Effects Of Wood Anatomy On The Mechanical Behavior Of Single-Bolted Connections

Audrey Zink-Sharp, John S. Stelmokas, Hong-mei Gu

Abstract


This study combined mechanical testing of full-size bolted connections, determination of micromechanical properties of individual growth rings within the full-size specimens, and video microscopy for anatomical and mechanical measurements. Hard maple (Acer spp.) and northern red oak (Quercus rubra) specimens representative of single-bolted connections were tested to failure in bearing stress and analyzed using video microscopy methods. Maximum crushing strength of individual growth rings was obtained from specimens that were 1 mm X 1 mm in cross section and 4 mm along the grain. Anatomical measurements of cell-wall thickness, percent vessels in a given area, and ray width were obtained for each species and correlated to failure mode. It was concluded that maple had a consistent failure mode, while oak had a variable failure mode. The difference in failure modes is attributed to the different anatomical structures of the two species, mainly, ray and vessel size. Bearing stress was not statistically significantly influenced by the different anatomical features; however, stiffness in compression was.

Keywords


Bearing stress;bolted timber connections;failure mode;micromechanical properties;video microscopy

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