The bending failure of full-culm bamboo is usually preceded by bending failure perpendicular to the fibers of the bamboo culm walls. Therefore, it is important to evaluate the stress perpendicular to the fiber that accompanies the bending of the bamboo culm. Brazier effect is considered one of the factors that cause this stress. In this paper, we discuss the bending failure mechanism and bending strength of round bamboo culms with formulation of the Brazier effect theory, numerical analysis, and experiments.
According to the Brazier effect theory, when the bending moment for the bamboo culm is small, the bending stress perpendicular to the fiber is about 6 % of the stress parallel to the fiber. Also, the finite element analysis results and the Brazier effect theory showed good agreement in some conditions. The stress perpendicular to the fiber by numerical analysis lies between the linear approximation and the Brazier effect theory and is affected by the internode length. As a result of the bending experiment using Madake bamboo, the stress distribution in the part of the bamboo culm that is not directly subjected to the external force agrees well with the Brazier effect theory. However, it was observed that at the point where the concentrated load was applied, a large additional bending stress perpendicular to the fiber was generated in the culm wall, leading to bending failure of the bamboo culm.