A contribution to the study of flexural reliability of steel-concrete composite beams designed according to NBR 8800:2008

Scherer, Maílson; Morsch, Inácio Benvegnu; de Vasconcellos Real, Mauro

doi:10.1590/S1983-41952024000200001

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ORIGINAL ARTICLE • Rev. IBRACON Estrut. Mater. 17 (2) • 2024 • https://doi.org/10.1590/S1983-41952024000200001 copy

This document is related to:

10.1590/S1983-41952024000200011

A contribution to the study of flexural reliability of steel-concrete composite beams designed according to NBR 8800:2008

Uma contribuição ao estudo da confiabilidade à flexão de vigas mistas de aço e concreto projetadas segundo a NBR 8800:2008

Authorship SCIMAGO INSTITUTIONS RANKINGS

Abstract

This work assesses the flexural reliability of compact sections and full-interaction steel-concrete composite beams designed according to NBR 8800:2008. Reliability indexes are obtained for different grades of concrete, slab heights, and load combination. The results show a lower level of safety in situations where live loads are predominant in the load combination. A partial safety factors calibration procedure is also proposed based on a target reliability index β_T = 3.5. It is shown that the calibrated partial safety factors reduce the variability of reliability indexes in the proposed design situations.

Keywords:
steel-concrete composite beams; structural reliability; NBR 8800; FORM; PSO

h (cm)	f_ck (MPa)
h (cm)	20	25	30
10.0	511.7	527.7	538.4
12.5	561.0	577.0	587.7
15.0	610.3	626.4	637.0

Random Variable	Description	Type of distribution	Mean (μ_x)	Standard Deviation (σ_X)	Ref.
f_c	Compressive strength of concrete	Normal	1.17·f_ck	0.15·μ_x	[¹⁷17 D. M. Santos, F. R. Stucchi, and A. T. Beck, “Confiabilidade de vigas projetadas de acordo com as normas brasileiras,” RIEM, vol. 7, no. 5, pp. 727–743, Oct 2014, http://dx.doi.org/10.1590/S1983-41952014000500002. http://dx.doi.org/10.1590/S1983-41952014... ]
f_y	Yield strength of the steel of the profile	Normal	1.08·f_yk	0.08·μ_x	[¹⁷17 D. M. Santos, F. R. Stucchi, and A. T. Beck, “Confiabilidade de vigas projetadas de acordo com as normas brasileiras,” RIEM, vol. 7, no. 5, pp. 727–743, Oct 2014, http://dx.doi.org/10.1590/S1983-41952014000500002. http://dx.doi.org/10.1590/S1983-41952014... ]
h	Concrete slab height	Normal	h_n*	5 mm	[²⁴24 F. Biondini, F. Bontempi, D. M. Frangopol, and P. G. Malerba, “Reliability of material and geometrically non-linear reinforced and prestressed concrete structures,” Comput. Struc., vol. 82, no. 13-14, pp. 1021–1031, May 2004, http://dx.doi.org/10.1016/j.compstruc.2004.03.010. http://dx.doi.org/10.1016/j.compstruc.20... ]
d	Steel profile height	Normal	d_n*	3 mm	[⁷7 W. C. Santiago, “Calibração baseada em confiabilidade dos coeficientes parciais de segurança das principais normas brasileiras de projeto estrutural, Doctoral dissertation, EESC-USP, São Carlos, Brasil, 2019.]
M_g	Dead load bending moment	Normal	1.05·M_Gk	0.10·μ_x	[²³23 B. Ellingwood and T. V. Galambos, “Probability-based criteria for structural design,” Struct. Saf., vol. 1, no. 1, pp. 15–26, Mar 1982, http://dx.doi.org/10.1016/0167-4730(82)90012-1. https://doi.org/ http://dx.doi.org/10.10... ]
M_q	Live load bending moment	Gumbel	0.92·M_Qk	0.25·μ_x	[²⁵25 L. G. L. Costa, W. C. Santiago, and A. T. Beck, “Probabilistic models for live loads in buildings: critical review, comparison to Brazilian design standards and calibration of partial safety factors,” RIEM, vol. 16, no. 2, pp. e16204, 2023, http://dx.doi.org/10.1590/S1983-41952023000200004. http://dx.doi.org/10.1590/S1983-41952023... ]
θ_R	Uncertainty parameter of the resistant model	Lognormal	1.00	0.05·μ_x	[¹⁷17 D. M. Santos, F. R. Stucchi, and A. T. Beck, “Confiabilidade de vigas projetadas de acordo com as normas brasileiras,” RIEM, vol. 7, no. 5, pp. 727–743, Oct 2014, http://dx.doi.org/10.1590/S1983-41952014000500002. http://dx.doi.org/10.1590/S1983-41952014... ]
θ_S	Uncertainty parameter of the load model	Lognormal	1.00	0.05·μ_x	[¹⁷17 D. M. Santos, F. R. Stucchi, and A. T. Beck, “Confiabilidade de vigas projetadas de acordo com as normas brasileiras,” RIEM, vol. 7, no. 5, pp. 727–743, Oct 2014, http://dx.doi.org/10.1590/S1983-41952014000500002. http://dx.doi.org/10.1590/S1983-41952014... ]

r	Partial safety factor
r	γ_c	γ_a1	γ_g	γ_q
0.00	0.90	1.22	1.33	-^* * For r = 0.00, the load combination has no live load.
0.25	0.90	1.21	1.28	1.37
0.50	0.88	1.13	1.18	1.91
1.00	0.88	1.08	1.12	2.14
1.50	0.88	1.06	1.10	2.19
2.00	0.88	1.05	1.08	2.21

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E-mail: arlene@ibracon.org.br

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[1] Corresponding author: Maílson Scherer. E-mail: mailson_scherer@hotmail.com

Limit states		Target reliability index β_T	Reference period
Serviceability	Irreversible	1.5	50 years
Serviceability	Irreversible	3.0	1 year
Ultimate	Low consequences of failure	3.1	50 years
	Low consequences of failure	4.1	1 year
	Medium consequences of failure	3.8	50 years
	Medium consequences of failure	4.7	1 year
	High consequences of failure	4.3	50 years
	High consequences of failure	5.1	1 year