GIDAI - Seguridad contra Incendios - Investigación

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International Congress

FIRE COMPUTER MODELING

UNIVERSIDAD DE CANTABRIA

Dpto. de Transportes y Tecnología de Proyectos y Procesos

GIDAI - Seguridad contra Incendios - Investigación y Tecnología

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International Congress

FIRE COMPUTER MODELlNG

Edited by:

Jorge A. Capote Daniel Alvear

Compiled by:

Mariano Lázaro David Lázaro

Virginia Alonso

Acknowledgements:

Servicio de Publicaciones (Universidad de Cantabria)

FIRE COMPUTER MODELlNG : international congress, [Santander, 19 de Octubre de 2012J I edited by Jorge A. Capote,

Daniel Alvear ; compiled by Mariano Lázaro, David Lázaro, Virginia Alonso-- Santander: Universidad de Cantabria, GIDAI, [2012J.

D.L SA-608-2012

ISBN 978-84-86116-69-9

1.lncendios - Simulación por Ordenador - Congresos I. Capote Abreu, Jorge A, ed. li!. 11. Alvear Portilla, Daniel, ed. li!. 111.

Lázaro Urrutia, Mariano 111. Universidad de Cantabria. Grupo de Investigación y Desarrollo de Actuaciones Industriales.

614.84 (063)

Printed: Gráficas Iguna, S.A.

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Hybrid

wood/steel

elements under tire

Barbosa,L.F.M'; Almeida, P.M.L. '; Fonseca, E.M,M. 2; Barreira, L.M.S" ; Coelho, D.C,S,3

! Mechanical Engineering, Polytechnic Institute of Bragança,

ABSTRACT

2 Department of Applied Mechanics, Polytechnic Institute of Bragança, !,2Campus de Sta , Apolónia, 5301-857, Bragança, Portugal,

3 Faculty of Engineering, Porto,

The main objective of this paper is to present a computational mo dei for the fire resistance of wood/steel hybrid elements, Different design solutions will be presented, The most important factors for fire safety in hybrid elements are the thermal effects degradation and the charring depth formation in wood materiais, and also the heat conduction extremely well in steel material. Unprotected steel elements under fire condition may suffer serious damage, The use of hybrid wood/steel elements could increase both structural strength and stiffness. Wood could be considered as an insulating material, the core section could remain at low temperature, function of fire exposure time and element cross section size. All presented results will permit to evaluate different design solutions, which facilitates the fire design of wood/steel hybrid elements, The presented study was conducted in arder to articulate the best constructive solution using the finite element method.

1 INTRODUCTION

In the past, buildings have been entirely constructed with steel or entirely with wood, but recently have begun to integrate with both different materiais, using hybrid wood/steel solutions, [1-2].

Hybrid structure does not merely indicate a framework member composed by a combination of different materiaIs, but a construction using different methods according specific structural functions [2]. For this reason, the use of hybrid materiais could increase the structural integrity, Steel material has many advantages over wood elements, strength, stability, resistance to woodworm, among others. Steel is incombustible and most of the times it can full recover strength after fire. However, steel has one significant disadvantage over wood, steel material conducted heat extremely well, [3J, Wood is a renewable resource, recently attracted by public attention, as an environmentalIy friendly material. This product is a building material with attractive attributes, as architectural and structural aspects. The wood when exposed to accidental actions, such as fire conditions, has a surrounding charring depth. However, this layer can delay the heating process to the wood core section, acting as an insulating. By comparison with other traditional materiais applied to the building construction, wood exhibits an exceptional strength, contrarily to that occurs with steel elements, where the structural collapse may result from the deterioration of mechanical prope11ies with temperature increase, [4].

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408 INTERNATIONAL CONGRESS FIRE COMPUTER MODELL"IG

The combination between wood and steel leads to economic and ecologic benefits, weight optimization, fire resistance increase, ealihquake resistance and an efficient assembJing [5]. Recently building codes and standards have been increasing the performance of structures in

fue. Several researches have presented experimental and munerical mo deis for the study of wood degradation in presence of high temperatures [6-8]. The charring rate of softwood Of

hardwood material exposed to fire conditions has been studied by researchers in different countries, [9-16]. Also, several studies have been presented to investigate the behaviour of steel elements under fire conditions, [17]. The greatest opportunity in fire research is the development of computational fire resistance models and experimental methodologies for hybrid materiais submitted to natural fire scenarios [18]. In this work the fust objective was to produce the temperature time history in different design solutions submitted to different fue scenarios. The second objective is to verifY the best constructive solution and compare the fue resistance. Ali mo deis were developed by the finite element method using ANSYS.

