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International Journal of Materials Engineering 2016, 6(3): 92-96
DOI: 10.5923/j.ijme.20160603.05
Full Characterization of Vatairea sp Wood Specie
Francisco A. Rocco Lahr1, Bruno H. C. Aftimus2, Felipe N. Arroyo3, Diego H. De Almeida4,
André L. Christoforo3,*, Eduardo Chahud5, Luiz A. M. Nunes Branco6
1Department of Structural Engineering (SET), São Paulo University (EESC/USP), São Carlos, Brazil
2Department of Civil Engineering, University Center of Educational Foundation of Barretos (UNIFEB), Barretos, Brazil
3Centre for Innovation and Technology in Composites - CITeC , Department of Civil Engineering (DECiv), Federal University of São
Carlos, São Carlos, Brazil
4Department of Engineering, Pitágoras College, Poços de Caldas, Brazil
5Department of Civil Engineering, Federal University of Minas Gerais (UFMG), Belo Horizonte, Brazil
6Faculty of Engineering and Architecture, FUMEC University, Belo Horizonte, Brazil
Abstract In Brazil, wood is a material which has been used for years in different purposes. The variety of Brazilian
tropical wood species is expressive, nonetheless only a few of them are considered in structural design. Taking in account
possibility of eventual shortages of these well-known wood species, characterization of alternative essences is presented as
fundamental for maintenance of wood supply for civil construction. In Brazil, the structural dimensioning and timber
characterization are specified by ABNT NBR 7190:1997 (Timber structures design), in its Annex B. This work aimed, with
the aid of Brazilian Code, determining physical (4) and mechanical (13) properties of Angelim Saia (Vatairea sp.). Besides,
with regression model (linear, exponential, geometric and logarithmic) based in analysis of variance (ANOVA), it was aimed
to estimate resistance values and stiffness in function of the density, once this is an easy-obtainable property for wood. From
a set of twelve aleatory pieces, twelve specimens were produced for each test type, totalizing 204 experimental measurements.
Results of mechanical properties showed compatible performance with other species already established for use in structure,
which shows the potential of Angelim Saia for structural purposes. From regression models for estimate strength and stiffness
values, it was possible conclude that not all properties can be estimate by density. Better results were showed by the
geometric model in estimation of hardness parallel to grain, who provided determination coefficient (R²) close to 70%.
Keywords Vatairea sp., Characterization, Density, Regression model
1. Introduction
Employing wood in construction is a practice carried out
for many years by humanity, since the necessity of store food,
overcoming obstacles, until the construction of shelters [1].
Initially, exploration of Amazon Tropical Forest was
selective and predatory, once demand concentrated once
only a few well-known wood species were extracted. This
undesirable exploitation led those species (already
completely characterized) to almost exhaustion, imposing to
the market improve receptivity for new species not yet with a
wide application [2].
Due to this high demand and few options, the prices of
used species increase, give a new moment to Brazilian
timber sector, being necessary define which new species can
substitute the traditional used species in construction [3, 4].
In addition, with the growing awareness of population
the use of materials which cause the minimum damage to the
* Corresponding author:
alchristoforo@gmail.com (André L. Christoforo)
Published online at http://journal.sapub.org/ijme
Copyright © 2016 Scientific & Academic Publishing. All Rights Reserved
environment, timber originates from planted forests becomes
also a building material to be widely considerable [5].
As such, Vatairea sp. is an interesting possibility, once
this species occurs in several Brazilian regions, including
Tocantins, Goiás and Bahia until São Paulo states. It is a very
tall tree, with middle-heavy wood and potential satisfactory
mechanical properties [6, 7].
However, before the using of a new species in any
situation, be in roofs, bridges, silos or any others, it is
necessary to determine its physical and mechanical
properties, thus promoting a better condition to use [5].
Full characterization of wood species involves
determination of their physical and mechanical properties,
obeying requirements of normative Codes. In Brazil, is the
NBR 7190 [8] who sets parameters for this characterization.
However, the inconvenience of several of these tests and
necessity of using heavy equipments, increase costs and
make fundamental rely this work to research centers [8].
