Contribuição ao estudo da instabilidade lateral de vigas pré-moldadas

Lima, Maria Cristina Vidigal de

doi:10.11606/t.18.2002.tde-29052006-171714

Cited by 8 publications

(24 citation statements)

References 18 publications

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“…In these situations, the provisory supports do not restraint the element against twist rotation and lateral deflection, as occurs in permanent phase. In general, transitory situations are considered critical for lateral buckling of precast beams, as presented by Lima [1] and [2], El Debs [3] and Krahl [4]. Typically, beams have low lateral flexural stiffness and when undergo rotation about its longitudinal axis part of the self-weight acts laterally.…”

Section: Introductionmentioning

confidence: 99%

Recommendations for verifying lateral stability of precast beams in transitory phases

Krahl

Lima

Debs

2015

Rev. IBRACON Estrut. Mater.

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ResumoThis paper presents recommendations for security check of precast beams in transitory phases, compare results of parametric analyzes with national and international code recommendations and confront the formulations used for the calculation of critical load of lateral instability. In transport and lifting phases, precast beams are susceptible to loss lateral stability because the established supports provides little restriction to the element rotate on its principal axis and move laterally. To recommend limits of slenderness, parametric analysis are performed using formulations based on bifurcacional instability, including eigenvalue problems with the finite element method. The results show that the safety limits for I beams and rectangular beams are different. For the analyzed cases and with reference to beam slenderness equation used by fib Model Code [13], the limit determined for rectangular beams would be 85 and for I beams 53, which could be taken as 50, as recommended by the code. Within the analyzed cases of I beams, only the fib Model Code [13] recommendation attend the slenderness limit for transitory phases.Este artigo objetiva apresentar recomendações para a verificação da segurança de vigas pré-moldadas em fases transitórias, comparar resultados de análises paramétricas com recomendações de normas nacionais e internacionais e confrontar as formulações utilizadas para o cálculo da carga crítica de instabilidade lateral. Nas fases transitórias de transporte e içamento, as vigas pré-moldadas são suscetíveis à perda de estabilidade lateral, porque a vinculação estabelecida oferece pequena restrição ao elemento de girar em torno de seu eixo e deslocar-se lateralmente. Para recomendar limites de esbeltez são realizadas análises paramétricas utilizando formulações baseadas em instabilidade bifurcacional, incluindo problemas de autovalor com o método dos elementos finitos. Os resultados mostram que os limites de segurança para vigas I e retangular são diferentes. Para os casos analisados e tomando como referência a equação de esbeltez de viga utilizada pelo fib Model Code [13], o limite determinado para vigas retangulares seria de 85 e para vigas de seção I seria de 53, o que poderia ser tomado igual a 50, como recomendado pela norma. Dentre os casos analisados de vigas I, somente a recomendação do fib Model Code [13] atende o limite de esbeltez para fases transitórias.Palavras-chave: instabilidade lateral de vigas, concreto pré-moldado, içamento, transporte, esbeltez.

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Section: Introductionmentioning

confidence: 99%

Recommendations for verifying lateral stability of precast beams in transitory phases

Krahl

Lima

Debs

2015

Rev. IBRACON Estrut. Mater.

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“…Furthermore, the initial rotation was recorded for all beams that can be the effect of eccentricity of the lifting cables and initial lateral displacements which induces rotation. (MAST, 1994) and (LIMA, 2002) presented results of tests to failure of precast prestressed and nonprestressed concrete beams, respectively, under controlled rotation imposed at both ends. These studies show the rotation capacity of concrete beams subjected only to self-weight.…”

Section: Reported Experimental Studiesmentioning

confidence: 99%

“…For the beam tested by (MAST, 1994), cracking was detected approximately at a rotation of 10 degrees, which corresponded to a lateral displacement of 127 mm and at failure a rotation of 32 degrees with 762 mm of lateral displacement at midspan. The cracking rotation for the beam tested by (LIMA, 2002) was 15 degrees and at failure 54 degrees. Both studies showed that the elements suffer small torsional strains along the span when subjected only to self-weight and to a controlled rotation imposed at both ends.…”

Section: Reported Experimental Studiesmentioning

confidence: 99%

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Lateral stability of ultra-high performance fiber-reinforced concrete beams with emphasis in transitory phases

Krahl¹

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Lateral stability of ultra-high performance fiber-reinforced concrete beams with emphasis in transitory phases Instabilidade lateral de vigas de concreto de ultra-alto desempenho reforçado com fibras com ênfase em fases transitórias São Carlos 2018 PABLO AUGUSTO KRAHL Lateral stability of ultra-high performance fiber-reinforced concrete beams with emphasis in transitory phases VERSÃO CORRIGIDA A versão original encontra-se na Escola de Engenharia de São Carlos Text presented to the São Carlos School of Engineering of the University of São Paulo as one of the requisites for obtaining the degree Doctor in Civil Engineering (Structures).