2 MATERIAL PROPERTIES

The most important factors for structural strength in wooden elements submitted to fire are the material properties degradation and the charring deplh formation. The wood density decreases with the material degradation caused by the pyrolysis process, in the presence of high temperatures. For wood temperatures around 280[°C] to 300[°C] are general1y prescribed as the start of pyrolysis, [19]. W ood bums leading to material degradation and decomposition. The wood therrnal properties are strongly affected by temperature and moisture content levei . The thermal behaviour of wood is complex, but has been well documented. Eurocode 5 [20] provides lhe design values for wood thermal properties, for density, therrnal conductivity and specific heat, figure 1. The values below about 350[°C] represent the properties of wood and above 350°C represent the properties of charred layer. The specie (Spruce) considered in thi study presents a value of density equal to 450[kg/m3].

The thermal properties of steel are function of the temperature and should be determined from Eurocode 3 [21]. The density of steel is considered constant and equal to 7850[kg/m3]. The

specific heat and the thermal conductivity of steel are represented in figure 2, [21].

Figure 3 gives the therrnal properties ofthe air with temperature dependence for specific heat, therrnal conductivity and density, [22].

The evolution offire temperature (Sa in [0C]) over time (t in [min]) was defined by standard fire curve. In this work the standard IS0834 fire curve was adopted, with the expression I, according the Eurocode 1 [23]:

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HYBRlD WOOD/STEEL ELEIvIENTS UNDER FIRE

Barbosa,L.F.M; Almeida, P.ML.; Fonseca, E.MM; Barreira, L.MS.; Coelho, D.c.s.

14 ~ --,,--- ---,

- Specific heat [JlkgKJ

2 '

1

I

....

_----250 500 750

Temperature [oq

-- Density [ g! cm ~]

~-- Thennal conductiv; ty

[W!mK)

1000 1250

Fig. 1. Thermal properties ofwood.

60~ --- -- --- ---- --~ ----~~~

- Specífic h~t(xlOO)[J/kgK]

50

10

--- TheJmal conductivity

[WímK]

~--~--~-~--~-~--~--~-~--~-~--~---

---250 500 750 1000

Temperature r"C]

Fig. 2. Thermal properties of steel.

1250

1.25 ~--- --- ---~ I'.

1.00

0.75

0.50

0.25

0.00 O

,

,

,

, , , ,

., .... , ... ,

- Specific h",t (,1000)[JlkgJ<)

- - Density [glcm;)

--- Thennal conductivity

[WimK)

-_

..

--

---

-_

.. ---_ .. ------

-_

.... ---_ ... ---_._--"'-_ ...

-._-

"' .... _ ... ---,--_._--

-_

..

250 500 750 1000 1250

Temperature [0C]

Fig. 3. Thermal properties of air.

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410

3 STUDIED MODELS

INTERNA TIONAL CONGRESS

FlRE COMPUTER MODELJNG

Table 1 represents three different geometries in study (Gl, G2 and G3), and the fire scenario, considering one side (lF) and three sides (3F). For each model, four different nodal positions were chosen to obtain the temperature evolution during one hour of fue exposure.

Geometries Fire at one side (1 F) Fire at three sides (3F)

, i

G1 - - - 'f

~

~

I I I I I

~

~

G2

G3

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HYBRlD WOOD/STEEL ELEMENTS UNDER FIRE

Barbosa,L. F. M ; Almeida, P.M L.; Fonseca, E.M M; Barreira, L.MS. ; Coelho, D.C.S. 41\

Table 2 represents a11 different combinations according to the material for each mode! (Wood, Steel, Wood-Steel). According to the fire scenario and the material combination, 24 different mo deis were considered in this study. Four of these models were considered with air in the internaI cavity. The air modelling permits to verify the heating conduction inside the void.

