Untitled - Biblioteca Digital do IPB

of computer based techniques, as well as laser-optics methods, nanotechnologies
and nanomaterials, among many other technological advances, added new dimension
and perspectives to minimize or prevent catastrophic failures of engineering systems,
structures and components.
This volume contains the extendedAbstracts of the 380 papers accepted for presentation
in the IRF2013-4 1h International Conference on In tegrity, Reliability and fa ilure held in
Funchal/Portugal, 23-27 June 2013. The book is complemented by an accompanying
CD-ROM containing the full length papers.
IRF2013 is part of a prestigious series of conferences that was initiated in 1999, in
Porto (Portugal), coordinated by the International Scientific Commiltee on Mechanics
and Materiais in Design. The conference altracted over 300 participants with 380
accepted submissions from 45 different countries around the world . These papers
were presented in June 23-27, 2013 in the magnificent city of Funchal, Madeira, and
the conference themes focused on nanoengineering, computational and structural
mechanics, micromechanics, experimental mechanics, advanced materiais, thermoftuid systems and case studies , among other engineering topics.
RECENT ADVANCES IN
INTEGRITY-RELlABILlTY -FAILURE
J.F. Silva Gomes, Shaker A. Meguid (Ed)
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Proceedings IRF2013
4th International Conference on Integrity, Reliability and Failure
FunchallPortugal, 23-27 June 2013
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The
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SYMPOSIUM_18
Safety Df Wooden Structures
Coordinators:
Elza M.M. Fonseca")
Departmenl af Applied Mechanics, Polylechnic Institule of Bragança. Portugal
Débora RS.M. Ferreira" )
Departmenl of Applied Mechanics, Polytechnic Institule Df Bragança, Portugal
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( 'Associale Edilors for lhe papers in Ihis Symposium
20J3
/NTEGRlTY. RELlAB/L1TY ANDFAILURE
PAPER REF: 3899
CONSERVATION OF WOODEN CHURCH IN THE VILLAGE
TRNOVÉ
Kahu-ína ZgútovlÍ, Marlin Pituiíák, Jurnj Srámck, Dominika ÕUfcková'")
Dcpartmcnt orTcchnology and Managcmcnl ofthc buildings, Faculty ofCivil Enginccring, Univcrsity ofZilina
(OIEmail: [email protected]
ABSTRACT
Culturally, it is importaot to upkeep national monuments and to preserve them for future
generations as historical heritagc. In the process af preserving historie sites it is very
important to choose a rernediable appropriate method which will conserve the authenticity Df
the object to lhe greatest extent. Determinatian Df the appropriate mcthod af remediat-ion is
essential to the object period of life and its usefulness. The presented paper describes the
diagnostics, remedial design and very successful reconstruction of the wooden church of St.
George in the village Tmove. This ehureh is the westemmost located wooden ehureh in
Slovakia. It is a national historie landmark and the first information about the ehureh dates
back to 1583.
KeYII'ords: wooden objects remediable, biotic factors , diagnostics, reversibility principie, the
principie of authenticity, the principie of rnoderation. replacement of damaged
wooden elements, grouting.
INTRODUCTION
The church in Tmove is a single-nave building built oflog8. Short nave facing east has almost
square ground plan. It accommodates sanctuary, presbytery and later built lower nf a &ame
structure filled with wooden plates. The tower, finished by a pavilion roof is only slightly
higher than a oave. Tbe roof is saddle shaped, covered with wooden shingles. Tbe church is
built ofwooden beams. precisely deposited so there are nearly 00 voids between them [I].
Year of construction of the church is unknown and ali its history is shrouded in mystery.
Nevertheless, there are many rumours regarding the age of the building. According to the
oldest extant written record, the church already existed in 1583. lo 2010, the
dendroehrooalogical dating of wooden elements specified these conjectures. Samples were
taken from logs from walls, roof and tower structure. Standard methods of chronology were
applied. In conclusion of examination, it was c1early deterrnined that the walls and roof of the
church were made of fir and spruce truncated in lhe period from 1610 to 1614. Tower
supporting columns were carved of fir truncated aI the tum of 1768/ 1769 [2].
DIAGNOSTICS AND REMEDIAL DESIGN
Repair works on the church, which was near the collapse, were under preparation for several
years. Proposal of a suitable method lo remedy damaged wooden structures which would
preserve safety af a sacral buildiog in use was based 00 ao accurate analysis af the situatiao.
which inputs were provided by a detailed survey of the structure directly 00 the object.
Because the main nave of the church with pre8bytery were partly deformed due to the natural
degradation of wood and damaged stability of the buildiog, a debatable implementation of a
Symp_18: Safely ofWooden Stmcfllres
639
41h Jnternatiol1a/ COllferellce 011 /l1tegrity, Reliability and Foi/tire
static security of the object was performed in the early nineteen-nineties. New concrcte
foundation \Vilh waterproofing was provided and the log work was supported by wooden
slruts in order to avoid further distortions. The solution was to be temporary. however it was
not lhe luckiest and the most suitable. Concrete foundation with concrete drainage gutter and
a supporting strueture disturb the appearanee of lhe ehureh, and ultimately increase the
adverse humidity conditians in the immediate vicinity af the church. The church tower frame
structure has beeo reinfarced back in the late nineteen-sixties. Steellongitudinal prefiles were
ineorporated and anehored in plaee and in the direetion of the original elements of the wooden
fiame, to separately lransfer ali load from lhe tower to the ground. Inside, the choir \Vas
supported by two wooden columns. Recent engineering - gealogical survey af subsoil showed
a serious problem, whieh could in the near future fundamentally endanger the slability of lhe
church. Slope, where it is located is unstable and shows a moderate movement.
Examination of canditians ofwaoden elements included the folIowing stages:
Wooden elements moisture content
Biologieal and olher damage lO wooden elements
Deformation, craç;ks and otber abiotic defects in the wooden elements
The survey was to define the extent of damage, to preserve safety ofbuilding when in use and
to preserve safety of the surrounding lombstones [3].
CONCLUSION AND RESULTS
Based on the detailed survey and definition of the damage, the remedying works have becn
proposed. The main task of remedial \Vas to preserve as much as possible of the original
building material as the object under considerarian is unique historical monument in lhe given
regian.
Wooden buildings of similar eharacter are mainly localed in the eastem par! of Slovakia.
Because restorers in Eastem Slovakia have a lot of experience with the preservation of such
historie sites and also have lhe necessary teehnology available, it was deeided to take lhe
chureh into parts and transfer il to Eastem Slovakia. There was perforrned a successful
reconstruction, which is evident from Figure I.
Fig. I - Church in Tmovc prior, during and after rcconstruclion
REFERENCES
[1]-The team of authors. 2010. Monograph of the village Tmove.
[2]-Ing. Tomas Kyncl. 2010. Dendrochronological survey of wooden elements at the Church
ofS t. George in Tmove: Research Report. Bmo: DendroLab. 2010. p 27.
[3]-Prof. Ing. Ladislav Reinprecht, CSc. 2010. Expert opinion on lhe conditions of lhe
wooden structures at the St. George Chureh in Tmove: expert opinion. Sliac. 20 I O. p. 34.
