Resistência ao cisalhamento de vigas de concreto reforçado com fibras de aço

The shear strength of steel fiber-reinforced concrete beams

Resumos

This research investigates the mechanical shear behavior of twelve reinforced concrete beams. The type of loading (normal or reverse), the presence or absence of steel fibers (30 kgf/m³), and the concrete compressive strength (40MPa, 60 MPa, or 80 MPa) were the mains test variables studied. The beams had nominally identical cross-sections, effective depths, and longitudinal and transverse reinforcements. The loads were increased at 10 kN intervals until shear failure occurred, defined by the yielding of the first stirrup. The ultimate shear loads observed in these tests were compared to three empirical and semi-empirical formulas proposed in the literature. Based on the test results it could be concluded that concrete compressive strength has no significant influence on the reduction of ultimate shear load caused by reverse loading. Reverse-loaded beams with fibers had approximately the same ultimate shear strength as concrete beams without fibers subjected to normal loading, regardless of the compressive strength of the concrete.

steel fiber; reinforced concrete; beam; reverse loading; shear strength

A. L. Moreno Junior^I; A. P. Vedoato^II

^IFaculdade de Engenharia Civil, Arquitetura e Urbanismo, Departamento de Estruturas, Unicamp, [e-mail], Av. Albert Einstein, 951 - Caixa Postal: 6021 - CEP: 13083-852, Campinas, Brazil

^IIFaculdade de Engenharia Civil, Arquitetura e Urbanismo, Departamento de Estruturas, Unicamp, [e-mail], Av. Albert Einstein, 951 - Caixa Postal: 6021 - CEP: 13083-852, Campinas, Brazil

ABSTRACT

This research investigates the mechanical shear behavior of twelve reinforced concrete beams. The type of loading (normal or reverse), the presence or absence of steel fibers (30 kgf/m³), and the concrete compressive strength (40MPa, 60 MPa, or 80 MPa) were the mains test variables studied. The beams had nominally identical cross-sections, effective depths, and longitudinal and transverse reinforcements. The loads were increased at 10 kN intervals until shear failure occurred, defined by the yielding of the first stirrup. The ultimate shear loads observed in these tests were compared to three empirical and semi-empirical formulas proposed in the literature. Based on the test results it could be concluded that concrete compressive strength has no significant influence on the reduction of ultimate shear load caused by reverse loading. Reverse-loaded beams with fibers had approximately the same ultimate shear strength as concrete beams without fibers subjected to normal loading, regardless of the compressive strength of the concrete.

Keywords: steel fiber; reinforced concrete; beam; reverse loading; shear strength.

RESUMO

Este trabalho investiga o comportamento ao esforço cortante de doze vigas em concreto com adição de fibras de aço. As principais variáveis estudadas foram o tipo de carregamento (normal ou reverso), a presença ou a ausência de fibras de aço (30kgf/m³) e a resistência do concreto à compressão (40 MPa, 60 MPa, ou 80 MPa). As vigas apresentavam seção transversal, altura útil e armaduras longitudinais e transversais nominalmente idênticas. Uma carga concentrada, no meio do vão da viga, foi aplicada em intervalos de 10 kN até a ruptura por cisalhamento, definida pelo escoamento do primeiro estribo em solicitação. A carga última de cisalhamento observada nos testes foi comparada com três formulas empíricas, e semi-empiricas, propostas na literatura. Baseando-se nos resultados dos testes, concluiu-se que a resistência à compressão do concreto não tem influencia significativa na parcela de redução da carga ultima de cisalhamento, promovida pela reversão do carregamento. Vigas sujeitas ao carregamento reverso e com fibras apresentaram, aproximadamente, a mesma resistência última de cisalhamento que as vigas sem fibras sujeitas ao carregamento normal, independentemente da resistência do concreto à compressão.

Palavras-chave: fibras de aço; concreto armado; viga; carregamento reverso; resistência ao cisalhamento.

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Full text available only in PDF format.

Received: 19 Aug 2010

Accepted: 03 Oct 2011

Available Online: 28 Nov 2011

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The shear strength of steel fiber-reinforced concrete beams

Resistência ao cisalhamento de vigas de concreto reforçado com fibras de aço

Datas de Publicação

• Publicação nesta coleção
  10 Set 2013
• Data do Fascículo
  Dez 2011

Histórico

• Recebido
  19 Ago 2010
• Aceito
  03 Out 2011