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“…Diversas causas podem influenciar para que a instabilidade ocorra. Dentre elas estão a esbeltez da peça (REVATHI; MENON, 2007;GIRIJA;MENON, 2011), imperfeições geométricas (HILL; DICK; TADROS, 2009), condições de transporte (MAST, 1993), de içamento (LIMA, 2002;KRAHL, 2014) e de apoio temporário da viga (KRAHL, 2014;HAMILTON, 2012;HURFF;KAHN, 2012a;HARPER;CONSOLAZIO, 2013).…”

Section: Capítulo 1 Introdução 11 Considerações Iniciaisunclassified

Estudo do comportamento de almofadas elastoméricas sob vigas pré-moldadas e análise da estabilidade lateral após a montagem

Reis¹

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AGRADECIMENTOS À Deus que é fonte de todo conhecimento, sabedoria e ciência. À Nossa Senhora da Abadia que sempre me concede muitas graças. À minha orientadora Maria Cristina pelo empenho e compreensão com que me auxiliou nesses anos. Ao professor Francisco que me ajudou na parte de modelagem numérica. À minha família, meus pais Antônio e Rita e meus irmãos Diego e Tiago, que me apoiaram nessa dura caminhada.Aos meus amigos de Uberlândia, que foram bons companheiros no dia-a-dia desta jornada, na faculdade, nos bares e na academia. Aos meus amigos de Santa Juliana, pelas festas e cervejadas, e que estão sempre dispostos a ajudar nas adversidades. Ao pessoal do grupo Kairós que me mostrou uma maneira diferente de enxergar os problemas da vida. À Universidade Federal de Uberlândia e à Faculdade de Engenharia Civil, que forneceram o apoio necessário à realização da pesquisa. À CAPES pelo apoio financeiro.Palavras chave: Instabilidade lateral. Tombamento. Almofadas de apoio elastoméricas. Vigas pré-moldadas.REIS, L. C. Estudo do comportamento de almofadas elastoméricas sob vigas prémoldadas e análise da estabilidade lateral após a montagem. ABSTRACTPrecast concrete girders on bearing pads are subjected to instability depending on several variables such as span length, initial imperfections, especially initial lateral sweep, and bearing pads behavior, regarding to stiffnesses and dimensions. On this work, numerical models are developed in the ANSYS Workbench 18.0 in order to assess the instability limit loads and the rotational stiffnesses of the pads in many combinations of span length, cross section of the girder and lateral sweep. Then, it was also evaluated the lift off phenomenon of the girder on the supports and the variation of stiffnesses in which situation. Finally, the variations of the limit loads considering changes in the bottom and top flanges dimensions is considered. The proposed models properly represented the girders over the bearing pads once the behavior are validated by experimental studies of the literature. The increase in spans and initial imperfections causes a decrease in the rollover limit load. The lift off effect is aggravated as the lateral eccentricities increase and also depends on the initial compression of the bearing pad. In the analyzed combinations, the reduction of the rotational stiffness is about 37% for the critical situation, which span length about 40 m and lateral sweep of L/300, with loss of contact between 50% and 60%. Variations of top and bottom flanges width, changing lateral moments of inertia, tend to vary the rollover limit load. Increasing the lateral inertia in about 35% results in an increase of 24% for the limit load for the cases analyzed in this study.

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Contribuição ao estudo da instabilidade lateral de vigas pré-moldadas

Cited by 8 publications

References 18 publications

Recommendations for verifying lateral stability of precast beams in transitory phases

Recommendations for verifying lateral stability of precast beams in transitory phases

Lateral stability of ultra-high performance fiber-reinforced concrete beams with emphasis in transitory phases

Estudo do comportamento de almofadas elastoméricas sob vigas pré-moldadas e análise da estabilidade lateral após a montagem

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