640
Frlnchal/Portugal, 23-27 JUlle 2013
/NTEGRlTY, RELIAB/LITY AND FA/LURE
PAPER REF: 4699
RECYCLED WOpDEN RAILROAD TIES
Edgar V.M. Cnrrasco W1, Leonardo B. Passos' Judy N.R. Mantilln 1
IOcpartrncnt of Structural Engineering, Federal Univcrsity af Minas Gerais, Belo Horizonte, Brazil
2School ofCivil Enginccring and Architccturc, FUMEC Univcrsity, Belo Horizonte, Brazil
(')EII/C1i/: [email protected]
ABSTRACT
j
n
11
Currently, due to environmental concem over high deforestation rates and the high cost af
railroad ties, railroad companies have drasticaIly reduced the use af these native wood
clements in railroads. Thus, other materiais such as sleel, plastic and wood from reforestation
(Eucalyptus) are being used in the manufacture of railroad ties. For the purpose of reducing
environrnental impact, a recycling process was proposed in which scrap wooden railroad ties,
which are discarded or sold at low prices by the authorized railroad company, are transformed
into glued laminated wooden railroad ties. This study presents the manufacturing stages of
recycled glued laminated . wooden railroad ties and lhe procedure for delermination of
elasticity modulus Ihrough the ultrasound method for lhe purpose of classifying the wooden
pieces lo optimize lhe mechanical behavior of lhe railroad tie. As a main conclusion, it was
found lhat it is passible to abtain one waoden railroad tic fram recycling af tive scrap railroad
ties, thus signiticant1y reducing environmental impact.
Keywords: railroad ties, glued laminated woad, recycling, ultrasound.
n
I.
h
INTRODUCTlON
As of the 19905, various changes in natural systems directly related to human aClivity have
led the planet lo environmental colIapse thal Ihreatens not only biodiversity, but also the
quality af life for human beings. Various spccies have already becn driven to extinctian,
natural cycles have been changed and the earth's climate itself has undergone significaol
variations due to a combination of atmospheric polIution and deforestation (Primack, 2006).
Recyclíng is ao altemative for minimizing these effecls. Glass, paper and plastic are currently
lhe mosl recycled products. Wood may also be recycled or reused.
In regard to use of wood in railroad ties, Heebink e Supetjeky, 1977 and Geimer, 1982
studied railroad ties composed af laminated particles (manufactured from scrap railroad tics
ground inlo smalI flakes of 0.508 mm thickness and 50.8 mm length). According to FPL
(Howe, 1976), in lhe 19705, railroad ties \Vere manufactured by the process of pressing of fine
laminas, in which Red Oak waod logs were cut up into Iaminas, dricd and glued iota bars in a
continuous processo
le
Therefore, with a view toward reuse af wood, recycling af scrap railroad ties was considered
for meler gauge railways, transforming the scrap ties in lo recycled railroad ties made of glued
laminaled wood (RT-GLULAM). The railroad ties were cut up into laminas and they were pul
together lateralIy and longitudinally. Before making the new railroad ti e, the laminas were
classified through the use of ultrasound techniques and then glued in a juxtaposed fashion
fonning lhe new railroad tie.
{3
Symp_ 18: SalefJl oI Wooden Sll1lclu,.es
:h
641
41" J"lemational Conferellce 011 Jlltegrity. Reliability alld Failure
RESULTS AND CONCLUSIONS
The types ofwooden railroad ties used in the produclion ofRT-GLULAM are shown in Fig. I
Fig. I - Classification of scrnp railroad lies
The manufacturing stages of the RT-GLULAM are shown in Fig. 2.
Fig. 2 - (a) classificntion and rncasurcment ofthc scrap railroad tie. (b) ultrasound lest, railroad lie and larnina,
(c) cutting up the rai lroad tie, (d) prcparation ofthc laminas, (e) gluing and prcssing oflhc RT-GLULAM,
(f) railroad tics (RT-GLULAM).
The study showed that it is possible lO obtain one wooden railroad lie (RT-GLULAM) from
recycling of tive scrap railroad ties, thus significantly reducing environrnental impacL
REFERENCES
[I]-Primack, R. B; Rodrigues, E. Biologia da Conservação. Londrina: Editora Planta, 2006,
pp.69-134.
[2]-Geimer, R. L. Feasibility of producing reconstituled railroad ties on a commereial scale.
Uniled Stales - Department of Agriculture, Foresl Service, Forest Producls Laboralory - FPL
411. 1982.7 p.
[3]-Heebink, B. C.; Superfesky, M. J. Recycling lhe wood crosslie: Researchers develop and
tesl laminated particle lie. Railway Track and SlTUctures. FPL. Foresl Service. 73 (7).
Ju1.l977. p. 26-31.
[4]-Howe, J. P.; Koch, P. Dowel-Laminaled Crosslies: Performance in Service, Technology
ofFabrication, and Future Promise. Forest Products Joumal. V. 26, n.5. p. 23-30. May, 1976.
642
FUl1chal/ Porlugal. 13-17 June 2013
INTEGRlTl'. RELlABILlTl' AND FAILURE
PAPER REF: 4524
DIMENSIONAL STABILITY OF WOOD IN PRESENCE OF W ATER
Déborn Ferreira t ·), Cristiana Pinto, Paula Borges, Elza Fonseca
Polytcchnic Institutc ofBragançu (IPB), Bragança, Portugal
(O)Email: [email protected]
•
~
ABSTRACT
Moisture is one ofthe most imporlant causes for building palhology. The material degradation
cao be affectcd by lhe presence ofw31er, both in vapour and liquid phase. Wood has a strong
hygroscopic behaviour, with a strong variation af moisture content and dimension stability
caused by modifications af lhe relative humidity af lhe surrounding air. The propcrties that
define lhe bchaviour af wood against temperature and rnoisture actions were studied in this
work. Hygroscopicity and shrinkage wcre given speeial attention.
Key",ords: hygroscopic, \Voad, experimental evaluation, dimensional changes.
INTRODUCTION
Waad is aur mast impartant raw material. It is important nol anly because it is used for
lileralJy hundreds af products, but alsa because it is a renewable natural resource. Through a
carefully and planned use, forests could provide a perpetuai supply of wood. Ali wood in
growing trees contains a considerable amount of waler as part of lhe photosynthesis and lhe
grawing processes. This water is commonly called sapo The main goal of this work is to study
the water movement in wood: firsl of ali, the drying process, which occurs before the
rnanufacture and use as finished wood products, and secondly lhe gain and loss of waler in
response lo changes in environrnental conditions that surroun.d lhe \Vood. The rnoi sture
content relationship has an important influence on wocd properties and performance (White et
ai, 1999).
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Wood is dimensionally stable when moisture content is greater than the fibre saturation point
(MCfs). Below MCfs wood dimensional changes and it gains moisture (swells) or loses
mois!ure in the fonm ofbound water. The levei ofMCfs depends on the relative humidity and
lemperature af lhe surrounding air. Shrinkage and swelling are lhe cause of rnany cf the
problerns that occur in wood during dryíng and in use, therefore, an understanding af them
will help minimize such problems. Splitling, warping, and open joints are examplcs af
problems that occur due to uneveo shrinkage .