By other side, a physical property easily determined in
usual experimental procedures is the apparent density (or
simply density), set by ratio between mass and volume a
12% of moisture content (as referenced in Annex B, NBR
7190:1997). As density is a basic physical property, their
International Journal of Materials Engineering 2016, 6(3): 92-96 93
values can, eventually, allow establish an adequate estimate
of the mechanical wood properties [9, 10].
Therefore, the aim of this work is determinate the physical
and mechanical properties of Vatairea sp. according to
pre-defined indications of Brazilian Code, as well as
research the possibility of estimating of mechanical
properties in function of density.
2. Material and Methods
In order to reach proper conditions to get the specimens,
Vatairea sp wood pieces were duly stored, until showing
moisture content by 12%, reference adopted by NBR
7190:1997 [8].
Mechanical tests were carried out in Wood and Timber
Structures Laboratory (LaMEM), Department of Structural
Engineering (SET), School of Engineering of São Carlos
(EESC), University of São Paulo (USP). Physical tests were
conducted in Federal University of Minas Gerais (UFMG)
and FUMEC University laboratories. Statistical procedures
were processed in Federal University of São Carlos
(UFSCar).
Physical and mechanical properties were obtained under
the requirements of test methods proposed by the Brazilian
Code [8], in its Annex B (Determination of timber properties
for structural purposes). The number of experimental
determinations is introduced in Table 1, for each property,
and it should be noted that, in total, 204 determinations were
made.
To estimate mechanical properties by density, regression
models (Expressions 1 to 4), reasoned on analysis of
variance (ANOVA), have been tested in order to establish
best fit between and each mechanical property investigated,
in a way to establish mathematical reasons among them
12
Y ab
ρ
= +⋅
[Lin - linear] (1)
12
b
Y ae
ρ
⋅
= ⋅
[Exp - exponential] (2)
12
()
Y a b Ln
ρ
= +⋅
[Log - logarithmic] (3)
12b
Ya
ρ
= ⋅
[Geo - geometric] (4)
ANOVA regression model was considered at confidence
level (α) 5%. Null hypothesis formulated consisted in the
non-representativeness of the tested models (H0: β=0) and as
alternative hypothesis (H1: β≠0) was taken their
representativeness. P-value upper than significance level
adopted implies accepting H0 (model tested is not
representative, i.e. variations in ρ12 are unable to explain
variations of the property), refuting it to otherwise (tested
model is representative), being Y the dependent variable
(value of properties studied).
Beyond use of ANOVA, that allows accepting or not the
representativeness of models tested, the values of
determination coefficient (R²) were obtained as way to
evaluate the capacity of variations ρ12 to explain the variable
analyzed. This enables, among the models considered
significant, elect the one of better fit.
Table 1. Physical and mechanical properties of Vatairea sp
Properties Abbreviation No Determinations
Density ρ12 12
Total radial shrinkage RRT 12
Total tangential shrinkage RTT 12
Strength in compression
parallel to the grain fc0 12
Strength in tension parallel to
the grain ft0 12
Strength in tension normal to
the grain ft90 12
Shear strength parallel to the
grain fv0 12
Cracking fs0 12
Conventional strength in static
bending fm 12
Longitudinal modulus of
elasticity in compression
parallel to the grain
Ec0 12
Longitudinal modulus of
elasticity in tension parallel to
the grain
Et0 12
Conventional modulus of
elasticity in static bending Em 12
Hardness parallel to the grain fH0 12
Hardness normal to the grain fH90 12
Toughness W 12
Strength in compression
normal to the grain fc90 12
Modulus of elasticity in
compression normal to the
grain
Ec90 12
3. Results and Discussion
Tables 2 and 3 present means (
x
), variation coefficients
(Cv), smallest (Min) and largest (Max) values for physical
and mechanical properties, respectively.
The obtained mean value for fc0 (64.2 MPa) is very close
to that of Protium heptaphyllum (59 MPa) [11]. According to
the authors, this permits utilization in all kinds of structures,
for their high strength, far larger than obtained to the Paricá
(Schizolobium amazonicum) - 24 MPa [9], Toona ciliate (27
MPa) and Eucalyptus benthamii (37 MPa) [13], proper for
light structures.
