Characterization of Tropical Wood Species for Use in Civil Constructions

The wood is one of the most applicable materials in industrial activit ies due to its availability allied to its satisfactory mechanical p roperties, presenting a good strength/density relation. Its versatility is fundamental fo r the large expansion of its use on structure building. The explorat ion, init ially selective, turned to be selective and also predatory, what lead to a shortage, raising systematically the prices until the moment where it was not anymore probable to use it on the quantities registered until then. The solution was to define species, between more than 5.000 variet ies in AmazonicaTropical Forest, which could substitute the 100 commercially used ones. However, due to technical limitations, these species cannot be completely characterized, what leads to a misusing of timber, once its behaviour is not known completely when it is under mechanical stresses. This research presents some results of the characterizat ion of the following timber species: Canelão, Envira Branca, Guarajá, Quaruba Rosinha and Breu Vermelho. These species are found close to Sinop (Mato Grosso Brazil), and the results obtained reveal clearly the potential of each species under mechanical stresses, showing that some of them can be good substitutes to the commonly wood speciesused.


Introduction
The wood, one of the most utilized materials on the human history, is directly related to usual human act ivities like living, overcoming natural obstacles, transportation and agriculture, among others.
Its versatility was always fundamental for the hu man needs and its wide availability was an important factor for a large expansion on its use in structure building, e.g. bridges, silos and roofs.
According to Souza [1] the explorat ion init ially selective, and then selective and predatory, happened due to the lack of informat ion about most of wood species. This lead to the exploration of the species which were alreadycharacterized, reducing the receptivity of the market to new and no trustable species.
The imminent shortage was responsible fo r a systematic rising in the prices, until the point where it was not anymore probable to use it on the quantities registered until now.
It is now a new mo ment to the Brazil wood sector, when it is necessary to define which species can commercially substitute the traditionally used species on structural constructions [2].
It is know that the Tropical Brazilian Forests occupy approximately 2.600.000 square kilo meters on the north and central-west regions of Brazil. According to Gonçalves et al [3], it is estimated that there are mo re than 5.000 species of trees in Amazonian Trop ical Forest, while only about 100 are used commercially and not more than 12 are exported to other countries.
In 1982, while there was a plan of the creation of trading posts for timber, with the objective of increasing the number of exported species, the National Institute of Forest Develop ment [4] reg istered that: less than 100 species were emp loyed on the timber industry on the Amazonian Region; national consumers had about 40 preferred species of timber; international consumers had few mo re than 10 preferred species of timber. Th is situation lead to a decision point on the research institutes related to timber.
Properties of species originated on the Amazonian Tropical Forest, already used for structural purposes, but without complete knowledge of their behavior under mechanical stresses are presented on [5][6][7][8][9][10][11][12]. However, due to technical limitations, it has not been possible to characterize co mpletely the referred species, what leads to a misuse of the timber, without the real knowledge of their behavior under mechanical stresses.
It is important to state that there are still indicatives that the Amazon Tropical Forest is suffering of selective and predatory explorat ion. The consequences of this reflect on the almost 20% of the original area already devastated in an irreversible way, accord ing to the National Institute of Space Research (INPE) [13], entity related to the Ministry of Science and Technology of Brazil. Thus, it is evident that an attitude needs to be taken to decrease the deforestation rate of the tropical forest, especially : −Stimu lus for the application of procedures to handle forests in an auto-sufficient way; −Spreading of the available information about alternative species characterized by research institutes; −Maintenance and development of programs to characterize native species; −Awareness of the market of t imber about the importance of substitution of species.
The present research is inserted in the present scenario, looking for characterize mechanically and physically the Brazilian forest timbers and, in part icular, the ones located in Sinop city (Mato Grosso -Brazil), contributing for its rational distribution on the consumer market. It was evaluated too the estimat ive of the strength properties of the wood species with known the density.

Material and Methods
In order to proceed with this work, were used five species of timber originated fro m certified areas of tropical forest, provided by the Syndicate of Timber Industries of Mato Grosso (SINDUSMAD) o f Sinop, being these: Canelão (Ocoteasp), Envira Branca (Xylopiasp), Guajará (Micropholisvenulosai), Quaruba Rosinha (Vochysiasp) and Breu Vermelho (Protiumsp).
These species were in pieces with no minal dimensions of 6cm×12cm×300cm. These passed by a drying process posteriorly, to reach a mo isture content of 12%, the recommended percentage by ABNT NBR 7190 [14]. Fro m these pieces, were extracted the samples for characterizat ion, standardized by the referred standard, with small dimensions and no defects. It is important to state that in future works these species will be characterized considering the p ieces with structural dimensions, making possible to analyse differences between them [15][16][17][18][19][20].
The tests to characterize the physical and mechanical properties were performed following the recommendations of the B Annex of the standard ABNT NRB 7190 [14]. Were For each one of the18 properties analysed, there were 12 samples [12], what resulted in 216 tests per species analysed.

Results and Conclusions
Tables fro m 1 to 5 present the average results (X m ), standard deviations (SD), and variation coefficients (VC) of each one of the properties analysed per species.

Conclusions
Considering the resultsobtained from regression between density andstrengthtensile parallel to the grain ofGuajará wood species of the physical and mechanical propert ies of the five species analysed, it is possible to conclude that: −Canelão, Guajará and Breu Vermelho wood species can be compared to Oit icicaAmarela and AngelimPedra, t wo species usually employed in Brazilian structures; −Quaruba Rosinhawood species can be compared to Quarubarana and LouroPreto, two species usually emp loyed in Brazilian structures; −Env ira Branca wood species can be compared to Canafístula e Guarucaia, also species commonly present in Bra zilian structural constructions.
According with the results, the timber species originated fro m No rth of MatoGrosso (Brazil) that were investigated on this work, can be emp loyed in structural projects substituting with the same or superior perfo rmance the species commonly used.
The results of the linear regression between density and tensile and comp ression strength parallel to the grain indicate that is possible determine the strength properties with knowledge the of de density of the wood species investigated.