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WORK IN PROGRESS
An experimental program was defined with the aim to evaluatc lhe dimensional stability af
hardwood and softwood species. The maritime pine softwood (Pinus pinaster) and the
chestnut and oak hardwood (Quercus prinus) of the North-east region of Portugal wi ll be
analyscd. A group of thirty specimens were made for each specimens of woad. The
experimental procedure will be mude according NP EN 614 and NP EN 615. The specimens
will be dricd in a ovcn-dry with the references conditions af T= I 03 uC±2°C. As the moisture
content of the specimens is changed, unti l achieving the hygroscopie equilibrium of the
S)'lIIp_18: Safet)' of Wooden Strllctllres
643
41h Internatiolla/ Con/erence 011 /megri(v. Refiabili(}I Qnd Fai/tlre
environrnent, the measurements were taken being possible to quantify the dimensional
variation suffered during this processo The geometry assumed for the specimens was
40x40x10, based on the NP EN 614 recommendations. For aU measurements, adiai g.uge
wa5 used with a calibrated precision equal to 0,00 I 111m coupled lo a steel base was used (Fig.l ).
For each measurernent, the moisture conteot in wood specimens will be calculated using an
oven-dry method suggested by NP EN 614. Therefore, it \ViU be possible to assess the weight
los5 of each specimeo for the three wood species.
.
The weight of moisture contained in a wood sample, as a percentage of its oven dry, is
expressed according the following equation:
me
where
waad.
II1c =tno isture
~
w" - W. X 100
W.
content; Wg=green weight of the wood and Wo=aven dry weight af the
The fallowing figures represeol lhe experimental setup used to measure lhe moisture conteol
in ali specimens. Fig. 2 represents the oven-dry method and Fig. 3 presents the geometry
assumed for the specimens based on NPEN 614 and NPEN 615.
Fig. I - Test sctup used to mensure
Fig. 2 - Ovcn-dry mcthod
Fig. 3 - Specimens wood scctions
Conclusions about lhe moisture content in hardwoods and softwoods of the North-east region
of Portugal will be included. In general, hardwoods typically have a % of moisture content
between 60-100%, while sofiwoods have different values according in on heartwood (30100%) or sapwood (110-220%).
REFERENCES
[1]-NP-614:1 973. Madeiras - Determinação do teor em água.
[2]-NP-615: 1973. Madeiras - Determinação da retração.
[3]-White, Robert H. e Dietenberger, Mark A. 1999. Wood Handbook - Wood as au
Engineering Material. Madison, Wisconsin: USDA - United States Dep.rtment of
Agriculture, 1999.
644
Fllllcha/IPortllgal, 23-27 June 20/3
INTEGRITY, RELfABILfTY AND FAILURE
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try
PAPER REF: 3917
EMBEDDING STRENGTH PARALLEL AND PERPENDICULAR TO
THE GRAIN UNDER THERMAL ACTION
Manuel Jcsús M:mriquez Figueroa l, PoliaDa Dias de Moraes1(O)
I Department ofBuilding Engineering, University af Magallancs, Punta Arenns, Chile
"Department of Civil Engincering, Federal University ofSanta Catarinn, Florianópolis, Brazil
{.)Email: [email protected]
ABSTRACT
This paper evaluates the embedding strenglh parallel and perpendicular lO lhe grain of Imee
different species af timber in 15 temperature leveis in the range af 20 to 230 °C. It was
concluded that the wood embedding strength decreases nonlinearly with the increase of
temperature.
Keywords: wood, embedding strength. temperature, fire.
INTRODUCTION
Although bolled joints are largely used on timber strutctures, they are lhe weak points
deserving special attcntion during designo In order to design them appropriately, it is
necessary to know the embedding strength of wood at room and high temperatures. Several
researches have been conducted 00 the intluence of temperature 00 the mechanical strength of
wood, which indicate that the mechanical properties of the wood decreases with increasing
tesl lemperature (Gerhards, 1982; Moraes el al.,2005; Manríquez and Moraes, 2009; 2010).
ion
cnt
30-
The abjective of this study is to evaluate the intluence af temperature on resistance af three
waad species fram planted farests: ElIca/yplus saligna, PillllS taeda and Schiz%biunI
amazonicllm. At room temperature, the samples had a moisture content af 12% and average
densities of 797 kg/m', 429 kg/m' and 378 kg/m', respectively. The samples of E/lcalypl/ls
saligna and Pinus laeda were composed of 300 specimens each, while the Schiz%biunl
Gmazol1icum sample consisted of 21 O specimens. They were tested at 15 different temperature
leveis situaled belween 20 and 230°C.
RESULTS AND CONCLUSIONS
an
of
'013
The resulls of embedding slrenglh parallel and perpendicular lo the grain of lhe Ihree wood
species are illustrated in Figures I and 2. At roam temperature, the average embedding
strengths parallel to the grain of the Euca/yplus saligna, Pil1l1s laeda and Sclziz%biunI
amazonicum were 65 MPa, 27 MPa and 29 MPa, respectively, while the average embedding
strenglhs perpendicular lo the grain wcre 29 MPa, 12 MPa and 13 MPa, respectively. It was
found thal meehanieal resistanee varies directly wilh lhe density of lhe wood speeies and Ihal
embedding slTength are nonlinear function of temperature, which was confinned by analysis
of variance tests applied to the comparison of the results obtained. At 230°C, the Ellca/ypllls
saligna, the Pinus taeda and lhe Schiz%biulll amazonicum presented 0,60, 0.41 and 0.58 of
embedding strength parallel to grain at roam temperature, respectively. For the same levei of
S)'mp_18: SaJet)' of Wooden Slmctures
645
41" Imematiol1al Coriferel1ce on/ntegrity, Reliability Gnd Failllre
temperature, these species present embedding strength perpendicular to grain 0.46; 0.61 and
0.43 ofthe strength at room temperature.
80
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:
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200
100
150
Tcmpcraturc e C)
EUCU(111/IIS saligl1a
250
Fig. 1 - Embcdding strcngth parallcl to the grain
40
Lt'So!l1d
Eucalyplw-saligl1l1
·
·• • ..= !I
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Fig. 1 - Embedding strength perpendicular to lhe grain
REFERENCES
[I]-Gerhards, C.C. Effect of the Moisture Content and Temperature on the Mechanical
Properties ofWood: An Analysis ofImmediate Effects. Wood and Fiber, 1982, v.14, n.1, pA36.
[2]-Manriquez, M.J.; Moraes, P.D. Comportamento da madeira a temperaturas elevadas.
Revista Ambiente Construido, 2009, 9, n.4, p. 157-174.
[3]-Manriquez, M.J.; Moraes, P.D. Influence af the temperature on the compression strength
parallel to grain ofparicá. Construction and Building MateriaIs" 20IO,v.24, p.99-I04.
