Em comparação com o concreto vibrado (CV) de mesma classe de resistência, o concreto autoadensável (CAA) tipicamente apresenta menor quantidade de agregado graúdo e, eventualmente, menor dimensão máxima deste agregado. Isto pode reduzir o engrenamento de agregados entre as superfícies de ruptura do CAA. Sendo o engrenamento dos agregados um parâmetro de influência importante na resistência à força cortante de vigas esbeltas, as vigas de CAA podem ter resistência à força cortante menor que a de vigas similares de CV. Este artigo resume estudos experimentais sobre a resistência à força cortante de vigas esbeltas de CAA sem e com armadura de cisalhamento. As resistências à força cortante de vigas de CAA são comparadas com as de vigas de CV e também com as calculadas segundo procedimentos de diferentes normas. É mostrado que as vigas de CAA com menor teor de agregados graúdos tendem a ter menor resistência à força cortante que vigas semelhantes de CV e que a diferença depende da composição dos concretos e das características das vigas.

Palavras-chave:
concreto autoadensável; vigas esbeltas; resistência à força cortante

Autoria

T. L. Resende

Universidade Federal dos Vales do Jequitinhonha e Mucuri, Instituto de Ciência, Engenharia e Tecnologia, Teófilo Otoni, MG, Brasil. thomas.lima@ufvjm.edu.brUniversidade Federal dos Vales do Jequitinhonha e MucuriBrazilTeófilo Otoni, MG, BrazilUniversidade Federal dos Vales do Jequitinhonha e Mucuri, Instituto de Ciência, Engenharia e Tecnologia, Teófilo Otoni, MG, Brasil. thomas.lima@ufvjm.edu.br

L. C. D. Shehata

Universidade Federal Fluminense, Departamento de Engenharia Civil, Niterói, RJ, Brasil. lidiashehata@vm.uff.brUniversidade Federal FluminenseBrazilNiterói, RJ, BrazilUniversidade Federal Fluminense, Departamento de Engenharia Civil, Niterói, RJ, Brasil. lidiashehata@vm.uff.br

I. A. E. M. Shehata

Universidade Federal do Rio de Janeiro, COPPE, Programa de Engenharia Civil, Rio de Janeiro, RJ, Brasil. ibrahim@coc.ufrj.brUniversidade Federal do Rio de JaneiroBrazilRio de Janeiro, RJ, BrazilUniversidade Federal do Rio de Janeiro, COPPE, Programa de Engenharia Civil, Rio de Janeiro, RJ, Brasil. ibrahim@coc.ufrj.br

SCIMAGO INSTITUTIONS RANKINGS

Figuras | Tabelas

Figuras (9)
Tabelas (3)

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Figure 1
Comparison between the ultimate shear stress of SCC and VC beams tested by Hassan, Hossain and Lachemi [¹³[13] Hassan, A.A.A., Hossain, K.M.A., Lachemi, M., Behavior of full scale self-consolidating concrete beams in shear, Cement & Concrete Composites, v.30, n.7, 2008, p. 588-596.,¹⁴[14] Hassan, A.A.A., Hossain, K.M.A., Lachemi, M., Strength, cracking and deflection performance of large-scale self-consolidating concrete beams subjected to shear failure, Engineering Structures, v.32, n.5, 2010, p. 1262-1271.] with A_s/(b_wh)=1.0%

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Figure 2
Comparison between the ultimate shear stress of SCC and VC beams tested by Hassan, Hossain and Lachemi [¹³[13] Hassan, A.A.A., Hossain, K.M.A., Lachemi, M., Behavior of full scale self-consolidating concrete beams in shear, Cement & Concrete Composites, v.30, n.7, 2008, p. 588-596.,¹⁴[14] Hassan, A.A.A., Hossain, K.M.A., Lachemi, M., Strength, cracking and deflection performance of large-scale self-consolidating concrete beams subjected to shear failure, Engineering Structures, v.32, n.5, 2010, p. 1262-1271.] with A_s/(b_wh)=2.0%

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Figure 3
Comparison between the normalized shear strength of VC and SCC beams tested by Lin and Chen [18] with a/d=3.0

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Figure 4
Normalized shear strength of the SCC beams with different types of coarse aggregate and ρ=1.68% tested by Safan [¹¹[11] Safan, M. A., Shear strength of concrete beams cast with self-compacting concrete containing different fillers and coarse aggregates, Canadian Journal of Civil Engineering v.39, n.7, 2012, p. 760-770.]

