Temperature field of composite steel and concrete slabs in fire situation

Composite steel decking concrete slabs are an important structural member in building construction. Research on its thermal behavior should be developed to understand its fire performance. In this paper, a comparison of the temperature distribution in the cross-section of steel decking concrete slabs subjected to fire is made through three different procedures: (a) standardized analytical, (b) experimental and (c) numerical. The analytical method was the one proposed in NBR 14323 standard. The experimental tests corresponding to eight real-scale fire tests on composite slabs carried out by the authors. The numerical tests were done for the same configurations of the experimental tests and used the FEA software Abaqus. Steel decking temperatures obtained with NBR 14323 methodologies showed good convergence with the experimental and numerical ones. The same was not observed for the concrete, positive and negative rebar.

Keywords:
fire, steel decking, concrete; composite slab, thermal behavior, experimental, numerical, analytical

Material	Non-normalized mixing ratio (kg/m³)	Mixing ratio
Portland cement	440	1.00
9.5 mm gravel	400	0.91
19 mm gravel	320	0.73
Industrial sand	320	0.73
Natural sand	960	2.18
Water	200 ± 20	0.45 ± 0.05

Material		Temperature (°C)
Material		20	100	200	300	400	500	600	700	800	900
Steel deck	$f_{y k, θ} / f_{y k}$	1.00	0.94	0.86	0.71	0.60	0.43	0.32	-	-	-
Concrete	$f_{c, θ} / f_{c k}$	1.00	1.00	1.00	0.95	0.85	0.65	0.31	0.28	0.21	0.10

Specimen	Positive rebars diameter (mm)	Negative rebars diameter (mm)
S1	No positive rebars	No negative rebars
S2	Ø6.3	No negative rebars
S3	Ø10	No negative rebars
S4	No positive rebars	Ø6.3
S5	No positive rebars	Ø10.0
S6	Ø6.3	Ø6.3
S7	Ø6.3	Ø6.3
S8	Ø6.3	Ø6.3

Time (min)	Temperature (°C)
	Standard	Numerical simulations
		Coordinates
		$X_{I}, Y_{I}$	$X_{I I}, Y_{I I}$	$X_{I I I}, Y_{I I I}$	$X_{I V}, Y_{I V}$	Average
60 (I)	510.6	626.0	662.3	510.0	569.8	592.0
90 (II)	635.3	697.7	735.0	575.0	600.8	652.1
120 (III)	719.0	764.7	785.4	633.2	627.0	702.6

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E-mail: arlene@ibracon.org.br

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[1] Corresponding author: Fabrício Longhi Bolina. E-mail: fabriciobolina@gmail.com