[4]-Moraes, P.D.; Rogaume, Y.; Triboulot, P. Influence of Temperature on the embedding
strength. Holz aIs Roh-und Werkstoff, , 2005, v.63, p.297-302.
646
Fllllchal/Portugal, 23-27 JUl1e l0 13
INTEGRITY, RELlABILlTY AND FAILURE
PAPER REF: 3964
STRESS REDISTRIBUTIONS PROVOKED BY THE USE OF
EXPANSIVE SYSTEMS IN TIMBER STRUCTURES
Jose G. Fucyo('l, Manuel Domingucz, .Jose A. Cabczas
Dcpartment ofMechanical Engineering, UnivcrsiLy Df Salamanca, Zamora, Spain
(.)Email: fueyo @usal.es
ABSTRACT
This work analyzes the potential use af new tcchnologies in timber structures which are
extensively applied in other structural materiais. Ao example is the use af dowel-type
fasteners with expansive kits which are very usual in concrete structures. The additional
strcsses imposed by these systems imply interesting advantages over the material rnechanical
behaviour. However, in timber, these advantages can be counteracted because its low
perpendicular to the grain tensile stress resistance. The aim of this work was to study the
stress redistributions provoked by the use of the expansive systems in timber structures and to
detennine if this technology can be used with this material.
Keywords: timber structures, FEM, dowel, connections.
INTRODUCTION
In the design of structural timber connections stands out the use of the dowcl-type fasteners.
This kind of joint is composed by one or more steel cy1indrical clements which work under
moment and shear forces and which transmit the loads between the different timber elements
through a compressive contact (Rodd, 2003). This contact between the steel and the timber is
the basic point to study. In the traditional systems it is modelled through a simplified
distribution of stresses proposed by Johansen in 1949. With slight changes, these very
simplified models are implemented today in the majority of the standards used in the design
and constructian af timber struetures, between them the european Euroeodes.
ai
4IS.
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In the last years, in the development of this type of joints, the designers have proposed
modifications imparted fram other fields, like the use of expansive systems, which are usual
in eoncrete struetures. The expansive dowel system is composed of the dowel and a second
piece with a fonn of a cylindrieal empty shell whieh surrounds the first one and provokes
compression stresses over the timber. This tcchnique has numerous advantages: it implies
easier and faster assemblies, reductions in previous preparations and adjustrnents, reductions
of the costs in case of reparations, etc. In timber, this technology has been hardly used,
beca use these advantages can be counteracted because the compression stresses introduced by
the expansive systems provoke perpendicular to the grain tensile stresses in the timber and
this material has low resistance under this kind ofstresses (Kharouf, 2003).
The results obtained using the Johansen models for the dowel type joints without expansive
systems, has been confinn during the last decades through a lot of studies made using
experimental methodology and the finite element rnethod. In the case ofthe use of expansive
dowel it is necessary to modify the rnodels used until now, taking into aceount the new
redistributions of stresses provoked by the expansive technology.
'13
Symp_18: Safety ofWooden S/mclllres
647
4'11 /nternational Conference onlntegrity. Reliability and Failllre
RESULTS AND CONCLUSIONS
The mechanical behaviour of. lhe dowel type connections when expansive systems are used,
has been analyzed. To accomplish this the new stress field redistributions wcre studied taken
into aceount the effect of different parameters just Iike the geometries, loads, constraints,
assembly methods and materiaIs.
Figure 1 left shows one of the models used to make the study. In lhe right lhe parallel to lhe
grain compression stresses provoked by the expansive system are shown. Similar information
was p~epared rei ative to the hazardous tensile perpendicular lO the grain slresses.
Socand plano
I
WiUg~
- ].323 .. +00
- ).3SZt+OO
-'7. 500 .. +00
-,.m,'"
-]. 162 .. +01
-1 .368<:+01
J-, 11111111111
-s. 441e+OO
Fig. I - Compression strcss distribution in the contact zonc.
The study concludes lhat under detennined geometric, load and constraint conditions, the
perpendicular to the grain tensile stresses can be 50 dangerou s that invalidate lhe advantagcs
of using this technology in timber structures. A second slep of this work using experimental
tests to confinn the results previously obtained using the finite element method is now
underway.
ACKNOWLEDGMENTS
This work was funded by the Spanish governrnent, VI Plan Nacional de Investigación
Científica, Desarrollo e lnnovación Tecnológica deI Ministerio de Economia y
Competitividad, within the framework ofresearch project BIA2012-36766.
REFERENCES
[I]-Johansen KW. Theory of timber connections. International Association of Bridge and
Structural Enginnering, 1949,9, p. 249-262.
[2]-Rodd PD, Leijten AJM. High Performance Dowel Type Joints. Progress In Structural
Engineering And MateriaIs, 2003, p. 77-89.
[3]-KbaroufN, Meelure G, Smith 1., Elasto-Plastie Modeling Df Wood Bolted Conneetion,.
Computers And Structures, 2003, p. 747-754.
648
Flmc/wl/Portllgal. 23-27 June 20 13
fNTEGRlTY, RELfABfLfTY AND FAfLURE
PAPEl< REF: 4057
d,
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s,
1e
lO
NUMERICAL MODEL TO EVALUA TE THE FIRE RESIST ANCE
IN WOODEN SLABS WITH CA VITIES
D. Coelho l ('), E.M.M. Fonseca!, P. Vila Rcal\ J.A. Faria!, A. Aredc·
I Faculty ofEnginccring, Univcrsity ar Porto, Porto, Portugal
~Polytcchnic Institulc ofSragança, Bragança, Portugal
JUniversity af Avciro, Avciro, Portugal
(O)Email: diana.coclho@gmaiLcom
ABSTRACT
The main objective af this paper is to develop a numerical madel for thermal analysis Df
wooden slabs with cavities, when subjected to the fire action. The temperature profiles, the
charring deplh layer and lhe charring rate will be determined using lhe finile element method
with ANSYS program, The numerical calculation of the temperature profiles will be obtained
through a transient and a noo-linear thermal analysis, where the material properties are
tcmperature dependent. These properties were established in accordance with the referenced
data and numerically calibrated. Two different models of wooden slabs with cavities were
studied. Ooe modeI characterizes a wood slab with void cavities and other with insulation
material. To characterize the fire resistance in wooden slabs with insulated cavities or void
cavities, different typical curves of charring depth layer will be obtained. A numerical
procedure is proposed to identify the heating action into the slab cavities. Ali numerical
results pennit the verification ofthe fire safety in wooden slabs with cavities.
Keywords: wooden slab, fire, insulated cavities, void cavities.