Table 2. Results obtained of physical properties of Vatairea sp
Stat. ρ12
(kg/m3) RRT (%) RTT
(%)
x
760 4.24 8.20
Cv 0.08 0.19 0.11
Mín 0.68 3.19 6.15
Máx 0.88 5.50 8.90
94 Francisco A. Rocco Lahr et al.: Full Characterization of Vatairea sp Wood Specie
Table 3. Results obtained of mechanical properties of Vatairea sp
Stat. fc0 (MPa) ft0 (MPa) ft90 (MPa) fv0 (MPa) fs0 (MPa) fm (MPa) Ec0 (MPa) Et0 (MPa)
x
64.2 96 3.0 15 0.8 113 19748 20214
Cv
0.14
0.22
0.21
0.12
0.16
0.20
0.16
0.14
Mín 46.7 33 1.9 12 0.6 76.6 13274 16037
Máx
76.3
152
4.3
17
1.0
137
25713
24555
Stat. Em (MPa) fH0 (MPa) fH90 (MPa) W (J) fc90 (MPa)
E
c90
(MPa)
x
18561
86.4
60.5
43
1.8
93.6
Cv
0.11
0.11
0.15
0.13
0.13
0.12
Mín
14357
68
49
33
1.4
76.4
Máx
22527
102
76
51
2.1
114.9
According to Brazilian Code, from the obtained value for
strength in compression parallel to the grain (fc0), Vatairea sp
be categorized as class C40 (dicotyledonous), presenting
characteristic value 51 MPa for that property.
The mean density (0.760 g/cm³) classifies Vatairea sp. as
a heavy timber [14], same characteristic of Minquartia
guianensis, Lecythis poiteaui, Mezilaurus itauba, Manilkara
huberi e Brosimum rubescens [10]. However, it must be
pointed out that density of these wood species varies
between 0.835 to 0.904 g/cm³, and they are widely applied in
heavy structures.
Density of Vatairea sp. is higher comparing with
Liquidambar sp. [15], Tectona grandis [9], Cedrela fissilis
and Hovenia dulcis [16], whose densities range between
0.478 to 0.577g/cm³; and naturally more dense that Toona
ciliata [12], Schizolobium amazonicum [5] e Gallesia
integrifolia [16], which presented density varying between
0.318 to 0.370g/cm³ and, under certain conditions, can be
employed in light structures.
Brazilian Code NBR 7190:1997 stipulates maximum
values for variation coefficient, so that the characterization
be qualified as compatible, being 18% for normal strengths
and 28% for tangential efforts. All properties attended these
parameters, except strength in tension parallel to the grain (ft0)
that exceeded the limit, presenting Cv 32%. Despite this
point, this characterization can be here considered as
obeying the normative requirements.
Table 4 and 5 show ANOVA results of the regression
models.
Table 4. Regression models obtained for strength properties of Vatairea sp
Models
P-value
a
b
R2
fc0
Lin
0.0024
-22.5178
0.1119
61.74%
Exp 0.0031 15.1567 0.0019 60.01%
Log
0.0019
-512.1278
87.2739
63.57%
Geo 0.0023 0.0042 1.4483 62.15%
Models P-value a b R
2
ft0
Lin 0.5216 169.7591 -0.0965 4.23%
Exp
0.6808
167.9310
-0.0008
1.76%
Log 0.5156 595.2275 -75.2330 4.35%
Geo
0.6653
6768.8975
-0.6497
1.95%
Models
P-value
a
b
R2
ft90
Lin
0.800
3.6277
-0.0008
0.67%
Exp 0.8284 3.5100 -0.0002 0.49%
Log
0.7920
7.4599
-0.6746
0.73%
Geo 0.8203 10.5414 -0.1934 0.54%
Models P-value a b R
2
fv0
Lin 0.1788 4.7696 0.0128 17.29%
Exp
0.1725
7.1856
0.0009
17.75%
Log 0.1742 -51.5459 9.9656 17.62%
Geo
0.1680
0.1299
0.7102
18.09%
Models
P-value
a
b
R2
fs0
Lin
0.0432
-0.1546
0.0013
34.85%
Exp 0.0388 0.2352 0.0017 36.09%
Log
0.0403
-5.8843
1.0136
35.66%
Geo 0.0360 0.0002 1.2841 36.94%
Models P-value a b R
2
fm
Lin 0.5497 161.0765 -0.0673 3.69%
Exp
0.5657
172.3715
-0.0006
3.41%
Log 0.5803 427.3822 -47.8819 3.16%
Geo
0.5942
2001.7127
-0.4406
2.94%
Models
P-value
a
b
R2
fH0
Lin
0.0009
-8.7266
0.1218
68.20%
Exp 0.0009 27.4957 0.0015 68.54%
Log
0.0008
-541.2850
