Numerical analysis of composite steel and concrete beams subjected to fire under different support conditions

Romagnoli, Lucas Coscia; Silva, Valdir Pignatta e

doi:10.1590/S1983-41952020000500013

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ORIGINAL ARTICLE • Rev. IBRACON Estrut. Mater. 13 (5) • 2020 • https://doi.org/10.1590/S1983-41952020000500013 copy

Numerical analysis of composite steel and concrete beams subjected to fire under different support conditions

Análise numérica de vigas mistas de aço e concreto em situação de incêndio sob diferentes condições de apoios

Authorship SCIMAGO INSTITUTIONS RANKINGS

abstract:

To evaluate the behavior of semi-continuous composite beams in fire, six finite elements numerical models with several steel profiles and slab dimensions were developed in ABAQUS software. The models took into account several behaviors usually suppressed in simplified analyzes such as: geometric and materials non-linearity properties and thermal expansion effects, including indirect stresses. Three support conditions were analyzed: simply supported (axial released), axial restrained and semi-continuous, totaling 18 analyzes. The different support conditions results were compared to each other and to the fire resistance time designed by simplified methods, which followed design code recommendations.

Keywords:
fire; composite steel concrete beam; semi-continuous; numerical analysis

$L_{m}$	$X_{1}$	$X_{2}$	$X_{3}$	$X_{4}$	$X_{5}$
0.5	6.432499	-1.02349	0.499770	0.302	-0.000118
1	4.249018	-0.91824	0.493256	0.373	-0.000135
2	2.578352	-0.77310	0.457589	0.443	-0.000140
3	1.845211	-0.68851	0.441610	0.479	-0.000133
4	1.448499	-0.63266	0.434033	0.501	-0.000124
5	1.202279	-0.59368	0.431480	0.517	-0.000115
6	1.036789	-0.56531	0.431575	0.527	-0.000106

Profile	Model 1	Model 2	Model 3	Model 4	Model 5	Model 6
Profile	W250x25.3	W460x106.0	W530x85.0	W250x89.0	W360x51.0	W610x174.0
$d$	257	469	535	260	355	616	mm
$t_{w}$	6.1	12.6	10.3	10.7	7.2	14.0	mm
$b_{f}$	102	194	166	256	171	325	mm
$t_{f}$	8.4	20.6	16.5	17.3	11.6	21.6	mm
Slab characteristics
$t_{c}$	8	8	12	12	18	18	cm
$b$	200	200	200	200	200	200	cm
$ρ$	0.48	2.41	1.32	1.36	0.52	1.68	%
$\emptyset$	10	20	20	20	16	25	mm
$s$	10	8	10	9	10	8	cm
General parameters
$L$	5.0	8.0	8.0	5.0	8.0	12.0	m
$n_{c s}$	20	60	68	72	40	132	un.
$M_{R d}^{+}$	194.2	1094.1	1141.1	712.2	658.1	2720.7	kN.m
$q$	62.1	136.8	142.6	227.9	82.3	151.1	kN/m
$0.7 q$	43.5	95.7	99.8	159.5	57.6	105.8	kN/m
FRT simpl.	<15	22	18	25	17	25	min.

Support Element	Condition
Support Element	Axial Released	Axial Restrained	Semi-continuous
Slab + Reinf. Mesh	Free	Fully restrained (X,Y and Z)	Fully restrained (X,Y and Z)
Upper flange	Free	Free	Free
Web	Y Restrained	Fully restrained (X,Y and Z)	Fully restrained (X,Y and Z)
Lower flange	Free	Free	Fully restrained (X,Y and Z)

	FRT Simpl. Method	FRT Num. Analysis	Num. Analysis Fail Criteria
Model 1	< 15 min	30 min	δ = L/20
Model 2	22 min	> 40 min	Not observed
Model 3	18 min	~23 min	δ = L/20
Model 4	25 min	40 min	δ = L/20
Model 5	17 min	~21 min	Numerical instability
Model 6	25 min	~26 min	Numerical instability

IBRACON - Instituto Brasileiro do Concreto Instituto Brasileiro do Concreto (IBRACON), Av. Queiroz Filho, nº 1700 sala 407/408 Torre D, Villa Lobos Office Park, CEP 05319-000, São Paulo, SP - Brasil, Tel. (55 11) 3735-0202, Fax: (55 11) 3733-2190 - São Paulo - SP - Brazil
E-mail: arlene@ibracon.org.br

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[1] Corresponding author: Lucas Coscia Romagnoli. E-mail: lucas.romagnoli@usp.br