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INTRODUCTION
Wood is a friendly material, attracted by engineers and architects, due the attractive attributes
such as architectural features, structural characteristics and a1so a renewable material. This
material when exposed to accidental actions, such as fire action, presents a decomposition
process, pyrolysis, and produces a surrounding charring depth layer. On the fire exposure side
a charcoal layer, without effective resistance, causes the reduction of the element crosssection. However, this charring depth layer can delay the heating process, from the exposed
side, lo the wood core section and acting as a good insulating material. Several researchers
have presented experiínental models and analytical methods to calculate the physical
degradation of ,wood due high temperatures (White, 1999), (Poon, 2003), (lanssens, 2004),
(Frangi, 2008), The main objectives ofthis work are:
nd
- Present a numerical mode! to obtain the sarne results from Frangi when uses experimental
wooden slabs;
ral
- Evaluate the thennal perfonnance of wooden slabs with insulated cavities or void
cavities, when subjected of a fire situation;
- Determine different stages of the charring rate Ihrough ali wooden slabs;
ns,
Jl3
- Present a numerical model who intends to be a replica of prefabricated wooden slabs
common in Nordic countries, and used in residential and commercial buildings;
Symp_18: Salety 01 Wooden Stmctllres
649
4111 l11ternot;onal Conference onlntegrity, Reliability ol1d Fai/llre
- Use two different insulated materiais (glass fiber and rock waol) in arder to evaluate the
thennal effect into lhe wooden slab cavities.
RESULTS AND CONCLUSIONS
This study considers a replica of a prefabricated wooden slab with cavities exposed to fire,
with two constructive solutions, figure I. In lhe first solution t lhe slab cavities have an
insulation material t and for the second solution the internai slab cavities have no insulation.
These models were based on lhe conslructivc solution proposed by Frangi. The numerical
model proved to be a great importance in the detennination of the charring depth layer in
wooden slabs with insulatcd cavities and void cavities. The temperature profiles obtained in
transient analysis t as well as lhe charring rate in different phases in wooden slabs with cavities
exposed to fire were calculated using the finite element melhod with ANSYS programo Two
different insulation materiais used into lhe wooden cavities were compared and the mineral
wool exerts higher proleclion in relation to the fiber glass, figure 2a. The results obtained
through lhe proposed numerical model have a good correlation between lhe values of Frangi
and Eurocode 5. As regards with the study ofthe wooden slab with void cavities, it is possible
to conclude that at the end af one hour of fire exposure, lhe structural resistance vanishes
completely, as represented in figure 2b.
I '
Fig. I - Prefabricated wooden slab with insulalcd and void cavities dimensions in mm.
JH. ';H
1.::: .:::: :;;:
;;:~
~ 1 . l!1l
JJ1. 111
;;:': a . " l
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;;:J7 . 17 ~
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Fig. 2 - Tempcralurcs in woodcn slab wilh insulated and void cavitics at the end of 3600s.
REFERENCES
[I)-White RH, Dietenberger MA. Fire Safety, Chapter 17, Wood Handbook: Wood as an
Engineering Material, Forest Products Laboratory, USDA Forest Service, 1999.
[2)-Poon L, England JP. Literature Review on the Contribution of Fire Resislant Timber
Construction to Heat Release Rale - Timber Development Association, Warrington Fire
Research Aust. Pty. Ltd., Project No.20633, version 2b, pp.I-78, 2003.
[3)-Janssens ML. Modeling of the lhennal degradation of structural wood members exposed
to fire. Fire and Materiais, 28, pp.199-207, 2004.
[4)-Frangi A, Knobloch M, Fontana M. EIsevier - Fire design oftimber slabs made ofhollow
core elements. EIsevier - Engeneering Structures, USA, 2008.
650
Funclzal/Porwgal, 23-27 June 2013
INTEGRITY, REUABILlTY AND FAILURE
PAPER REF: 4089
NUMERlCAL MODEL TO ASSESS THE FlRE BEHA VIOUR OF
CELLULAR WOOD SLABS WITH DRlLLINGS
E.M.M. Fonseca(O), L.M.S. Barreira, J.M. Mcirclcs, P.A.G. Piloto
Polytcchnic Institute ofBragança, Bragança, Portugal
(')ElIIai/: cronscca@ ipb.pt
J
ABSTRACT
S
The main gaal of this paper is to develop a numetical model to
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cellular wood slabs with different drillings. A transient thennal analysis with nonlinear
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the fire behaviour af
material behaviour will be solvcd with ANSYS programo The presented numerical model is
based on a constructive solution proposed by Frangi and Fontana. The numerical results
obtained will be compared with the experimental rcsults from the reference, The developed
numerical model allows future studies and simultaneously characterizes the effeet of
perforations in woaden slabs to minimize the fire risk. The numerical model can easily be
adjusted for olher constructive solutions, lo facilitate the verification of safety in case of tire,
in buildings with several wood floors and slabs assemblies.
Keywords: cellular wood slab, fire, drilling, perforation.
INTRODUCTlON
Wood is a natural material with good structural characteristics. Wood is strong in relation to
its weight (Mackerle, 2005), Many wood constructions are used and the focus of this work is
to present a typical cellular slab for floors or roofs assemblies. The cavities ofthese elements
could be filled with insulalion or wood-based fiberboards.
Different works have been presented by researchers presenting analytical methods and
experimental procedures to evaluate the physical degradation of wood due tire action (Whitc,
1999), (Poon, 2003), (lanssens, 2004), (Frangi, 2004).
When wood is exposed to fire produces a surrounding charring depth layer. This charcoal
layer has no mechanical resistance and causes a rcduction in the cross-section element. The
size of the wood slabs and the provided insulation play an important role on tire safety. AIso,
the size of the perforations in \Vooden slabs could delay the heating process though the
thickness of lhe slab.
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re
The main objective of this work is to present a numerical model to compare the experimental
results from Frangi el ai (Frangi, 2004) using lhe cellular wood slab wilh drillings subjected lo
fire. The effecl of size drilling and the use of internaI fibreboard malerial will be verified to
evaluate the thennal effect into the cellular wood slab.
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RESULTS AND CONCLUSIONS
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This study considers a cellular wood slab with different types of drillings, and with or wilhout
internaI tibreboard, exposed to tire, as represented in the figure 1. Thennal properties are
considered according lhe Eurocode 5 (CEN, 2003). The elIect of fire is considered using the
13
Symp _18: Safety of Wooden Struclllres
lO
651
4th Internatiol1al Confereuce 011 lntegrity. Reliability al1d Fai/lira
appropriatc boundary conditions due to convection and radiation. Thc tcmperaturc
environment follows the standard fire ISO 834 curve.
~'""""... b)
Fig. 1 - Applications of ccllular wood slab wilh driltings. 3D CAD a) without fibreboard, b) wilh fibrcboard.
Figure 2 represents the temperalure evolution at one side fire exposure in a cellular wood slab
without fibreboard. The effect of the drilling size is visible and produces a delay in the
charring layer formation.
Fig. 2 - Tempcratures in ecllulnr wood slab, without fibrcboard insu lation.
REFERENCES
[I]-Maekerle l., Finite element analyses in wood researeh: a bibliography, Wood Sei Technol
Vo1.39, pp.579-600, 2005.
[2]-White RH, Dietenberger MA. Fire Safety, Chapter 17, Wood Handbook: Wood as al1
Engineering Material, Forest Produets Laboratory, USDA Forest Service, 1999.
