Effects of Different Connection Types on Mechanical Behavior of Cross-lap Joints of Phyllostachys makinoi Culms

Mechanical properties and behaviors of bamboo joined by different connections were considered in this work. Makino bamboo (Phyllostachys makinoi) culms from Taiwan were used as the connection material to explore the form of cross-lap joints. Since the cross-lap joint is a common joint in bamboo structures, the mechanical properties of tension, slip, and rotation were evaluated for three types of joints: lashing joint, iron wire joint, and steel bracket joint, under different load conditions. The results showed that the ultimate load of bamboo culms under lateral partial compression has a positive correlation with the number of bamboo nodes and the relative distance to the base-section of the bamboo culms. The mid-sections and end-sections have similar uniaxial compressions in the transverse orientation. According to results of tensile testing, the tensile stiffness of the three joint types is as follows in descending order: iron wire joint, lashing joint, and steel bracket joint, with the reverse order for ultimate load testing. In terms of slip testing, the withstanding of ultimate loads and increases in slip stiffness can be attributed to bamboo nodes that assist in creating slip stiffness in lashing joint. However, ultimately, steel bracket joints hold the highest slip stiffness. Our findings for rotation stiffness value show the following tendency: steel bracket joint > lashing joint > iron wire joint.