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Figure 5
Comparison of the ultimate shear stresses of high strength SCC and VC beams with f_c≅ 70MPa and small values of ρ_wf_yw [¹²[12] Resende, T. L., Shehata, L.C.D., Shehata, I.A.E.M., Shear strength of self-compacting concrete beams with small amounts of stirrups, Structural Concrete (accepted for publication, DOI: 10.1002/suco.201400084), 2015.
https://doi.org/10.1002/suco.201400084... ]

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Figure 6
Values of V_u/V_R of beams without shear reinforcement as a function of V_u/(b_wd)

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Figure 7
a Values of V_u/V_R of beams with shear reinforcement as a function of V_u/(b_wd) (Continue)

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Figure 7b
Values of V_u/V_R of beams with shear reinforcement as a function of V_u/(b_wd) (Continuation)

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Figure 8
Values of ρ_w,minf_ywk specified in different codes as a function of f_ck

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Table 1
Ranges of relevant parameters of the beams

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Table 2
Summary of procedures for shear strength calculation

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Table 3
Statistical data of V_u/V_R

Figure 1 Comparison between the ultimate shear stress of SCC and VC beams tested by Hassan, Hossain and Lachemi [¹³[13] Hassan, A.A.A., Hossain, K.M.A., Lachemi, M., Behavior of full scale self-consolidating concrete beams in shear, Cement & Concrete Composites, v.30, n.7, 2008, p. 588-596.,¹⁴[14] Hassan, A.A.A., Hossain, K.M.A., Lachemi, M., Strength, cracking and deflection performance of large-scale self-consolidating concrete beams subjected to shear failure, Engineering Structures, v.32, n.5, 2010, p. 1262-1271.] with A_s/(b_wh)=1.0%

Figure 2 Comparison between the ultimate shear stress of SCC and VC beams tested by Hassan, Hossain and Lachemi [¹³[13] Hassan, A.A.A., Hossain, K.M.A., Lachemi, M., Behavior of full scale self-consolidating concrete beams in shear, Cement & Concrete Composites, v.30, n.7, 2008, p. 588-596.,¹⁴[14] Hassan, A.A.A., Hossain, K.M.A., Lachemi, M., Strength, cracking and deflection performance of large-scale self-consolidating concrete beams subjected to shear failure, Engineering Structures, v.32, n.5, 2010, p. 1262-1271.] with A_s/(b_wh)=2.0%

Figure 3 Comparison between the normalized shear strength of VC and SCC beams tested by Lin and Chen [18] with a/d=3.0

Figure 4 Normalized shear strength of the SCC beams with different types of coarse aggregate and ρ=1.68% tested by Safan [¹¹[11] Safan, M. A., Shear strength of concrete beams cast with self-compacting concrete containing different fillers and coarse aggregates, Canadian Journal of Civil Engineering v.39, n.7, 2012, p. 760-770.]

Figure 5 Comparison of the ultimate shear stresses of high strength SCC and VC beams with f_c≅ 70MPa and small values of ρ_wf_yw [¹²[12] Resende, T. L., Shehata, L.C.D., Shehata, I.A.E.M., Shear strength of self-compacting concrete beams with small amounts of stirrups, Structural Concrete (accepted for publication, DOI: 10.1002/suco.201400084), 2015.
https://doi.org/10.1002/suco.201400084... ]

Figure 6 Values of V_u/V_R of beams without shear reinforcement as a function of V_u/(b_wd)

Figure 7 a Values of V_u/V_R of beams with shear reinforcement as a function of V_u/(b_wd) (Continue)

Figure 7b Values of V_u/V_R of beams with shear reinforcement as a function of V_u/(b_wd) (Continuation)