[3]-Poon L, England lP. Literalure Review on the Contribution of Fire Resistant Timbcr
Construction to Heat Releasc Rate - Timber Developrncnt Association, Warrington Firc
Research Aus!. Pty. Lld., Projeet No.20633, version 2b, pp.I-78, 2003.
[4]-Janssens ML. Modeling of the thennal degradation of struetural wood members exposed
to fire. Fire and Materiais, Vol. 28, pp.199-207, 2004.
[5]-Frangi A, Fontana M., Untersuehungen zum Brandverhalten von Holzdeeken aus
Hohlkastenelementen. Institut Rir Baustatik und Konstruktion, Zurieh, 2004.
[6]-ENI995-1-2: 2003 . Euroeode 5: Design of timber struelures - Part 1-2: Struetural fire
designo CEN - Comité Euron.CEN - Comité Européen de Nonnalisation, 2003.
652
Flmcl1allPortugal. 23-27 Jlll1e 2013
INTEGRlTY. RELlABILlTY AND FAILURE
PAPER REF: 465 1
MODEL FlRE OF TWO STOREY WOODEN - FRAME BUILDING
Linda Mukovická Osvllldová l (*', Anton Osvllld 1• Martin Pctho 1
IDcpartrncnl a f fire cnginccring, Faculty af spccial cnginccring, Univcrsity ofZilina, Zilina, Slovak rcpublic
1Safi rs,s.r.o, Sarcty Fire Syslcm company, Ruzombcrok, Slovak rcpublic
(O.Email: cstrangc3 @gma il.com
ABSTRACT
The aim af thi s work was testing \Vooden building against fire in real condition. It was a two-.
storey wooden building of prefabricaled panel construetion ground size of 4.9 x 3.7 m, wilh a
height af 5.6 meters. Expect addition, visual observations were made temperahlre
measurement by using thermocouples at predetennined locations. Several thennocouples
\Vere fixed already during the construction af a buildiog. Using measuri og exchanges \Vere
recorded an d evaluated 00 the temperature at selectcd posí tions
ab
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KeyJVoJ'{ls : \Vooden building, fire test, thennocouples.
INTRODUCTION
TIle gradual deepeníng of the knowlcdge of the internai structure, chemical composltwn,
physical properties of wood and its mechanical properties induces intense developrnent af
techniques and technology of processing and multi-use. ControI parameters of wood in
relntion to the fire are needed especially in tenns of wooden houses. In woaden houses
emergence and development of fire can influence and regulate in many ways - not just
material. The material should always on the first place.
CONSTRUCTION
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fire
The object of lhe test was based 00 model building wood, where cooditians were simulated in
the course af a real fire. It was a two-storey building of prefabricated pane I construction
ground size of4.9 x 3.7 m, with a height of5.6 meters.
Exterior wa lls, ceiling, roof and waUs composition were designed with fire resistant building
system for low-eoergy and pass ive energy-based multi-storey buildings of wood and were
designed for fire resislance in lhree slales limit (R - resistance, E - whole and I - insu lation) 45
minutes. The composition of externai cladding, as well as the supporting structure nlong the
static calculation ofthe exact calculations "fire" according to Eurocode 5
Fire load of wood fuel representing the weight of 30 kg/m' of area, which \Vas initialed by the
incendiary substance and left lhe stage to a fully developed fire. lt simulaled course of fire
interior furnished furniture, textiles and other combustible materiaIs.
EXPERfMENTAL WORK
Expect addition, visual observations were made temperature measurement by using
thennocouples at predetennined locations. Several thennocouples \Vere fi xed already during
21113
Sylllp_18: Safety of Woodell St/'lIclllres
653
41h Inlemational COIIJerellce 011 fntegrily, Reliability and Failul'e
the construction of the building. Using measuring exchanges were recordcd and evaluated on
the temperature at selected positions. Totally was docked 48 points for the measurement af
temperature, whích will be progressively evaluated. This article Iists some; the whole
experiment wiII be evaIuated in the monograph.
Measured was also the temperature in the arca of buming wood as a fuel. FueI was OSB
boards lhat were pIaced throughout the arca, and after applying the initiator fire. Maintain the
highest temperature of about 20 to 50 minute experiment. Then the temperature started to
decrease, (combllstion of fueI) , space is cooIed and the experiment was in 60 minutes
finished.
Fig. I . Building during the cxpcrirncnt
RESULTS AND CONCLUSION
The building stands at the end of the· experimcnt and is stable. Afier cooling the interior of li
Fire and Rescue Service and the findings of a static sa fety insp ections are canied out of the
building. lnterior fac ing shaws signs af fire bum. Static's is nol di sturbed; individual wooden
parts of the interior are no signs of fire. Model fire was intense, ali fuel bumed in space at the
same time, which was ignited by lhe initiator real fire deveIops less intense and not in the
\Vhole arca at once.
The question IIls it possibIe to build a wood structure that can withstand fire?" can be
answered in positive. Can you ask counter-"What do statistics fires?" Every building of 3ny
material can be subject lO fire. The scope of fire intensity is always lhe initiator, layou l
construction, poor quality of work canied out and a number of other short comings that
aIways reveals the fire. I. If yOll use quality materiais, be subject to qllality craftsmanship,
applied to the elements of fire protection and fire \Vooden house is safe.
REFERENCES
[I]-Osvald, A.: Wooden building cf fire. Zvolen : Technical University in Zvolen, 2011, 336
s. ISBN 978-80-228-2220-6.
[2]-Osvaldová. L. : Fire retardanlS. Arpos, 18-1 9, 2005, s. 18-21 , ISSN 1335-59 10.
[3]-Osvaldová, L., Kopylová, E.: Fire retardation of spruces \Vood. In: Wood Fire and Safety.
Zvolen : Vydavatel'stvo Technickej univerzity vo Zvolene, 2004 s. 211 - 217, ISBN 80-2281319-2.
654
FUlJchal/Portllgal. 23-27 lIme 2013
INTEGRlTY, RELlABILlTY AND FAILURE
PAPER REF: 4102
A CONTRIBUTION TO ASSESS THE STRUCTURAL
VULNERABILITY OF TRADITIONAL TIMBER
PAVEMENTS
Marcos Teixeira ' , Debora FcrrcirllZ("', Vílor Cunhal.l, Artur Fcio 4, José Lousadas• Humberto Varum', João
Miranda Guedes', Jorge Pintal,a
IEnginccring Dcpnrtrncnt, EeT, Tras·os-M ontcs e Alto Douro Univcrsity, Vila Real, Portugal
2Polytcchnic Institutc ofBragança (IPB), Bragança, Portugal
31SrSE, Minha University, Guimarncs. Portugal
4 Lusiada Univcrsity, V.N. Famalicão, Portugal
5Forcst Dcpartmcnt, Trás-as-Montes c Alto Douro Univcrsily, Vila Real, Portugal
6Civil Enginccring Dcpartment, Avciro Univcrsity, Avciro, Portugal
7Civil Enginccring Departmenl, FEUP. Porto Univcrsity, Porto, Portugal
8Associatcd Laborotory 13N, Avciro, Portugal
(O)Email: [email protected]
ABSTRACT
In general, timber pavements are the main horizontal structural elements af lhe Portuguese
traditional buildings. Since these lypes ofbuildings required to be preserved, the maintenance
of timber pavements is crucial. However and unfortunately, lhe demolition af the interior of
traditional buildings still is a curreol building option in rehabilitation processes, This building
scenaria is more expressive in privale estate, in particular, in private dwellings. This option
may be due lo the lack of technical knowledge conceming timber pavemenls, Therefore, this
paper inlcnds to give a contribution in this matter by proposing an expedite melhodology able
lO assess the structural vulnerability oflhese types ofhorizonlal structural elements. Mapping
the different structural vulnerabilily degrees of a lraditional timber pavemenl may give
guidance for maintenance, inspection ami/or reinforcement design processes.