94.2800
69.20%
Geo 0.0007 0.0460 1.1315 69.74%
Models P-value a b R
2
fH90
Lin 0.0014 -27.1222 0.1168 65.38%
Exp
0.0014
14.2239
0.0019
65.81%
Log 0.0011 -542.3691 91.1028 67.28%
Geo
0.0010
0.0030
1.4954
67.77%
Models
P-value
a
b
R2
W
Lin
0.6467
34.3649
14.5716
2.18%
Exp 0.6584 35.1095 0.3274 2.03%
Log
0.6212
48.7810
12.0624
2.53%
Geo 0.6345 48.5297 0.2703 2.35%
Models P-value a b R
2
fc90
Lin 0.1817 0.7530 0.0013 17.08%
Exp
0.1825
0.9714
0.0008
17.02%
Log 0.1655 -5.3329 1.0724 18.29%
Geo
0.1658
0.0278
0.6262
18.26%
International Journal of Materials Engineering 2016, 6(3): 92-96 95
Table 5. Regression models obtained for stiffness properties of Vatairea sp
Models P-value a b R
2
Ec90
Lin 0.1572 1055.7369 -1.1937 18.95%
Exp
0.1399
2838.0686
-0.0042
20.45%
Log 0.1410 6452.3906 -950.7389 20.35%
Geo
0.1255
6452.25E+8
-3.3742
21.84%
Models
P-value
a
b
R2
Ec0
Lin
0.0095
-8594.3112
37.0888
50.58%
Exp 0.0095 4228.4203 0.0020 50.60%
Log
0.0074
-173640.0982
29143.3296
52.87%
Geo 0.0072 0.5677 1.5738 53.08%
Models P-value a b R
2
Et0
Lin 0.1593 6137.6575 18.4202 18.78%
Exp
0.1496
9830.1373
0.0009
19.58%
Log 0.1512 -75390.5941 14407.4663 19.45%
Geo
0.1415
157.8448
0.7301
20.30%
Models
P-value
a
b
R2
Em
Lin
0.0353
3625.5189
19.5447
37.15%
Exp 0.0352 8094.3915 0.0011 37.20%
Log
0.0315
-82802.3614
15275.3311
38.42%
Geo 0.0310 67.9929 0.8445 38.59%
(a)
(b)
(c)
Figure 1. Regression models: relation between density and strength in
compression parallel to the grain (a); density and hardness parallel to the
grain (b); density and hardness normal to the grain (c)
P-values obtained for fc0, fs0, Ec0, Em, fH0 and fH90 were
lower than 0.05. This implies that the obtained settings for
these properties are significant. The determination
coefficients (R²) vary from 34 to 69%. Estimative of fH0, fH90
e fc0 in function of density reached R² upper than 60%, what
implies a satisfactory quality of the proposed adjustments
[17].
The geometric model provided the higher values of R²,
emphasizing that to fourteen of the mechanical properties
estimated by density, only 6 provided significant
adjustments, and of these six properties, only three showed
coefficient R² higher to 60% (fH0, fH90 and fc0).
Figure 1 presents the better settings of tested models
(Table 4).
4. Conclusions
The results obtained of this research allow concluding
that:
- Based on the variation coefficient, Vatairea sp.
characterization can be considered according to the
required by Brazilian standard;
- Following the premises of Brazilian Code, Vatairea sp.
is categorized as C40 (dicotyledonous), by presenting a
characteristic value of strength in compression parallel
to the grain (fc0,k) 51 MPa, indicating a potential good
performance for light and heavy structures;
- The regression models presented significant estimates
and good quality in adjusting (R² bigger than 60%)
only for three among the fourteen mechanical
properties investigated: strength in compression
parallel to the grain, hardness parallel to the grain and
hardness normal to the grain;
- The regression models geometric presented the better
settings, followed by logarithmic models.
ACKNOWLEDGMENTS
By all support provided, the authors are grateful to Higher
Education Improvement Coordination (CAPES); National
Council for Scientific and Technological Development
(CNPq); and to the four Universities involved.
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