Alternative model to determine the characteristic strength value of wood in the compression parallel to the grain
Keywords:
Characteristic value, mechanical properties, probability distribution, Tabebuia spp., woodAbstract
Wood strength values are calculated based on the characteristic value, which corresponds to the 5 % percentile of a given probability distribution model. For a few number of samples (12 samples), the Brazilian standard ABNT NBR (7190) establishes an estimator of the characteristic compressive strength parallel to grain of the wood, which may provide a different result when compared with the characteristic value coming from a suitable probability distribution model. Considering the strength results in the parallel compression to the grain of 45 wood species of the hardwood group, Normal, LogNormal, Weibull and Exponential probability distribution models were used for each specie with the purpose of determining the one with the highest adhesion. Calculated the characteristic values by the best probability model distribution, an analysis of variance (ANOVA) was performed in the estimation of the characteristic value of compressive strength, making it possible to identify the most significant terms of the models as well as the quality of the adjustment obtained on such models. The proposed regression model (R2 adj= 96,56 %) proved to be equivalent to the empirical model of the Brazilian standard. The model proposed here only depends on the mean and the lowest value obtained from the compressive strength in the parallel direction to the grain.
Downloads
References
Andrade JR. J.R.; Almeida, D.H.; Almeida, T.H.; Christoforo, A.L.; Stamato, G.C.; Lahr, F.A.R. 2014. Avaliação das estruturas de cobertura em madeira de um galpão de estoques de produtos químicos. Amb Constr 14(3): 75-85. https://doi.org/10.1590/S1678-86212014000300006
Arruda, L.M.; Del Menezzi, C.H.S.; Andrade, A. 2015. Utilization of a thermomechanical process to enhance properties of a hardwood used for flooring. Braz J Wood Sci 6(3): 223-231. http://dx.doi.org/10.15210/cmad.v6i3.7144
Baar, J; Tippner, J.; Rademacher, P. 2015. Prediction of mechanical properties – modulus of rupture and modulus of elasticity of five tropical species by nondestructive methods. Maderas-Cienc Tecnol 17(2): 239-252. http://dx.doi.org/10.4067/S0718-221X2015005000023
Cavalheiro, R.S.; Almeida, D.H.; Almeida, T.H.; Christoforo, A.L.; Lahr, F.A.R. 2016. Density as estimator of shrinkage for some Brazilian Wood species. Int J Mater Eng 6(3):107-112. https://doi.org/107-112. 10.5923/j.ijme.20160603.08
Chen, Y.; Guo, W.; 2017. Nondestructive evaluation and reliability analysis for determining the mechanical properties of old wood of ancient timber structure. BioResources 12(2): 2310-2325. https://ojs.cnr.ncsu.edu/index.php/BioRes/article/view/BioRes_12_2_2310_Chen_Nondestructive_Evaluation_Reliability_Analysis
Christoforo, A.L.; Aftimus, B.H.C.; Panzera, T.H.; Machado, G.O.; Lahr, F.A.R. 2017. Physico-mechanical characterization of the Anadenanthera columbrina Wood specie. Eng Agric 37(2): 376-384. https://doi.org/10.1590/1809-4430-eng.agric.v37n2p376-384/2017
Ferro, F.S.; Icimoto, F.H.; Almeida, D.H.; Christoforo, A.L.; Lahr, F.A.R. 2015. Influência da posição dos instrumentos de medida na determinação do módulo de elasticidade da madeira na compressão paralela às fibras (Ec0). Rev Árvore 39(4): 743-749. https://doi.org/10.1590/0100-67622015000400017
Freitas, A.S.; Gonçalez, J.C.; Del Menezzi, C.H. 2016. Tratamento termomecânico e seus efeitos nas propriedades da Simarouba amara (Aubl.). FLORAM 23(4): 565-572. https://doi.org/10.1590/2179-8087.144115
Lahr, F.A.R.; Christoforo, A.L.; Varanda, L.D.; Araujo, V.A.; Chahud, E.; Branco, L.A.M.N.; 2017. Shear and longitudinal modulus of elasticity in wood. relations based on static bending tests. Acta Sci-Techol 39: 433-437. https://doi.org/10.4025/actascitechnol.v39i4.30512
Minitab. 2017. Minitab software version 18. MINITAB, State College, PA, United States of America. https://www.minitab.com/
Pinto, E.M.; Espinosa, M.M.; Calil JR, C. 2004. Métodos para Determinação do Valor Característico da Resistência à Compressão Paralela às Fibras da Madeira. Madeira: Arquitetura e Engenharia 5(14): 1-6. http://madeira.set.eesc.usp.br/article/view/264
Steege, H.; Vaessen, R.W.; Lopez, D.C.; Sabatier, D.; Antonelli, A.; Oliveira, S. M.; Pitman, N.C.A.; Jorgensen, P.M.; Salomão, R.P. 2016. The discovery of the Amazonian tree flora with an update checklist of all known tree taxa. Sci Rep 6(29549): 1-15. https://doi.org/10.1038/srep29549
Weerahandi, S. 1995. ANOVA under Unequal Error Variances. Biometrics 51(2): 589-599. https://doi.org/10.2307/2532947