Keywords: traditional timber pavements, slructural timber elements, structural vulnerability,
patholagy, mitigation, sustainability
INTRODUCTION
6
Granile, schist and tabique buildiog are traditional Portuguese buildings. The differentiation
of lhese types of buildings is basically related to the type of the respective main externaI
vertical structural elements. In ali the cases, the main externaI vertical struclural elemeot is a
wall and inslead of a column. Granite masonry, schist masonry and tabique wall are the ma in
externaI vertical structural elements of the granite, the schist and the labique traditional
buildings, respectively. There is also lhe case of rnixed type in which, ao integrated
combination of the above identificd vertical structural elements is possible. For instance, tbis
building scenario is highly expecled in tabique buildings because stone masonry (e.g. granite
or schist) placed at the ground 1100r leveI usually support the upper externaI tabique walls, In
general, these types of traditional buildings have interesting building patterns such as, local
and natural building materiais, and an interior limber camponent tendency. In fact, the
pavements, the stairs, the roofs structure and the partition walls are preferentially timber
structural components. In the cantext of traditional timbcr pavements, they are essentiaIly a
braced beamed load distribution structural systems,
Symp _18: Safety ofWooden Stl1lclures
655
41/' /mematiol/al Conference 011 /ntegrity, ReliabilitJ' ond Foilllre
Apart of supporting dead and live loads, the timber pavements also support the self-weight of
the partition walls. Meanwhile, they are essentially directly supported on the externaI walls
and, therefore, lhey also may have an important braeing eontribulion of lhe overall building.
These technical aspecls lead us to the conclusion lhat lhe traditianal tirnbcr pavements may
have an important role in the overall struetural integrity of lraditional buildings. Pathology
phenomenon, material and structural damages, and structural failure sccnarias are some
aspects that have to be considered conceming maintenance, inspection, structural reinforcing
design and rehabilitation processes of traditional timber pavemenls. Additionally, lhe aging
effect, lhe facl that wood is ao organic building material (resulting in a heterogenic and
anisotropic material), the building may be in servicc and no original design is likely to
happen. are a1so aspects lhat have to be considered in these processes. Therefore, these
processes may end up being complex. On the other hand, in the perspectives of cultural, social
ideotity, sustainability and economical, to preserve lhe lraditional buildings is a \Vise option.
Unfortunately, this option is still frequently neglected and mainly conceming lhe
rehabilitation of privale traditional estate (e.g. dwellings), in which the demolition of the
existing tirnber structural elements is a common decision. In other to invert this situation,
technical knowledge dissemination among the community is required. In this respecl, this
pape r intends to contribute by given a step forward 00 lhe structural vulnerability assessmelll
of traditional building pavements and by integrating the typical pathology damages of
structural timber elements with the criticai structural point concept.
The most structurally vulnerable parts of a traditional timber pavement may be identificd
which may be extremely useful in the processes identified above. A similar approaeh has been
dane for the traditional timber roof structures (Murta, 2011) This paper is structured as
follows: firstly, the traditional building topic is put into context. In particular, the main types
of the traditional buildings of the Trás-os-Montes e Alto Douro region are briefly identified
and described; secondly, some structural timber systems of traditional pavernents are
presented and described; thirdly, the most common timber pathologies are identified and
exemplified; fourthly, a proposal of an expedite methodology for the assessment of lhe
structural vulnerability of tradilional tirnber pavements is done; finally, the maio conclusions
are drawn.
RESULTS ANO CONCLUSIONS
The main traditional buildings of the north-cast part of Portugal are identified and briefly
described. Some typical timber pavements are presented and also their most frequent
pathologies. An expedite methodology for the structural vulnerability assessment of these
types ofhorizontal slructural elements is explained and proposed.
REFERENCES
[I]-Murta, A., Pinto, l., Humberto Varum, H. (2011) - Structural vuloerability of lwo
tradioooal Portuguese timber structural systems. Engineering Failure Analysis (20 11 ),
doi: 10.1 O16/j.engfailanaI.20 I 0.12.0 17.
656
FUl1chal/Portugal, 23-27 Jun e 20/3
INTEGRJTY, RELlABILlTY AND F AILURE
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PAPER REF: 4624
INFLUENCE OVER THE STRESSES OF THE SIZE AND POSITION OF
THE PUNCHED METAL PLA TES STRUCTURAL TIMBER JOINTS
Jose G. Fucyo,O),Josc A. Cabczas, Manuel Domingucz
Dcpartmenl af Mcchanical Enginecring, Univcrsity af Salamanca, Zamora, Spain
(. )Email: fucyo @usal.cs
ABSTRACT
Punched metal plates are uscd in timber structures to JGmt two ar more single timber
elements. Their capacity lo transrnit loads depends on two parameters: the anchorage capacity
between the Iimber and the plates and the strcngth capacity of the plates. The aim of the
present work was to gaio further insight ioto the influence af the size and position Df the
plates, considering its length and height independently, as well as ils horizontal and vertical
position relative to the joint. More specifically, the purpose was to determine the correlation
bctwcen the parameters previously indicatcd and the leveI of stresses that appear in the joint.
The study used a finite eIements software to design several parametric models, which allowed
a detailed anaIysis ofthe stress state in the pIates and timber eIements.
KeYJVords: timber joints, finite clements, punched metal plates.
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INTRODUCTION
Punched metal plates are made oflight-gauge galvanized mild steel plates in which nails have
been punched oul to one side oflhe plale by a stamping processo Thejoinls are buill placing a
pair of nail pIates on opposite faces of the timber elernents. Using press or rollcr equiprnent
the projected nails are embedded into the timber. In Europe, the design of this class of joints
is regulated by the Eurocode 5 (CEN, 2004).
Thc connections rnade with punched metal pIate fasteners can fail in two situations. The first
happens when lhe anchorage or adherence capacily between the plates and lhe timber is
exceeded. This provokes the sliding between them as shown in the left part offigure I
(Ellegard, 2002). The second failure possibility is related to lhe plates. It occurs when the
forces transmitted through them surpass their strenglh properties. Depending on the kind of
force working on the plates, it couId be a tension, a compression or a shear failure (Karadelis,
2000) as shown in lhe right part of figure I. Both failure situations depend on several
parametcrs. Between the most representatives, in this work, the influence of the size and the
position ofthe plates in relalionship with the elemenls thal they Iink are going to be studied.
lO
.),
RESULTS AND CONCLUSIONS
Figure 2 shows some of the several results obtained in this work. In the Ieft, it shows the
compression and shear stresses in the pIate in reIationship with its rei ative x-position in the
joint. In the right, it can be seen lhe same stresses as a function ofthe length ofthe plate.