G2-1F-W G2-3F-W

G3-1F-S G3-3F-S

G2-1 F-S G2-3F-S

G3-1 F-S-air G3-3F-S-air

Wood-Stee\ (WS)

G2-1F-WS G2-3F-WS

G3-1F-WS G3-3F-WS Table 2. 24 models andjire acliol1.

Steel-Wood (SW)

G2-1F-SW G2-3F-SW

G3-1 F-WS-air G3-3F-WS-air

The boundary conditions considered in a11 analysis are convection and radiation, according to the temperature evolution in fire . A transient thermal analysis was defined with ANSYS. A two dimensional finite element with eight nodes (PLANE77) was considered. AlI temperatures were obtained during one hour of fire exposure.

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412

Time history, O to 3600[s]

1000 - - "

900 _ _ _ _ _ _ _ _ _ -::=.,.,.=-'=_'='_ - ~-- ~ -' - ISO S ~

soo --- ~--- - - ---

-"'. --- _ 7 '~ --- -- Node I 2: 600 ~ ,,$'

--;::: 500 ,-- ,..-- - - . . .

-.

'

~ 400 -.'- - - · - -Nú<lc2

~ 300

10U - 'No.k3

100

o '," . -o ~oo HOV 1200 !(1()() 1000 2400 2J;(}) 3200 3600 -·· · Nvdc·-t

Timc b J

G1-1F-W

1000

700 "

E hOO •

i:

'"

'00

---,O<> "

100 ~ ... ' ; :~.:.:..::.~- .. ~.'" :.r-- .•• --:-:.; ,; ,:;:.~ ••. -.-..::;:' .. ..:-~

1000

900

'00 700

E

600

~

[ 500

;:: 400

"

300

200

100 o

o 400 1100 1200 1600 :!00l 1400 2800 3100

G1-1F-S

- 15011)4

- - K.ó!

· ··I\oocl

-ISO í!34

- - Nodc I

- · Nod,, 3

o 400 ROO 1200 lól.:l 2000 2-\.00 2800 :UIll) 3600 --·Nooc4

1000

700

E...,

~ 500 .

!

400 :

300 '

200

lO<>

G1-1F-WS

o ---...:..--==:.=:=- ---:- =- ~-====- - ~

-1501134

-- f'\o« I

- ·1\",1..:3

o 400 800 IZOO 1600 lDOO 2400 2XOO 3200 )tiOO ---'P\odo.:'" TinlCls!

G1-1F-SW

INTERNA TIONAL CONGRESS

FIRE COMPUTER MODELING

Temperatures at the end of 3600[s]

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HYBRlD WOOD/STEEL ELEMENTS UNDER FIRE

Barbosa,L.F.M; Almeida, P.ML , Fonseca, E.MM; Barreira, L.MS.; Coelho, D.es.

1000

900 ,ou

300

:(1)

I~I

Time history, O to 3600[s]

- ISQS3J

-- N.:xkl

--Nooc)

U ~' _ _ ' _ _ J"""""" """':;;:'=': ;:;:_ '::: ':~:=:'; ;:_~:"=_ ' _ ' ~_ ': _:

o 400 SOO I:!OO lóOO 1000 2400 21.100 3200 3600 "" N(MJc4

Timc(s)

Temperatures at the end of 3600[s]

i

413

G1-3F-W ~J:"! .~d.~~~i.I · bl.:J:..§..1? ·i:!>·:""':.~!:"'~ll:-bl".J;'-1 n . ~!!.'Ji . ú'!,._"? '~i

' OI) - [SOI:l.M

,~,

)011

1)

o 400 Il0l1 1200 1600 2110U ;woo 2Il00 l:!lD ) (,00 ---· ~0lk:4

1000

900 $OU

1000

HOtl

70()

2600

~ 500 E 400 .

é'

300

20(1

11lO

l'it't<' I ~ l

G1-3F-S

- lS0!CU

-- Nod..: !

400 1.100 1100 -1600 2000 2400 28()() .nou 3600 --·- Nodc4

Timc [s]

G1-3F-WS

- 1$0834

--Nudcl

• . -Nodc2

- ·Nm t ~.\

o L-- 7 --"--' - -" "" ~= ;':':'-':_' ''

_-o "'00 800 1:'00 16QO 2000 24()() 2800 3200 3600 ·-·-:-.lode4

Timelli]

G1-3F-SW

I

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414

1000

900

'""

Time history, O to 3600[s]

700 7

-G wo - ~ , ~ -- .

