A comprehensive evaluation of the effects of bamboo nodes on the mechanical properties of bamboo culms

Architectural pavilions made of round bamboo are undergoing rapid development due to their appealing appearance and low carbon footprint, but their structural analysis is challenging due to the existence of bamboo nodes. Generally, bamboo nodes provide positive effects on the mechanical behavior of bamboo culms in terms of evolution. However, the loading conditions of bamboo culms used in buildings greatly differ from the natural conditions. Some studies have been conducted on this issue but come to different conclusions. In this regard, this work conducts a comprehensive study on the effects of bamboo nodes on the mechanical properties of bamboo culms. A total of 168 specimens divided into four types were tested, including compressive, tensile and shear tests parallel to the grain and radial compressive tests. The load–displacement curves and failure modes were analyzed. The analysis of variance method was used to evaluate the effects of bamboo nodes on the mechanical properties. A comprehensive discussion based on fiber morphology is presented to explain the effects of nodes under different load conditions. Additionally, the fiber distribution in the diaphragm was observed, and the compressive strength of the diaphragm was tested. It was found that the bamboo node had significant effects on the tensile strength and radial compressive modulus. Compared to the bamboo culm without nodes, the tensile strength of bamboo culm with nodes decreased by 47%, while the node could improve the pipe stiffness by 123%. In compressive and shear tests parallel to the grain, the bamboo node showed slight effects on the strength. The differences in both strengths were all within 9% in value. Based on the geometric model, the relationship between the fiber morphology and the mechanical properties was built. In short, the bamboo node showed less improvement in compressive and shear tests parallel to the grain but should be carefully considered in tensile conditions due to its weakening effect.