Experimental Study and Analysis of the Pullout Properties of Glued-In Rods Inserted Parallel to Grain in Side-Pressure Laminated Bamboo Lumber

Abstract

Glued-in rod connections (GIRc) in timber or bamboo joints are characterized by high stiffness, strength, and aesthetic appeal. In this study, pullout tests were conducted on 42 specimens of GIRc in side-pressure laminated bamboo lumber (SPLBL) parallel to grain to investigate their failure modes and characteristics. The effects of edge distance, adhesive layer thickness, and slenderness ratio on the mechanical properties of GIRc in SPLBL were discussed. According to the experimental results, four failure modes were observed: splitting failure of SPLBL, splitting failure of the glue layer of SPLBL, pullout failure of the threaded rod, and yielding failure of the threaded rod. The first two failure modes can be avoided by increasing the edge distance and modifying the production process of GIRc, while the load-bearing capacities of the latter two failure modes are primarily determined by the slenderness ratio and the mechanical properties of the threaded rods. The strength and stiffness of the specimens increased with edge distance and slenderness ratio, reaching a peak at an adhesive layer thickness of 2 mm. One-way ANOVA indicated that the slenderness ratio significantly affects the mechanical properties of the specimens. The applicability of existing load-bearing capacity calculation models was discussed. Based on the existing models and experimental data, a prediction equation for the load-bearing capacity of GIRc in SPLBL was proposed. This prediction equation was validated against a database including various engineered bamboo materials, rod materials, and adhesive layer thicknesses, demonstrating superior generality compared to other equations. Finally, a reliability analysis of the GIRc in SPLBL was conducted using the central point method of the first-order second-moment method, and an approximate solution for the critical anchorage slenderness ratio was obtained. The prediction equation and the reliability analysis results can serve as references for the engineering design of GIRc in bamboo structures.