-'-

,-~ 500 - ,r

~ .\00 '

!

)00 __ L ;

~---'---100

O ~ -- ----~- ~ - " --- - --

--- I $O:U4

-- Node I

- -NOOc 3

() 400 SOO 1200 1600 2000 1400 2ROO 3~OO 3600 ----Nodc4

lUOO \lOO 100 o 1000 .00 800 300 200 100 O 1000 '00 7W

E

600

!

'00

"-~400

Tim\"{.' ] G2-1 F-W

- IS08 ~

-- ""rlI! I

~ =

..

----· --1\0&: 2

O

_. :~

.. _ ..

-=~ ~-- _ ._ - _ . _ . _ ~. ~- _

...

4M llM 1200 It.OO lOO') 2400 ~OO ]200 3600 - -·l\otlc4

Tintel sl

G2-1F-S

- ISO 834

-- Nooe 1

_ . Nodc3

~: =":': .:=.~ ~~ : :: ::~~ =-. ~~ =- ._ ... ---_ ... -.. __ .... .

O 400 &00 1100 1600 2000 2-100 2800 3200 :1600 ---·Nm!,,--I

Ti n:c{s)

G2-1F-WS

- :50834

-- '.Jode!

· ··X00..:2

3{)o , •

200

100

O ~--- - -- --~ -- -- - --

----N<hk:i

() 400 1i00 IlOO 1600 2000 2400 ZSOQ 3~OO 3600 ----Nodc4

Ti ru.: (s)

G2-1F-SW

INTERNATIONAL CONGRESS

FlRE COMPUTER MODELING

Temperatures at the end of 3600[s]

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HYBRlD WOOD/STEEL ELEMENTS UNDER FIRE

Barbosa,L.F.M.; Almeida, P.ML.; Fonseca, E.MM ; Barreira, L.M S.; Coelho, D.es.

Time hislory, O lo 3600[s]

-ISÚlI.l4

· · · N,Jdc2

- ·NoJc )

100 {' / ' . /

Ú '-- --- --- ---

-.-o .\(1<) ~oo I:!OO 1600 2000 2400 21\00 .t:!oo j6(l(} ---·NOI.I<.:-I

1000

900 '00

70D

600

500

400

}OO '00

1000

900

'00

7~)

i:

,

6(}O

I

500 ~ 400

JOO ;,'

200

"

Timc[sJ

G2-3F-W

- I5OS):;

-- No'.!" I

-100 ~OO l!OO 1600 100() 2400 2800 3200 3600 ----Nooc 4

Tim" fsl

G2-3F-S

- ISON3.1

-- Nodc l

· · -J\'odc2

- 'NodcJ

400 800 1200 1600 !OOU 2400 2800 J:OO J600 -··· N«I,,-I Time[sj

G2-3F-WS

- ISO!l14

-- Nodc 1

· · -Nlldc2

- ' NoJc ) 100 ,';

o ~ .--- -- - - -- --- , -. - ..

---o ..\00 ~OO l~ OO 1600 ~OOO 2400 2l!OO J200 3600 ---·Nüdc4

Tll1'c [s]

G2-3F-SW

Temperalures aI lhe end of 3600[s]

,---

j

!Itl!':'j,.y·;ó;:,m:

i

===--h ,x-.,~7~s.:·7~:~.b~.7il!_ . Y.ffiS4& . S<;."%5 . '>;"

Table 6. Model G2 and fire scenario (3F).

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416 1000 900 800

'00

100

Time history, O to 3600[s]

-ISO ":3.J

-- Nodc3

-':::"::':~:,..:..:.:: :'~ .. :._---_ .. -~.---- -'--

----.tOO !)()O 1200 16W 2000 ~400 21<00 .l:!IX1 J600 ----Í'iOOt 4

1000

"'lo 'I'" 700

E60tJ

I

soo

t

400

300

",,,

'00 o Tltn.; [s] G3-1F-S - lSOK3<J

-- Node 1

---Node:?:

~;.:.:_:.:':':: _ :":':"=' - -_ ..