Figure 8 Values of ρ_w,minf_ywk specified in different codes as a function of f_ck

Table 1 Ranges of relevant parameters of the beams

Parameter	Range	Parameter	Range
Shear span to effective depth ratio a/d	2.5 to 3.8	Effective depth to tensile reinforcement d (mm)	100 to 668
Cylinder compressive strength f_c (MPa)	25 to 75	Longitudinal tensile reinforcement ratio ρ (%)	1.0 to 4.5
Maximum aggregate size d_max(mm)	10 to 19	Transverse reinforcement index ρ_wf_yw (MPa)	0.0 to 1.8

Table 2 Summary of procedures for shear strength calculation

Procedure		θ (°)	V_R
ABNT NBR 6118:2014	Model I	45	V_c+V_s
ABNT NBR 6118:2014	Model II	30 to 45
ACI 318:2014*		45
EN 1992-1-1:2004**		21.8 to 45	V_c or V_s
FIB MC 2010***	Level I	30 to 45
	Level II	(20+10000ε_x) to 45
	Level III	(20+10000ε_x) to 45	V_c+V_s

^*
(exception to this limit is permitted in beams with ρ_w> ρ_w,min)
^**
< 2 ; ρ < 0.02
^***
; ε_x is the longitudinal strain at the mid-depth, approximated to half the strain in the tensile longitudinal reinforcement; V_R,max,θmin is the upper limit to the shear resistance correspondent to the limit stress in the diagonal concrete struts considering θ=θ_min. For members without transverse reinforcement, only Levels I and II are applicable

Table 3 Statistical data of V_u/V_R

Procedure	ρ_wf_yw= 0				ρ_wf_yw ≥ ρ_w,minf_ywk
Procedure	Average	Median	Coef. Var.	V_u/V_R<1	Average	Median	Coef. Var.	V_u/V_R<1
	SCC
NBR 6118:2014^I	—	—	—	—	1.55	1.59	0.172	0.0%
NBR 6118:2014^II	—	—	—	—	1.32	1.37	0.170	3.2%
ACI 318:2014^*	1.29	1.31	0.158	5.4%	1.64	1.75	0.228	5.7%
ACI 318:2014	1.26	1.29	0.149	7.1%	1.56	1.62	0.225	8.6%
EN 1992-1-1:2004	1.05	1.04	0.116	32%	1.49	1.46	0.215	0.0%
FIB MC 2010^I	1.64	1.63	0.145	0.0%	2.14	2.11	0.215	0.0%
FIB MC 2010^II	1.23	1.22	0.118	1.8%	1.90	1.83	0.237	0.0%
FIB MC 2010^III	—	—	—	—	1.48	1.46	0.230	8.8%
	VC
NBR 6118:2014^I	—	—	—	—	1.58	1.52	0.178	0.0%
NBR 6118:2014^II	—	—	—	—	1.34	1.27	0.174	0.0%
ACI 318:2014^*	1.30	1.33	0.196	15%	1.74	1.64	0.168	0.0%
ACI 318:2014	1.26	1.31	0.187	15%	1.64	1.56	0.164	0.0%
EN 1992-1-1:2004	1.09	1.08	0.121	25%	1.46	1.46	0.175	0.0%
FIB MC 2010^I	1.81	1.73	0.153	0.0%	2.11	2.11	0.175	0.0%
FIB MC 2010^II	1.28	1.29	0.127	5.0%	1.85	1.85	0.184	0.0%
FIB MC 2010^III	—	—	—	—	1.50	1.46	0.177	0.0%

^*
More simplified formula of V_c ; I, II, III: Model or level of approximation

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[TFN1] ^*
(exception to this limit is permitted in beams with ρ_w> ρ_w,min)

[TFN2] ^**
< 2 ; ρ < 0.02

[TFN3] ^***
; ε_x is the longitudinal strain at the mid-depth, approximated to half the strain in the tensile longitudinal reinforcement; V_R,max,θmin is the upper limit to the shear resistance correspondent to the limit stress in the diagonal concrete struts considering θ=θ_min. For members without transverse reinforcement, only Levels I and II are applicable