob ação conjunta de torção, flexão bi-lateral e força axial. O modelo adequado a situações onde a torção é predominante sobre a flexão baseia-se na analogia ao comportamento de treliça espacial e na extensão da teoria dos campos diagonais comprimidos. Os resultados numéricos obtidos foram satisfatoriamente comparados aos experimentais disponíveis na literatura técnica. Nos casos onde a flexão é predominate, utilizou-se um modelo numérico que permite calcular a rigidez à torção após a fissuração por flexão da viga, sendo este o recomendado para as análises das fases transitórias de içamento por cabos. Duas vigas longas e esbeltas de concreto armado...

Análise estrutural de vigas treliçadas de aço com mesa de concreto

Trindade, Luiz Gustavo Cruz
Fonte: Universidade Estadual Paulista (UNESP) Publicador: Universidade Estadual Paulista (UNESP)
Tipo: Dissertação de Mestrado Formato: 176 f. : il.
POR
Relevância na Pesquisa
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Pós-graduação em Engenharia Civil - FEIS; Mixed steel-concrete trusses, very efficient alternatives to overcome large spans, are generally used in commercial and industrial buildings, and railway and road bridges. In many cases, in order to enable the passage of ducts, truss beam type steel-joist must be considered. In this work, the failure capacity and the rupture mode of a simply supported steel-joist truss with 13,6 meters wide, modified warren type, has been determined by an analytical procedure as well as numerical modeling considering both a bi-dimensional linear analysis and a three-dimensional elasto-plastic analysis. In the study, permanent and variable actions have been considered as well as the prescriptions of the Brazilian code, being the results compared to the numerical analysis. It has been verified that for mixed and isolated steel-joist trusses, the diagonal and amounts have presented small values for internal forces and regions next to the support have reached the yielding limit. Despite of that, the mixed action for the mixed trusses has been observed. Besides, the load resistance force design has been verified for both the analytical and numerical analysis, being the bigger displacements computed with the numerical modeling; As treliças mistas em aço-concreto...

Um estudo sobre ligações do tipo YT de barras afastadas de seções tubulares circulares laminadas de aço; A study of gap YT joints circular hollow steel sections

Rosilene de Fatima Vieira
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 26/02/2007 PT
Relevância na Pesquisa
16.37%
Este trabalho apresenta os resultados de uma análise teórica, experimental e numérica, de uma ligação YT utilizada em estruturas metálicas planas, tendo como ponto de partida a verificação do comportamento global da ligação. Será avaliada uma ligação de treliça do tipo YT com diferentes afastamentos entre as barras "gap". As barras que compõem a ligação, aqui apresentada, possuem seções transversais tubulares circulares, vazadas de parede fina, soldadas entre si. O modo de colapso da ligação foi devido à plastificação da parede do banzo (uma diagonal tracionando a parede do banzo e o montante comprimindo). Um efeito de abaulamento da seção transversal do banzo na região do afastamento foi observado. O dimensionamento da ligação segue o Método dos Estados Limites, no qual as resistências de cálculo são verificadas. As barras envolvidas nesta ligação também sofrem a influência de momentos fletores. O estudo foi realizado através de uma análise comparativa entre uma solução analítica fornecida por normas técnicas internacionais, uma análise experimental e uma modelagem numérica utilizando-se o programa Ansys. A modelagem numérica, tendo como referência a análise experimental, foi realizada utilizando os elementos SHELL 181 e SHELL63...

Análise estática de torres metálicas treliçadas autoportantes para linhas de transmissão; Static analysis of self-supporting latticed steel towers for transmission lines

Singh, Kellen de Souza
Fonte: Universidade de Brasília Publicador: Universidade de Brasília
Tipo: Dissertação
POR
Relevância na Pesquisa
16.53%
Dissertação (mestrado)—Universidade de Brasília, Faculdade de Tecnologia, Departamento de Engenharia Civil e Ambiental, 2009.; Este trabalho descreve o estudo do comportamento de torres metálicas autoportantes submetidas à ação do vento. Inicialmente foram modificadas algumas sub-rotinas dos programas desenvolvidos por Menin (2002). Assim, foram desenvolvidos novos programas: GTAU que gera a geometria das torres autoportantes e AETAU que realiza a análise estática. Nesses programas, a determinação da força estática do vento é determinada a partir dos critérios da NBR 6123 e NBR 5422. As torres foram modeladas utilizando um modelo matemático não linear que permite alongamentos nos elementos de cabos e treliças para a introdução das forças de prétensionamento, além de considerar o efeito da variação da temperatura. Completando o estudo, é realizada uma análise comparativa entre os resultados dos deslocamentos dos cabos, obtidos no programa AETAU, com a flecha obtida através da equação da parábola. Além disso, foram comparados os resultados da força axial (tração) dos cabos, obtidos no programa AETAU, com os resultados obtidos com o programa SAP2000 Advanced v. 12.0.0. Os dados obtidos através da análise estática revelaram que os programas desenvolvidos foram capazes de simular o comportamento dos cabos quando submetidos à ação do vento e peso próprio. Observando-se os resultados da análise sem vento de todos os modelos analisados...

