search
for
 About Bioline  All Journals  Testimonials  Membership  News


Ciência Florestal
Centro de Pesquisas Florestais - CEPEF, Departamento de Ciências Florestais - DCFL, Programa de Pós Graduação em Engenharia Florestal - PPGEF
ISSN: 0103-9954
EISSN: 0103-9954
Vol. 24, No. 4, 2014, pp. 967-976
Bioline Code: cf14091
Full paper language: English
Document type: Research Article
Document available free of charge

Ciência Florestal, Vol. 24, No. 4, 2014, pp. 967-976

 en INFLUENCE OF THE ANGLE BETWEEN APPLIED FORCE AND WOOD GRAIN DIRECTION ON SHEAR STRENGTH
Logsdon, Norman Barros; Finger, Zenesio & de Jesus, José Manoel Henriques

Abstract

Wood is an anisotropic material and its resistance characteristics vary with the angle between the effort and the fiber direction (α). The Brazilian Code NBR 7190 – Design of Wooden Structures, foresees the strength correction to the normal stress, whenever α > 6°, and it recommends to apply Hankinson’s expression to design values. However, this referred code is omitted about this correction to the tangential stress. Besides, there is not experimental confirmation about the validity of using this expression on design values, originating from characteristic values. The objectives of this work were: to search in the bibliography other used expressions; to verify the validity of these expressions, to represent the variation of the shear strength, with the α angle; and, to verify the validity of application of these expressions in characteristic values. For this, a sample formed by twelve boards was used. From each board, specimens to shear tests were retired, with different fibers inclinations, which were tested in agreement with current NBR 7190, supplying the shear strength, for different α values. Four models (Hankinson, Sin, Karlsen and Keylwerth) were evaluated, using the pairing and deviation tests. The model that best represented the phenomenon, in both cases, was Keylwerth’s.

Keywords
shear strength; characteristic strength; fibers inclination

 
 pt INFLUÊNCIA DO ÂNGULO ENTRE O ESFORÇO APLICADO E A DIREÇÃO DAS FIBRAS DA MADEIRA SOBRE A RESISTÊNCIA AO CISALHAMENTO
Logsdon, Norman Barros; Finger, Zenesio & de Jesus, José Manoel Henriques

Resumo

A madeira e um material anisotropico e suas caracteristicas de resistencia variam com o angulo entre o esforco e a direcao das fibras (α). A norma brasileira NBR 7190 . Projeto de Estruturas de Madeira preve a correcao da resistencia as tensoes normais, sempre que α > 6°, e recomenda aplicar a expressao de Hankinson aos valores de calculo. Entretanto, a referida norma e omissa sobre esta correcao as tensoes tangenciais. Alem disso, nao ha comprovacao experimental sobre a validade de utilizar esta expressao em valores de calculo, oriundos de valores caracteristicos. Foram objetivos deste trabalho: pesquisar na bibliografia outras expressoes utilizadas; verificar a validade destas expressoes para representar a variacao das resistencias ao cisalhamento com o angulo α e verificar a validade de aplicacao destas expressoes em valores caracteristicos. Para isto, utilizou-se uma amostra formada por doze pranchas de madeira. De cada prancha foram retirados corpos de prova de cisalhamento, com diferentes inclinacoes das fibras, que foram ensaiados em acordo com a atual NBR 7190, fornecendo as resistencias ao cisalhamento, para diferentes α. Quatro modelos (Hankinson, Senos, Karlsen e Keylwerth) foram avaliados, utilizando-se os testes de pairing e dos desvios. O modelo que melhor representou o fenomeno, nos dois casos, foi o de Keylwerth.

Palavras-chave
resistência ao cisalhamento; resistência característica; inclinação das fibras

 
© Copyright 2014 - Ciência Florestal
Alternative site location: http://cascavel.ufsm.br/revistas/ojs-2.2.2/index.php/cienciaflorestal/index

Home Faq Resources Email Bioline
© Bioline International, 1989 - 2024, Site last up-dated on 01-Sep-2022.
Site created and maintained by the Reference Center on Environmental Information, CRIA, Brazil
System hosted by the Google Cloud Platform, GCP, Brazil