Experimental Research On Pull-out Properties Of GluBam Glued-in Rods

Recently, modern bamboo structures are developping rapidly. For some heavy bamboo structures, conventional connections may not be suitable according to the stiffness and bearing capacity of joint. Glued-in rod, as a new type of connection way utilized in timber structures, has high rigidity and bearing capacity. It shows significant advantages in the heavy bamboo structures. However, the relevant research in the field is very few until now.Several important factors about glued-in rod connection, such as section length, rod diameter, slenderness ratio and glue-line thickness, have been studied in this paper. All the research can be divided into two parts:one is the bond-slip behavior of glued-in rod and the other is about the stress distribution on the GluBam-adhesive interface. This research provides fundamental data for the practice of the glued-in rod connection of GluBam structures. The main tests and results are summarized as following:The paper gains test data of 96 GluBam specimens loading under pull-pull tests and analyzes the influence of each parameter on the bond-slip behaviors, such as the ultimate load, stiffness and ductility. The results show that failure modes can be classified into three types, such as GluBam splitting, rod pulling out from GluBam and rod yielding. When section length a is small, GluBam splitting is prone to occur. So the minimum section length a should be 7 times of rod diameter dr;slenderness ratio ? also has an obvious influence on the bond-slip behavior. Tests suggest that there is a critical value for slenderness ratio for glued- in rod connection. When it reaches the critical value ?cr, the rod will yield. From test data, ?cr is about 12.5 for rod of M12, and 15 for rod of M16 and M20. Moreover, increasing rod diameters and glue-line thicknesses can induce the GluBam splitting.Total 32 specimens with strain gages attached internally are also conducted under pull-pull test. The research reveals that four parameters have their own influence on the stress distribution on the GluBam-adhesive interface. Based on linear elastic assumption, the paper presents a carrying capacity model. The calculating results coincide with the experimental data well.Finally, a formula for ultimate load proves for GluBam glued-in rod connection by regression analysis. Reliability analysis of this new connection is also performed and the recommended slenderness ratio with a certain reliability is given. According to the relevant suggestions in the timber structures and the results of this test, design recommendations about GluBam glued-in rod connection are also provided, such as section length should be 7 times of rod diameter, M20 is the maximum diameter of rod in this connection, slenderness ratio can't be less than its critical value but no more than the ultimate value and the glue-line thickness with 2 mm is fit to the connection.