-o .tOO 1100 1200 1(>0() ;:000 2400 2800 3200 3(;00 ----N(xk4

900

",Q

700

E 600

~ $00

"

J

400 J 01l

200

Tim ;:r~J

G3-1 F-S-air

100 ~_...::_-:.;..: ~;..: _: ~ ;~~_~ ::~_~~ : _:: = : _____________ .. ____ _

"

-1~ OX~

.... "'<'lI,: 1

li 400 800 1200 lóOO 2000 2400 2800 3200 3600 ----:"\'OIj",4

1000

'JOO !

~ L.

700 :

E r..oo '

~m

..

~

...

"'"

"'"

100

T imcLs]

G3-1F-WS

~-""",: _ ._:",,:,,::_;';'::_= ~- -:---.: :'::_:':' :: ~. _ •• __

._--_._---_.-•

- ISO X.'4

-- Nudc I

- - No';,,)

o .JOO lIllfl 1200 1600 ZOOl} ! .. oo .v;un J:!OO J hnJ - ' -N<Jtk4

G3-1 F-WS-air

INTERl\ATIONAL CONGRESS

FIRE COMPUTER MODELlNG

Temperatures ai lhe end of 3600[s]

,

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HYBRlD WOOD/STEEL ELEMENTS UNDER FIRE

Barbosa, L.F.M; Almeida, P.ML.; Fonseca, E.MM; Barreira, L.M S.; Coelho, D.C.S.

li""

900

Time history, O to 3600[s]

·WO 1100 12()(J 1600 2000 24011 2S00 3200 .'600 ----.Nodc4 limeis]

Temperatures aI the end of 3600[5]

-

==""""'"

417

G3-3F-S _ _ :"Ii.:.~~ 7):a.~~3 './: .. ~&.Z~~ .• )' <I<".1I9-'~:' · ;.:.~") , 6í:l

1000

900

SOl)

700

~ (>OI) j ~OO

"-~ .100

,jO(J

1000

")lI

700

E

600

i

500

~

~ 400

~OÜ

'00

1000

'''''

800

200

- 150 834

-- NoJcl

· · -Nvdcl

- - '1odl:.1

400 SÔO 1200 1600 2000 2400 2~OO noo J6QíJ ----N<Jdc4

rin..:[s1

G3-3F-S-air

-l SO~J4

- ·NodcJ

400 XelO 1200 l (ri)!) ZOOU 2400 1800 .1Z(XI .1600

--l'imc[sJ

G3-3F-WS

-150834

.-'

-· NOOt3

400 800 I!OO 1600 2000 2400 2800 3200 3600 ---- NotL: 4 Tímc[s}

G3-3F-WS-air

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418

4 RESUL TS ANO OISCUSSION

INTERNA TTONAL CONGRESS

F/RE COMPUTER MODELING

After ali simulations it is possible to identify different conclusions. The fire exposure at tlu'ee sides is the worst situation. For the same period of time, the temperature increases, in a11 elements. The interface between charred and noncharred wood is the demarcation plane between black and brown material and is characterized by a temperature of 300°C, according Emocode 5 [20].

Considering all different geometries and materiais:

-For model G 1, the elements that have wood in front of the fire exposure, protects the core section. For materiais with steeI in front of the fire, the heat conduction is very high and quickly heats a11 components.

-In the model G2, the wood elements in fIOnt of the fire are very thin, and quickly lose their resistance due the char layer formation, compromising the remaining structure. In this model the steel material has better performance.

-For mo deI G3, when wood material is extemally applied to the steel profile, plays an important role as insulation, reducing the temperature inside steel. In the cases where both (outside and inside of the model) are made of steel, the temperature in the inner pro file is higher, than the previous solution.

According to these results, it can be seen that wood elements present lower temperatures than steel, and the maximum temperature in the model is always inside the char layer. The hybrid modeI can perforrn well under fire conditions. Regarding the best design solution for a11 studied models, it is concluded that the hybrid model 3F-G3-WS has a good fire resistance even for three sides exposure, showing the ability of wood to protect the steel.

REFERENCES

1. U.S. Department of Housing and Urban Development, Stee1 Framing Alliance and NAHB Research Center Inc., Hybrid Wood and Steel Sole Plate Connection Wa11s to Floors Testing Report, American IIOn and Steel Institute / Steel Framing A11iance, 2003, Revision 2006, Research Report RP03-4.

