Experimental and theoretical analysis on shear behavior of inclined screws in bamboo-to-bamboo joints

Screw connections have been widely adopted in bamboo and timber structural joints owing to their ease of fabrication, convenient installation, and clear load-transfer mechanism. Therefore, investigating the shear behavior of cross-inclined screws is of great significance for improving the theoretical framework governing bamboo structural joints. To evaluate the shear behavior of cross-inclined screws in reconstituted bamboo, monotonic static loading tests were conducted on ten groups of reconstituted bamboo joints with screw connections. This study focused on the impacts of screw diameter, penetration depth, embedding angle, and embedding configuration on the failure characteristic, slip development and shear capacity of the connections. The experiments revealed that the typical failure characteristics of inclined screw connections in reconstituted bamboo mainly included pull-out failure of shear-tension screws, penetration failure of shear-tension screws into the reconstituted bamboo panel, and double-hinge flexural failure of screws. In general, the load-slip curves of the cross-inclined screw connections exhibited three distinct stages: an initial linear growth stage, a nonlinear development stage, and a post-peak load-carrying capacity degradation stage. With increasing screw diameter and penetration length, the shear resistance and the slip stiffness of screw connections increased markedly. Compared with the screw connections having a screw embedding angle of ±60°, the shear resistance of screw connections with embedding angles of ±45° and ±30° increased by 20.2% and 66.0%, respectively, while the corresponding shear stiffness increased by 17.3% and 60.7%. Under different embedding configurations, the pure shear-tension screw connections exhibited the highest shear resistance, whereas the pure shear-compression screw connections showed the lowest shear resistance. The ±45° cross-inclined screws achieved the highest shear stiffness and exhibited superior overall shear performance. Based on the load-transfer characteristics and failure mechanisms of the screw connections, an analytical approach was developed to predict the shear resistance of inclined screws in bamboo joints.