NUMERICAL SIMULATION OFTHE TEMP ERATURE FIELD
IN A WOOD-CONCRETE COMPOSITE CROSS SECTION IN
FIRE
Julio Cesar Molina1, Carlito Calil Junior2
ABSTRACT: In this work was evaluated the behavior of wood-concrete composite beams with cross-section T in fire
situation focusing on the metallic connection system used in the wood-concrete interface. It was performed the numerical
simulation of the temperature in a cross section of the composite beam from the use of ANSYS software, version 10.0,
which is based on the Finite Element Method. The evolution of the temperature was performed based on ISO 834:1999
standard. The numerical results show the temperatures for different points of the cross section considering a total time of 60
minutes of exposure to fire.
KEYWORDS: Composite beams, timber-concrete, numerical model, fire
1 INTRODUCTION 123
Nowadays is of great interest the analysis of structural
elements in fire so that we can ensure the safety of the
system in relation to the premature failure. In this context,
fire resistance is defined as the ability of a material or
structural element to remain during a certain time,
performing the functions for which it was designed, under
the action of fire.
2 NUMERICAL MODEL
The numerical modelling was performed from a bidimensional model using the software ANSYS, version
10.0, that has with base the Finite Element Method (FEM).
The temperature in the composite cross section was
measured for a total of 60 minutes of exposition to fire.
Figure 1 shows the configuration of the composite cross
section considered in the numerical model.
In Brazil most studies has been a character essentially
numeric because the first horizontal furnace of Brazil for
the tests in structural elements began in operating at the
beginning of the second half of 2012.
The main aim of this work was the simulation, through
numerical modeling, of the temperature field in a woodconcrete composite beam, of section T, with connectors
(12.5 mm of diameter) formed by steel rods in vertical
position to the grain.
From the numerical model proposed will be possible the
presentation of the main finite elements used in the
numerical model which consider the variation of
temperature and determinate the depth of carbonization of
wood besides the temperature into the concrete and the
temperature in the connection area with reasonable
approximation.
1
Julio Cesar Molina, University of São Paulo, 400 Trabalhador
São carlense Avenue, São Carlos, São Paulo, Brazil. Email:
[email protected]
2
Carlito Calil Junior, University of São Paulo, Brazil
Figure 1: Cross section of the composite beam with steel
connector considered in the model
2.1 FINITE ELEMENTES
The numerical model developed in this work was
performed with base in pre-definite elements and available
in the internal library of the software ANSYS. The cross
section from the composite beam was modelled for bidimensional elements of type plan (PLANE 77) and for the
elements type surface (SURF 151) which were used for the
implementation of boundary conditions of convection and
radiation to the model. The element SURF 151 has two or
tree nodes and considers a extra node located out of mesh
of finite elements to the control of temperature other nodes
with shown in figure 3.
Figure 4 show some results of temperature obtained for the
analysed cross section considering a time of 30 minutes of
exposition to fire.
2.2 MESH OF FINIT ELEMENTS
The mesh of finite elements related to the composite cross
section was discretized in plan elements (PLANE177)
having each element dimensions of 1 cm x 1 cm totalling
1020 finite elements as shown in Figure 2.
Figure 4: Temperature field obtained in the numeric
analysis by the software ANSYS for time of 30 minutes
4 CONCLUSIONS
Figure 2: Mesh of finite elements used in the model
The surface showed in the top of concrete was used for
simulation of a constant value for the temperature equal to
20 oC. The cross section was exposed to the fire only on
three sides, i. e, the top surface of the concrete slab has not
been exposed with show Figure 3.
The results of the numeric model developed were shown
satisfactory when compared to the experimental and
numerical results obtained by [1] and [2]. The model
presented can be used for the determination of the
temperature in the cross section with reasonable approach.
ACKNOWLEDGEMENT
The authors thank FAPESP (São Paulo State Research
Support Foundation, Brazil) for its financial backing of
this work.
REFERENCES
Figure 3: Border (radiation and convection) exposed to the
standard fire and fire on three sides of the section
The ISO 834:1999 standard recommends the Equation (1)
to the curve of standard fire model.
θg = θ0 + 345 log(8t + 1)
(1)
where θg = temperature of the gases in the environment in
flame (0C), θ0 = temperature of the gases in the moment
(usually taken equal to 20 0C) and t = time (minutes)
3 RESULTS
3.1 TEMPERATURE IN CROSS SECTION
The results of the temperature field were obtained for the
cross section considering a total time of 60 minutes of
exposition in fire according Equation (1) presented in [3].
[1] E. M. Pinto, “Determinação de um modelo de taxa de
carbonização transversal a grã para o eucalyptus
citriodora e eucalyptus grandis,” Ph.D. dissertation,
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de Engenharia de são Carlos da Universidade de São
Paulo, São Carlos-SP, Brazil, 2005.
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dissertation, Departamento Engenharia de Estruturas
da Escola de Engenharia de São Carlos da
Universidade de São Paulo, São Carlos-SP, Brazil,
2007.
[3] International Standard. Fire resistance tests - Elements
of building construction, Part 1: General requirements,
ISO 834-1:1999.
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Junior, “Análises numérica e experimental da
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madeira, São Pedro, Brazil, 2006, pp. 1-15
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mistas em situação de incêndio-modelagem e
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