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Resumo uso de painéis de madeira tem ganhado destaque na indústria da construção civil. Os painéis MDP não atingem requisitos estruturais, ao contrário dos painéis OSB e compensado. Uma alternativa a fim de aprimorar o uso de painéis de partículas de madeira consiste no reforço desses com lâminas de madeira (painéis híbridos). Esta pesquisa objetivou avaliar o potencial de uso de painéis híbridos fabricados com partículas e lâminas de madeira de Pinus sp. e com resina poliuretana bicomponente à base de óleo de mamona, obedecendo à norma ABNT NBR 14810-2. Os resultados das propriedades físicas e mecânicas foram comparados com os requisitos normativos para painéis OSB (EN 300) e compensados (DIN 68792), e também com os resultados de painéis comerciais OSB e compensado. Os painéis híbridos atenderam os requisitos normativos para painéis comerciais OSB e compensado, indicados para uso estrutural. A análise estatística indicou a superioridade das propriedades físicas e mecânica dos painéis híbridos quando comparados com os resultados dos painéis OSB e compensado comerciais, resultado esse também justificado pelo uso da resina à base de mamona.Palavras-chave: Painel de madeira compensada. Painel OSB. Painel MDP. Resina poliuretana à base de óleo de mamona. AbstractThe use of wood panels has been gaining prominence in the construction industry. MDP panels do not meet structural requirements, unlike OSB and plywood panels. An alternative solution to improve the use of wood particleboard is the reinforcement of wood particleboards (hybrid panels). This research study aimed to evaluate the potential of using hybrid panels made with wood particles and veneers of Pinus sp. and with castor-based bicomponent polyurethane resin, meeting the Brazilian Standard ABNT NBR 14810-2. The physical and mechanical properties results were compared with the normative requirements for OSB (EN 300) and plywood panels (DIN 68792), as well as with the results of commercial plywood OSB panels. Hybrid panels met the standard requirements for OSB and plywood commercial panels indicated for structural use. The statistical analysis indicated the superiority of the physical and mechanical properties of the hybrid panels when compared to the results of the OSB and commercial plywood panels, a result that is also due to the use of the castor resin.

Accurate estimation of average modulus of elasticity in compression parallel to the grain (Ec0) is of paramount importance for rational sizing of timber structures, given the use of this property in the estimation of stability of compressed parts (ultimate limit state, ULS) and in calculation of excessive strains (serviceability limit state, SLS). In Brazil, if values cannot be experimentally determined, ABNT NBR 7190 (1997) allows for estimation of Ec0 through relations to average modulus of elasticity both in tension parallel to the grain (Et0) (Ec0 = Et0) and in bending (EM) (Ec0 = EM/0.90). This research aimed to access the efficiency of these relations by testing 30 tropical wood species. The analysis of variance results showed that Ec0 and Et0 were statistically equal. However, Ec0 and EM/0.90 were not statistically equal, and the method of least squares resulted in a coefficient of 0.98, which was 8.89% higher than the one suggested by ABNT NBR 7190 (1997) and close to 1, thus, validating the results of ANOVA, which pointed on the equivalence between Ec0 and EM (Ec0 = EM). As an alternative to simplified equations of the standard, two-parameter regression models were used. The geometric model with R² = 91.67% proved to be the model of best fit, which demonstrated that Ec0 could be calculated as a function of EM.

As wood is an orthotropic and natural material, there are several properties required for its use in civil construction. The apparent density has been used to estimate physical and mechanical properties of wood, as it is easy to determine experimentally, unlike other determinations, which involve the use of equipment available only in large research centers. Using the Brazilian standard ABNT NBR 7190 and linear and non-linear regression models, this research aimed to evaluate their accuracy in estimating the compressive strength parallel to the fibers (fc0) as well as their characteristic value (fc0,k). This study considered 72 tropical wood species from native forests that were divided into the 4 strength classes of this standard. For the set formed by all species, the linear polynomial model was the best fit, resulting in a determination coefficient of just over 70%.

The modeling of reinforced concrete structures has taken advantage of the increasing progress on Computational Mechanics, in such way that complex phenomena, such as cracking and crushing, creep, reinforcement yielding, steel-concrete bond loss, can be modeled in a reasonable realistic way, using the proper set of numerical and computational resources. Among several options, the ones based on the Finite Element Method (FEM) allow complex analysis simulations of reinforced concrete structures, including the interaction of different nonlinear effects. This paper deals with the nonlinear finite element analysis of the bond-slip between reinforcing steel and concrete, taking into account an experimental study previously performed. The FEM analysis presented uses a combination of resources where the material behavior of concrete is described by the Microplane Constitutive Model, and an embedded reinforcement model is used to represent steel inside the concrete and take into account the effect of bond-slip. The FEM models were created using the INSANE (INteractive Structural ANalysis Environment) computational system, open source software that has a set of FEM tools for nonlinear analysis of reinforced concrete structures. The correlations between numerical-experimentals results and several parameters validate the proposed combination of resources and identifies the significance of various effects on the response.

No abstract

Wood is a material used for various purposes since ancient times and is mainly used in civil and rural construction and industry. Due to the predatory exploitation of known trees, it is necessary to characterize new species for use in urban and rural structures as alternatives of species commonly used. This study aimed to determine the physical and mechanical properties of Guarucaia wood (Peltophorum vogelianum Benth.) based on the Brazilian standard ABNT NBR 7190 (1997) and estimate the strength and stiffness as a function of apparent density using the analysis of variance and also estimate stiffness as a function of its strength. The mechanical properties of P. vogelianum were considered compatible for structural use when compared with others used for the same purpose, being classified in the class C50 of dicotyledon species and evidencing the possibility of its use for structural purposes. According to the results of the poor quality in the fit of regression models in the statistical analysis, the strength and stiffness could not be estimated as a function of apparent density nor stiffness properties as a function of their respective strengths.

The connections with bonded-in steel bars present excellent aesthetics, trustworthy performance, high strength and stiffness, and are more economic compared to the equivalent traditional mechanical connections. Nonetheless, their use in an economic and safe way depends on the deeply knowledge about influences on the pull out behaviour and on many different connection work conditions. Among these parameters, it can be pointed out with great relevance, the diameter variation of the bars used, which influence directly on the adherence surface on the anchorage area. In this work, the experiment was conducted in order to evaluate the effects of steel bar diameter variations of bonded-in with the epoxy resin Compound, in three directions (0, 45and 90º) between the rods and the wood fibers. The wood natural variability was considered through random sample of a batch of structural Pinus oocarpa Shiedetimbers. In each observation, with a total of seven combinations of variables, six replications were presented. The steel bars used were highly stiffness ones (CA-50), with threaded surface solicited into the axial direction under monotonic loadings, with two consecutive load cycles. Thereafter statistical analysis, the results are presented and commented in a comparative way.