Abstracts
In a preliminary study that aims to define the minimum shear reinforcement of flat slabs that, leading to a punching shear failure surfasse that crosses that reinforcement, can avoid a sudden failure, nine slabs with 1800 mm x 1800 mm x 130 mm dimensions were tested. Their main variables were the number of shear reinforcement layers of the stud type, the cross-section area of that reinforcement in each circumferential layer and the diameter of the studs. In the attempt to define the minimum punching reinforcement of the slabs, a parameter κ, equal to the total force in the transverse reinforcement inside a truncated cone bounded by the shear crack divided by the punching strength of a similar slab without shear reinforcement, was used. The values of κ of the slabs varied between 0.27 and 1.03 and the punching failure surface crossed the shear reinforcement when κ was smaller than around 0.70. The value of κ equal to 0.6 was defined as close to the minimum for slabs with effective depth of 90 mm and flexure reinforcement ratio of 1.38%. In comparison with the slab with no shear reinforcement, slabs having κ of that order had a punching strength and rotation increase of about 10% and 30%, respectively.
flat slabs; minimum shear reinforcement; reinforced concrete
Dando início a estudo que visa definir a armadura transversal mínima de lajes-cogumelo de concreto armado que, levando a uma superfície de ruptura por punção atravessando essa armadura, pode evitar uma ruptura brusca, foram testadas nove lajes de dimensões 1800 mm x 1800 mm x 130 mm. Suas principais variáveis foram o número de camadas de armadura de cisalhamento do tipo studs, a área dessa armadura em cada camada circunferencial e o diâmetro dos studs. Na tentativa da definição da armadura mínima de punção das lajes, utilizou-se o parâmetro κ, igual à força total da armadura transversal situada dentro de tronco de cone de ruptura delimitado pela fissura de cisalhamento dividida pela resistência à punção de laje semelhante sem armadura de cisalhamento. Os valores de κ das lajes variaram de 0,27 a 1,03 e ocorreu superfície de ruptura cruzando as camadas de studs quando κ foi menor que cerca de 0,70. Definiu-se o valor de κ igual a 0,6 como próximo daquele mínimo para lajes com altura efetiva igual a 90 mm e taxa de armadura de flexão de 1,38%. Para as lajes com valor de κ dessa ordem, em relação à laje sem armadura transversal, os acréscimos de resistência à punção e de rotação foram, respectivamente, cerca de 10% e 30%.
lajes-cogumelo; armadura transversal mínima; concreto armado
Study on minimum shear reinforcement of reinforced concrete flat slabs
A. P. R. VazI ; R. B. Gomes I I ; L. C. D. Shehata I I I
ISaneamento de Goiás S/A, SANEAGO, anapjansen@gmail.com, Avenida Fued JoséSebba 570, Jardim Goiás, Goiânia, Goiás, GO, CEP 74805-100
IIEscola de Engenharia Civil, Universidade Federal de Goiás, UFG, rgomes@eec.ufg.br, Praça Universitária s/n., Setor Universitário, Goiânia, Goiás, GO, CEP 74605-220
IIIEscola de Engenharia, Departamento de Engenharia Civil, UFF, lidiashehata@vm.uff.br; COPPE-UFRJ, lidia@coc.ufrj.br, Caixa Postal 68506, Rio de Janeiro, RJ, CEP 21945-970
ABSTRACT
In a preliminary study that aims to define the minimum shear reinforcement of flat slabs that, leading to a punching shear failure surfasse that crosses that reinforcement, can avoid a sudden failure, nine slabs with 1800 mm x 1800 mm x 130 mm dimensions were tested. Their main variables were the number of shear reinforcement layers of the stud type, the cross-section area of that reinforcement in each circumferential layer and the diameter of the studs. In the attempt to define the minimum punching reinforcement of the slabs, a parameter κ, equal to the total force in the transverse reinforcement inside a truncated cone bounded by the shear crack divided by the punching strength of a similar slab without shear reinforcement, was used. The values of κ of the slabs varied between 0.27 and 1.03 and the punching failure surface crossed the shear reinforcement when κ was smaller than around 0.70. The value of κ equal to 0.6 was defined as close to the minimum for slabs with effective depth of 90 mm and flexure reinforcement ratio of 1.38%. In comparison with the slab with no shear reinforcement, slabs having κ of that order had a punching strength and rotation increase of about 10% and 30%, respectively.
Keywords: flat slabs, minimum shear reinforcement, reinforced concrete
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REFERENCES
- [01] GOMES, R.B. e REGAN, P.E. Punching resistance of rc flat slabs with shear reinforcement. Journal of Structural Engineering, EUA, v. 125, n. 6, p. 684-692, junho 1999.
- [02] SILVA, J.A. Punção em lajes cogumelo: pilares retangulares, furos e armadura de cisalhamento. Dissertação (Mestrado em Engenharia Civil). Universidade Federal de Goiás, Goiânia, Goiás, 2003.
- [03] MUSSE, T.H. Punção em lajes cogumelo - fibras de aço e armaduras de cisalhamento. Dissertação (Mestrado em Engenharia Civil). Universidade Federal de Goiás, Goiânia, Goiás, 2004.
- [04] BORGES, L.L.J. Comportamento ao puncionamento de lajes cogumelo de concreto armado com pilares retangulares e furos de grandes dimensões. Tese (Doutorado em Estruturas e Construção Civil), Publicação E.TD-002A/04, Universidade de Brasília, Brasília, DF, 2004.
- [05] GOMES, R.B. e REGAN, P.E. . Punching strength of slabs reinforced for shear with offcuts of rolled steel I section. Magazine of Concrete Research, v. 51, n. 2, p. 121-129, 1999.
- [06] VAZ, A.P.R., Resistência à punção em lajes cogumelo de concreto armado: uma contribuição para definição de armadura mínima de cisalhamento. Dissertação (Mestrado em Engenharia Civil), Escola de Engenharia Civil, Universidade Federal de Goiás, Goiânia, Goiás, 2007.
Publication Dates
-
Publication in this collection
18 Sept 2014 -
Date of issue
Mar 2009
History
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Received
08 Aug 2008 -
Accepted
08 Aug 2008