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
46.84%
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...

Shear capacity assessment of tuff panels strengthened with FRP diagonal layout

Marcari, Giancarlo; Oliveira, Daniel V.; Fabbrocino, G.; Lourenço, Paulo B.
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
Publicado em //2011 ENG
Relevância na Pesquisa
26.37%
A quantitative analysis of the in-plane shear capacity of tuff masonry panels externally reinforced with FRP diagonal layout has been carried out. The objective is to provide a rational approach to the definition of the contributions from masonry and FRP to the lateral in-plane resistance of strengthened panels. Relevant experimental results of monotonic shear-compression tests are carefully analysed. A truss model approach, combined with a proper masonry strength criterion for masonry is proposed and validated. A comparison between computed and experimental data confirms the validity of the procedure in view of practical applications and code recommendations.

Influence of distinct reinforcing schemes on the shear ressistance of masonry

Vasconcelos, Graça; Alves, Pedro; 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
26.37%
One of the major concerns about the use of unreinforced masonry in seismic prone regions is its inadequate behavior under seismic loads, which has been shown from recent earthquakes. If fact, it has been seen that unreinforced masonry buildings present commonly considerable in-plane damage, which is associated to the low shear resistance of unreinforced masonry and to low capacity to dissipate energy. The improvement of the overall behavior of structural masonry under shear can be achieved by the addition of horizontal and vertical reinforcement. Tgis paper presents the results of a series of diagonal compression tests carried out on concrete block masonry with distinct types of reinforcement’s arrangements. It was seen that the better configuration for the reinforcement arrangement is the combination of vertical and horizontal reinforcements leading simultaneously to the improvement of shear strength and ductility.

In-plane behavior of tuff masonry panels strengthened with FRP diagonal layout

Marcari, Giancarlo; Oliveira, Daniel V.; Fabbrocino, G.; Lourenço, Paulo B.
Fonte: The Mansory Society Publicador: The Mansory Society
Tipo: Conferência ou Objeto de Conferência
Publicado em 04/01/2013 ENG
Relevância na Pesquisa
36.47%
The present paper deals with a quantitative analysis of the shear strength behavior of masonry panels strengthened with diagonal layout. The objective of the study is to progress towards understanding the shear strength contributions from masonry and FRP to the lateral resistance of strengthened panels. To this aim, relevant experimental results of monotonic shear-compression tests are analyzed. The local behavior of the reinforcement is investigated in terms of FRP strain profiles (i.e. the transferrable tension force within FRP), and its effects on the global response of the panels assessed. The experimental results show the effectiveness of the anchorage system in restraining the FRP at the anchored edges, avoiding premature failure due to FRP debonding. As a result, the specimens were allowed to develop their full lateral resistance. A truss model approach, combined with a proper masonry strength criterion for masonry is proposed and validated. A comparison between computed and experimental data confirms the validity of the procedure in view of practical applications and code recommendations.

Non-linear shear model for R/C piers

GUEDES Joao-Miranda; PINTO VIEIRA Artur; PEGON Pierre
Fonte: Publications Office of the European Union Publicador: Publications Office of the European Union
Tipo: EUR - Scientific and Technical Research Reports Formato: CD-ROM
ENG
Relevância na Pesquisa
16.19%
The work presented has been developed within the Prenormative Research in support of EuroCode 8 (PREC8) programme of the European Commission. The EuroCode 8 (EC8) are the provisional European standards for the design of civil engineering structures in seismic prone areas. This programme included experimental test on a series of bridge structures that have been tested under Pseudo-Dynamic conditions. Experimental tests were carried out to study the behaviour of bridge piers under cyclic loading. The results from these tests underlined the need to improve an existing fiber model to represent the non-linear behaviour of structures where the influence of the shear forces is not negligible. Thus, a strut-and-tie formulation coupled with the classic fibre model for flexural forces was developed. This formulation is based on the analogy of a R/C structure damaged with diagonal cracking with a truss made of concrete diagonals and steel ties. The model is applied to a set of bridge piers tested at the ELSA laboratory and the results are compared with the experimental response.; JRC.DG.G.5-European laboratory for structural assessment