2. Toshihiro, A., Marin, K., Naoyuki, 1., Masato, M., Kuniaki, I. T. O., Design of a Hybrid Structure Consistillg of a Steel Beam String Structure and a Woodell HP Shell Reinforced by Aramid Fiber Sheets, Journal of the International Association for Shell and Spatial

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HYBRID WOOD/STEEL ELEMENTS UNDER FJRE

Barbosa,L.F. M ; Almeida, P.ML.; Fonseca, E.MM; Barreira, L.MS.; Co elho, D.es. 419

3. Jan, K. , Phil,

c.,

Making Steel Framing as Thermally Efficient as Wood Most Current Developments from ORNL, Proceedings of the Thirteenth Symposium on Improving Bui1ding Systems in Hot and Humid C1imates, Houston, TX, ESL-HH-02-05 -40, 20-22 May 2002.

4. Fonseca, E. M. M., Barreira, L., Experimental and Numerica1 Method for Determining Wood Char-Layer at High Temperatures due an Anaerobic Heating, International

Journ al olSalety and Security Engineering, 1, No. 1, 2011 , pp. 65-76.

5. Kamyar T., Wo1fgang W., Tamir P., Michael K., Steel reinforced timber structures for multi storey buildings, WCTE, World Conference Timber Engineering, 2012.

6. White, R. H. , Dietenberger, M. A. , Fire Safety, Chapter 17, Wood Handbook: Wood as an Engineering Material, Forest Products Laboratory, 1999, USDA Forest Service. 7. Poon, L., England, l P., Literature Review on the Contribution ofFire Resistant Timber

Construction to Heat Release Rate - Timber Development Association, Warrington Fire Research Aust. Pty. Ltd., pp.l -78, 2003, Project NO.20633 version 2b.

8. Janssens, M. L., Modeling of the thermal degradation of structural wood members exposed to fire, Fire and MateriaIs , 28, 2004, pp. 1 99-207.

9. Schaffer, E. L., Chan'ing rate of selected woods transverse to grain, Forest Products Laboratory, 1967, Madison (WI), Research paper FPL 69.

10. White, R. H., Charring rates of different wood species, PhD dissertation, 1988, Madison University ofWisconsin, Madison (WI) ,

11. White, R, H" Erik V, Nordheim, E. V., Charring rate ofwood for ASTM E1l9 exposure,

Fire Technol, 28, N" 1, 1992.

12. Konig, l, Walleij, L., One-dimensional charring of timber exposed to standard and parametric fires in initially unprotected and postprotection situations. Swed Inst Wood Technol Res, 1999.

13. Gardner, W. D., Syme, D. R., Charring of glued-laminated beams of eight austra1ian-grown timber species and the effect of 13 mm gypsum p1asterboard protection on their charring, Sydney, 1991, N.S.W. Technical report nO.5,

14. Co1lier, P. C. R., Charring rates oftimber, Branz, New Zealand, 1992, Study reporto 15. Pun, C. Y. , Seng, H, K. , Midon, M. S., Malik, A. R. , Timber design handbook. FRIM,

1997, Malayan Forest Records no.42.

16. Cachim, P. B., Franssen, l M., Assessment of Eurocode 5 Charring rate Calculation Methods, Fire Technology, 46, 2010, pp. 169-18l.

17. Nwosu, D. I , Kodur, V. K. R , Behaviour of stee1 frames under fire conditions, Cano J.

Civ. Eng., 26, 1999, pp. 156-167.

18. Joo-Saeng P., Jun-Jae L. , Fire Resistance of Light-framed Wood Floors Exposed to Real and Standard Fire, Journal 01 Fire Sciences, 22, 2004, pp. 449-471.

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420 INTERNATIONAL FIRE COMPUTER MODELlNG CONGRESS

20. EN 1995-1-2:2004. Eurocode 5: Design oftimber structures, Part 1-2: General-Structural fire design, CEN, 2004.

21. EN 199312: 1995 . Eurocode 3: Design of Structures Part 12: General Rules -Structural Pire Design, CEN, 1995.

22. Holman, J. P., Transferência de Calor, 1983, McGraw-Hill, São Paulo.

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