Whereas a variation in the position of the pIates hardIy has a significant effect on the
anchorage stress leveis, the strcsses change differently in the pIate. With a modification in the
13
Symp_18: SaJety of Wooden Sfructures
657
4/II /n/ernationa/ Conference O/I /lIteg/'ity , Reliability and Fai/lIre
X-posltlOn, only the S22 stresses are affecled, whereas lhe S 12 stresses hardly change.
Regarding the y-position, if it changes, lhe cffect is very significanl in both SI2 and S22
stresses.
Regarding the plate size chaoge, its effect 00 the anchorage stresses is remarkablc. This effect
occurs wilh modificalions in bolh the hei ght and lhe lenglh, and is relalcd to lhe variation of
the arca which transmits the anchorage stresses betweeo the timber and lhe plate.
Fig. I - Anchorage and strcngth capac ity failurc s ofthc punched melai plate joints.
o
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Fig. 2 - Compression and shcar stresses as n function ofthe x·position and lhe Icngth ofthc plale.
ACKNOWLEDGMENTS
This work was funded by lhe University of Salamanca, within the framework of research
projecl KAPB.
REFERENCES
[1]-CEN Oesign of Timber Structures. Part l-I. EN 1995-1-1 Eurocode 5. European
Committee for Slandardization. Brussels. 2004.
[2]-Ellegaard P. Analysis of timber joints wilh punched melai plate fasteners, PhO Thcsis.
Aalborg University, Oenmark. 2002.
[3]-Karadelis JN, Brown P. Punched melai plate timber fasteners under fatigue loading.
Construction and Building Materiais, 2000, 14, p. 99-108.
FlllJcha//Porlllgal, 23-2 7 JUIIC 20/3
/NTEGRlTY, RELlABILlTYAND FAILURE
PAPER REF: 4090
THERMAL ANALYSIS OF WOOD-STEEL HYBRID CONSTRUCTION
I
E.M.M. Fonscca(*', H.I\'I .E. Rumos, H.J.G. Silva, D.R.S.M. Ferreira
Polytcchnic Inslitulc af Bragança, Bragança, Portugal
(* IEmail: [email protected]
f
ABSTRACT
The main objective of this work is to provi de the thermal analysis in wood-steel hybrid
elemenls for building constructions under fire conditions. A transient thennal analysis \Vith
nonlinear material behaviour will be solved with ANSYS programo The use of wood-steel
hybrid models has major advantages as increascd fire resistance, and improvcd high strength.
Wood is a Iightweight material, easy to assemble, great architectural features, thermal and
acoustic characteristics. However, lhe high vulnerabílity af wooden clements under fire,
involves evaluating their behaviour accurately. Its physical behaviour is conditioned by the
charring layer fonnation, which may allow the insulation into the structural scction. The steel
is a curreot use material allowing high structural strength. However, steel is a 000combustible material, aod when compared with wood is a very good conductor of heat.
Consequently, the unprotectcd sections of steel under fire quickly heats , and the fire
resistance decreases considerably. The numerical modelling of thesc hybrid models, providing
the analysis at high temperatures, is complicated due to the heat produced, to form a layer of
carbonizalion surrounding lhe wood, and also the properties of both materiais are nontincar.
Using a computer model, it wilI become possible to calculate lhe fire resistance of these
hybrid elements, an important parameter for safety and design rules.
KeYlVords: wood-stcel, hybrid construction, tire, numerical model.
INTROOUCTION
rch
The use of hybrid materiaIs could increase the structural integrity of the construction
elements. Steel material has many advantages over wood elements, strength, stabilily,
resistance lo woodwonn, among olhers. Steel is incombustible and most of lhe times it can
full recover strenglh afier fire but, steel material conducts heat extremely well, (lan et aI,
2002), (Barbosa et aI, 2012). Wood is a renewable resouree, rceently attraeted by public
attention. Wood is a natural material with good structural characteristics. The wood when
exposed to accidental actions, such as fire conditions, has a surrouDding charring depth.
However, lhis layer can delay the heating process lO the core section, acting as an insulating.
[n Ihi, work wood-stcel hybrid pro files subjected to fire are presented lo verify the best
solution used in design construction. The complexity of tbis analysis nccds some numerical
techniques with high performance, which is the case of the fioite element analysis.
!sis.
ling.
20/3
RESULTS ANO CONCLUSIONS
The thermal properties of steel and wood are function of the temperature and should be
determined from the Eurocode 3 (CEN 1995) and Eurocode 5 (CEN 2004), as represented in
figure I.
S,"IIIP_18: Safely of IVooden Struclllres
659
4/1• /llJemaJional Conference on /lItegriJy, ReliabiliJy anel Failllre
" --Tr-----------------=_~."=o=.'~-~,nc.,'"'·,
- - D<T<l1y
II,,"'I
--- Tho=oI~."ry
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- -
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....-
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Fig. I - Stccl and wood thermal properties,
Conclusions are prcsented and discussed about lbe importance of lhe temperaturc field
obtained in wood-slee! hybrid sections using a finite element modelling.
According to the rcsults, wood elerncnts present lower temperatures than steel, and lhe
maximum temperature is always inside lhe char layer, The wood-steel hybrid profile can to
perform well under fire conditions. Regarding the design construction (outside wood af the
steel profile), it is concluded that it has a good fire resistance, even for the three sides fire
exposure, showing the ability ofwood to protect the stecl, as shown in figure 2.
CAO model
20 numerical anlllysis
-
3D numerical nnulysis
,
1-'.;' ('j.ff, ij":..?"ii,í,ji ,\1
<li
a'::: :
, -'
o
<li
II
IJ~
21l"C·300"C
Fig. 2· Tempcraturcs in wood-stcel hybrid profilc at the end of3600s.
REFERENCES
[I]-Jan, K., Phil, C" Making Sleel Framing as Thermally Efficient as Wood Most Currenl
Developments ITom ORNL, Proceedings of the Thirleenlh Symposium on Improving
Building Systems in Hol and Humid Climates, Houslon, TX, ESL-HH-02-05-40, 2002,
[2]-Barbosa, L.F,M.; Almeida, P,M.L.; Fonseca, E.M.M.; Barreira, L.M.S.; Coelho, D,C,S.;
Hybrid waod/steel elements under fire, lntemational Congress Fire Computer Modeling,
Universidad de Canlabria, pp. 407-420, ISBN 978-84-86 116-69-9, 20 12,
[3]-EN 1993-1-2:1995. Eurocode 3: Design of Structures - Part 1-2: General Rules Structural Fire Design, CEN, 1995.
[4]-EN 1995-1-2:2004. Eurocode 5: Design of timber structures, Part 1-2: General-Struclural
fire design, CEN, 2004.
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