Modal analysis and active vibration control of the Naval Postgraduate School Space Truss

Johnson, Scott E.; Vlattas, John
Fonte: Monterey, California. Naval Postgraduate School Publicador: Monterey, California. Naval Postgraduate School
Tipo: Tese de Doutorado Formato: xix, 228 p.;28 cm.
EN_US
Relevância na Pesquisa
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Approved for public release, distribution is unlimited; This thesis examines active control of the Naval Postgraduate School (NPS) Space Truss using a piezoceramic stack actuator. Preceding the development of an active control mechanism for the NPS space truss, modal testing was performed to identify the modal properties of the truss. An impact hammer provided excitation to the truss and accelerometers easured the truss' response. Two data acquisition systems were used independently to gather and analyze data. For active control, an active strut, consisting of a piezoceramic stack, a force transducer, and mechanical interfaces, was substituted in place of a critical diagonal strut and acted as a control actuator. The frequency response of the system was determined and a integral plus double-integral force feedback control law was designed and implemented. A linear proof mass actuator was employed to excite one of the truss' vibrational modes. The controller then suppressed the vibration along the length of the structure resulting in power attenuation on the order of 10- 15 dB. Various combinations of velocity and position feedback gains were investigated in order to optimize the control action. Additional testing was performed to determine the controller's sensitivity over a frequency band.; http://www.archive.org/details/modalanalysisact00john; Lieutenant...

Investigation of the effect of stiffness of members upon the solution of Vierendeel trusses

Manning, John Joseph; Eding, L. H.
Fonte: Rensselaer Polytechnic Institute Publicador: Rensselaer Polytechnic Institute
Tipo: Tese de Doutorado
EN_US
Relevância na Pesquisa
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This thesis document was issued under the authority of another institution, not NPS. At the time it was written, a copy was added to the NPS Library collection for reasons not now known.  It has been included in the digital archive for its historical value to NPS.  Not believed to be a CIVINS (Civilian Institutions) title.; A Vierendeel Truss is composed of a series of rectangular or trapezoidal panels without diagonal members. It is named for its inventor, Professor Arthur Vierendeel of the University of Louvain in Belgium, 'i'his type of truss has been popular in Europe, particularly in Belgium, since 1896 when the first bridge of this type was built in that country. In the United States its use to date has be-;n limited to concrete viaduct bents, small roof trusses, and rigid frame foundations for buildings. It has been reported that a bridge using a concrete Vierendeel Truss system has been built recently on the West Coast, but as yet there is no printed matter available on that project..; http://www.archive.org/details/investigationofe00mann; Lieutenant (j.g.), United States Navy; Lieutenant (j.g.), United States Navy

A rational approach to predicting the buckling length of compression chords in prefabricated timber truss roof structures braced by means of diagonal bracing

Burdzik,W M G; Dekker,N W
Fonte: Journal of the South African Institution of Civil Engineering Publicador: Journal of the South African Institution of Civil Engineering
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/04/2012 EN
Relevância na Pesquisa
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In South Africa, timber-trussed roofs supporting concrete tiles have for many years often been braced solely by means of diagonal braces. Failures have shown that the diagonal brace was inadequate for larger span roofs, and the use of diagonal bracing has subsequently been limited to spans of less or equal to 10 m. When designing the compression chords of a timber truss in a braced roof, SANS 10163:1 (2003) recommends a minimum effective length for out-of-plane buckling of not less than 15 x b, which is 540 mm for a 36 mm wide member. This effective or out-of-plane buckling length of the top chord was later assumed to be equal to the spacing of the trusses. With the availability of PC-based packages that are able to perform three-dimensional buckling analyses, it is perhaps useful to investigate the validity of using the effective length equal to the truss spacing, and then also the 10 m limit on span for roofs braced by means of diagonal braces. A common error made when analysing three-dimensional buckling problems is to assume connectivity on the centreline of the members, thereby neglecting eccentricity between the centreline of the bracing and the centreline of the member being braced (see Figure 1). In timber-trussed roofs, the diagonal brace is nailed to the underside of the top chord of a number of adjacent trusses. The brace runs at more or less 45° and triangulation appears to be complete when viewed on plan...